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Hardy JC, Pool EH, Bruystens JGH, Zhou X, Li Q, Zhou DR, Palay M, Tan G, Chen L, Choi JLC, Lee HN, Strack S, Wang D, Taylor SS, Mehta S, Zhang J. Molecular determinants and signaling effects of PKA RIα phase separation. Mol Cell 2024; 84:1570-1584.e7. [PMID: 38537638 PMCID: PMC11031308 DOI: 10.1016/j.molcel.2024.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 12/07/2023] [Accepted: 03/01/2024] [Indexed: 04/09/2024]
Abstract
Spatiotemporal regulation of intracellular signaling molecules, such as the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA), ensures proper cellular function. Liquid-liquid phase separation (LLPS) of the ubiquitous PKA regulatory subunit RIα promotes cAMP compartmentation and signaling specificity. However, the molecular determinants of RIα LLPS remain unclear. Here, we reveal that two separate dimerization interfaces, combined with the cAMP-induced unleashing of the PKA catalytic subunit (PKA-C) from the pseudosubstrate inhibitory sequence, drive RIα condensate formation in the cytosol of mammalian cells, which is antagonized by docking to A-kinase anchoring proteins. Strikingly, we find that the RIα pseudosubstrate region is critically involved in forming a non-canonical R:C complex, which recruits active PKA-C to RIα condensates to maintain low basal PKA activity in the cytosol. Our results suggest that RIα LLPS not only facilitates cAMP compartmentation but also spatially restrains active PKA-C, thus highlighting the functional versatility of biomolecular condensates in driving signaling specificity.
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Affiliation(s)
- Julia C Hardy
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Shu Chien-Gene Lay Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Emily H Pool
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jessica G H Bruystens
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xin Zhou
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Qingrong Li
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Daojia R Zhou
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Shu Chien-Gene Lay Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Max Palay
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Gerald Tan
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Lisa Chen
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jaclyn L C Choi
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ha Neul Lee
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stefan Strack
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Dong Wang
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA; Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Susan S Taylor
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Sohum Mehta
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jin Zhang
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA; Shu Chien-Gene Lay Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA; Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA.
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2
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Chen C, Merrill RA, Jong CJ, Strack S. Driving mitochondrial fission improves cognitive, but not motor deficits in a mouse model of Ataxia of Charlevoix-Saguenay. Res Sq 2024:rs.3.rs-4178088. [PMID: 38659734 PMCID: PMC11042405 DOI: 10.21203/rs.3.rs-4178088/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by loss-of-function mutation in the SACS gene, which encodes sacsin, a putative HSP70-HSP90 co-chaperone. Previous studies with Sacs knock-out (KO) mice and patient-derived fibroblasts suggested that SACSIN mutations inhibit the function of the mitochondrial fission enzyme dynamin-related protein 1 (Drp1). This in turn resulted in mitochondrial hyperfusion and dysfunction. We experimentally tested this hypothesis by genetically manipulating the mitochondrial fission/fusion equilibrium, creating double KO (DKO) mice that also lack positive (PP2A/Bβ2) and negative (PKA/AKAP1) regulators of Drp1. Neither promoting mitochondrial fusion (Bβ2 KO) nor fission (Akap1 KO) influenced progression of motor symptoms in Sacs KO mice. However, our studies identified profound learning and memory deficits in aged Sacs KO mice. Moreover, this cognitive impairment was rescued in a gene dose-dependent manner by deletion of the Drp1 inhibitor PKA/Akap1. Our results are inconsistent with mitochondrial dysfunction as a primary pathogenic mechanism in ARSACS. Instead, they imply that promoting mitochondrial fission may be beneficial at later stages of the disease when pathology extends to brain regions subserving learning and memory.
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Glebov-McCloud AGP, Saide WS, Gaine ME, Strack S. Protein Kinase A in neurological disorders. J Neurodev Disord 2024; 16:9. [PMID: 38481146 PMCID: PMC10936040 DOI: 10.1186/s11689-024-09525-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 02/29/2024] [Indexed: 03/17/2024] Open
Abstract
Cyclic adenosine 3', 5' monophosphate (cAMP)-dependent Protein Kinase A (PKA) is a multi-functional serine/threonine kinase that regulates a wide variety of physiological processes including gene transcription, metabolism, and synaptic plasticity. Genomic sequencing studies have identified both germline and somatic variants of the catalytic and regulatory subunits of PKA in patients with metabolic and neurodevelopmental disorders. In this review we discuss the classical cAMP/PKA signaling pathway and the disease phenotypes that result from PKA variants. This review highlights distinct isoform-specific cognitive deficits that occur in both PKA catalytic and regulatory subunits, and how tissue-specific distribution of these isoforms may contribute to neurodevelopmental disorders in comparison to more generalized endocrine dysfunction.
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Affiliation(s)
- Alexander G P Glebov-McCloud
- Department of Neuroscience and Pharmacology, Bowen Science Building, University of Iowa, Carver College of Medicine, 51 Newton Road, Iowa City, IA, 52242, USA
| | - Walter S Saide
- Department of Neuroscience and Pharmacology, Bowen Science Building, University of Iowa, Carver College of Medicine, 51 Newton Road, Iowa City, IA, 52242, USA
| | - Marie E Gaine
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy Building, College of Pharmacy, University of Iowa, 180 S. Grand Ave, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, Intellectual and Developmental Disabilities Research Center, Iowa City, IA, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, Bowen Science Building, University of Iowa, Carver College of Medicine, 51 Newton Road, Iowa City, IA, 52242, USA.
- Iowa Neuroscience Institute, Intellectual and Developmental Disabilities Research Center, Iowa City, IA, USA.
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Wu CG, Balakrishnan VK, Merrill RA, Parihar PS, Konovolov K, Chen YC, Xu Z, Wei H, Sundaresan R, Cui Q, Wadzinski BE, Swingle MR, Musiyenko A, Chung WK, Honkanen RE, Suzuki A, Huang X, Strack S, Xing Y. B56δ long-disordered arms form a dynamic PP2A regulation interface coupled with global allostery and Jordan's syndrome mutations. Proc Natl Acad Sci U S A 2024; 121:e2310727120. [PMID: 38150499 PMCID: PMC10769853 DOI: 10.1073/pnas.2310727120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 11/27/2023] [Indexed: 12/29/2023] Open
Abstract
Intrinsically disordered regions (IDR) and short linear motifs (SLiMs) play pivotal roles in the intricate signaling networks governed by phosphatases and kinases. B56δ (encoded by PPP2R5D) is a regulatory subunit of protein phosphatase 2A (PP2A) with long IDRs that harbor a substrate-mimicking SLiM and multiple phosphorylation sites. De novo missense mutations in PPP2R5D cause intellectual disabilities (ID), macrocephaly, Parkinsonism, and a broad range of neurological symptoms. Our single-particle cryo-EM structures of the PP2A-B56δ holoenzyme reveal that the long, disordered arms at the B56δ termini fold against each other and the holoenzyme core. This architecture suppresses both the phosphatase active site and the substrate-binding protein groove, thereby stabilizing the enzyme in a closed latent form with dual autoinhibition. The resulting interface spans over 190 Å and harbors unfavorable contacts, activation phosphorylation sites, and nearly all residues with ID-associated mutations. Our studies suggest that this dynamic interface is coupled to an allosteric network responsive to phosphorylation and altered globally by mutations. Furthermore, we found that ID mutations increase the holoenzyme activity and perturb the phosphorylation rates, and the severe variants significantly increase the mitotic duration and error rates compared to the normal variant.
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Affiliation(s)
- Cheng-Guo Wu
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
- Biophysics Program, University of Wisconsin at Madison, Madison, WI53706
| | - Vijaya K. Balakrishnan
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
| | - Ronald A. Merrill
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA52242
| | - Pankaj S. Parihar
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
| | - Kirill Konovolov
- Chemistry Department, University of Wisconsin at Madison, Madison, WI53706
| | - Yu-Chia Chen
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
- Molecular and Cellular Pharmacology Program, University of Wisconsin at Madison, Madison, WI53706
| | - Zhen Xu
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA52242
| | - Hui Wei
- The Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY10027
| | - Ramya Sundaresan
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
| | - Qiang Cui
- Department of Chemistry, Boston University, Boston, MA02215
| | | | - Mark R. Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL36688
| | - Alla Musiyenko
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL36688
| | - Wendy K. Chung
- Department of Pediatrics, Boston Children’s Hospital, Harvard Medical School, Boston, MA02215
| | - Richard E. Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL36688
| | - Aussie Suzuki
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
- Biophysics Program, University of Wisconsin at Madison, Madison, WI53706
- Molecular and Cellular Pharmacology Program, University of Wisconsin at Madison, Madison, WI53706
| | - Xuhui Huang
- Biophysics Program, University of Wisconsin at Madison, Madison, WI53706
- Chemistry Department, University of Wisconsin at Madison, Madison, WI53706
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA52242
| | - Yongna Xing
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, WI53705
- Biophysics Program, University of Wisconsin at Madison, Madison, WI53706
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5
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Hardy JC, Pool EH, Bruystens JGH, Zhou X, Li Q, Zhou DR, Palay M, Tan G, Chen L, Choi JLC, Lee HN, Strack S, Wang D, Taylor SS, Mehta S, Zhang J. Molecular Determinants and Signaling Effects of PKA RIα Phase Separation. bioRxiv 2023:2023.12.10.570836. [PMID: 38168176 PMCID: PMC10760030 DOI: 10.1101/2023.12.10.570836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Spatiotemporal regulation of intracellular signaling molecules, such as the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA), ensures the specific execution of various cellular functions. Liquid-liquid phase separation (LLPS) of the ubiquitously expressed PKA regulatory subunit RIα was recently identified as a major driver of cAMP compartmentation and signaling specificity. However, the molecular determinants of RIα LLPS remain unclear. Here, we reveal that two separate dimerization interfaces combined with the cAMP-induced release of the PKA catalytic subunit (PKA-C) from the pseudosubstrate inhibitory sequence are required to drive RIα condensate formation in cytosol, which is antagonized by docking to A-kinase anchoring proteins. Strikingly, we find that the RIα pseudosubstrate region is critically involved in the formation of a non-canonical R:C complex, which serves to maintain low basal PKA activity in the cytosol by enabling the recruitment of active PKA-C to RIα condensates. Our results suggest that RIα LLPS not only facilitates cAMP compartmentation but also spatially restrains active PKA-C, thus highlighting the functional versatility of biomolecular condensates in driving signaling specificity.
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Bastola T, Perkins GA, Kim KY, Choi S, Kwon JW, Shen Z, Strack S, Ju WK. Role of A-Kinase Anchoring Protein 1 in Retinal Ganglion Cells: Neurodegeneration and Neuroprotection. Cells 2023; 12:1539. [PMID: 37296658 PMCID: PMC10252895 DOI: 10.3390/cells12111539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 05/21/2023] [Accepted: 06/01/2023] [Indexed: 06/12/2023] Open
Abstract
A-Kinase anchoring protein 1 (AKAP1) is a multifunctional mitochondrial scaffold protein that regulates mitochondrial dynamics, bioenergetics, and calcium homeostasis by anchoring several proteins, including protein kinase A, to the outer mitochondrial membrane. Glaucoma is a complex, multifactorial disease characterized by a slow and progressive degeneration of the optic nerve and retinal ganglion cells (RGCs), ultimately resulting in vision loss. Impairment of the mitochondrial network and function is linked to glaucomatous neurodegeneration. Loss of AKAP1 induces dynamin-related protein 1 dephosphorylation-mediated mitochondrial fragmentation and loss of RGCs. Elevated intraocular pressure triggers a significant reduction in AKAP1 protein expression in the glaucomatous retina. Amplification of AKAP1 expression protects RGCs from oxidative stress. Hence, modulation of AKAP1 could be considered a potential therapeutic target for neuroprotective intervention in glaucoma and other mitochondria-associated optic neuropathies. This review covers the current research on the role of AKAP1 in the maintenance of mitochondrial dynamics, bioenergetics, and mitophagy in RGCs and provides a scientific basis to identify and develop new therapeutic strategies that could protect RGCs and their axons in glaucoma.
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Affiliation(s)
- Tonking Bastola
- Hamilton Glaucoma Center and Shiley Eye Institute, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093, USA; (T.B.); (S.C.); (J.-W.K.); (Z.S.)
| | - Guy A. Perkins
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA; (G.A.P.); (K.-Y.K.)
| | - Keun-Young Kim
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA; (G.A.P.); (K.-Y.K.)
| | - Seunghwan Choi
- Hamilton Glaucoma Center and Shiley Eye Institute, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093, USA; (T.B.); (S.C.); (J.-W.K.); (Z.S.)
| | - Jin-Woo Kwon
- Hamilton Glaucoma Center and Shiley Eye Institute, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093, USA; (T.B.); (S.C.); (J.-W.K.); (Z.S.)
- Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
- Department of Ophthalmology and Visual Science, St. Vincent’s Hospital, Jungbu-daero 93, Paldal-gu, Suwon 16247, Republic of Korea
| | - Ziyao Shen
- Hamilton Glaucoma Center and Shiley Eye Institute, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093, USA; (T.B.); (S.C.); (J.-W.K.); (Z.S.)
| | - Stefan Strack
- Department of Pharmacology, Iowa Neuroscience Institute, University of Iowa, Iowa City, IA 52242, USA;
| | - Won-Kyu Ju
- Hamilton Glaucoma Center and Shiley Eye Institute, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093, USA; (T.B.); (S.C.); (J.-W.K.); (Z.S.)
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7
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Brennecke BR, Yang US, Liu S, Ilerisoy FS, Ilerisoy BN, Joglekar A, Kim LB, Peachee SJ, Richtsmeier SL, Stephens SB, Sander EA, Strack S, Moninger TO, Ankrum JA, Imai Y. Utilization of commercial collagens for preparing well-differentiated human beta cells for confocal microscopy. Front Endocrinol (Lausanne) 2023; 14:1187216. [PMID: 37305047 PMCID: PMC10248405 DOI: 10.3389/fendo.2023.1187216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 05/09/2023] [Indexed: 06/13/2023] Open
Abstract
Introduction With technical advances, confocal and super-resolution microscopy have become powerful tools to dissect cellular pathophysiology. Cell attachment to glass surfaces compatible with advanced imaging is critical prerequisite but remains a considerable challenge for human beta cells. Recently, Phelps et al. reported that human beta cells plated on type IV collagen (Col IV) and cultured in neuronal medium preserve beta cell characteristics. Methods We examined human islet cells plated on two commercial sources of Col IV (C6745 and C5533) and type V collagen (Col V) for differences in cell morphology by confocal microscopy and secretory function by glucose-stimulated insulin secretion (GSIS). Collagens were authenticated by mass spectrometry and fluorescent collagen-binding adhesion protein CNA35. Results All three preparations allowed attachment of beta cells with high nuclear localization of NKX6.1, indicating a well-differentiated status. All collagen preparations supported robust GSIS. However, the morphology of islet cells differed between the 3 preparations. C5533 showed preferable features as an imaging platform with the greatest cell spread and limited stacking of cells followed by Col V and C6745. A significant difference in attachment behavior of C6745 was attributed to the low collagen contents of this preparation indicating importance of authentication of coating material. Human islet cells plated on C5533 showed dynamic changes in mitochondria and lipid droplets (LDs) in response to an uncoupling agent 2-[2-[4-(trifluoromethoxy)phenyl]hydrazinylidene]-propanedinitrile (FCCP) or high glucose + oleic acid. Discussion An authenticated preparation of Col IV provides a simple platform to apply advanced imaging for studies of human islet cell function and morphology.
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Affiliation(s)
- Brianna R. Brennecke
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - USeong Yang
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Fatma S. Ilerisoy
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Beyza N. Ilerisoy
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Aditya Joglekar
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Lucy B. Kim
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Spencer J. Peachee
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Syreine L. Richtsmeier
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Samuel B. Stephens
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
| | - Edward A. Sander
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, United States
| | - Thomas O. Moninger
- Central Microscopy Research Facility, Roy G. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - James A. Ankrum
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA, United States
| | - Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, United States
- Medical Service, Endocrinology Section, Iowa City Veterans Affairs Medical Center, Iowa City, IA, United States
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8
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Wu CG, Balakrishnan VK, Parihar PS, Konovolov K, Chen YC, Merrill RA, Wei H, Carragher B, Sundaresan R, Cui Q, Wadzinski BE, Swingle MR, Musiyenko A, Honkanen R, Chung WK, Suzuki A, Strack S, Huang X, Xing Y. Extended regulation interface coupled to the allosteric network and disease mutations in the PP2A-B56δ holoenzyme. bioRxiv 2023:2023.03.09.530109. [PMID: 37066309 PMCID: PMC10103954 DOI: 10.1101/2023.03.09.530109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
An increasing number of mutations associated with devastating human diseases are diagnosed by whole-genome/exon sequencing. Recurrent de novo missense mutations have been discovered in B56δ (encoded by PPP2R5D), a regulatory subunit of protein phosphatase 2A (PP2A), that cause intellectual disabilities (ID), macrocephaly, Parkinsonism, and a broad range of neurological symptoms. Single-particle cryo-EM structures show that the PP2A-B56δ holoenzyme possesses closed latent and open active forms. In the closed form, the long, disordered arms of B56δ termini fold against each other and the holoenzyme core, establishing dual autoinhibition of the phosphatase active site and the substrate-binding protein groove. The resulting interface spans over 190 Å and harbors unfavorable contacts, activation phosphorylation sites, and nearly all residues with ID-associated mutations. Our studies suggest that this dynamic interface is close to an allosteric network responsive to activation phosphorylation and altered globally by mutations. Furthermore, we found that ID mutations perturb the activation phosphorylation rates, and the severe variants significantly increase the mitotic duration and error rates compared to the wild variant.
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Affiliation(s)
- Cheng-Guo Wu
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
- Biophysics program, University of Wisconsin at Madison, Wisconsin 53706, USA
| | - Vijaya K. Balakrishnan
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
| | - Pankaj S. Parihar
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
| | - Kirill Konovolov
- Chemistry Department, University of Wisconsin at Madison, Wisconsin 53706, USA
| | - Yu-Chia Chen
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
- Molecular and Cellular Pharmacology program, University of Wisconsin at Madison, Wisconsin 53706, USA
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Hui Wei
- New York Structural biology Center, New York, NY 10027, USA
| | | | - Ramya Sundaresan
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
| | - Qiang Cui
- Department of Chemistry, Metcalf Center for Science & Engineering, Boston University, Boston, MA 02215, USA
| | - Brian E. Wadzinski
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Mark R. Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Alla Musiyenko
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Richard Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Wendy K. Chung
- Departments of Pediatrics and Medicine, Columbia University, New York, NY 10032, USA
| | - Aussie Suzuki
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
- Biophysics program, University of Wisconsin at Madison, Wisconsin 53706, USA
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Xuhui Huang
- Biophysics program, University of Wisconsin at Madison, Wisconsin 53706, USA
- Chemistry Department, University of Wisconsin at Madison, Wisconsin 53706, USA
| | - Yongna Xing
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin at Madison, School of Medicine and Public Health, Madison, Wisconsin 53705, USA
- Biophysics program, University of Wisconsin at Madison, Wisconsin 53706, USA
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9
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Guo DF, Merrill RA, Qian L, Hsu Y, Zhang Q, Lin Z, Thedens DR, Usachev YM, Grumbach I, Sheffield VC, Strack S, Rahmouni K. The BBSome regulates mitochondria dynamics and function. Mol Metab 2023; 67:101654. [PMID: 36513220 PMCID: PMC9792363 DOI: 10.1016/j.molmet.2022.101654] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVE The essential role of mitochondria in regulation of metabolic function and other physiological processes has garnered enormous interest in understanding the mechanisms controlling the function of this organelle. We assessed the role of the BBSome, a protein complex composed of eight Bardet-Biedl syndrome (BBS) proteins, in the control of mitochondria dynamic and function. METHODS We used a multidisciplinary approach that include CRISPR/Cas9 technology-mediated generation of a stable Bbs1 gene knockout hypothalamic N39 neuronal cell line. We also analyzed the phenotype of BBSome deficient mice in presence or absence of the gene encoding A-kinase anchoring protein 1 (AKAP1). RESULTS Our data show that the BBSome play an important role in the regulation of mitochondria dynamics and function. Disruption of the BBSome cause mitochondria hyperfusion in cell lines, fibroblasts derived from patients as well as in hypothalamic neurons and brown adipocytes of mice. The morphological changes in mitochondria translate into functional abnormalities as indicated by the reduced oxygen consumption rate and altered mitochondrial distribution and calcium handling. Mechanistically, we demonstrate that the BBSome modulates the activity of dynamin-like protein 1 (DRP1), a key regulator of mitochondrial fission, by regulating its phosphorylation and translocation to the mitochondria. Notably, rescuing the decrease in DRP1 activity through deletion of one copy of the gene encoding AKAP1 was effective to normalize the defects in mitochondrial morphology and activity induced by BBSome deficiency. Importantly, this was associated with improvement in several of the phenotypes caused by loss of the BBSome such as the neuroanatomical abnormalities, metabolic alterations and obesity highlighting the importance of mitochondria defects in the pathophysiology of BBS. CONCLUSIONS These findings demonstrate a critical role of the BBSome in the modulation of mitochondria function and point to mitochondrial defects as a key disease mechanism in BBS.
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Affiliation(s)
- Deng-Fu Guo
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Veterans Affairs Health Care System, Iowa City, IA, USA
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Lan Qian
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Ying Hsu
- Veterans Affairs Health Care System, Iowa City, IA, USA
| | - Qihong Zhang
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Zhihong Lin
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Daniel R Thedens
- Department of Radiology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Yuriy M Usachev
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Isabella Grumbach
- Veterans Affairs Health Care System, Iowa City, IA, USA; Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Val C Sheffield
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Kamal Rahmouni
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Veterans Affairs Health Care System, Iowa City, IA, USA; Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Obesity Research and Education Initiative, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
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10
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Guo DF, Morgan DA, Zhao Y, Merrill RA, Strack S, Rahmouni K. Abstract 109: Mitochondrial Akap1 Protein Is Required For Diet-induced Obesity, Glucose Dysregulation And Hypertension. Hypertension 2022. [DOI: 10.1161/hyp.79.suppl_1.109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mitochondria are best known as the powerhouse of the cell playing a critical role in energy metabolism with important implications in the development of obesity, a major cause of type 2 diabetes and hypertension. A-kinase anchoring protein 1 (AKAP1) is a mitochondrial scaffold protein that promote protein kinase A (PKA)-mediated phosphorylation of Drp1(Ser637) by increasing the local concentration of PKA at the outer mitochondrial membrane. However, the role of AKAP1 in the regulation of body weight, glucose homeostasis and blood pressure is not known. We used AKAP1 deficient mice to understand the physiological significance of this protein. Male and female AKAP1
-/-
and AKAP1
+/-
mice fed normal chow exhibit normal body weight relative to littermate controls. In contrast, AKAP1
-/-
and AKAP1
+/-
mice fed high fat high/sucrose diet (HFHSD) display attenuated weight gain compared to controls (male: 39.5
+
1.7 and 42.5
+
1.6 vs 47.3
+
2.3g, and female: 29.7
+
1.3 and 29.2
+
1.8 vs 32.5
+
1.5g). This was associated with significant decreased in fat mass in AKAP1
-/-
(male:16.2
+
0.9g and female: 8.7
+
1.1g) and AKAP1
+/-
(male:15.0
+
2.5g and female: 9.2
+
1.0g) mice compared to controls (male: 21.2
+
1.7g and female: 13.9
+
1.6g) whereas lean mass was not different between the three groups. Glucose tolerance test revealed that female AKAP1
-/-
mice have improved glucose handling, and insulin tolerance test showed that insulin sensitivity is better in male AKAP1
-/-
mice than controls. Notably, blood pressure was significantly lower in HFHSD-fed male AKAP1
-/-
(systolic: 124.4
+
6 mmHg) and AKAP1
+/-
(116.4
+
3 mmHg) mice vs control mice (146.4
+
5 mmHg). These findings demonstrated the importance of AKAP1 in the development of obesity and associated diabetes and hypertension. Our data also point to mitochondria function as a potential therapeutic target for treatment of common obesity and related diseases.
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11
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Li Y, Balakrishnan VK, Rowse M, Wu CG, Bravos AP, Yadav VK, Ivarsson YI, Strack S, Novikova IV, Xing Y. Coupling to short linear motifs creates versatile PME-1 activities in PP2A holoenzyme demethylation and inhibition. eLife 2022; 11:79736. [PMID: 35924897 PMCID: PMC9398451 DOI: 10.7554/elife.79736] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 08/03/2022] [Indexed: 11/30/2022] Open
Abstract
Protein phosphatase 2A (PP2A) holoenzymes target broad substrates by recognizing short motifs via regulatory subunits. PP2A methylesterase 1 (PME-1) is a cancer-promoting enzyme and undergoes methylesterase activation upon binding to the PP2A core enzyme. Here, we showed that PME-1 readily demethylates different families of PP2A holoenzymes and blocks substrate recognition in vitro. The high-resolution cryoelectron microscopy structure of a PP2A-B56 holoenzyme–PME-1 complex reveals that PME-1 disordered regions, including a substrate-mimicking motif, tether to the B56 regulatory subunit at remote sites. They occupy the holoenzyme substrate-binding groove and allow large structural shifts in both holoenzyme and PME-1 to enable multipartite contacts at structured cores to activate the methylesterase. B56 interface mutations selectively block PME-1 activity toward PP2A-B56 holoenzymes and affect the methylation of a fraction of total cellular PP2A. The B56 interface mutations allow us to uncover B56-specific PME-1 functions in p53 signaling. Our studies reveal multiple mechanisms of PME-1 in suppressing holoenzyme functions and versatile PME-1 activities derived from coupling substrate-mimicking motifs to dynamic structured cores.
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Affiliation(s)
- Yitong Li
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
| | | | - Michael Rowse
- Indiana University - Purdue University Columbus, Columbus, United States
| | - Cheng-Guo Wu
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
| | | | - Vikash K Yadav
- 5Department of Chemistry, Uppsala University, Uppsala, Sweden
| | - YIva Ivarsson
- 5Department of Chemistry, Uppsala University, Uppsala, Sweden
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, United States
| | - Irina V Novikova
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, United States
| | - Yongna Xing
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
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12
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Sandal P, Jong CJ, Merrill RA, Song J, Strack S. Protein phosphatase 2A - structure, function and role in neurodevelopmental disorders. J Cell Sci 2021; 134:270819. [PMID: 34228795 DOI: 10.1242/jcs.248187] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Neurodevelopmental disorders (NDDs), including intellectual disability (ID), autism and schizophrenia, have high socioeconomic impact, yet poorly understood etiologies. A recent surge of large-scale genome or exome sequencing studies has identified a multitude of mostly de novo mutations in subunits of the protein phosphatase 2A (PP2A) holoenzyme that are strongly associated with NDDs. PP2A is responsible for at least 50% of total Ser/Thr dephosphorylation in most cell types and is predominantly found as trimeric holoenzymes composed of catalytic (C), scaffolding (A) and variable regulatory (B) subunits. PP2A can exist in nearly 100 different subunit combinations in mammalian cells, dictating distinct localizations, substrates and regulatory mechanisms. PP2A is well established as a regulator of cell division, growth, and differentiation, and the roles of PP2A in cancer and various neurodegenerative disorders, such as Alzheimer's disease, have been reviewed in detail. This Review summarizes and discusses recent reports on NDDs associated with mutations of PP2A subunits and PP2A-associated proteins. We also discuss the potential impact of these mutations on the structure and function of the PP2A holoenzymes and the etiology of NDDs.
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Affiliation(s)
- Priyanka Sandal
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242, USA
| | - Chian Ju Jong
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242, USA
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242, USA
| | - Jianing Song
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242, USA
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13
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Mishra A, Liu S, Promes J, Harata M, Sivitz W, Fink B, Bhardwaj G, O'Neill BT, Kang C, Sah R, Strack S, Stephens S, King T, Jackson L, Greenberg AS, Anokye-Danso F, Ahima RS, Ankrum J, Imai Y. Perilipin 2 downregulation in β cells impairs insulin secretion under nutritional stress and damages mitochondria. JCI Insight 2021; 6:144341. [PMID: 33784258 PMCID: PMC8262280 DOI: 10.1172/jci.insight.144341] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 03/24/2021] [Indexed: 12/15/2022] Open
Abstract
Perilipin 2 (PLIN2) is a lipid droplet (LD) protein in β cells that increases under nutritional stress. Downregulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was downregulated in mouse β cells, INS1 cells, and human islet cells. β Cell–specific deletion of PLIN2 in mice on a high-fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Downregulation of PLIN2 in INS1 cells blunted GSIS after 24-hour incubation with 0.2 mM palmitic acid. Downregulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Downregulation of PLIN2 decreased specific OXPHOS proteins in all 3 models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2-deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress, as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells has an important role in preserving insulin secretion, β cell metabolism, and mitochondrial function under nutritional stress.
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Affiliation(s)
- Akansha Mishra
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Joseph Promes
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Mikako Harata
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - William Sivitz
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Brian Fink
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Gourav Bhardwaj
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Brian T O'Neill
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Chen Kang
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Samuel Stephens
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Timothy King
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia, USA
| | - Laura Jackson
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia, USA
| | - Andrew S Greenberg
- Obesity and Metabolism Laboratory, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, USA
| | | | - Rexford S Ahima
- Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - James Ankrum
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
| | - Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
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14
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Rysted JE, Lin Z, Walters GC, Rauckhorst AJ, Noterman M, Liu G, Taylor EB, Strack S, Usachev YM. Distinct properties of Ca 2+ efflux from brain, heart and liver mitochondria: The effects of Na +, Li + and the mitochondrial Na +/Ca 2+ exchange inhibitor CGP37157. Cell Calcium 2021; 96:102382. [PMID: 33684833 DOI: 10.1016/j.ceca.2021.102382] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 02/15/2021] [Accepted: 02/18/2021] [Indexed: 10/22/2022]
Abstract
Mitochondrial Ca2+ transport is essential for regulating cell bioenergetics, Ca2+ signaling and cell death. Mitochondria accumulate Ca2+ via the mitochondrial Ca2+ uniporter (MCU), whereas Ca2+ is extruded by the mitochondrial Na+/Ca2+ (mtNCX) and H+/Ca2+ exchangers. The balance between these processes is essential for preventing toxic mitochondrial Ca2+ overload. Recent work demonstrated that MCU activity varies significantly among tissues, likely reflecting tissue-specific Ca2+ signaling and energy needs. It is less clear whether this diversity in MCU activity is matched by tissue-specific diversity in mitochondrial Ca2+ extrusion. Here we compared properties of mitochondrial Ca2+ extrusion in three tissues with prominent mitochondria function: brain, heart and liver. At the transcript level, expression of the Na+/Ca2+/Li+ exchanger (NCLX), which has been proposed to mediate mtNCX transport, was significantly greater in liver than in brain or heart. At the functional level, Na+ robustly activated Ca2+ efflux from brain and heart mitochondria, but not from liver mitochondria. The mtNCX inhibitor CGP37157 blocked Ca2+ efflux from brain and heart mitochondria but had no effect in liver mitochondria. Replacement of Na+ with Li+ to test the involvement of NCLX, resulted in a slowing of mitochondrial Ca2+ efflux by ∼70 %. Collectively, our findings suggest that mtNCX is responsible for Ca2+ extrusion from the mitochondria of the brain and heart, but plays only a small, if any, role in mitochondria of the liver. They also reveal that Li+ is significantly less effective than Na+ in driving mitochondrial Ca2+ efflux.
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Affiliation(s)
- Jacob E Rysted
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Zhihong Lin
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Grant C Walters
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Adam J Rauckhorst
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Maria Noterman
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Guanghao Liu
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Eric B Taylor
- Department of Molecular Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa College of Medicine, Iowa City, IA, 52242, USA
| | - Yuriy M Usachev
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa College of Medicine, Iowa City, IA, 52242, USA.
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15
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Song J, Merrill RA, Usachev AY, Strack S. The X-linked intellectual disability gene product and E3 ubiquitin ligase KLHL15 degrades doublecortin proteins to constrain neuronal dendritogenesis. J Biol Chem 2020; 296:100082. [PMID: 33199366 PMCID: PMC7948412 DOI: 10.1074/jbc.ra120.016210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 10/27/2020] [Accepted: 11/16/2020] [Indexed: 11/13/2022] Open
Abstract
Proper brain development and function requires finely controlled mechanisms for protein turnover, and disruption of genes involved in proteostasis is a common cause of neurodevelopmental disorders. Kelch-like 15 (KLHL15) is a substrate adaptor for cullin3-containing E3 ubiquitin ligases, and KLHL15 gene mutations were recently described as a cause of severe X-linked intellectual disability. Here, we used a bioinformatics approach to identify a family of neuronal microtubule-associated proteins as KLHL15 substrates, which are themselves critical for early brain development. We biochemically validated doublecortin (DCX), also an X-linked disease protein, and doublecortin-like kinase 1 and 2 as bona fide KLHL15 interactors and mapped KLHL15 interaction regions to their tandem DCX domains. Shared with two previously identified KLHL15 substrates, a FRY tripeptide at the C-terminal edge of the second DCX domain is necessary for KLHL15-mediated ubiquitination of DCX and doublecortin-like kinase 1 and 2 and subsequent proteasomal degradation. Conversely, silencing endogenous KLHL15 markedly stabilizes these DCX domain-containing proteins and prolongs their half-life. Functionally, overexpression of KLHL15 in the presence of WT DCX reduces dendritic complexity of cultured hippocampal neurons, whereas neurons expressing FRY-mutant DCX are resistant to KLHL15. Collectively, our findings highlight the critical importance of the E3 ubiquitin ligase adaptor KLHL15 in proteostasis of neuronal microtubule-associated proteins and identify a regulatory network important for development of the mammalian nervous system.
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Affiliation(s)
- Jianing Song
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Andrew Y Usachev
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA.
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16
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Jong CJ, Merrill RA, Wilkerson EM, Herring LE, Graves LM, Strack S. Reduction of protein phosphatase 2A (PP2A) complexity reveals cellular functions and dephosphorylation motifs of the PP2A/B'δ holoenzyme. J Biol Chem 2020; 295:5654-5668. [PMID: 32156701 PMCID: PMC7186168 DOI: 10.1074/jbc.ra119.011270] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 02/21/2020] [Indexed: 12/17/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a large enzyme family responsible for most cellular Ser/Thr dephosphorylation events. PP2A substrate specificity, localization, and regulation by second messengers rely on more than a dozen regulatory subunits (including B/R2, B'/R5, and B″/R3), which form the PP2A heterotrimeric holoenzyme by associating with a dimer comprising scaffolding (A) and catalytic (C) subunits. Because of partial redundancy and high endogenous expression of PP2A holoenzymes, traditional approaches of overexpressing, knocking down, or knocking out PP2A regulatory subunits have yielded only limited insights into their biological roles and substrates. To this end, here we sought to reduce the complexity of cellular PP2A holoenzymes. We used tetracycline-inducible expression of pairs of scaffolding and regulatory subunits with complementary charge-reversal substitutions in their interaction interfaces. For each of the three regulatory subunit families, we engineered A/B charge-swap variants that could bind to one another, but not to endogenous A and B subunits. Because endogenous Aα was targeted by a co-induced shRNA, endogenous B subunits were rapidly degraded, resulting in expression of predominantly a single PP2A heterotrimer composed of the A/B charge-swap pair and the endogenous catalytic subunit. Using B'δ/PPP2R5D, we show that PP2A complexity reduction, but not PP2A overexpression, reveals a role of this holoenzyme in suppression of extracellular signal-regulated kinase signaling and protein kinase A substrate dephosphorylation. When combined with global phosphoproteomics, the PP2A/B'δ reduction approach identified consensus dephosphorylation motifs in its substrates and suggested that residues surrounding the phosphorylation site play roles in PP2A substrate specificity.
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Affiliation(s)
- Chian Ju Jong
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Emily M Wilkerson
- Michael Hooker Proteomics Facility, University of North Carolina, Chapel Hill, North Carolina 27516
| | - Laura E Herring
- Michael Hooker Proteomics Facility, University of North Carolina, Chapel Hill, North Carolina 27516
| | - Lee M Graves
- Michael Hooker Proteomics Facility, University of North Carolina, Chapel Hill, North Carolina 27516
| | - Stefan Strack
- Department of Neuroscience and Pharmacology and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242.
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17
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Edwards G, Perkins GA, Kim KY, Kong Y, Lee Y, Choi SH, Liu Y, Skowronska-Krawczyk D, Weinreb RN, Zangwill L, Strack S, Ju WK. Loss of AKAP1 triggers Drp1 dephosphorylation-mediated mitochondrial fission and loss in retinal ganglion cells. Cell Death Dis 2020; 11:254. [PMID: 32312949 PMCID: PMC7170863 DOI: 10.1038/s41419-020-2456-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 04/06/2020] [Accepted: 04/07/2020] [Indexed: 12/14/2022]
Abstract
Impairment of mitochondrial structure and function is strongly linked to glaucoma pathogenesis. Despite the widely appreciated disease relevance of mitochondrial dysfunction and loss, the molecular mechanisms underlying mitochondrial fragmentation and metabolic stress in glaucoma are poorly understood. We demonstrate here that glaucomatous retinal ganglion cells (RGCs) show loss of A-kinase anchoring protein 1 (AKAP1), activation of calcineurin (CaN) and reduction of dynamin-related protein 1 (Drp1) phosphorylation at serine 637 (Ser637). These findings suggest that AKAP1-mediated phosphorylation of Drp1 at Ser637 has a critical role in RGC survival in glaucomatous neurodegeneration. Male mice lacking AKAP1 show increases in CaN and total Drp1 levels, as well as a decrease in Drp1 phosphorylation at Ser637 in the retina. Ultrastructural analysis of mitochondria shows that loss of AKAP1 triggers mitochondrial fragmentation and loss, as well as mitophagosome formation in RGCs. Loss of AKAP1 deregulates oxidative phosphorylation (OXPHOS) complexes (Cxs) by increasing CxII and decreasing CxIII-V, leading to metabolic and oxidative stress. Also, loss of AKAP1 decreases Akt phosphorylation at Serine 473 (Ser473) and threonine 308 (Thr308) and activates the Bim/Bax signaling pathway in the retina. These results suggest that loss of AKAP1 has a critical role in RGC dysfunction by decreasing Drp1 phosphorylation at Ser637, deregulating OXPHOS, decreasing Akt phosphorylation at Ser473 and Thr308, and activating the Bim/Bax pathway in glaucomatous neurodegeneration. Thus, we propose that overexpression of AKAP1 or modulation of Drp1 phosphorylation at Ser637 are potential therapeutic strategies for neuroprotective intervention in glaucoma and other mitochondria-related optic neuropathies.
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Affiliation(s)
- Genea Edwards
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Guy A Perkins
- National Center for Microscopy and Imaging Research and Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - Keun-Young Kim
- National Center for Microscopy and Imaging Research and Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - YeEun Kong
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Yonghoon Lee
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Soo-Ho Choi
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Yujia Liu
- Department of Pharmacology and Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, USA
| | - Dorota Skowronska-Krawczyk
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Robert N Weinreb
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Linda Zangwill
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Stefan Strack
- Department of Pharmacology and Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, USA
| | - Won-Kyu Ju
- Hamilton Glaucoma Center and Shiley Eye Center, The Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA.
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18
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Ponce JM, Coen G, Spitler KM, Dragisic N, Martins I, Hinton A, Mungai M, Tadinada SM, Zhang H, Oudit GY, Song L, Li N, Sicinski P, Strack S, Abel ED, Mitchell C, Hall DD, Grueter CE. Stress-Induced Cyclin C Translocation Regulates Cardiac Mitochondrial Dynamics. J Am Heart Assoc 2020; 9:e014366. [PMID: 32248761 PMCID: PMC7428645 DOI: 10.1161/jaha.119.014366] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 01/24/2020] [Indexed: 12/14/2022]
Abstract
Background Nuclear-to-mitochondrial communication regulating gene expression and mitochondrial function is a critical process following cardiac ischemic injury. In this study, we determined that cyclin C, a component of the Mediator complex, regulates cardiac and mitochondrial function in part by modifying mitochondrial fission. We tested the hypothesis that cyclin C functions as a transcriptional cofactor in the nucleus and a signaling molecule stimulating mitochondrial fission in response to stimuli such as cardiac ischemia. Methods and Results We utilized gain- and loss-of-function mouse models in which the CCNC (cyclin C) gene was constitutively expressed (transgenic, CycC cTg) or deleted (knockout, CycC cKO) in cardiomyocytes. The knockout and transgenic mice exhibited decreased cardiac function and altered mitochondria morphology. The hearts of knockout mice had enlarged mitochondria with increased length and area, whereas mitochondria from the hearts of transgenic mice were significantly smaller, demonstrating a role for cyclin C in regulating mitochondrial dynamics in vivo. Hearts from knockout mice displayed altered gene transcription and metabolic function, suggesting that cyclin C is essential for maintaining normal cardiac function. In vitro and in vivo studies revealed that cyclin C translocates to the cytoplasm, enhancing mitochondria fission following stress. We demonstrated that cyclin C interacts with Cdk1 (cyclin-dependent kinase 1) in vivo following ischemia/reperfusion injury and that, consequently, pretreatment with a Cdk1 inhibitor results in reduced mitochondrial fission. This finding suggests a potential therapeutic target to regulate mitochondrial dynamics in response to stress. Conclusions Our study revealed that cyclin C acts as a nuclear-to-mitochondrial signaling factor that regulates both cardiac hypertrophic gene expression and mitochondrial fission. This finding provides new insights into the regulation of cardiac energy metabolism following acute ischemic injury.
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MESH Headings
- Animals
- CDC2 Protein Kinase/antagonists & inhibitors
- CDC2 Protein Kinase/metabolism
- Cells, Cultured
- Cyclin C/deficiency
- Cyclin C/genetics
- Cyclin C/metabolism
- Disease Models, Animal
- Energy Metabolism/drug effects
- Humans
- Mice, Inbred C57BL
- Mice, Knockout
- Mitochondria, Heart/drug effects
- Mitochondria, Heart/metabolism
- Mitochondria, Heart/pathology
- Mitochondrial Dynamics/drug effects
- Myocardial Reperfusion Injury/genetics
- Myocardial Reperfusion Injury/metabolism
- Myocardial Reperfusion Injury/pathology
- Myocardial Reperfusion Injury/prevention & control
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Protein Kinase Inhibitors/pharmacology
- Protein Transport
- Rats, Wistar
- Signal Transduction
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Affiliation(s)
- Jessica M. Ponce
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Interdisciplinary Graduate Program in GeneticsUniversity of IowaIowa CityIA
| | - Grace Coen
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
| | - Kathryn M. Spitler
- Department of BiochemistryCarver College of MedicineUniversity of IowaIowa CityIA
| | - Nikola Dragisic
- Stead Family Department of PediatricsUniversity of IowaIowa CityIA
| | - Ines Martins
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
| | - Antentor Hinton
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Fraternal Order of Eagles Diabetes Research CenterDivision of Endocrinology and MetabolismCarver College of MedicineUniversity of IowaIowa CityIA
| | - Margaret Mungai
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Fraternal Order of Eagles Diabetes Research CenterDivision of Endocrinology and MetabolismCarver College of MedicineUniversity of IowaIowa CityIA
| | - Satya Murthy Tadinada
- Department of Pharmacology and Iowa Neuroscience InstituteCarver College of MedicineUniversity of IowaIowa CityIA
| | - Hao Zhang
- Mazankowski Alberta Heart Institute Canada Research Chair in Heart FailureDivision of Cardiology2C2 Walter Mackenzie Health Sciences Centre EdmontonAlbertaCanada
| | - Gavin Y. Oudit
- Mazankowski Alberta Heart Institute Canada Research Chair in Heart FailureDivision of Cardiology2C2 Walter Mackenzie Health Sciences Centre EdmontonAlbertaCanada
| | - Long‐Sheng Song
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Fraternal Order of Eagles Diabetes Research CenterDivision of Endocrinology and MetabolismCarver College of MedicineUniversity of IowaIowa CityIA
- Iowa City Veterans Affairs Medical CenterIowa CityIA
| | - Na Li
- Department of Cancer BiologyDana‐Farber Cancer InstituteBostonMA
- Department of GeneticsHarvard Medical SchoolBostonMA
| | - Peter Sicinski
- Department of Cancer BiologyDana‐Farber Cancer InstituteBostonMA
- Department of GeneticsHarvard Medical SchoolBostonMA
| | - Stefan Strack
- Department of Pharmacology and Iowa Neuroscience InstituteCarver College of MedicineUniversity of IowaIowa CityIA
| | - E. Dale Abel
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Fraternal Order of Eagles Diabetes Research CenterDivision of Endocrinology and MetabolismCarver College of MedicineUniversity of IowaIowa CityIA
| | - Colleen Mitchell
- Department of Mathematics and Delta CenterUniversity of IowaIowa CityIA
| | - Duane D. Hall
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
| | - Chad E. Grueter
- Abboud Cardiovascular Research CenterDivision of Cardiovascular MedicineDepartment of Internal MedicineCarver College of MedicineUniversity of IowaIowa CityIA
- Interdisciplinary Graduate Program in GeneticsUniversity of IowaIowa CityIA
- Fraternal Order of Eagles Diabetes Research CenterDivision of Endocrinology and MetabolismCarver College of MedicineUniversity of IowaIowa CityIA
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19
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Haushalter KJ, Schilling JM, Song Y, Sastri M, Perkins GA, Strack S, Taylor SS, Patel HH. Cardiac ischemia-reperfusion injury induces ROS-dependent loss of PKA regulatory subunit RIα. Am J Physiol Heart Circ Physiol 2019; 317:H1231-H1242. [PMID: 31674811 PMCID: PMC6962616 DOI: 10.1152/ajpheart.00237.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 10/21/2019] [Accepted: 10/21/2019] [Indexed: 12/27/2022]
Abstract
Type I PKA regulatory α-subunit (RIα; encoded by the Prkar1a gene) serves as the predominant inhibitor protein of the catalytic subunit of cAMP-dependent protein kinase (PKAc). However, recent evidence suggests that PKA signaling can be initiated by cAMP-independent events, especially within the context of cellular oxidative stress such as ischemia-reperfusion (I/R) injury. We determined whether RIα is actively involved in the regulation of PKA activity via reactive oxygen species (ROS)-dependent mechanisms during I/R stress in the heart. Induction of ex vivo global I/R injury in mouse hearts selectively downregulated RIα protein expression, whereas RII subunit expression appears to remain unaltered. Cardiac myocyte cell culture models were used to determine that oxidant stimulus (i.e., H2O2) alone is sufficient to induce RIα protein downregulation. Transient increase of RIα expression (via adenoviral overexpression) negatively affects cell survival and function upon oxidative stress as measured by increased induction of apoptosis and decreased mitochondrial respiration. Furthermore, analysis of mitochondrial subcellular fractions in heart tissue showed that PKA-associated proteins are enriched in subsarcolemmal mitochondria (SSM) fractions and that loss of RIα is most pronounced at SSM upon I/R injury. These data were supported via electron microscopy in A-kinase anchoring protein 1 (AKAP1)-knockout mice, where loss of AKAP1 expression leads to aberrant mitochondrial morphology manifested in SSM but not interfibrillar mitochondria. Thus, we conclude that modification of RIα via ROS-dependent mechanisms induced by I/R injury has the potential to sensitize PKA signaling in the cell without the direct use of the canonical cAMP-dependent activation pathway.NEW & NOTEWORTHY We uncovered a previously undescribed phenomenon involving oxidation-induced activation of PKA signaling in the progression of cardiac ischemia-reperfusion injury. Type I PKA regulatory subunit RIα, but not type II PKA regulatory subunits, is dynamically regulated by oxidative stress to trigger the activation of the catalytic subunit of PKA in cardiac myocytes. This effect may play a critical role in the regulation of subsarcolemmal mitochondria function upon the induction of ischemic injury in the heart.
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Affiliation(s)
- Kristofer J Haushalter
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
- Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Jan M Schilling
- Veterans Affairs San Diego Healthcare System, San Diego, California
- Department of Anesthesiology, University of California, San Diego, La Jolla, California
| | - Young Song
- Veterans Affairs San Diego Healthcare System, San Diego, California
- Department of Anesthesiology and Pain Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - Mira Sastri
- Department of Pharmacology, University of California, San Diego, La Jolla, California
| | - Guy A Perkins
- National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California
| | - Stefan Strack
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Susan S Taylor
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
- Department of Pharmacology, University of California, San Diego, La Jolla, California
| | - Hemal H Patel
- Veterans Affairs San Diego Healthcare System, San Diego, California
- Department of Anesthesiology, University of California, San Diego, La Jolla, California
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20
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Merrill RA, Song J, Kephart RA, Klomp AJ, Noack CE, Strack S. A robust and economical pulse-chase protocol to measure the turnover of HaloTag fusion proteins. J Biol Chem 2019; 294:16164-16171. [PMID: 31511325 DOI: 10.1074/jbc.ra119.010596] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 08/25/2019] [Indexed: 11/06/2022] Open
Abstract
The self-labeling protein HaloTag has been used extensively to determine the localization and turnover of proteins of interest at the single-cell level. To this end, halogen-substituted alkanes attached to diverse fluorophores are commercially available that allow specific, irreversible labeling of HaloTag fusion proteins; however, measurement of protein of interest half-life by pulse-chase of HaloTag ligands is not widely employed because residual unbound ligand continues to label newly synthesized HaloTag fusions even after extensive washing. Excess unlabeled HaloTag ligand can be used as a blocker of undesired labeling, but this is not economical. In this study, we screened several inexpensive, low-molecular-weight haloalkanes as blocking agents in pulse-chase labeling experiments with the cell-permeable tetramethylrhodamine HaloTag ligand. We identified 7-bromoheptanol as a high-affinity, low-toxicity HaloTag-blocking agent that permits protein turnover measurements at both the cell population (by blotting) and single-cell (by imaging) levels. We show that the HaloTag pulse-chase approach is a nontoxic alternative to inhibition of protein synthesis with cycloheximide and extend protein turnover assays to long-lived proteins.
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Affiliation(s)
- Ronald A Merrill
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Jianing Song
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Rikki A Kephart
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Annette J Klomp
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Claire E Noack
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa 52242
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21
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Koval OM, Nguyen EK, Santhana V, Fidler TP, Sebag SC, Rasmussen TP, Mittauer DJ, Strack S, Goswami PC, Abel ED, Grumbach IM. Loss of MCU prevents mitochondrial fusion in G 1-S phase and blocks cell cycle progression and proliferation. Sci Signal 2019; 12:12/579/eaav1439. [PMID: 31040260 DOI: 10.1126/scisignal.aav1439] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The role of the mitochondrial Ca2+ uniporter (MCU) in physiologic cell proliferation remains to be defined. Here, we demonstrated that the MCU was required to match mitochondrial function to metabolic demands during the cell cycle. During the G1-S transition (the cycle phase with the highest mitochondrial ATP output), mitochondrial fusion, oxygen consumption, and Ca2+ uptake increased in wild-type cells but not in cells lacking MCU. In proliferating wild-type control cells, the addition of the growth factors promoted the activation of the Ca2+/calmodulin-dependent kinase II (CaMKII) and the phosphorylation of the mitochondrial fission factor Drp1 at Ser616 The lack of the MCU was associated with baseline activation of CaMKII, mitochondrial fragmentation due to increased Drp1 phosphorylation, and impaired mitochondrial respiration and glycolysis. The mitochondrial fission/fusion ratio and proliferation in MCU-deficient cells recovered after MCU restoration or inhibition of mitochondrial fragmentation or of CaMKII in the cytosol. Our data highlight a key function for the MCU in mitochondrial adaptation to the metabolic demands during cell cycle progression. Cytosolic CaMKII and the MCU participate in a regulatory circuit, whereby mitochondrial Ca2+ uptake affects cell proliferation through Drp1.
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Affiliation(s)
- Olha M Koval
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Emily K Nguyen
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Velarchana Santhana
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Trevor P Fidler
- Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.,Department of Molecular Medicine, Columbia University Medical Center, New York, NY 10032, USA
| | - Sara C Sebag
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Tyler P Rasmussen
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Dylan J Mittauer
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Stefan Strack
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Prabhat C Goswami
- Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242, USA
| | - E Dale Abel
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.,Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Isabella M Grumbach
- Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA. .,Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.,Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242, USA.,Veterans Affairs Healthcare System, Iowa City, IA 52246, USA
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22
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Umesalma S, Kaemmer CA, Kohlmeyer JL, Letney B, Schab AM, Reilly JA, Sheehy RM, Hagen J, Tiwari N, Zhan F, Leidinger MR, O'Dorisio TM, Dillon J, Merrill RA, Meyerholz DK, Perl AL, Brown BJ, Braun TA, Scott AT, Ginader T, Taghiyev AF, Zamba GK, Howe JR, Strack S, Bellizzi AM, Narla G, Darbro BW, Quelle FW, Quelle DE. RABL6A inhibits tumor-suppressive PP2A/AKT signaling to drive pancreatic neuroendocrine tumor growth. J Clin Invest 2019; 129:1641-1653. [PMID: 30721156 DOI: 10.1172/jci123049] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 01/24/2019] [Indexed: 12/15/2022] Open
Abstract
Hyperactivated AKT/mTOR signaling is a hallmark of pancreatic neuroendocrine tumors (PNETs). Drugs targeting this pathway are used clinically, but tumor resistance invariably develops. A better understanding of factors regulating AKT/mTOR signaling and PNET pathogenesis is needed to improve current therapies. We discovered that RABL6A, a new oncogenic driver of PNET proliferation, is required for AKT activity. Silencing RABL6A caused PNET cell-cycle arrest that coincided with selective loss of AKT-S473 (not T308) phosphorylation and AKT/mTOR inactivation. Restoration of AKT phosphorylation rescued the G1 phase block triggered by RABL6A silencing. Mechanistically, loss of AKT-S473 phosphorylation in RABL6A-depleted cells was the result of increased protein phosphatase 2A (PP2A) activity. Inhibition of PP2A restored phosphorylation of AKT-S473 in RABL6A-depleted cells, whereas PP2A reactivation using a specific small-molecule activator of PP2A (SMAP) abolished that phosphorylation. Moreover, SMAP treatment effectively killed PNET cells in a RABL6A-dependent manner and suppressed PNET growth in vivo. The present work identifies RABL6A as a new inhibitor of the PP2A tumor suppressor and an essential activator of AKT in PNET cells. Our findings offer what we believe is a novel strategy of PP2A reactivation for treatment of PNETs as well as other human cancers driven by RABL6A overexpression and PP2A inactivation.
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Affiliation(s)
| | | | | | | | | | | | - Ryan M Sheehy
- Department of Pharmacology.,Free Radical & Radiation Biology Training Program
| | | | | | | | - Mariah R Leidinger
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - David K Meyerholz
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Abbey L Perl
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | | | | | | | | | - Agshin F Taghiyev
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - Andrew M Bellizzi
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Goutham Narla
- Department of Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Benjamin W Darbro
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | - Dawn E Quelle
- Department of Pharmacology.,Molecular Medicine Graduate Program.,Free Radical & Radiation Biology Training Program.,Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
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23
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Nguyen EK, Koval OM, Noble P, Broadhurst K, Allamargot C, Wu M, Strack S, Thiel WH, Grumbach IM. CaMKII (Ca 2+/Calmodulin-Dependent Kinase II) in Mitochondria of Smooth Muscle Cells Controls Mitochondrial Mobility, Migration, and Neointima Formation. Arterioscler Thromb Vasc Biol 2018; 38:1333-1345. [PMID: 29599132 DOI: 10.1161/atvbaha.118.310951] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/12/2018] [Indexed: 12/19/2022]
Abstract
OBJECTIVE The main objective of this study is to define the mechanisms by which mitochondria control vascular smooth muscle cell (VSMC) migration and impact neointimal hyperplasia. APPROACH AND RESULTS The multifunctional CaMKII (Ca2+/calmodulin-dependent kinase II) in the mitochondrial matrix of VSMC drove a feed-forward circuit with the mitochondrial Ca2+ uniporter (MCU) to promote matrix Ca2+ influx. MCU was necessary for the activation of mitochondrial CaMKII (mtCaMKII), whereas mtCaMKII phosphorylated MCU at the regulatory site S92 that promotes Ca2+ entry. mtCaMKII was necessary and sufficient for platelet-derived growth factor-induced mitochondrial Ca2+ uptake. This effect was dependent on MCU. mtCaMKII and MCU inhibition abrogated VSMC migration and mitochondrial translocation to the leading edge. Overexpression of wild-type MCU, but not MCU S92A, mutant in MCU-/- VSMC rescued migration and mitochondrial mobility. Inhibition of microtubule, but not of actin assembly, blocked mitochondrial mobility. The outer mitochondrial membrane GTPase Miro-1 promotes mitochondrial mobility via microtubule transport but arrests it in subcellular domains of high Ca2+ concentrations. In Miro-1-/- VSMC, mitochondrial mobility and VSMC migration were abolished, and overexpression of mtCaMKII or a CaMKII inhibitory peptide in mitochondria (mtCaMKIIN) had no effect. Consistently, inhibition of mtCaMKII increased and prolonged cytosolic Ca2+ transients. mtCaMKII inhibition diminished phosphorylation of focal adhesion kinase and myosin light chain, leading to reduced focal adhesion turnover and cytoskeletal remodeling. In a transgenic model of selective mitochondrial CaMKII inhibition in VSMC, neointimal hyperplasia was significantly reduced after vascular injury. CONCLUSIONS These findings identify mitochondrial CaMKII as a key regulator of mitochondrial Ca2+ uptake via MCU, thereby controlling mitochondrial translocation and VSMC migration after vascular injury.
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Affiliation(s)
- Emily K Nguyen
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.).,Interdisciplinary Program in Molecular and Cellular Biology (E.K.N.)
| | - Olha M Koval
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.)
| | - Paige Noble
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.)
| | - Kim Broadhurst
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.)
| | | | - Meng Wu
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy (M.W.).,High Throughput Screening Facility (M.W.).,Department of Biochemistry, Carver College of Medicine (M.W.)
| | - Stefan Strack
- Department of Pharmacology, Carver College of Medicine (S.S.)
| | - William H Thiel
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.).,François Abboud Cardiovascular Research Center (W.H.T., I.M.G.)
| | - Isabella M Grumbach
- From the Department of Internal Medicine, Carver College of Medicine (E.K.N., O.M.K., P.N., K.B., W.H.T., I.M.G.) .,François Abboud Cardiovascular Research Center (W.H.T., I.M.G.).,Iowa City Veterans Affairs Healthcare System (I.M.G.), University of Iowa, Iowa City
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24
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Ji WK, Chakrabarti R, Fan X, Schoenfeld L, Strack S, Higgs HN. Receptor-mediated Drp1 oligomerization on endoplasmic reticulum. J Cell Biol 2017; 216:4123-4139. [PMID: 29158231 PMCID: PMC5716263 DOI: 10.1083/jcb.201610057] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 06/01/2017] [Accepted: 09/18/2017] [Indexed: 12/24/2022] Open
Abstract
Drp1 is a dynamin guanosine triphosphatase important for mitochondrial and peroxisomal division. Drp1 oligomerization and mitochondrial recruitment are regulated by multiple factors, including interaction with mitochondrial receptors such as Mff, MiD49, MiD51, and Fis. In addition, both endoplasmic reticulum (ER) and actin filaments play positive roles in mitochondrial division, but mechanisms for their roles are poorly defined. Here, we find that a population of Drp1 oligomers is associated with ER in mammalian cells and is distinct from mitochondrial or peroxisomal Drp1 populations. Subpopulations of Mff and Fis1, which are tail-anchored proteins, also localize to ER. Drp1 oligomers assemble on ER, from which they can transfer to mitochondria. Suppression of Mff or inhibition of actin polymerization through the formin INF2 significantly reduces all Drp1 oligomer populations (mitochondrial, peroxisomal, and ER bound) and mitochondrial division, whereas Mff targeting to ER has a stimulatory effect on division. Our results suggest that ER can function as a platform for Drp1 oligomerization, and that ER-associated Drp1 contributes to mitochondrial division.
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Affiliation(s)
- Wei-Ke Ji
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Rajarshi Chakrabarti
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Xintao Fan
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Lori Schoenfeld
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH
| | - Stefan Strack
- Department of Pharmacology, Carver School of Medicine, University of Iowa, Iowa City, IA
| | - Henry N Higgs
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH
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25
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Morita M, Prudent J, Basu K, Goyon V, Katsumura S, Hulea L, Pearl D, Siddiqui N, Strack S, McGuirk S, St-Pierre J, Larsson O, Topisirovic I, Vali H, McBride HM, Bergeron JJ, Sonenberg N. mTOR Controls Mitochondrial Dynamics and Cell Survival via MTFP1. Mol Cell 2017; 67:922-935.e5. [PMID: 28918902 DOI: 10.1016/j.molcel.2017.08.013] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 06/27/2017] [Accepted: 08/18/2017] [Indexed: 02/02/2023]
Abstract
The mechanisms that link environmental and intracellular stimuli to mitochondrial functions, including fission/fusion, ATP production, metabolite biogenesis, and apoptosis, are not well understood. Here, we demonstrate that the nutrient-sensing mechanistic/mammalian target of rapamycin complex 1 (mTORC1) stimulates translation of mitochondrial fission process 1 (MTFP1) to control mitochondrial fission and apoptosis. Expression of MTFP1 is coupled to pro-fission phosphorylation and mitochondrial recruitment of the fission GTPase dynamin-related protein 1 (DRP1). Potent active-site mTOR inhibitors engender mitochondrial hyperfusion due to the diminished translation of MTFP1, which is mediated by translation initiation factor 4E (eIF4E)-binding proteins (4E-BPs). Uncoupling MTFP1 levels from the mTORC1/4E-BP pathway upon mTOR inhibition blocks the hyperfusion response and leads to apoptosis by converting mTOR inhibitor action from cytostatic to cytotoxic. These data provide direct evidence for cell survival upon mTOR inhibition through mitochondrial hyperfusion employing MTFP1 as a critical effector of mTORC1 to govern cell fate decisions.
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Affiliation(s)
- Masahiro Morita
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada; Department of Molecular Medicine and Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
| | - Julien Prudent
- Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada; Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Kaustuv Basu
- Department of Anatomy and Cell Biology and Facility for Electron Microscopy Research, McGill University, Montreal, QC H3A 0C7, Canada
| | - Vanessa Goyon
- Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada
| | - Sakie Katsumura
- Department of Molecular Medicine and Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Laura Hulea
- Lady Davis Institute, SMBD JGH, McGill University, Montreal, QC H3T 1E2, Canada; Department of Oncology, McGill University, Montreal, QC H3T 1E2, Canada
| | - Dana Pearl
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada
| | - Nadeem Siddiqui
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada
| | - Stefan Strack
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - Shawn McGuirk
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada
| | - Julie St-Pierre
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada
| | - Ola Larsson
- Department of Oncology-Pathology, Karolinska Institutet, Stockholm 171 76, Sweden
| | - Ivan Topisirovic
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada; Lady Davis Institute, SMBD JGH, McGill University, Montreal, QC H3T 1E2, Canada; Department of Oncology, McGill University, Montreal, QC H3T 1E2, Canada
| | - Hojatollah Vali
- Department of Anatomy and Cell Biology and Facility for Electron Microscopy Research, McGill University, Montreal, QC H3A 0C7, Canada
| | - Heidi M McBride
- Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada.
| | - John J Bergeron
- Department of Medicine, McGill University Health Centre Research Institute, Montreal, QC H4A 3J1, Canada.
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada.
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Strack S, Diabaté S, Müller J, Raskob W. Organically Bound Tritium Formation and Translocation in Crop Plants, Modelling and Experimental Results. ACTA ACUST UNITED AC 2017. [DOI: 10.13182/fst95-a30528] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- S. Strack
- Forschungszentrum Karlsruhe Hauptabteilung Sicherheit, Abteilung Umweltschutz Postfach 3640, D - 76021 Karlsruhe, Germany Tel. (49) 7247 - 82 2708
| | - S. Diabaté
- Forschungszentrum Karlsruhe Hauptabteilung Sicherheit, Abteilung Umweltschutz Postfach 3640, D - 76021 Karlsruhe, Germany Tel. (49) 7247 - 82 2708
| | - J. Müller
- Forschungszentrum Karlsruhe Hauptabteilung Sicherheit, Abteilung Umweltschutz Postfach 3640, D - 76021 Karlsruhe, Germany Tel. (49) 7247 - 82 2708
| | - W. Raskob
- Forschungszentrum Karlsruhe Institut für Neutronenphvsik und Reaktortechnik Postfach 3640, D - 76021 Karlsruhe, Germany
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Mapuskar KA, Flippo KH, Schoenfeld JD, Riley DP, Strack S, Hejleh TA, Furqan M, Monga V, Domann FE, Buatti JM, Goswami PC, Spitz DR, Allen BG. Mitochondrial Superoxide Increases Age-Associated Susceptibility of Human Dermal Fibroblasts to Radiation and Chemotherapy. Cancer Res 2017; 77:5054-5067. [PMID: 28765155 DOI: 10.1158/0008-5472.can-17-0106] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 06/01/2017] [Accepted: 07/19/2017] [Indexed: 01/10/2023]
Abstract
Elderly cancer patients treated with ionizing radiation (IR) or chemotherapy experience more frequent and greater normal tissue toxicity relative to younger patients. The current study demonstrates that exponentially growing fibroblasts from elderly (old) male donor subjects (70, 72, and 78 years) are significantly more sensitive to clonogenic killing mediated by platinum-based chemotherapy and IR (∼70%-80% killing) relative to young fibroblasts (5 months and 1 year; ∼10%-20% killing) and adult fibroblasts (20 years old; ∼10%-30% killing). Old fibroblasts also displayed significantly increased (2-4-fold) steady-state levels of O2•-, O2 consumption, and mitochondrial membrane potential as well as significantly decreased (40%-50%) electron transport chain (ETC) complex I, II, IV, V, and aconitase (70%) activities, decreased ATP levels, and significantly altered mitochondrial structure. Following adenoviral-mediated overexpression of SOD2 activity (5-7-fold), mitochondrial ETC activity and aconitase activity were restored, demonstrating a role for mitochondrial O2•- in these effects. Old fibroblasts also demonstrated elevated levels of endogenous DNA damage that were increased following treatment with IR and chemotherapy. Most importantly, treatment with the small-molecule, superoxide dismutase mimetic (GC4419; 0.25 μmol/L) significantly mitigated the increased sensitivity of old fibroblasts to IR and chemotherapy and partially restored mitochondrial function without affecting IR or chemotherapy-induced cancer cell killing. These results support the hypothesis that age-associated increased O2•- and resulting DNA damage mediate the increased susceptibility of old fibroblasts to IR and chemotherapy that can be mitigated by GC4419. Cancer Res; 77(18); 5054-67. ©2017 AACR.
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Affiliation(s)
- Kranti A Mapuskar
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa
| | - Kyle H Flippo
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa
| | | | | | - Stefan Strack
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa
| | - Taher Abu Hejleh
- Department of Internal Medicine, The University of Iowa, Iowa City, Iowa
| | - Muhammad Furqan
- Department of Internal Medicine, The University of Iowa, Iowa City, Iowa
| | - Varun Monga
- Department of Internal Medicine, The University of Iowa, Iowa City, Iowa
| | - Frederick E Domann
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa
| | - John M Buatti
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa
| | - Prabhat C Goswami
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa
| | - Douglas R Spitz
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa
| | - Bryan G Allen
- Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa.
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Strack S, Diabaté S, Raskob W. Organically Bound Tritium in Plants: Insights Gained by Long-Term Experience in Experimental and Modeling Research. Fusion Science and Technology 2017. [DOI: 10.13182/fst05-a1033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- S. Strack
- Forschungszentrum Karlsruhe GmbH, Institut fϼr Toxikologie and Genetik &
| | - S. Diabaté
- Forschungszentrum Karlsruhe GmbH, Institut fϼr Toxikologie and Genetik &
| | - W. Raskob
- Institut fϼr Kern- und Energietechnik, Postfach 3640, D-76021 Karlsruhe, Germany
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Melintescu A, Galeriu D, Diabaté S, Strack S. Preparatory Steps for a Robust Dynamic Model for Organically Bound Tritium Dynamics in Agricultural Crops. Fusion Science and Technology 2017. [DOI: 10.13182/fst14-t59] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- A. Melintescu
- “Horia Hulubei” National Institute for Physics and Nuclear Engineering, 30 Reactorului St., POB MG-6, Bucharest – Magurele, RO-077125, Romania
| | - D. Galeriu
- “Horia Hulubei” National Institute for Physics and Nuclear Engineering, 30 Reactorului St., POB MG-6, Bucharest – Magurele, RO-077125, Romania
| | - S. Diabaté
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen Germany
| | - S. Strack
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen Germany
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Honrath B, Matschke L, Meyer T, Magerhans L, Perocchi F, Ganjam GK, Zischka H, Krasel C, Gerding A, Bakker BM, Bünemann M, Strack S, Decher N, Culmsee C, Dolga AM. SK2 channels regulate mitochondrial respiration and mitochondrial Ca 2+ uptake. Cell Death Differ 2017; 24:761-773. [PMID: 28282037 DOI: 10.1038/cdd.2017.2] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/29/2016] [Accepted: 12/14/2016] [Indexed: 02/06/2023] Open
Abstract
Mitochondrial calcium ([Ca2+]m) overload and changes in mitochondrial metabolism are key players in neuronal death. Small conductance calcium-activated potassium (SK) channels provide protection in different paradigms of neuronal cell death. Recently, SK channels were identified at the inner mitochondrial membrane, however, their particular role in the observed neuroprotection remains unclear. Here, we show a potential neuroprotective mechanism that involves attenuation of [Ca2+]m uptake upon SK channel activation as detected by time lapse mitochondrial Ca2+ measurements with the Ca2+-binding mitochondria-targeted aequorin and FRET-based [Ca2+]m probes. High-resolution respirometry revealed a reduction in mitochondrial respiration and complex I activity upon pharmacological activation and overexpression of mitochondrial SK2 channels resulting in reduced mitochondrial ROS formation. Overexpression of mitochondria-targeted SK2 channels enhanced mitochondrial resilience against neuronal death, and this effect was inhibited by overexpression of a mitochondria-targeted dominant-negative SK2 channel. These findings suggest that SK channels provide neuroprotection by reducing [Ca2+]m uptake and mitochondrial respiration in conditions, where sustained mitochondrial damage determines progressive neuronal death.
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Affiliation(s)
- Birgit Honrath
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany.,Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Behavioural and Cognitive Neurosciences (BCN), Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands
| | - Lina Matschke
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Tammo Meyer
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Behavioural and Cognitive Neurosciences (BCN), Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands
| | - Lena Magerhans
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany
| | - Fabiana Perocchi
- Gene Center/Department of Biochemistry, Ludwig-Maximilians Universität München, Munich, Germany.,Institute for Obesity and Diabetes, Helmholtz Zentrum München, Neuherberg, Germany
| | - Goutham K Ganjam
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany
| | - Hans Zischka
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Cornelius Krasel
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany
| | - Albert Gerding
- Center for Liver, Digestive and Metabolic Diseases, Department of Pediatrics & Systems Biology Center for Energy Metabolism and Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Barbara M Bakker
- Center for Liver, Digestive and Metabolic Diseases, Department of Pediatrics & Systems Biology Center for Energy Metabolism and Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Moritz Bünemann
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany
| | - Stefan Strack
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany
| | - Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany.,Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Behavioural and Cognitive Neurosciences (BCN), Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands
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Abstract
Mitochondria fulfill numerous cellular functions including ATP production, Ca2+ buffering, neurotransmitter synthesis and degradation, ROS production and sequestration, apoptosis and intermediate metabolism. Mitochondrial dynamics, a collective term for the processes of mitochondrial fission, fusion and transport, governs mitochondrial function and localization within the cell. Correct balance of mitochondrial dynamics is especially important in neurons as mutations in fission and fusion enzymes cause peripheral neuropathies and impaired development of the nervous system in humans. Regulation of mitochondrial dynamics is partly accomplished through post-translational modification of mitochondrial fission and fusion enzymes, in turn influencing mitochondrial bioenergetics and transport. The importance of post-translational regulation is highlighted by numerous neurodegenerative disorders associated with post-translational modification of the mitochondrial fission enzyme Drp1. Not surprisingly, mitochondrial dynamics also play an important physiological role in the development of the nervous system and synaptic plasticity. Here, we highlight recent findings underlying the mechanisms and regulation of mitochondrial dynamics in relation to neurological disease, as well as the development and plasticity of the nervous system.
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Affiliation(s)
- Kyle H Flippo
- Department of Pharmacology, University of Iowa, Iowa City, USA
| | - Stefan Strack
- Department of Pharmacology, University of Iowa, Iowa City, USA
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33
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Hatch AL, Ji WK, Merrill RA, Strack S, Higgs HN. Actin filaments as dynamic reservoirs for Drp1 recruitment. Mol Biol Cell 2016; 27:3109-3121. [PMID: 27559132 PMCID: PMC5063618 DOI: 10.1091/mbc.e16-03-0193] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/19/2016] [Indexed: 11/11/2022] Open
Abstract
Drp1 is a dynamin-family GTPase recruited to mitochondria and peroxisomes, where it oligomerizes and drives membrane fission. Regulation of mitochondrial Drp1 recruitment is not fully understood. We previously showed that Drp1 binds actin filaments directly, and actin polymerization is necessary for mitochondrial Drp1 oligomerization in mammals. Here we show the Drp1/actin interaction displays unusual properties that are influenced by several factors. At saturation, only a fraction Drp1 binds actin filaments, and the off-rate of actin-bound Drp1 is significantly increased by unbound Drp1. GDP and GTP accelerate and decelerate Drp1/actin binding dynamics, respectively. Actin has a biphasic effect on Drp1 GTP hydrolysis, increasing at low actin:Drp1 ratio but returning to baseline at high ratio. Drp1 also bundles filaments. Bundles have reduced dynamics but follow the same trends as single filaments. Drp1 preferentially incorporates into bundles at higher ionic strength. We measure Drp1 concentration to be ∼0.5 μM in U2OS cell cytosol, suggesting the actin-binding affinity measured here (Kd = 0.6 μM) is in the physiologically relevant range. The ability of Drp1 to bind actin filaments in a highly dynamic manner provides potential for actin filaments to serve as reservoirs of oligomerization-competent Drp1 that can be accessed for mitochondrial fission.
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Affiliation(s)
- Anna L Hatch
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755
| | - Wei-Ke Ji
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755
| | - Ronald A Merrill
- Department of Pharmacology, Carver School of Medicine, University of Iowa, Iowa City, IA 52242
| | - Stefan Strack
- Department of Pharmacology, Carver School of Medicine, University of Iowa, Iowa City, IA 52242
| | - Henry N Higgs
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755
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Ji WK, Hatch AL, Merrill RA, Strack S, Higgs HN. Actin filaments target the oligomeric maturation of the dynamin GTPase Drp1 to mitochondrial fission sites. eLife 2015; 4:e11553. [PMID: 26609810 PMCID: PMC4755738 DOI: 10.7554/elife.11553] [Citation(s) in RCA: 216] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 11/25/2015] [Indexed: 12/19/2022] Open
Abstract
While the dynamin GTPase Drp1 plays a critical role during mitochondrial fission, mechanisms controlling its recruitment to fission sites are unclear. A current assumption is that cytosolic Drp1 is recruited directly to fission sites immediately prior to fission. Using live-cell microscopy, we find evidence for a different model, progressive maturation of Drp1 oligomers on mitochondria through incorporation of smaller mitochondrially-bound Drp1 units. Maturation of a stable Drp1 oligomer does not forcibly lead to fission. Drp1 oligomers also translocate directionally along mitochondria. Ionomycin, a calcium ionophore, causes rapid mitochondrial accumulation of actin filaments followed by Drp1 accumulation at the fission site, and increases fission rate. Inhibiting actin polymerization, myosin IIA, or the formin INF2 reduces both un-stimulated and ionomycin-induced Drp1 accumulation and mitochondrial fission. Actin filaments bind purified Drp1 and increase GTPase activity in a manner that is synergistic with the mitochondrial protein Mff, suggesting a role for direct Drp1/actin interaction. We propose that Drp1 is in dynamic equilibrium on mitochondria in a fission-independent manner, and that fission factors such as actin filaments target productive oligomerization to fission sites. DOI:http://dx.doi.org/10.7554/eLife.11553.001 Inside cells, structures called mitochondria supply the energy needed to carry out the processes that sustain life. Mitochondria constantly divide (a process known as fission) or fuse together, which helps to keep them in good working condition and well distributed around the cell. Several neurological disorders, including Parkinson’s disease and Alzheimer’s, are associated with problems that affect mitochondrial fission. Many different molecules work together to help mitochondria divide, including a protein called Drp1. A number of Drp1 molecules can associate with each other to form an “oligomer” in the shape of a ring around a mitochondrion. The ring then constricts to split the mitochondrion in two. It is often assumed that Drp1 molecules are recruited to the mitochondria immediately before fission and then form the oligomer ring. However, by using microscopy to track the movement of fluorescently labeled Drp1 molecules in human cells, Ji, Hatch et al. now suggest that Drp1 is continuously binding to and releasing from mitochondria, regardless of the need for fission. The experiments showed that when bound to surface of the mitochondrion, Drp1 switches between assembling and disassembling the oligomer ring. This process of Drp1 assembly and oligomerization on mitochondria is called maturation. Specific signals for fission can push Drp1 toward maturation, which then leads to fission. Ji, Hatch et al. found that one such signal is the assembly of filaments of a protein called actin. Preventing actin filaments from forming reduced the amount of Drp1 that accumulated at mitochondria, and resulted in the mitochondria dividing less frequently. Further biochemical experiments also revealed that actin interacts directly with Drp1 and stimulates Drp1 activity, helping the ring to organize and assist mitochondrial fission. The formation of actin filaments is not the only mechanism that can recruit Drp1 to mitochondria. Future work should investigate whether other mechanisms work with actin to recruit Drp1. As with actin filaments, other signals might be predicted to influence the balance of maturation and disassembly of Drp1 oligomers. DOI:http://dx.doi.org/10.7554/eLife.11553.002
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Affiliation(s)
- Wei-ke Ji
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
| | - Anna L Hatch
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
| | - Ronald A Merrill
- Department of Pharmacology, The University of Iowa, Iowa City, United States
| | - Stefan Strack
- Department of Pharmacology, The University of Iowa, Iowa City, United States
| | - Henry N Higgs
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
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Gupte RP, Kadunganattil S, Shepherd AJ, Merrill R, Planer W, Bruchas MR, Strack S, Mohapatra DP. Convergent phosphomodulation of the major neuronal dendritic potassium channel Kv4.2 by pituitary adenylate cyclase-activating polypeptide. Neuropharmacology 2015; 101:291-308. [PMID: 26456351 DOI: 10.1016/j.neuropharm.2015.10.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/29/2015] [Accepted: 10/03/2015] [Indexed: 12/30/2022]
Abstract
The endogenous neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is secreted by both neuronal and non-neuronal cells in the brain and spinal cord, in response to pathological conditions such as stroke, seizures, chronic inflammatory and neuropathic pain. PACAP has been shown to exert various neuromodulatory and neuroprotective effects. However, direct influence of PACAP on the function of intrinsically excitable ion channels that are critical to both hyperexcitation as well as cell death, remain largely unexplored. The major dendritic K(+) channel Kv4.2 is a critical regulator of neuronal excitability, back-propagating action potentials in the dendrites, and modulation of synaptic inputs. We identified, cloned and characterized the downstream signaling originating from the activation of three PACAP receptor (PAC1) isoforms that are expressed in rodent hippocampal neurons that also exhibit abundant expression of Kv4.2 protein. Activation of PAC1 by PACAP leads to phosphorylation of Kv4.2 and downregulation of channel currents, which can be attenuated by inhibition of either PKA or ERK1/2 activity. Mechanistically, this dynamic downregulation of Kv4.2 function is a consequence of reduction in the density of surface channels, without any influence on the voltage-dependence of channel activation. Interestingly, PKA-induced effects on Kv4.2 were mediated by ERK1/2 phosphorylation of the channel at two critical residues, but not by direct channel phosphorylation by PKA, suggesting a convergent phosphomodulatory signaling cascade. Altogether, our findings suggest a novel GPCR-channel signaling crosstalk between PACAP/PAC1 and Kv4.2 channel in a manner that could lead to neuronal hyperexcitability.
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Affiliation(s)
- Raeesa P Gupte
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Suraj Kadunganattil
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Andrew J Shepherd
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ronald Merrill
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - William Planer
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael R Bruchas
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stefan Strack
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Durga P Mohapatra
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA.
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36
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Jin Z, Chung JW, Mei W, Strack S, He C, Lau GW, Yang J. Regulation of nuclear-cytoplasmic shuttling and function of Family with sequence similarity 13, member A (Fam13a), by B56-containing PP2As and Akt. Mol Biol Cell 2015; 26:1160-73. [PMID: 25609086 PMCID: PMC4357514 DOI: 10.1091/mbc.e14-08-1276] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Recent genome-wide association studies reveal that the FAM13A gene is associated with human lung function and a variety of lung diseases, including chronic obstructive pulmonary disease, asthma, lung cancer, and pulmonary fibrosis. The biological functions of Fam13a, however, have not been studied. In an effort to identify novel substrates of B56-containing PP2As, we found that B56-containing PP2As and Akt act antagonistically to control reversible phosphorylation of Fam13a on Ser-322. We show that Ser-322 phosphorylation acts as a molecular switch to control the subcellular distribution of Fam13a. Fam13a shuttles between the nucleus and cytoplasm. When Ser-322 is phosphorylated by Akt, the binding between Fam13a and 14-3-3 is enhanced, leading to cytoplasmic sequestration of Fam13a. B56-containing PP2As dephosphorylate phospho-Ser-322 and promote nuclear localization of Fam13a. We generated Fam13a-knockout mice. Fam13a-mutant mice are viable and healthy, indicating that Fam13a is dispensable for embryonic development and physiological functions in adult animals. Intriguingly, Fam13a has the ability to activate the Wnt pathway. Although Wnt signaling remains largely normal in Fam13a-knockout lungs, depletion of Fam13a in human lung cancer cells causes an obvious reduction in Wnt signaling activity. Our work provides important clues to elucidating the mechanism by which Fam13a may contribute to human lung diseases.
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Affiliation(s)
- Zhigang Jin
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802
| | - Jin Wei Chung
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802
| | - Wenyan Mei
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802
| | - Stefan Strack
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52242
| | - Chunyan He
- Department of Epidemiology, Richard M. Fairbanks School of Public Health, Indiana University, Indianapolis, IN 46202
| | - Gee W Lau
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802
| | - Jing Yang
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802
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Joiner MLA, Koval OM, Li J, He BJ, Allamargot C, Gao Z, Luczak ED, Hall DD, Fink BD, Chen B, Yang J, Moore SA, Scholz TD, Strack S, Mohler PJ, Sivitz WI, Song LS, Anderson ME. Joiner et al. reply. Nature 2014; 513:E3. [PMID: 25254481 DOI: 10.1038/nature13627] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mei-Ling A Joiner
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
| | - Olha M Koval
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Jingdong Li
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
| | - B Julie He
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
| | - Chantal Allamargot
- University of Iowa Central Microscopy Research Facility, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Zhan Gao
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Elizabeth D Luczak
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
| | - Duane D Hall
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Brian D Fink
- Iowa City Veterans Affairs Medical, Iowa City, Iowa 52246, USA
| | - Biyi Chen
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Jinying Yang
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Steven A Moore
- 1] Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Thomas D Scholz
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Stefan Strack
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Peter J Mohler
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
| | - William I Sivitz
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Iowa City Veterans Affairs Medical, Iowa City, Iowa 52246, USA
| | - Long-Sheng Song
- Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
| | - Mark E Anderson
- 1] Department of Internal Medicine and Cardiovascular Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [2] Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA [3] Department of Molecular Physiology &Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, USA (M.A.J.); The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA (J.L., P.J.M.); Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA (B.J.H.); Johns Hopkins University School of Medicine, 1830 East Monument Street, 9th Floor, Suite 9026, Baltimore, Maryland 21287, USA (E.D.L., M.E.A.)
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Nifoussi SK, Ratcliffe NR, Ornstein DL, Kasof G, Strack S, Craig RW. Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells. J Biol Chem 2014; 289:21950-9. [PMID: 24939844 DOI: 10.1074/jbc.m114.587873] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Abundant, sustained expression of prosurvival Mcl-1 is an important determinant of viability and drug resistance in cancer cells. The Mcl-1 protein contains PEST sequences (enriched in proline, glutamic acid, serine, and threonine) and is normally subject to rapid turnover via multiple different pathways. One of these pathways involves a phosphodegron in the PEST region, where Thr-163 phosphorylation primes for Ser-159 phosphorylation by glycogen synthase kinase-3. Turnover via this phosphodegron-targeted pathway is reduced in Mcl-1-overexpressing BL41-3 Burkitt lymphoma and other cancer cells; turnover is further slowed in the presence of phorbol ester-induced ERK activation, resulting in Mcl-1 stabilization and an exacerbation of chemoresistance. The present studies focused on Mcl-1 dephosphorylation, which was also found to profoundly influence turnover. Exposure of BL41-3 cells to an inhibitor of protein phosphatase 2A (PP2A), okadaic acid, resulted in a rapid increase in phosphorylation at Thr-163 and Ser-159, along with a precipitous decrease in Mcl-1 expression. The decline in Mcl-1 expression preceded the appearance of cell death markers and was not slowed in the presence of phorbol ester. Upon exposure to calyculin A, which also potently inhibits PP2A, versus tautomycin, which does not, only the former increased Thr-163/Ser-159 phosphorylation and decreased Mcl-1 expression. Mcl-1 co-immunoprecipitated with PP2A upon transfection into CHO cells, and PP2A/Aα knockdown recapitulated the increase in Mcl-1 phosphorylation and decrease in expression. In sum, inhibition of PP2A prevents Mcl-1 dephosphorylation and results in rapid loss of this prosurvival protein in chemoresistant cancer cells.
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Affiliation(s)
- Shanna K Nifoussi
- From the Departments of Pharmacology and Toxicology and the Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766
| | - Nora R Ratcliffe
- Pathology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, the Veterans Affairs Medical Center, White River Junction, Vermont 05001
| | - Deborah L Ornstein
- Pathology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - Gary Kasof
- Cell Signaling Technology, Danvers, Massachusetts 01923, and
| | - Stefan Strack
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242
| | - Ruth W Craig
- From the Departments of Pharmacology and Toxicology and the Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766,
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Rice M, Dagda R, Strack S. Role of protein phosphatase 2A in modulating autophagy and mitophagy (LB220). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.lb220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Monica Rice
- Pharmacology University of Nevada School of MedicineRenoNVUnited States
| | - Ruben Dagda
- Pharmacology University of Nevada School of MedicineRenoNVUnited States
| | - Stefan Strack
- Pharmacology University of Iowa Carver College of MedicineIowa CityIAUnited States
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40
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Merrill RA, Strack S. Mitochondria: a kinase anchoring protein 1, a signaling platform for mitochondrial form and function. Int J Biochem Cell Biol 2014; 48:92-6. [PMID: 24412345 DOI: 10.1016/j.biocel.2013.12.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 11/28/2013] [Accepted: 12/26/2013] [Indexed: 12/31/2022]
Abstract
Mitochondria are best known for their role as cellular power plants, but they also serve as signaling hubs, regulating cellular proliferation, differentiation, and survival. A kinase anchoring protein 1 (AKAP1) is a scaffold protein that recruits protein kinase A (PKA) and other signaling proteins, as well as RNA, to the outer mitochondrial membrane. AKAP1 thereby integrates several second messenger cascades to modulate mitochondrial function and associated physiological and pathophysiological outcomes. Here, we review what is currently known about AKAP1's macromolecular interactions in health and disease states, including obesity. We also discuss dynamin-related protein 1 (Drp1), the enzyme that catalyzes mitochondrial fission, as one of the key substrates of the PKA/AKAP1 signaling complex in neurons. Recent evidence suggests that AKAP1 has critical roles in neuronal development and survival, which are mediated by inhibitory phosphorylation of Drp1 and maintenance of mitochondrial integrity.
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Affiliation(s)
| | - Stefan Strack
- Department of Pharmacology, University of Iowa, Iowa City, USA.
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41
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Abstract
The splice isoform Drp1-x01 promotes mitochondrial fission and is regulated by Cdk phosphorylation-dependent changes in microtubule association. Fission and fusion reactions determine mitochondrial morphology and function. Dynamin-related protein 1 (Drp1) is a guanosine triphosphate–hydrolyzing mechanoenzyme important for mitochondrial fission and programmed cell death. Drp1 is subject to alternative splicing of three exons with previously unknown functional significance. Here, we report that splice variants including the third but excluding the second alternative exon (x01) localized to and copurified with microtubule bundles as dynamic polymers that resemble fission complexes on mitochondria. A major isoform in immune cells, Drp1-x01 required oligomeric assembly and Arg residues in alternative exon 3 for microtubule targeting. Drp1-x01 stabilized and bundled microtubules and attenuated staurosporine-induced mitochondrial fragmentation and apoptosis. Phosphorylation of a conserved Ser residue adjacent to the microtubule-binding exon released Drp1-x01 from microtubules and promoted mitochondrial fragmentation in a splice form–specific manner. Phosphorylation by Cdk1 contributed to dissociation of Drp1-x01 from mitotic microtubules, whereas Cdk5-mediated phosphorylation modulated Drp1-x01 targeting to interphase microtubules. Thus, alternative splicing generates a latent, cytoskeletal pool of Drp1 that is selectively mobilized by cyclin-dependent kinase signaling.
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Affiliation(s)
- Stefan Strack
- Department of Pharmacology, University of Iowa, Iowa City, IA 52246, USA.
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42
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Slupe AM, Merrill RA, Flippo KH, Lobas MA, Houtman JCD, Strack S. A calcineurin docking motif (LXVP) in dynamin-related protein 1 contributes to mitochondrial fragmentation and ischemic neuronal injury. J Biol Chem 2013; 288:12353-65. [PMID: 23486469 PMCID: PMC3636919 DOI: 10.1074/jbc.m113.459677] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fission and fusion events dynamically control the shape and function of mitochondria. The activity of the mitochondrial fission enzyme dynamin-related protein 1 (Drp1) is finely tuned by several post-translational modifications. Phosphorylation of Ser-656 by cAMP-dependent protein kinase (PKA) inhibits Drp1, whereas dephosphorylation by a mitochondrial protein phosphatase 2A isoform and the calcium-calmodulin-dependent phosphatase calcineurin (CaN) activates Drp1. Here, we identify a conserved CaN docking site on Drp1, an LXVP motif, which mediates the interaction between the phosphatase and mechanoenzyme. We mutated the LXVP motif in Drp1 to either increase or decrease similarity to the prototypical LXVP motif in the transcription factor NFAT, and assessed stability of the mutant Drp1-CaN complexes by affinity precipitation and isothermal titration calorimetry. Furthermore, we quantified effects of LXVP mutations on Drp1 dephosphorylation kinetics in vitro and in intact cells. With tools for bidirectional control of the CaN-Drp1 signaling axis in hand, we demonstrate that the Drp1 LXVP motif shapes mitochondria in neuronal and non-neuronal cells, and that CaN-mediated Drp1 dephosphorylation promotes neuronal death following oxygen-glucose deprivation. These results point to the CaN-Drp1 complex as a potential target for neuroprotective therapy of ischemic stroke.
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Affiliation(s)
- Andrew M Slupe
- Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, USA
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Galeriu D, Melintescu A, Strack S, Atarashi-Andoh M, Kim SB. An overview of organically bound tritium experiments in plants following a short atmospheric HTO exposure. J Environ Radioact 2013; 118:40-56. [PMID: 23246588 DOI: 10.1016/j.jenvrad.2012.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 11/05/2012] [Accepted: 11/06/2012] [Indexed: 06/01/2023]
Abstract
The need for a less conservative, but reliable risk assessment of accidental tritium releases is emphasized in the present debate on the nuclear energy future. The development of a standard conceptual model for accidental tritium releases must be based on the process level analysis and the appropriate experimental database. Tritium transfer from atmosphere to plants and the subsequent conversion into organically bound tritium (OBT) strongly depends on the plant characteristics, seasons, and meteorological conditions, which have a large variability. The present study presents an overview of the relevant experimental data for the short term exposure, including the unpublished information, also. Plenty of experimental data is provided for wheat, rice, and soybean and some for potato, bean, cherry tomato, radish, cabbage, and tangerine as well. Tritiated water (HTO) uptake by plants during the daytime and nighttime has an important role in further OBT synthesis. OBT formation in crops depends on the development stage, length, and condition of exposure. OBT translocation to the edible plant parts differs between the crops analyzed. OBT formation during the nighttime is comparable with that during the daytime. The present study is a preliminary step for the development of a robust model of crop contamination after an HTO accidental release.
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Affiliation(s)
- D Galeriu
- Horia Hulubei National Institute of Physics and Nuclear Engineering, Department of Life and Environmental Physics, 30 Reactorului St., PO Box MG-6, RO-077125 Bucharest-Magurele, Romania
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Oberg EA, Nifoussi SK, Gingras AC, Strack S. Selective proteasomal degradation of the B'β subunit of protein phosphatase 2A by the E3 ubiquitin ligase adaptor Kelch-like 15. J Biol Chem 2012; 287:43378-89. [PMID: 23135275 DOI: 10.1074/jbc.m112.420281] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Protein phosphatase 2A (PP2A), a ubiquitous and pleiotropic regulator of intracellular signaling, is composed of a core dimer (AC) bound to a variable (B) regulatory subunit. PP2A is an enzyme family of dozens of heterotrimers with different subcellular locations and cellular substrates dictated by the B subunit. B'β is a brain-specific PP2A regulatory subunit that mediates dephosphorylation of Ca(2+)/calmodulin-dependent protein kinase II and tyrosine hydroxylase. Unbiased proteomic screens for B'β interactors identified Cullin3 (Cul3), a scaffolding component of E3 ubiquitin ligase complexes, and the previously uncharacterized Kelch-like 15 (KLHL15). KLHL15 is one of ∼40 Kelch-like proteins, many of which have been identified as adaptors for the recruitment of substrates to Cul3-based E3 ubiquitin ligases. Here, we report that KLHL15-Cul3 specifically targets B'β to promote turnover of the PP2A subunit by ubiquitylation and proteasomal degradation. Comparison of KLHL15 and B'β tissue expression profiles suggests that the E3 ligase adaptor contributes to selective expression of the PP2A/B'β holoenzyme in the brain. We mapped KLHL15 residues critical for homodimerization as well as interaction with Cul3 and B'β. Explaining PP2A subunit selectivity, the divergent N terminus of B'β was found necessary and sufficient for KLHL15-mediated degradation, with Tyr-52 having an obligatory role. Although KLHL15 can interact with the PP2A/B'β heterotrimer, it only degrades B'β, thus promoting exchange with other regulatory subunits. E3 ligase adaptor-mediated control of PP2A holoenzyme composition thereby adds another layer of regulation to cellular dephosphorylation events.
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Affiliation(s)
- Elizabeth A Oberg
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
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Ulrich JD, Kim MS, Houlihan PR, Shutov LP, Mohapatra DP, Strack S, Usachev YM. Distinct activation properties of the nuclear factor of activated T-cells (NFAT) isoforms NFATc3 and NFATc4 in neurons. J Biol Chem 2012; 287:37594-609. [PMID: 22977251 DOI: 10.1074/jbc.m112.365197] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The Ca(2+)/calcineurin-dependent transcription factor NFAT (nuclear factor of activated T-cells) is implicated in regulating dendritic and axonal development, synaptogenesis, and neuronal survival. Despite the increasing appreciation for the importance of NFAT-dependent transcription in the nervous system, the regulation and function of specific NFAT isoforms in neurons are poorly understood. Here, we compare the activation of NFATc3 and NFATc4 in hippocampal and dorsal root ganglion neurons following electrically evoked elevations of intracellular Ca(2+) concentration ([Ca(2+)](i)). We find that NFATc3 undergoes rapid dephosphorylation and nuclear translocation that are essentially complete within 20 min, although NFATc4 remains phosphorylated and localized to the cytosol, only exhibiting nuclear localization following prolonged (1-3 h) depolarization. Knocking down NFATc3, but not NFATc4, strongly diminished NFAT-mediated transcription induced by mild depolarization in neurons. By analyzing NFATc3/NFATc4 chimeras, we find that the region containing the serine-rich region-1 (SRR1) mildly affects initial NFAT translocation, although the region containing the serine-proline repeats is critical for determining the magnitude of NFAT activation and nuclear localization upon depolarization. Knockdown of glycogen synthase kinase 3β (GSK3β) significantly increased the depolarization-induced nuclear localization of NFATc4. In contrast, inhibition of p38 or mammalian target of rapamycin (mTOR) kinases had no significant effect on nuclear import of NFATc4. Thus, electrically evoked [Ca(2+)](i) elevation in neurons rapidly and strongly activates NFATc3, whereas activation of NFATc4 requires a coincident increase in [Ca(2+)](i) and suppression of GSK3β, with differences in the serine-proline-containing region giving rise to these distinct activation properties of NFATc3 and NFATc4.
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Affiliation(s)
- Jason D Ulrich
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
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46
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Merrill RA, Slupe AM, Strack S. N-terminal phosphorylation of protein phosphatase 2A/Bβ2 regulates translocation to mitochondria, dynamin-related protein 1 dephosphorylation, and neuronal survival. FEBS J 2012; 280:662-73. [PMID: 22583914 DOI: 10.1111/j.1742-4658.2012.08631.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neuron-specific Bβ2 regulatory subunit of protein phosphatase 2A (PP2A), a product of the spinocerebellar ataxia type 12 disease gene PPP2R2B, recruits heterotrimeric PP2A to the outer mitochondrial membrane (OMM) through its N-terminal mitochondrial targeting sequence. OMM-localized PP2A/Bβ2 induces mitochondrial fragmentation, thereby increasing susceptibility to neuronal insults. Here, we report that PP2A/Bβ2 activates the mitochondrial fission enzyme dynamin-related protein 1 (Drp1) by dephosphorylating Ser656, a highly conserved inhibitory phosphorylation site targeted by the neuroprotective protein kinase A-A kinase anchoring protein 1 complex. We further show that translocation of PP2A/Bβ2 to mitochondria is regulated by phosphorylation of Bβ2 at three N-terminal serines. Phosphomimetic substitution of Ser20, Ser21, and Ser22 renders Bβ2 cytosolic, blocks Drp1 dephosphorylation and mitochondrial fragmentation, and abolishes the ability of Bβ2 overexpression to induce apoptosis in cultured hippocampal neurons. Alanine substitution of Ser20-Ser22 to prevent phosphorylation has the opposite effect, promoting association of Bβ2 with mitochondria, Drp1 dephosphorylation, mitochondrial fission, and neuronal death. OMM translocation of Bβ2 can be attenuated by mutation of residues in close proximity to the catalytic site, but only if Ser20-Ser22 are available for phosphorylation, suggesting that PP2A/Bβ2 autodephosphorylation is necessary for OMM association, probably by uncovering the net positive charge of the mitochondrial targeting sequence. These results reveal another layer of complexity in the regulation of the mitochondrial fission-fusion equilibrium and its physiological and pathophysiological consequences in the nervous system.
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Affiliation(s)
- Ronald A Merrill
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
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Abstract
The mechanoenzyme dynamin-related protein 1 (Drp1) hydrolyzes GTP to power mitochondrial fission, a process required for organelle biogenesis, quality control, transport, and apoptosis. The pleckstrin homology domain of dynamin is essential for targeting to and severing of lipid tubules, but the function of the corresponding variable domain (VD, or insert B) of Drp1 is unknown. We replaced the VD of Drp1 with a panel of linker sequences of varying length and secondary structure composition and found that the VD is dispensable for mitochondrial recruitment, association with the Drp1-anchoring protein Mff (mitochondrial fission factor), and basal and protonophore-induced mitochondrial fragmentation. Indeed, several ΔVD mutants constitutively localized to the outer mitochondrial membrane (OMM) and fragmented mitochondria more efficiently than wild-type Drp1. Consistent with an autoinhibitory role of the VD, we identified Arg-376 in the Drp1 stalk domain as necessary for Mff interaction, assembly into spirals, and mitochondrial fission. Switching the length of N- and C-terminal α-helical segments in the VD-replacing linker converted Drp1 from constitutively active and OMM-localized to inactive and cytosolic. Other hypoactive ΔVD mutants formed stable and characteristically shaped aggregates, including extended filaments. Phosphorylation of a PKA site bordering the VD disassembled the filamentous ΔVD mutant and accelerated cytosolic diffusion of full-length Drp1. We propose a model for regulation of Drp1-dependent mitochondrial fission, in which posttranslational modifications in or near the VD alter the conformation of a membrane-proximal oligomerization interface to influence Drp1 assembly rate and/or geometry. This in turn modulates Arg-376-dependent OMM targeting of Drp1 via multivalent interactions with Mff.
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Affiliation(s)
- Stefan Strack
- Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242, USA.
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Baucum AJ, Strack S, Colbran RJ. Age-dependent targeting of protein phosphatase 1 to Ca2+/calmodulin-dependent protein kinase II by spinophilin in mouse striatum. PLoS One 2012; 7:e31554. [PMID: 22348105 PMCID: PMC3278457 DOI: 10.1371/journal.pone.0031554] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 01/11/2012] [Indexed: 12/02/2022] Open
Abstract
Mechanisms underlying age-dependent changes of dendritic spines on striatal medium spiny neurons are poorly understood. Spinophilin is an F-actin- and protein phosphatase 1 (PP1)-binding protein that targets PP1 to multiple downstream effectors to modulate dendritic spine morphology and function. We found that calcium/calmodulin-dependent protein kinase II (CaMKII) directly and indirectly associates with N- and C-terminal domains of spinophilin, but F-actin can displace CaMKII from the N-terminal domain. Spinophilin co-localizes PP1 with CaMKII on the F-actin cytoskeleton in heterologous cells, and spinophilin co-localizes with synaptic CaMKII in neuronal cultures. Thr286 autophosphorylation enhances the binding of CaMKII to spinophilin in vitro and in vivo. Although there is no change in total levels of Thr286 autophosphorylation, maturation from postnatal day 21 into adulthood robustly enhances the levels of CaMKII that co-immunoprecipitate with spinophilin from mouse striatal extracts. Moreover, N- and C-terminal domain fragments of spinophilin bind more CaMKII from adult vs. postnatal day 21 striatal lysates. Total levels of other proteins that interact with C-terminal domains of spinophilin decrease during maturation, perhaps reducing competition for CaMKII binding to the C-terminal domain. In contrast, total levels of α-internexin and binding of α-internexin to the spinophilin N-terminal domain increases with maturation, perhaps bridging an indirect interaction with CaMKII. Moreover, there is an increase in the levels of myosin Va, α-internexin, spinophilin, and PP1 in striatal CaMKII immune complexes isolated from adult and aged mice compared to those from postnatal day 21. These changes in spinophilin/CaMKII interactomes may contribute to changes in striatal dendritic spine density, morphology, and function during normal postnatal maturation and aging.
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Affiliation(s)
- Anthony J Baucum
- Department of Molecular Physiology and Biophysics, Vanderbilt-Kennedy Center, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America.
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Jin Z, Mei W, Strack S, Jia J, Yang J. The antagonistic action of B56-containing protein phosphatase 2As and casein kinase 2 controls the phosphorylation and Gli turnover function of Daz interacting protein 1. J Biol Chem 2011; 286:36171-9. [PMID: 21878643 DOI: 10.1074/jbc.m111.274761] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Hedgehog (Hh) pathway is evolutionarily conserved and plays critical roles during embryonic development and adult tissue homeostasis. Defective Hh signaling has been linked to a wide range of birth defects and cancers. Hh family proteins regulate the expression of their downstream target genes through the control of proteolytic processing and the transcriptional activation function of Gli transcription factors. Although Hh-dependent regulation of Gli has been studied extensively, other Gli regulatory mechanisms remain relatively unappreciated. Here we report our identification of a novel signaling cascade that controls the stability of Gli proteins. This cascade consists of Daz interacting protein 1 (Dzip1), casein kinase 2 (CK2), and B56 containing protein phosphatase 2As (PP2As). We provide evidence that Dzip1 is involved in a novel Gli turnover pathway. We show that CK2 directly phosphorylates Dzip1 at four serine residues, Ser-664/665/706/714. B56-containing PP2As, through binding to a domain located between amino acid residue 474 and 550 of Dzip1, dephosphorylate Dzip1 on these CK2 sites. Our mutagenesis analysis further demonstrates that the unphosphorylatable form of Dzip1 is more potent in promoting Gli turnover. Consistently, we found that the stability of Gli proteins was decreased upon CK2 inhibition and increased by inhibition of B56-containing PP2As. Thus, reversible phosphorylation of Dzip1, which is controlled by the antagonistic action of CK2 and B56-containing PP2As, has an important impact on the stability of Gli transcription factors and Hh signaling.
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Affiliation(s)
- Zhigang Jin
- The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, the Ohio State University, Columbus, Ohio 43205, USA
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Slupe AM, Merrill RA, Strack S. Determinants for Substrate Specificity of Protein Phosphatase 2A. Enzyme Res 2011; 2011:398751. [PMID: 21755039 PMCID: PMC3132988 DOI: 10.4061/2011/398751] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 04/28/2011] [Indexed: 12/22/2022] Open
Abstract
Protein phosphatase 2A- (PP2A-) catalyzed dephosphorylation of target substrate proteins is widespread and critical for cellular function. PP2A is predominantly found as a heterotrimeric complex of a catalytic subunit (C), a scaffolding subunit (A), and one member of 4 families of regulatory subunits (B). Substrate specificity of the holoenzyme complex is determined by the subcellular locale the complex is confined to, selective incorporation of the B subunit, interactions with endogenous inhibitory proteins, and specific intermolecular interactions between PP2A and target substrates. Here, we discuss recent studies that have advanced our understanding of the molecular determinants for PP2A substrate specificity.
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Affiliation(s)
- Andrew M Slupe
- Department of Pharmacology, University of Iowa, 2-432 BSB, Iowa City, IA 52242, USA
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