1
|
Klement K, Brückner M, Bernkopf DB. Phosphorylation of axin within biomolecular condensates counteracts its tankyrase-mediated degradation. J Cell Sci 2023; 136:jcs261214. [PMID: 37721093 PMCID: PMC10652037 DOI: 10.1242/jcs.261214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 09/08/2023] [Indexed: 09/19/2023] Open
Abstract
Axin (also known as AXIN1) is a central negative regulator of the proto-oncogenic Wnt/β-catenin signaling pathway, as axin condensates provide a scaffold for the assembly of a multiprotein complex degrading β-catenin. Axin, in turn, is degraded through tankyrase. Consequently, tankyrase small-molecule inhibitors block Wnt signaling by stabilizing axin, revealing potential for cancer therapy. Here, we discovered that axin is phosphorylated by casein kinase 1 alpha 1 (CSNK1A1, also known as CK1α) at an N-terminal casein kinase 1 consensus motif, and that this phosphorylation is antagonized by the catalytic subunit alpha of protein phosphatase 1 (PPP1CA, hereafter referred to as PP1). Axin condensates promoted phosphorylation by enriching CK1α over PP1. Importantly, the phosphorylation took place within the tankyrase-binding site, electrostatically and/or sterically hindering axin-tankyrase interaction, and counteracting tankyrase-mediated degradation of axin. Thus, the presented data propose a novel mechanism regulating axin stability, with implications for Wnt signaling, cancer therapy and self-organization of biomolecular condensates.
Collapse
Affiliation(s)
- Katharina Klement
- Experimental Medicine II, Nikolaus-Fiebiger-Center, Friedrich-Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Martina Brückner
- Experimental Medicine II, Nikolaus-Fiebiger-Center, Friedrich-Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Dominic B. Bernkopf
- Experimental Medicine II, Nikolaus-Fiebiger-Center, Friedrich-Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany
| |
Collapse
|
2
|
Piovesana M, Wood AKM, Smith DP, Deery MJ, Bayliss R, Carrera E, Wellner N, Kosik O, Napier JA, Kurup S, Matthes MC. A point mutation in the kinase domain of CRK10 leads to xylem vessel collapse and activation of defence responses in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:3104-3121. [PMID: 36869735 DOI: 10.1093/jxb/erad080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 02/27/2023] [Indexed: 05/21/2023]
Abstract
Cysteine-rich receptor-like kinases (CRKs) are a large family of plasma membrane-bound receptors ubiquitous in higher plants. However, despite their prominence, their biological roles have remained largely elusive so far. In this study we report the characterization of an Arabidopsis mutant named crk10-A397T in which alanine 397 has been replaced by a threonine in the αC helix of the kinase domain of CRK10, known to be a crucial regulatory module in mammalian kinases. The crk10-A397T mutant is a dwarf that displays collapsed xylem vessels in the root and hypocotyl, whereas the vasculature of the inflorescence develops normally. In situ phosphorylation assays with His-tagged wild type and crk10-A397T versions of the CRK10 kinase domain revealed that both alleles are active kinases capable of autophosphorylation, with the newly introduced threonine acting as an additional phosphorylation site in crk10-A397T. Transcriptomic analysis of wild type and crk10-A397T mutant hypocotyls revealed that biotic and abiotic stress-responsive genes are constitutively up-regulated in the mutant, and a root-infection assay with the vascular pathogen Fusarium oxysporum demonstrated that the mutant has enhanced resistance to this pathogen compared with wild type plants. Taken together our results suggest that crk10-A397T is a gain-of-function allele of CRK10, the first such mutant to have been identified for a CRK in Arabidopsis.
Collapse
Affiliation(s)
- Maiara Piovesana
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
- College of Life and Environmental Sciences, Streatham Campus, Exeter EX4 4PY, UK
| | - Ana K M Wood
- Department of Biointeractions and Crop Protection, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Daniel P Smith
- Department of Computational and Analytical Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Michael J Deery
- Cambridge Centre for Proteomics, University of Cambridge, Cambridge CB2 1QR, UK
| | - Richard Bayliss
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Esther Carrera
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politècnica de València, Valencia 46022, Spain
| | | | - Ondrej Kosik
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Johnathan A Napier
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Smita Kurup
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Michaela C Matthes
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK
| |
Collapse
|
3
|
Valentim M, Brahmbhatt A, Tupling A. Skeletal and cardiac muscle calcium transport regulation in health and disease. Biosci Rep 2022; 42:BSR20211997. [PMID: 36413081 PMCID: PMC9744722 DOI: 10.1042/bsr20211997] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 11/04/2022] [Accepted: 11/22/2022] [Indexed: 11/23/2022] Open
Abstract
In healthy muscle, the rapid release of calcium ions (Ca2+) with excitation-contraction (E-C) coupling, results in elevations in Ca2+ concentrations which can exceed 10-fold that of resting values. The sizable transient changes in Ca2+ concentrations are necessary for the activation of signaling pathways, which rely on Ca2+ as a second messenger, including those involved with force generation, fiber type distribution and hypertrophy. However, prolonged elevations in intracellular Ca2+ can result in the unwanted activation of Ca2+ signaling pathways that cause muscle damage, dysfunction, and disease. Muscle employs several calcium handling and calcium transport proteins that function to rapidly return Ca2+ concentrations back to resting levels following contraction. This review will detail our current understanding of calcium handling during the decay phase of intracellular calcium transients in healthy skeletal and cardiac muscle. We will also discuss how impairments in Ca2+ transport can occur and how mishandling of Ca2+ can lead to the pathogenesis and/or progression of skeletal muscle myopathies and cardiomyopathies.
Collapse
Affiliation(s)
- Mark A. Valentim
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Aditya N. Brahmbhatt
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - A. Russell Tupling
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| |
Collapse
|
4
|
Soni S, Martens MD, Takahara S, Silver HL, Maayah ZH, Ussher JR, Ferdaoussi M, Dyck JRB. Exogenous ketone ester administration attenuates systemic inflammation and reduces organ damage in a lipopolysaccharide model of sepsis. Biochim Biophys Acta Mol Basis Dis 2022; 1868:166507. [PMID: 35902007 DOI: 10.1016/j.bbadis.2022.166507] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/19/2022] [Accepted: 07/21/2022] [Indexed: 12/20/2022]
Abstract
AIMS Sepsis is a life-threatening condition of organ dysfunction caused by dysregulated inflammation which predisposes patients to developing cardiovascular disease. The ketone β-hydroxybutyrate is reported to be cardioprotective in cardiovascular disease and this may be due to their signaling properties that contribute to reducing inflammation. While exogenous ketone esters (KE) increase blood ketone levels, it remains unknown whether KEs can reduce the enhanced inflammatory response and multi-organ dysfunction that is observed in sepsis. Thus, this study assesses whether a recently developed and clinically safe KE can effectively improve the inflammatory response and organ dysfunction in sepsis. METHODS AND RESULTS To assess the anti-inflammatory effects of a KE, we utilized a model of lipopolysaccharide (LPS)-induced sepsis in which an enhanced inflammatory response results in multi-organ dysfunction. Oral administration of KE for three days prior to LPS-injection significantly protected mice against the profound systemic inflammation compared to their vehicle-treated counterparts. In assessing organ dysfunction, KE protected mice from sepsis-induced cardiac dysfunction as well as renal dysfunction and fibrosis. Furthermore, KE administration attenuated the sepsis-induced inflammation in the heart, kidney, and liver. Moreover, these protective effects occurred independent of changes to enzymes involved in ketone metabolism. CONCLUSION These data show that the use of an exogenous KE attenuates the dysregulated systemic and organ inflammation as well as organ dysfunction in a model of severe inflammation. We postulate that this exogenous KE is an appealing and promising approach to capitalize on the protective anti-inflammatory effects of ketones in sepsis and/or other inflammatory responses.
Collapse
Affiliation(s)
- Shubham Soni
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Matthew D Martens
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Shingo Takahara
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Division of Cardiovascular Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Heidi L Silver
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Zaid H Maayah
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - John R Ussher
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Mourad Ferdaoussi
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jason R B Dyck
- Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
| |
Collapse
|
5
|
Zhao J, Pan B, Fina M, Huang Y, Shimogawa M, Luk KC, Rhoades E, Petersson EJ, Dong DW, Kashina A. α-Synuclein arginylation in the human brain. Transl Neurodegener 2022; 11:20. [PMID: 35395956 PMCID: PMC8991655 DOI: 10.1186/s40035-022-00295-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 03/23/2022] [Indexed: 12/11/2022] Open
Abstract
Background Alpha-synuclein (α-syn) exhibits pathological misfolding in many human neurodegenerative disorders. We previously showed that α-syn is arginylated in the mouse brain and that lack of arginylation leads to neurodegeneration in mice.
Methods Here, we tested α-syn arginylation in human brain pathology using newly derived antibodies in combination with Western blotting, biochemical assays, and experiments in live neurons. Results We found that α-syn was arginylated in the human brain on E46 and E83, two sites previously implicated in α-syn pathology and familial cases of Parkinson’s disease. The levels of arginylation in different brain samples ranged between ~ 3% and ~ 50% of the total α-syn pool, and this arginylation nearly exclusively concentrated in the subcellular α-syn fraction that sedimented at low centrifugation speeds and appeared to be simultaneously targeted by multiple posttranslational modifications. Arginylated α-syn was less susceptible to S129 phosphorylation and pathological aggregation in neurons. The arginylation level inversely correlated with the overall α-syn levels and with patient age, suggesting a possible causal relationship between arginylation decline and α-syn-dependent neuropathology. Conclusion We propose that α-syn arginylation constitutes a potential neuroprotective mechanism that prevents its abnormal accumulation during neurodegeneration and aging in the human brain. Supplementary Information The online version contains supplementary material available at 10.1186/s40035-022-00295-0.
Collapse
Affiliation(s)
- Jun Zhao
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, 19104, USA
| | - Buyan Pan
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania, 19104, USA
| | - Marie Fina
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, 19104, USA
| | - Yun Huang
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, 19104, USA
| | - Marie Shimogawa
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania, 19104, USA
| | - Kelvin C Luk
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, 19104, USA
| | - Elizabeth Rhoades
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania, 19104, USA
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania, 19104, USA
| | - Dawei W Dong
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, 19104, USA
| | - Anna Kashina
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, 19104, USA.
| |
Collapse
|
6
|
Hollomon JM, Liu Z, Rusin SF, Jenkins NP, Smith AK, Koeppen K, Kettenbach AN, Myers LC, Hogan DA. The Candida albicans Cdk8-dependent phosphoproteome reveals repression of hyphal growth through a Flo8-dependent pathway. PLoS Genet 2022; 18:e1009622. [PMID: 34982775 PMCID: PMC8769334 DOI: 10.1371/journal.pgen.1009622] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 01/19/2022] [Accepted: 12/06/2021] [Indexed: 12/26/2022] Open
Abstract
Ssn3, also known as Cdk8, is a member of the four protein Cdk8 submodule within the multi-subunit Mediator complex involved in the co-regulation of transcription. In Candida albicans, the loss of Ssn3 kinase activity affects multiple phenotypes including cellular morphology, metabolism, nutrient acquisition, immune cell interactions, and drug resistance. In these studies, we generated a strain in which Ssn3 was replaced with a functional variant of Ssn3 that can be rapidly and selectively inhibited by the ATP analog 3-MB-PP1. Consistent with ssn3 null mutant and kinase dead phenotypes, inhibition of Ssn3 kinase activity promoted hypha formation. Furthermore, the increased expression of hypha-specific genes was the strongest transcriptional signal upon inhibition of Ssn3 in transcriptomics analyses. Rapid inactivation of Ssn3 was used for phosphoproteomic studies performed to identify Ssn3 kinase substrates associated with filamentation potential. Both previously validated and novel Ssn3 targets were identified. Protein phosphorylation sites that were reduced specifically upon Ssn3 inhibition included two sites in Flo8 which is a transcription factor known to positively regulate C. albicans morphology. Mutation of the two Flo8 phosphosites (threonine 589 and serine 620) was sufficient to increase Flo8-HA levels and Flo8 dependent transcriptional and morphological changes, suggesting that Ssn3 kinase activity negatively regulates Flo8.Under embedded conditions, when ssn3Δ/Δ and efg1Δ/Δ mutants were hyperfilamentous, FLO8 was essential for hypha formation. Previous work has also shown that loss of Ssn3 activity leads to increased alkalinization of medium with amino acids. Here, we show that the ssn3Δ/Δ medium alkalinization phenotype, which is dependent on STP2, a transcription factor involved in amino acid utilization, also requires FLO8 and EFG1. Together, these data show that Ssn3 activity can modulate Flo8 and its direct and indirect interactions in different ways, and underscores the potential importance of considering Ssn3 function in the control of transcription factor activities. In Candida albicans, Ssn3 kinase activity co-regulates the transcription of numerous genes involved in hyphal growth, metabolism and nutrient acquisition, immune cell interactions, and drug resistance. Using a strain in which Ssn3 could be rapidly and selectively inhibited, we identified both known and novel Ssn3 targets. We identified two phosphosites in Flo8, a regulator of morphology and virulence, that were shown to negatively regulate Flo8 levels and activity. The data and tools presented here will enable a better understanding of how Ssn3 impacts transcriptional and post-transcriptional regulation in order to coordinate processes during physiological and morphological transitions as well as during steady state growth.
Collapse
Affiliation(s)
- Jeffrey M. Hollomon
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Zhongle Liu
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Scott F. Rusin
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- Norris Cotton Cancer Center, Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Nicole P. Jenkins
- Norris Cotton Cancer Center, Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Allia K. Smith
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Katja Koeppen
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Arminja N. Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- Norris Cotton Cancer Center, Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Lawrence C. Myers
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- Department of Medical Education, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- * E-mail: (LCM); (DAH)
| | - Deborah A. Hogan
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- * E-mail: (LCM); (DAH)
| |
Collapse
|
7
|
Kim SI, Lee KH, Kwak JS, Kwon DH, Song JT, Seo HS. Overexpression of Rice Os S1Fa1 Gene Confers Drought Tolerance in Arabidopsis. PLANTS 2021; 10:plants10102181. [PMID: 34685986 PMCID: PMC8541125 DOI: 10.3390/plants10102181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/06/2021] [Accepted: 10/11/2021] [Indexed: 12/05/2022]
Abstract
Small peptides and proteins play critical regulatory roles in plant development and environmental stress responses; however, only a few of these molecules have been identified and characterized to date because of their poor annotation and other experimental challenges. Here, we present that rice (Oryza sativa L.) OsS1Fa1, a small 76-amino acid protein, confers drought stress tolerance in Arabidopsis thaliana. OsS1Fa1 was highly expressed in leaf, culm, and root tissues of rice seedlings during vegetative growth and was significantly induced under drought stress. OsS1Fa1 overexpression in Arabidopsis induced the expression of selected drought-responsive genes and enhanced the survival rate of transgenic lines under drought. The proteasome inhibitor MG132 protected the OsS1Fa1 protein from degradation. Together, our data indicate that the small protein OsS1Fa1 is induced by drought and is post-translationally regulated, and the ectopic expression of OsS1Fa1 protects plants from drought stress.
Collapse
Affiliation(s)
- Sung-Il Kim
- Department of Agriculture, Forestry and Bioresources, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea; (S.-I.K.); (K.H.L.); (J.S.K.); (D.H.K.)
| | - Kyu Ho Lee
- Department of Agriculture, Forestry and Bioresources, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea; (S.-I.K.); (K.H.L.); (J.S.K.); (D.H.K.)
| | - Jun Soo Kwak
- Department of Agriculture, Forestry and Bioresources, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea; (S.-I.K.); (K.H.L.); (J.S.K.); (D.H.K.)
| | - Dae Hwan Kwon
- Department of Agriculture, Forestry and Bioresources, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea; (S.-I.K.); (K.H.L.); (J.S.K.); (D.H.K.)
| | - Jong Tae Song
- Department of Applied Biosciences, Kyungpook National University, Daegu 41566, Korea;
| | - Hak Soo Seo
- Department of Agriculture, Forestry and Bioresources, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea; (S.-I.K.); (K.H.L.); (J.S.K.); (D.H.K.)
- Correspondence: ; Tel.: +82-2-880-4548; Fax: +82-2-873-2056
| |
Collapse
|
8
|
Woulfe KC, Jeffrey DA, Pires Da Silva J, Wilson CE, Mahaffey JH, Lau E, Slavov D, Hailu F, Karimpour-Fard A, Dockstader K, Bristow MR, Stauffer BL, Miyamoto SD, Sucharov CC. Serum response factor deletion 5 regulates phospholamban phosphorylation and calcium uptake. J Mol Cell Cardiol 2021; 159:28-37. [PMID: 34139234 PMCID: PMC8546760 DOI: 10.1016/j.yjmcc.2021.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 05/25/2021] [Accepted: 06/13/2021] [Indexed: 11/25/2022]
Abstract
AIMS Pediatric dilated cardiomyopathy (pDCM) is characterized by unique age-dependent molecular mechanisms that include myocellular responses to therapy. We previously showed that pDCM, but not adult DCM patients respond to phosphodiesterase 3 inhibitors (PDE3i) by increasing levels of the second messenger cAMP and consequent phosphorylation of phospholamban (PLN). However, the molecular mechanisms involved in the differential pediatric and adult response to PDE3i are not clear. METHODS AND RESULTS Quantification of serum response factor (SRF) isoforms from the left ventricle of explanted hearts showed that PDE3i treatment affects expression of SRF isoforms in pDCM hearts. An SRF isoform lacking exon 5 (SRFdel5) was highly expressed in the hearts of pediatric, but not adult DCM patients treated with PDE3i. To determine the functional consequence of expression of SRFdel5, we overexpressed full length SRF or SRFdel5 in cultured cardiomyocytes with and without adrenergic stimulation. Compared to a control adenovirus, expression of SRFdel5 increased phosphorylation of PLN, negatively affected expression of the phosphatase that promotes dephosphorylation of PLN (PP2Cε), and promoted faster calcium reuptake, whereas expression of full length SRF attenuated calcium reuptake through blunted phosphorylation of PLN. CONCLUSIONS Taken together, these data indicate that expression of SRFdel5 in pDCM hearts in response to PDE3i contributes to improved function through regulating PLN phosphorylation and thereby calcium reuptake.
Collapse
Affiliation(s)
- Kathleen C Woulfe
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Danielle A Jeffrey
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Julie Pires Da Silva
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Cortney E Wilson
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Jennifer H Mahaffey
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Edward Lau
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Dobromir Slavov
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Frehiwet Hailu
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Anis Karimpour-Fard
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Karen Dockstader
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Michael R Bristow
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Brian L Stauffer
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States; Denver Health Medical Center, Denver, CO, United States
| | - Shelley D Miyamoto
- Department of Pediatrics, University of Colorado Anschutz Medical Campus, Children's Hospital of Colorado, Aurora, CO, United States
| | - Carmen C Sucharov
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.
| |
Collapse
|
9
|
Li Y, Zhang Y, Hu Q, Egranov SD, Xing Z, Zhang Z, Liang K, Ye Y, Pan Y, Chatterjee SS, Mistretta B, Nguyen TK, Hawke DH, Gunaratne PH, Hung MC, Han L, Yang L, Lin C. Functional significance of gain-of-function H19 lncRNA in skeletal muscle differentiation and anti-obesity effects. Genome Med 2021; 13:137. [PMID: 34454586 PMCID: PMC8403366 DOI: 10.1186/s13073-021-00937-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 07/09/2021] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Exercise training is well established as the most effective way to enhance muscle performance and muscle building. The composition of skeletal muscle fiber type affects systemic energy expenditures, and perturbations in metabolic homeostasis contribute to the onset of obesity and other metabolic dysfunctions. Long noncoding RNAs (lncRNAs) have been demonstrated to play critical roles in diverse cellular processes and diseases, including human cancers; however, the functional importance of lncRNAs in muscle performance, energy balance, and obesity remains elusive. We previously reported that the lncRNA H19 regulates the poly-ubiquitination and protein stability of dystrophin (DMD) in muscular dystrophy. METHODS Here, we identified mouse/human H19-interacting proteins using mouse/human skeletal muscle tissues and liquid chromatography-mass spectrometry (LC-MS). Human induced pluripotent stem-derived skeletal muscle cells (iPSC-SkMC) from a healthy donor and Becker Muscular Dystrophy (BMD) patients were utilized to study DMD post-translational modifications and associated proteins. We identified a gain-of-function (GOF) mutant of H19 and characterized the effects on myoblast differentiation and fusion to myotubes using iPSCs. We then conjugated H19 RNA gain-of-function oligonucleotides (Rgof) with the skeletal muscle enrichment peptide agrin (referred to as AGR-H19-Rgof) and evaluated AGR-H19-Rgof's effects on skeletal muscle performance using wild-type (WT) C57BL/6 J mice and its anti-obesity effects using high-fat diet (HFD)- and leptin deficiency-induced obese mouse models. RESULTS We demonstrated that both human and mouse H19 associated with DMD and that the H19 GOF exhibited enhanced interaction with DMD compared to WT H19. DMD was found to associate with serine/threonine-protein kinase MRCK alpha (MRCKα) and α-synuclein (SNCA) in iPSC-SkMC derived from BMD patients. Inhibition of MRCKα and SNCA-mediated phosphorylation of DMD antagonized the interaction between H19 and DMD. These signaling events led to improved skeletal muscle cell differentiation and myotube fusion. The administration of AGR-H19-Rgof improved the muscle mass, muscle performance, and base metabolic rate of WT mice. Furthermore, mice treated with AGR-H19-Rgof exhibited resistance to HFD- or leptin deficiency-induced obesity. CONCLUSIONS Our study suggested the functional importance of the H19 GOF mutant in enhancing muscle performance and anti-obesity effects.
Collapse
Affiliation(s)
- Yajuan Li
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Yaohua Zhang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Qingsong Hu
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Sergey D Egranov
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Zhen Xing
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
- Current address: Sanofi U.S., Boston, MA, 02139, USA
| | - Zhao Zhang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, 77030, USA
| | - Ke Liang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Youqiong Ye
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, 77030, USA
| | - Yinghong Pan
- Department of Biochemistry and Biology, University of Houston, Houston, TX, 77204, USA
- Current address: UPMC Genome Center, Pittsburgh, PA, 15232, USA
| | - Sujash S Chatterjee
- Department of Biochemistry and Biology, University of Houston, Houston, TX, 77204, USA
| | - Brandon Mistretta
- Department of Biochemistry and Biology, University of Houston, Houston, TX, 77204, USA
| | - Tina K Nguyen
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - David H Hawke
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Preethi H Gunaratne
- Department of Biochemistry and Biology, University of Houston, Houston, TX, 77204, USA
| | - Mien-Chie Hung
- Graduate Institute of Biomedical Sciences, Research Center for Cancer Biology, and Center for Molecular Medicine, China Medical University, Taichung, 404, Taiwan
- Department of Biotechnology, Asia University, Taichung, 413, Taiwan
| | - Leng Han
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, 77030, USA
- Center for Epigenetics and Disease Prevention, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, 77030, USA
| | - Liuqing Yang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
- Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
| | - Chunru Lin
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
- Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
| |
Collapse
|
10
|
Shankar TS, Ramadurai DKA, Steinhorst K, Sommakia S, Badolia R, Thodou Krokidi A, Calder D, Navankasattusas S, Sander P, Kwon OS, Aravamudhan A, Ling J, Dendorfer A, Xie C, Kwon O, Cheng EHY, Whitehead KJ, Gudermann T, Richardson RS, Sachse FB, Schredelseker J, Spitzer KW, Chaudhuri D, Drakos SG. Cardiac-specific deletion of voltage dependent anion channel 2 leads to dilated cardiomyopathy by altering calcium homeostasis. Nat Commun 2021; 12:4583. [PMID: 34321484 PMCID: PMC8319341 DOI: 10.1038/s41467-021-24869-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/06/2021] [Indexed: 12/13/2022] Open
Abstract
Voltage dependent anion channel 2 (VDAC2) is an outer mitochondrial membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. However, the specific role of VDAC2 in intracellular calcium dynamics and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac ventricular myocyte-specific developmental deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium causes severe impairment in excitation-contraction coupling by altering both intracellular and mitochondrial calcium signaling. We also observed adverse cardiac remodeling which progressed to severe cardiomyopathy and death. Reintroduction of VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype. Activation of VDAC2 by efsevin increased cardiac contractile force in a mouse model of pressure-overload induced heart failure. In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing cellular calcium signaling. Through this unique role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.
Collapse
Affiliation(s)
- Thirupura S Shankar
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Dinesh K A Ramadurai
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Kira Steinhorst
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, Munich, Germany
| | - Salah Sommakia
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Rachit Badolia
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Aspasia Thodou Krokidi
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Dallen Calder
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Sutip Navankasattusas
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Paulina Sander
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, Munich, Germany
| | - Oh Sung Kwon
- Department of Kinesiology, University of Connecticut, Storrs, CT, USA
- Geriatric Research, Education, and Clinical Center, Salt Lake City VA Medical Center, Salt Lake City, UT, USA
| | - Aishwarya Aravamudhan
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Jing Ling
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Andreas Dendorfer
- Walter-Brendel-Center of Experimental Medicine, Ludwig-Maximilians Universität Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Changmin Xie
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Ohyun Kwon
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | | | - Kevin J Whitehead
- Division of Cardiovascular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Thomas Gudermann
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Russel S Richardson
- Geriatric Research, Education, and Clinical Center, Salt Lake City VA Medical Center, Salt Lake City, UT, USA
| | - Frank B Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Johann Schredelseker
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Kenneth W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
- Division of Cardiovascular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Dipayan Chaudhuri
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
- Division of Cardiovascular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Stavros G Drakos
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA.
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA.
- Division of Cardiovascular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA.
| |
Collapse
|
11
|
Koch D, Alexandrovich A, Funk F, Kho AL, Schmitt JP, Gautel M. Molecular noise filtering in the β-adrenergic signaling network by phospholamban pentamers. Cell Rep 2021; 36:109448. [PMID: 34320358 PMCID: PMC8333238 DOI: 10.1016/j.celrep.2021.109448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 04/16/2021] [Accepted: 07/05/2021] [Indexed: 02/07/2023] Open
Abstract
Phospholamban (PLN) is an important regulator of cardiac calcium handling due to its ability to inhibit the calcium ATPase SERCA. β-Adrenergic stimulation reverses SERCA inhibition via PLN phosphorylation and facilitates fast calcium reuptake. PLN also forms pentamers whose physiological significance has remained elusive. Using mathematical modeling combined with biochemical and cell biological experiments, we show that pentamers regulate both the dynamics and steady-state levels of monomer phosphorylation. Substrate competition by pentamers and a feed-forward loop involving inhibitor-1 can delay monomer phosphorylation by protein kinase A (PKA), whereas cooperative pentamer dephosphorylation enables bistable PLN steady-state phosphorylation. Simulations show that phosphorylation delay and bistability act as complementary filters that reduce the effect of random fluctuations in PKA activity, thereby ensuring consistent monomer phosphorylation and SERCA activity despite noisy upstream signals. Preliminary analyses suggest that the PLN mutation R14del could impair noise filtering, offering a new perspective on how this mutation causes cardiac arrhythmias.
Collapse
Affiliation(s)
- Daniel Koch
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK.
| | | | - Florian Funk
- Institute of Pharmacology and Clinical Pharmacology, and Cardiovascular Research Institute Düsseldorf (CARID), University Hospital Düsseldorf, 40225 Düsseldorf, Germany
| | - Ay Lin Kho
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Joachim P Schmitt
- Institute of Pharmacology and Clinical Pharmacology, and Cardiovascular Research Institute Düsseldorf (CARID), University Hospital Düsseldorf, 40225 Düsseldorf, Germany
| | - Mathias Gautel
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| |
Collapse
|
12
|
Loss of the transcriptional repressor Rev-erbα upregulates metabolism and proliferation in cultured mouse embryonic fibroblasts. Sci Rep 2021; 11:12356. [PMID: 34117285 PMCID: PMC8196003 DOI: 10.1038/s41598-021-91516-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 05/19/2021] [Indexed: 12/04/2022] Open
Abstract
The transcriptional repressor Rev-erbα is known to down-regulate fatty acid metabolism and gluconeogenesis gene expression. In animal models, disruption of Rev-erbα results in global changes in exercise performance, oxidative capacity, and blood glucose levels. However, the complete extent to which Rev-erbα-mediated transcriptional repression of metabolism impacts cell function remains unknown. We hypothesized that loss of Rev-erbα in a mouse embryonic fibroblast (MEF) model would result in global changes in metabolism. MEFs lacking Rev-erbα exhibited a hypermetabolic phenotype, demonstrating increased levels of glycolysis and oxidative phosphorylation. Rev-erbα deletion increased expression of hexokinase II, transketolase, and ribose-5-phosphate isomerase genes involved in glycolysis and the pentose phosphate pathway (PPP), and these effects were not mediated by the transcriptional activator BMAL1. Upregulation of oxidative phosphorylation was not accompanied by an increase in mitochondrial biogenesis or numbers. Rev-erbα repressed proliferation via glycolysis, but not the PPP. When treated with H2O2, cell viability was reduced in Rev-erbα knockout MEFs, accompanied by increased ratio of oxidized/reduced NADPH, suggesting that perturbation of the PPP reduces capacity to mount an antioxidant defense. These findings uncover novel mechanisms by which glycolysis and the PPP are modulated through Rev-erbα, and provide new insights into how Rev-erbα impacts proliferation.
Collapse
|
13
|
Neumann J, Binter MB, Fehse C, Marušáková M, Büxel ML, Kirchhefer U, Hofmann B, Gergs U. Amitriptyline functionally antagonizes cardiac H 2 histamine receptors in transgenic mice and human atria. Naunyn Schmiedebergs Arch Pharmacol 2021; 394:1251-1262. [PMID: 33625558 PMCID: PMC8208937 DOI: 10.1007/s00210-021-02065-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 02/09/2021] [Indexed: 11/29/2022]
Abstract
We have previously shown that histamine (2-(1H-imidazol-4-yl)ethanamine) exerted concentration-dependent positive inotropic effects (PIE) or positive chronotropic effects (PCE) on isolated left and right atria, respectively, of transgenic (H2R-TG) mice that overexpress the human H2 histamine receptor (H2R) in the heart; however, the effects were not seen in their wild-type (WT) littermates. Amitriptyline, which is still a highly prescribed antidepressant drug, was reported to act as antagonist on H2Rs. Here, we wanted to determine whether the histamine effects in H2R-TG were antagonized by amitriptyline. Contractile studies were performed on isolated left and right atrial preparations, isolated perfused hearts from H2R-TG and WT mice and human atrial preparations. Amitriptyline shifted the concentration-dependent PIE of histamine (1 nM-10 μM) to higher concentrations (rightward shift) in left atrial preparations from H2R-TG. Similarly, in isolated perfused hearts from H2R-TG and WT mice, histamine increased the contractile parameters and the phosphorylation state of phospholamban (PLB) at serine 16 in the H2R-TG mice, but not in the WT mice. However, the increases in contractility and PLB phosphorylation were attenuated by the addition of amitriptyline in perfused hearts from H2R-TG. In isolated electrically stimulated human atria, the PIE of histamine that was applied in increasing concentrations from 1 nM to 10 μM was reduced by 10-μM amitriptyline. In summary, we present functional evidence that amitriptyline also acts as an antagonist of contractility at H2Rs in H2R-TG mouse hearts and in the human heart which might in part explain the side effects of amitriptyline.
Collapse
Affiliation(s)
- Joachim Neumann
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany
| | - Maximilian Benedikt Binter
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany
| | - Charlotte Fehse
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany
| | - Margaréta Marušáková
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany.,Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovakia
| | - Maren Luise Büxel
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Westfälische Wilhelms-Universität, Domagkstr. 12, D-48149, Münster, Germany
| | - Britt Hofmann
- Cardiac Surgery, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06120, Halle, Germany
| | - Ulrich Gergs
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097, Halle, Germany.
| |
Collapse
|
14
|
Alt-RPL36 downregulates the PI3K-AKT-mTOR signaling pathway by interacting with TMEM24. Nat Commun 2021; 12:508. [PMID: 33479206 PMCID: PMC7820019 DOI: 10.1038/s41467-020-20841-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 12/21/2020] [Indexed: 12/11/2022] Open
Abstract
Thousands of human small and alternative open reading frames (smORFs and alt-ORFs, respectively) have recently been annotated. Many alt-ORFs are co-encoded with canonical proteins in multicistronic configurations, but few of their functions are known. Here, we report the detection of alt-RPL36, a protein co-encoded with human RPL36. Alt-RPL36 partially localizes to the endoplasmic reticulum, where it interacts with TMEM24, which transports the phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) precursor phosphatidylinositol from the endoplasmic reticulum to the plasma membrane. Knock-out of alt-RPL36 increases plasma membrane PI(4,5)P2 levels, upregulates PI3K-AKT-mTOR signaling, and increases cell size. Alt-RPL36 contains four phosphoserine residues, point mutations of which abolish interaction with TMEM24 and, consequently, alt-RPL36 effects on PI3K signaling and cell size. These results implicate alt-RPL36 as an upstream regulator of PI3K-AKT-mTOR signaling. More broadly, the RPL36 transcript encodes two sequence-independent polypeptides that co-regulate translation via different molecular mechanisms, expanding our knowledge of multicistronic human gene functions. Many alternative ORFs are co-encoded with characterized proteins, but their function is often not understood. Here, the authors discover that ribosomal protein L36 is co-encoded with alternative protein, which they identify as an upstream regulator of PI3K-AKT-mTOR signaling.
Collapse
|
15
|
Benítez MJ, Cuadros R, Jiménez JS. Phosphorylation and Dephosphorylation of Tau Protein by the Catalytic Subunit of PKA, as Probed by Electrophoretic Mobility Retard. J Alzheimers Dis 2021; 79:1143-1156. [PMID: 33386804 PMCID: PMC7990467 DOI: 10.3233/jad-201077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background: Tau is a microtubule associated protein that regulates the stability of microtubules and the microtubule-dependent axonal transport. Its hyperphosphorylated form is one of the hallmarks of Alzheimer’s disease and other tauopathies and the major component of the paired helical filaments that form the abnormal proteinaceous tangles found in these neurodegenerative diseases. It is generally accepted that the phosphorylation extent of tau is the result of an equilibrium in the activity of protein kinases and phosphatases. Disruption of the balance between both types of enzyme activities has been assumed to be at the origin of tau hyperphosphorylation and the subsequent toxicity and progress of the disease. Objective: We explore the possibility that, beside the phosphatase action on phosphorylated tau, the catalytic subunit of PKA catalyzes both tau phosphorylation and also tau dephosphorylation, depending on the ATP/ADP ratio. Methods: We use the shift in the relative electrophoretic mobility suffered by different phosphorylated forms of tau, as a sensor of the catalytic action of the enzyme. Results: The results are in agreement with the long-known thermodynamic reversibility of the phosphorylation reaction (ATP + Protein = ADP+Phospho-Protein) catalyzed by PKA and many other protein kinases. Conclusion: The results contribute to put the compartmentalized energy state of the neuron and the mitochondrial-functions disruption upstream of tau-related pathologies.
Collapse
Affiliation(s)
- María J Benítez
- Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, Madrid, Spain
| | - Raquel Cuadros
- Centro de Biología Molecular Severo Ochoa, CSIC, Madrid, Spain
| | - Juan S Jiménez
- Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, Madrid, Spain
| |
Collapse
|
16
|
Cao X, Khitun A, Na Z, Dumitrescu DG, Kubica M, Olatunji E, Slavoff SA. Comparative Proteomic Profiling of Unannotated Microproteins and Alternative Proteins in Human Cell Lines. J Proteome Res 2020; 19:3418-3426. [PMID: 32449352 DOI: 10.1021/acs.jproteome.0c00254] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ribosome profiling and mass spectrometry have revealed thousands of small and alternative open reading frames (sm/alt-ORFs) that are translated into polypeptides variously termed as microproteins and alt-proteins in mammalian cells. Some micro-/alt-proteins exhibit stress-, cell-type-, and/or tissue-specific expression; understanding this regulated expression will be critical to elucidating their functions. While differential translation has been inferred by ribosome profiling, quantitative mass spectrometry-based proteomics is needed for direct comparison of microprotein and alt-protein expression between samples and conditions. However, while label-free quantitative proteomics has been applied to detect stress-dependent expression of bacterial microproteins, this approach has not yet been demonstrated for analysis of differential expression of unannotated ORFs in the more complex human proteome. Here, we present global micro-/alt-protein quantitation in two human leukemia cell lines, K562 and MOLT4. We identify 12 unannotated proteins that are differentially expressed in these cell lines. The expression of six micro/alt-proteins from cDNA was validated biochemically, and two were found to localize to the nucleus. Thus, we demonstrate that label-free comparative proteomics enables quantitation of micro-/alt-protein expression between human cell lines. We anticipate that this workflow will enable the discovery of regulated sm/alt-ORF products across many biological conditions in human cells.
Collapse
Affiliation(s)
- Xiongwen Cao
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States
| | - Alexandra Khitun
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States
| | - Zhenkun Na
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States
| | - Daniel G Dumitrescu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Marcelina Kubica
- Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States
| | - Elizabeth Olatunji
- Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States
| | - Sarah A Slavoff
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Chemical Biology Institute, Yale University, West Haven, Connecticut06516, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut06529, United States
| |
Collapse
|
17
|
McCann JL, Klein MM, Leland EM, Law EK, Brown WL, Salamango DJ, Harris RS. The DNA deaminase APOBEC3B interacts with the cell-cycle protein CDK4 and disrupts CDK4-mediated nuclear import of Cyclin D1. J Biol Chem 2019; 294:12099-12111. [PMID: 31217276 PMCID: PMC6690700 DOI: 10.1074/jbc.ra119.008443] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 05/27/2019] [Indexed: 12/13/2022] Open
Abstract
Apolipoprotein B mRNA editing enzyme catalytic subunit-like protein 3B (APOBEC3B or A3B), as other APOBEC3 members, is a single-stranded (ss)DNA cytosine deaminase with antiviral activity. A3B is also overexpressed in multiple tumor types, such as carcinomas of the bladder, cervix, lung, head/neck, and breast. A3B generates both dispersed and clustered C-to-T and C-to-G mutations in intrinsically preferred trinucleotide motifs (TCA/TCG/TCT). A3B-catalyzed mutations are likely to promote tumor evolution and cancer progression and, as such, are associated with poor clinical outcomes. However, little is known about cellular processes that regulate A3B. Here, we used a proteomics approach involving affinity purification coupled to MS with human 293T cells to identify cellular proteins that interact with A3B. This approach revealed a specific interaction with cyclin-dependent kinase 4 (CDK4). We validated and mapped this interaction by co-immunoprecipitation experiments. Functional studies and immunofluorescence microscopy experiments in multiple cell lines revealed that A3B is not a substrate for CDK4-Cyclin D1 phosphorylation nor is its deaminase activity modulated. Instead, we found that A3B is capable of disrupting the CDK4-dependent nuclear import of Cyclin D1. We propose that this interaction may favor a more potent antiviral response and simultaneously facilitate cancer mutagenesis.
Collapse
Affiliation(s)
- Jennifer L McCann
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455; Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455
| | - Madeline M Klein
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Evelyn M Leland
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Emily K Law
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455; Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455; Howard Hughes Medical Institute, University of Minnesota, Minneapolis, Minnesota 55455
| | - William L Brown
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455; Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455
| | - Daniel J Salamango
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455; Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455.
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455; Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455; Howard Hughes Medical Institute, University of Minnesota, Minneapolis, Minnesota 55455.
| |
Collapse
|
18
|
Keceli G, Majumdar A, Thorpe CN, Jun S, Tocchetti CG, Lee DI, Mahaney JE, Paolocci N, Toscano JP. Nitroxyl (HNO) targets phospholamban cysteines 41 and 46 to enhance cardiac function. J Gen Physiol 2019; 151:758-770. [PMID: 30842219 PMCID: PMC6571998 DOI: 10.1085/jgp.201812208] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 02/15/2019] [Indexed: 11/20/2022] Open
Abstract
Nitroxyl (HNO) positively modulates myocardial function by accelerating Ca2+ reuptake into the sarcoplasmic reticulum (SR). HNO-induced enhancement of myocardial Ca2+ cycling and function is due to the modification of cysteines in the transmembrane domain of phospholamban (PLN), which results in activation of SR Ca2+-ATPase (SERCA2a) by functionally uncoupling PLN from SERCA2a. However, which cysteines are modified by HNO, and whether HNO induces reversible disulfides or single cysteine sulfinamides (RS(O)NH2) that are less easily reversed by reductants, remain to be determined. Using an 15N-edited NMR method for sulfinamide detection, we first demonstrate that Cys46 and Cys41 are the main targets of HNO reactivity with PLN. Supporting this conclusion, mutation of PLN cysteines 46 and 41 to alanine reduces the HNO-induced enhancement of SERCA2a activity. Treatment of WT-PLN with HNO leads to sulfinamide formation when the HNO donor is in excess, whereas disulfide formation is expected to dominate when the HNO/thiol stoichiometry approaches a 1:1 ratio that is more similar to that anticipated in vivo under normal, physiological conditions. Thus, 15N-edited NMR spectroscopy detects redox changes on thiols that are unique to HNO, greatly advancing the ability to detect HNO footprints in biological systems, while further differentiating HNO-induced post-translational modifications from those imparted by other reactive nitrogen or oxygen species. The present study confirms the potential of HNO as a signaling molecule in the cardiovascular system.
Collapse
Affiliation(s)
- Gizem Keceli
- Department of Chemistry, Johns Hopkins University, Baltimore, MD.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | - Ananya Majumdar
- Biomolecular NMR Center, Johns Hopkins University, Baltimore, MD
| | - Chevon N Thorpe
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Seungho Jun
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | | | - Dong I Lee
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | | | - Nazareno Paolocci
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD.,Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - John P Toscano
- Department of Chemistry, Johns Hopkins University, Baltimore, MD
| |
Collapse
|
19
|
Zeng N, D'Souza RF, Figueiredo VC, Markworth JF, Roberts LA, Peake JM, Mitchell CJ, Cameron-Smith D. Acute resistance exercise induces Sestrin2 phosphorylation and p62 dephosphorylation in human skeletal muscle. Physiol Rep 2018; 5:5/24/e13526. [PMID: 29263116 PMCID: PMC5742699 DOI: 10.14814/phy2.13526] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 11/02/2017] [Accepted: 11/03/2017] [Indexed: 02/07/2023] Open
Abstract
Sestrins (1, 2, 3) are a family of stress-inducible proteins capable of attenuating oxidative stress, regulating metabolism, and stimulating autophagy. Sequestosome1 (p62) is also a stress-inducible multifunctional protein acting as a signaling hub for oxidative stress and selective autophagy. It is unclear whether Sestrin and p62Ser403 are regulated acutely or chronically by resistance exercise (RE) or training (RT) in human skeletal muscle. Therefore, the acute and chronic effects of RE on Sestrin and p62 in human skeletal muscle were examined through two studies. In Study 1, nine active men (22.1 ± 2.2 years) performed a bout of single-leg strength exercises and muscle biopsies were collected before, 2, 24, and 48 h after exercise. In Study 2, 10 active men (21.3 ± 1.9 years) strength trained for 12 weeks (2 days per week) and biopsies were collected pre- and post-training. Acutely, 2 h postexercise, phosphorylation of p62Ser403 was downregulated, while there was a mobility shift of Sestrin2, indicative of increased phosphorylation. Forty-eight hours postexercise, the protein expression of both Sestrin1 and total p62 increased. Chronic exercise had no impact on the gene or protein expression of Sestrin2/3 or p62, but Sestrin1 protein was upregulated. These findings demonstrated an inverse relationship between Sestrin2 and p62 phosphorylation after a single bout of RE, indicating they are transiently regulated. Contrarily, 12 weeks of RT increased protein expression of Sestrin1, suggesting that despite the strong sequence homology of the Sestrin family, they are differentially regulated in response to acute RE and chronic RT.
Collapse
Affiliation(s)
- Nina Zeng
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand
| | - Randall F D'Souza
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand
| | - Vandre C Figueiredo
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand.,Centre for Muscle Biology, College of Health Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - James F Markworth
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand.,Department of Orthopedic Surgery, University of Michigan, Ann Arbor, Michigan, USA
| | - Llion A Roberts
- School of Allied Health Sciences & Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia.,Sport Performance Innovation and Knowledge Excellence, Queensland Academy of Sport, Brisbane, Australia
| | - Jonathan M Peake
- Sport Performance Innovation and Knowledge Excellence, Queensland Academy of Sport, Brisbane, Australia.,School of Biomedical Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
| | - Cameron J Mitchell
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand
| | - David Cameron-Smith
- Liggins Institute The University of Auckland, Private Bag 92019, Victoria Street West, Auckland, 1142, New Zealand .,Food & Bio-based Products Group, AgResearch, Palmerston North, 4474, New Zealand.,Riddet Institute, Palmerston North, 4442, New Zealand
| |
Collapse
|
20
|
Murray AS, Varela FA, Hyland TE, Schoenbeck AJ, White JM, Tanabe LM, Todi SV, List K. Phosphorylation of the type II transmembrane serine protease, TMPRSS13, in hepatocyte growth factor activator inhibitor-1 and -2-mediated cell-surface localization. J Biol Chem 2017; 292:14867-14884. [PMID: 28710277 DOI: 10.1074/jbc.m117.775999] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Revised: 06/12/2017] [Indexed: 12/22/2022] Open
Abstract
TMPRSS13 is a member of the type II transmembrane serine protease (TTSP) family. Although various TTSPs have been characterized in detail biochemically and functionally, the basic properties of TMPRSS13 remain unclear. Here, we investigate the activation, inhibition, post-translational modification, and localization of TMPRSS13. We show that TMPRSS13 is a glycosylated, active protease and that its own proteolytic activity mediates zymogen cleavage. Full-length, active TMPRSS13 exhibits impaired cell-surface expression in the absence of the cognate Kunitz-type serine protease inhibitors, hepatocyte growth factor activator inhibitor (HAI)-1 or HAI-2. Concomitant presence of TMPRSS13 with either HAI-1 or -2 mediates phosphorylation of residues in the intracellular domain of the protease, and it coincides with efficient transport of the protease to the cell surface and its subsequent shedding. Cell-surface labeling experiments indicate that the dominant form of TMPRSS13 on the cell surface is phosphorylated, whereas intracellular TMPRSS13 is predominantly non-phosphorylated. These data provide novel insight into the cellular properties of TMPRSS13 and highlight phosphorylation of TMPRSS13 as a novel post-translational modification of this TTSP family member and potentially other members of this family of proteases.
Collapse
Affiliation(s)
- Andrew S Murray
- From the Departments of Pharmacology.,Oncology, and.,Cancer Biology Graduate Program, and.,the Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Fausto A Varela
- From the Departments of Pharmacology.,Pharmacology Graduate Program, and
| | | | | | - Jordan M White
- From the Departments of Pharmacology.,Oncology, and.,Cancer Biology Graduate Program, and.,the Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201
| | | | | | - Karin List
- From the Departments of Pharmacology, .,Oncology, and.,the Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201
| |
Collapse
|
21
|
Brumbaugh K, Liao WC, Houchins JP, Cooper J, Stoesz S. Phosphosite-Specific Antibodies: A Brief Update on Generation and Applications. Methods Mol Biol 2017; 1554:1-40. [PMID: 28185181 DOI: 10.1007/978-1-4939-6759-9_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Phosphate addition is a posttranslational modification of proteins, and this modification can affect the activity and other properties of intracellular proteins. Different animal species can be used to generate phosphosite-specific antibodies as either polyclonals or monoclonals, and each approach offers its own benefits and disadvantages. The validation of phosphosite-specific antibodies requires multiple techniques and tactics to demonstrate their specificity. These antibodies can be used in arrays, flow cytometry, and imaging platforms. The specificity of phosphosite-specific antibodies is vital for their use in proteomics and profiling of disease.
Collapse
Affiliation(s)
- Kathy Brumbaugh
- Bio-Techne, Inc., 614 McKinley Place NE, Minneapolis, MN, 55413, USA.
| | - Wen-Chie Liao
- Bio-Techne, Inc., 614 McKinley Place NE, Minneapolis, MN, 55413, USA
| | - J P Houchins
- Bio-Techne, Inc., 614 McKinley Place NE, Minneapolis, MN, 55413, USA
| | - Jeff Cooper
- Bio-Techne, Inc., 614 McKinley Place NE, Minneapolis, MN, 55413, USA
| | - Steve Stoesz
- Bio-Techne, Inc., 614 McKinley Place NE, Minneapolis, MN, 55413, USA
| |
Collapse
|
22
|
Li X, Cox JT, Huang W, Kane M, Tang K, Bieberich CJ. Quantifying Kinase-Specific Phosphorylation Stoichiometry Using Stable Isotope Labeling In a Reverse In-Gel Kinase Assay. Anal Chem 2016; 88:11468-11475. [PMID: 27808495 DOI: 10.1021/acs.analchem.6b02599] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Despite recent advancements in large-scale phosphoproteomics, methods to quantify kinase-specific phosphorylation stoichiometry of protein substrates are lacking. We developed a method to quantify kinase-specific phosphorylation stoichiometry by combining the reverse in-gel kinase assay (RIKA) with high-resolution liquid chromatography-mass spectrometry (LC-MS). Beginning with predetermined ratios of phosphorylated to nonphosphorylated protein kinase CK2 (CK2) substrate molecules, we employed 18O-labeled adenosine triphosphate (18O-ATP) as the phosphate donor in a RIKA, then quantified the ratio of 18O- versus 16O-labeled tryptic phosphopeptide using high mass accuracy mass spectrometry (MS). We demonstrate that the phosphorylation stoichiometry determined by this method across a broad percent phosphorylation range correlated extremely well with the predicted value (correlation coefficient = 0.99). This approach provides a quantitative alternative to antibody-based methods of determining the extent of phosphorylation of a substrate pool.
Collapse
Affiliation(s)
- Xiang Li
- Department of Biological Sciences, University of Maryland Baltimore County , Baltimore, Maryland 21250, United States
| | - Jonathan T Cox
- Biological Sciences Division, Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - Weiliang Huang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland , Baltimore, Maryland 21201, United States
| | - Maureen Kane
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland , Baltimore, Maryland 21201, United States
| | - Keqi Tang
- Biological Sciences Division, Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - Charles J Bieberich
- Department of Biological Sciences, University of Maryland Baltimore County , Baltimore, Maryland 21250, United States.,Marlene and Stewart Greenebaum Cancer Center, University of Maryland Baltimore , Baltimore, Maryland 21201, United States
| |
Collapse
|
23
|
Khadria AS, Senes A. Fluorophores, environments, and quantification techniques in the analysis of transmembrane helix interaction using FRET. Biopolymers 2016; 104:247-64. [PMID: 25968159 DOI: 10.1002/bip.22667] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/15/2015] [Accepted: 05/04/2015] [Indexed: 12/31/2022]
Abstract
Förster resonance energy transfer (FRET) has been widely used as a spectroscopic tool in vitro to study the interactions between transmembrane (TM) helices in detergent and lipid environments. This technique has been instrumental to many studies that have greatly contributed to quantitative understanding of the physical principles that govern helix-helix interactions in the membrane. These studies have also improved our understanding of the biological role of oligomerization in membrane proteins. In this review, we focus on the combinations of fluorophores used, the membrane mimetic environments, and measurement techniques that have been applied to study model systems as well as biological oligomeric complexes in vitro. We highlight the different formalisms used to calculate FRET efficiency and the challenges associated with accurate quantification. The goal is to provide the reader with a comparative summary of the relevant literature for planning and designing FRET experiments aimed at measuring TM helix-helix associations.
Collapse
Affiliation(s)
- Ambalika S Khadria
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706
| | - Alessandro Senes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706
| |
Collapse
|
24
|
Shaikh SA, Sahoo SK, Periasamy M. Phospholamban and sarcolipin: Are they functionally redundant or distinct regulators of the Sarco(Endo)Plasmic Reticulum Calcium ATPase? J Mol Cell Cardiol 2015; 91:81-91. [PMID: 26743715 DOI: 10.1016/j.yjmcc.2015.12.030] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 12/10/2015] [Accepted: 12/29/2015] [Indexed: 10/22/2022]
Abstract
In muscle, the Sarco(Endo)plasmic Reticulum Calcium ATPase (SERCA) activity is regulated by two distinct proteins, PLB and SLN, which are highly conserved throughout vertebrate evolution. PLB is predominantly expressed in the cardiac muscle, while SLN is abundant in skeletal muscle. SLN is also found in the cardiac atria and to a lesser extent in the ventricle. PLB regulation of SERCA is central to cardiac function, both at rest and during extreme physiological demand. Compared to PLB, the physiological relevance of SLN remained a mystery until recently and some even thought it was redundant in function. Studies on SLN suggest that it is an uncoupler of the SERCA pump activity and can increase ATP hydrolysis resulting in heat production. Using genetically engineered mouse models for SLN and PLB, we showed that SLN, not PLB, is required for muscle-based thermogenesis. However, the mechanism of how SLN binding to SERCA results in uncoupling SERCA Ca(2+) transport from its ATPase activity remains unclear. In this review, we discuss recent advances in understanding how PLB and SLN differ in their interaction with SERCA. We will also explore whether structural differences in the cytosolic domain of PLB and SLN are the basis for their unique function and physiological roles in cardiac and skeletal muscle.
Collapse
Affiliation(s)
- Sana A Shaikh
- Center for Metabolic Origins of Disease, Cardiovascular Metabolism Program, Sanford Burnham Prebys Medical Discovery Institute, Lake Nona, FL. 6400 Sanger Road, Orlando, FL 32827, United States
| | - Sanjaya K Sahoo
- Center for Metabolic Origins of Disease, Cardiovascular Metabolism Program, Sanford Burnham Prebys Medical Discovery Institute, Lake Nona, FL. 6400 Sanger Road, Orlando, FL 32827, United States
| | - Muthu Periasamy
- Center for Metabolic Origins of Disease, Cardiovascular Metabolism Program, Sanford Burnham Prebys Medical Discovery Institute, Lake Nona, FL. 6400 Sanger Road, Orlando, FL 32827, United States.
| |
Collapse
|
25
|
Danger Y, Danard S, Gringoire V, Peyrard T, Riou P, Semana G, Vérité F. Characterization of a new human monoclonal antibody directed against the Vel antigen. Vox Sang 2015; 110:172-8. [PMID: 26382919 DOI: 10.1111/vox.12321] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 06/01/2015] [Accepted: 07/11/2015] [Indexed: 12/01/2022]
Abstract
BACKGROUND AND OBJECTIVES The Vel blood group antigen is a poorly characterized high-prevalence antigen. Until now, anti-Vel antibodies have been observed in only alloimmunized Vel-negative individuals. In this study, we aimed to establish a human hybridoma cell line secreting the first anti-Vel monoclonal antibody (mAb), clone SpG213Dc. MATERIALS AND METHODS Peripheral blood lymphocytes from a French Vel-negative woman with anti-Vel in her plasma were transformed with Epstein-Barr virus and then hybridized with the myeloma cell line Sp2/O-Ag14 using the polyethylene glycol (PEG) method. A specific anti-Vel mAb was successfully produced and was extensively characterized by serological, flow cytometry and Western blot analyses. RESULTS One human anti-Vel-secreting clone was produced and the secreted anti-Vel mAb (SpG213Dc) was examined. The specificity of the SpG213Dc mAb was assessed by its reactivity against a panel of nine genotyped RBCs including, respectively, three Vel-negative and six Vel-positive (three wild-type homozygous and three heterozygous) samples using flow cytometry method. Vel-positive RBCs were specifically stained and were subsequently used to perform Western blot and immunoprecipitation analysis of the Vel antigen. CONCLUSION Serological characterization of the new monoclonal anti-Vel SpG213Dc showed a heterogeneous level of expression of the Vel antigen on the different RBCs. Our results suggest that the mAb SpG213Dc can be reliably used as a blood grouping reagent, thus allowing the mass-scale phenotyping of blood donors to strengthen rare blood banks with Vel-negative RBC units.
Collapse
Affiliation(s)
- Y Danger
- EFS Bretagne, Rennes, France.,Structure Fédérative BioSit UMS 3480 CNRS-US18 Inserm, Rennes, France
| | | | | | - T Peyrard
- Institut National de la Transfusion Sanguine, Département Centre National de Référence pour les Groupes Sanguins, Paris, France.,INSERM UMR_S1134, Paris, France.,Laboratoire d'Excellence LABEX GR-Ex, Paris, France
| | - P Riou
- EFS Bretagne, Rennes, France
| | | | - F Vérité
- EFS Bretagne, Rennes, France.,Structure Fédérative BioSit UMS 3480 CNRS-US18 Inserm, Rennes, France
| |
Collapse
|
26
|
Phospholamban pentamers attenuate PKA-dependent phosphorylation of monomers. J Mol Cell Cardiol 2015; 80:90-7. [DOI: 10.1016/j.yjmcc.2014.12.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/29/2014] [Accepted: 12/23/2014] [Indexed: 11/18/2022]
|
27
|
Abrol N, de Tombe PP, Robia SL. Acute inotropic and lusitropic effects of cardiomyopathic R9C mutation of phospholamban. J Biol Chem 2015; 290:7130-40. [PMID: 25593317 DOI: 10.1074/jbc.m114.630319] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A naturally occurring R9C mutation of phospholamban (PLB) triggers cardiomyopathy and premature death by altering regulation of sarco/endoplasmic reticulum calcium-ATPase (SERCA). The goal of this study was to investigate the acute physiological consequences of the R9C-PLB mutation on cardiomyocyte calcium kinetics and contractility. We measured the physiological consequences of R9C-PLB mutation on calcium transients and sarcomere shortening in adult cardiomyocytes. In contrast to studies of chronic R9C-PLB expression in transgenic mice, we found that acute expression of R9C-PLB exerts a positively inotropic and lusitropic effect in cardiomyocytes. Importantly, R9C-PLB exhibited blunted sensitivity to frequency potentiation and β-adrenergic stimulation, two major physiological mechanisms for the regulation of cardiac performance. To identify the molecular mechanism of R9C pathology, we quantified the effect of R9C on PLB oligomerization and PLB-SERCA binding. FRET measurements in live cells revealed that R9C-PLB exhibited an increased propensity for oligomerization, and this was further increased by oxidative stress. The R9C also decreased PLB binding to SERCA and altered the structure of the PLB-SERCA regulatory complex. The structural change after oxidative modification of R9C-PLB was similar to that observed after PLB phosphorylation. We conclude that R9C mutation of PLB decreases SERCA inhibition by decreasing the amount of the regulatory complex and altering its conformation. This has an acute inotropic/lusitropic effect but yields negative consequences of impaired frequency potentiation and blunted β-adrenergic responsiveness. We envision a self-reinforcing mechanism beginning with phosphomimetic R9C-PLB oxidation and loss of SERCA inhibition, leading to impaired calcium regulation and heart failure.
Collapse
Affiliation(s)
- Neha Abrol
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60163
| | - Pieter P de Tombe
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60163
| | - Seth L Robia
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60163
| |
Collapse
|
28
|
Ayala E, Downey JS, Mashburn-Warren L, Senadheera DB, Cvitkovitch DG, Goodman SD. A biochemical characterization of the DNA binding activity of the response regulator VicR from Streptococcus mutans. PLoS One 2014; 9:e108027. [PMID: 25229632 PMCID: PMC4168254 DOI: 10.1371/journal.pone.0108027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 08/18/2014] [Indexed: 02/03/2023] Open
Abstract
Two-component systems (TCSs) are ubiquitous among bacteria and are among the most elegant and effective sensing systems in nature. They allow for efficient adaptive responses to rapidly changing environmental conditions. In this study, we investigated the biochemical characteristics of the Streptococcus mutans protein VicR, an essential response regulator that is part of the VicRK TCS. We dissected the DNA binding requirements of the recognition sequences for VicR in its phosphorylated and unphosphorylated forms. In doing so, we were able to make predictions for the expansion of the VicR regulon within S. mutans. With the ever increasing number of bacteria that are rapidly becoming resistant to even the antibiotics of last resort, TCSs such as the VicRK provide promising targets for a new class of antimicrobials.
Collapse
Affiliation(s)
- Eduardo Ayala
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
| | - Jennifer S. Downey
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
| | - Lauren Mashburn-Warren
- Center for Microbial Pathogenesis, The Research Institute, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
| | - Dilani B. Senadheera
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Canada
| | - Dennis G. Cvitkovitch
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Canada
| | - Steven D. Goodman
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
- Center for Microbial Pathogenesis, The Research Institute, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- * E-mail:
| |
Collapse
|
29
|
Hughes E, Middleton DA. Comparison of the structure and function of phospholamban and the arginine-14 deficient mutant associated with dilated cardiomyopathy. PLoS One 2014; 9:e106746. [PMID: 25225809 PMCID: PMC4165587 DOI: 10.1371/journal.pone.0106746] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 08/01/2014] [Indexed: 12/20/2022] Open
Abstract
Phospholamban (PLB) is a pentameric protein that plays an important role in regulating cardiac contractility via a reversible inhibitory association with the sarcoplasmic reticulum Ca2+ATPase (SERCA), the enzyme responsible for maintaining correct calcium homeostasis. Here we study the functional and biophysical characteristics of a PLB mutant associated with human dilated cardiomyopathy (DCM), with a deletion of arginine at position 14 (PLBR14Δ). In agreement with recent findings, we find that PLBR14Δ has a reduced inhibitory effect on SERCA compared to wild type PLB (PLBWT) when reconstituted into lipid membranes. The mutation also leads to a large reduction in the protein kinase A-catalysed phosphorylation of Ser-16 in the cytoplasmic domain of PLBR14Δ. Measurements on SERCA co-reconstituted with an equimolar mixture of PLBWT and PLBR14Δ (representing the lethal heterozygous state associated with DCM) indicates that the loss-of-function mutation has a dominant effect on PLBWT functionality and phosphorylation capacity, suggesting that mixed PLBWT/PLBR14Δ pentamers are formed that have characteristics typical of the mutant protein. Structural and biophysical analysis of PLBR14Δ indicates that the mutation perturbs slightly the helical structure of the PLB cytoplasmic domain and reduces its affinity for the phospholipid bilayer surface, thereby altering the orientation of the cytoplasmic domain relative to the wild-type protein. These results indicate that the structure and function consequences of the R14 deletion have profound effects on the regulation of SERCA which may contribute to the aetiology of DCM.
Collapse
Affiliation(s)
- Eleri Hughes
- Department of Chemistry, Lancaster University, Lancaster, United Kingdom
| | - David A Middleton
- Department of Chemistry, Lancaster University, Lancaster, United Kingdom
| |
Collapse
|
30
|
Hesselink RW, Findlay JBC. Expression, characterization and ligand specificity of lipocalin-1 interacting membrane receptor (LIMR). Mol Membr Biol 2014; 30:327-37. [PMID: 23964685 DOI: 10.3109/09687688.2013.823018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Human lipocalin-1 interacting membrane receptor (LIMR) was the first lipocalin receptor to be identified, as a specific receptor for lipocalin-1 (Lcn1). Subsequently LIMR has been reported to interact with other ligands as well, notably with the bovine lipocalin β-lactoglobulin (BLG) and with the unrelated secretoglobin uteroglobin (UG). To study the ligand-binding behaviour of this prototypic lipocalin receptor in more detail, a system was developed for the recombinant expression of LIMR in Drosophila Schneider 2 (S2) cells, and for the subsequent solubilization and purification of the protein. The receptor forms dimers or larger oligomers when solubilized in n-dodecyl β-D-maltoside (DDM). The full-length, functional receptor was captured onto a surface plasmon resonance (SPR) chip via an α-V5 antibody, and the binding of various potential ligands was followed in time. In this way, LIMR was shown to be highly specific for Lcn1, binding the lipocalin with low micromolar to high nanomolar affinity. No interactions with any of the other putative ligands could be detected, raising doubts about the physiological relevance of the reported binding of BLG and UG to the receptor.
Collapse
|
31
|
Fleta-Soriano E, Martinez JP, Hinkelmann B, Gerth K, Washausen P, Diez J, Frank R, Sasse F, Meyerhans A. The myxobacterial metabolite ratjadone A inhibits HIV infection by blocking the Rev/CRM1-mediated nuclear export pathway. Microb Cell Fact 2014; 13:17. [PMID: 24475978 PMCID: PMC3910686 DOI: 10.1186/1475-2859-13-17] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 01/24/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The nuclear export of unspliced and partially spliced HIV-1 mRNA is mediated by the recognition of a leucine-rich nuclear export signal (NES) in the HIV Rev protein by the host protein CRM1/Exportin1. This makes the CRM1-Rev complex an attractive target for the development of new antiviral drugs. Here we tested the anti-HIV efficacy of ratjadone A, a CRM1 inhibitor derived from myxobacteria. RESULTS Ratjadone A inhibits HIV infection in vitro in a dose-dependent manner with EC₅₀ values at the nanomolar range. The inhibitory effect of ratjadone A occurs around 12 hours post-infection and is specific for the Rev/CRM1-mediated nuclear export pathway. By using a drug affinity responsive target stability (DARTS) assay we could demonstrate that ratjadone A interferes with the formation of the CRM1-Rev-NES complex by binding to CRM1 but not to Rev. CONCLUSION Ratjadone A exhibits strong anti-HIV activity but low selectivity due to toxic effects. Although this limits its potential use as a therapeutic drug, further studies with derivatives of ratjadones might help to overcome these difficulties in the future.
Collapse
Affiliation(s)
- Eric Fleta-Soriano
- Infection Biology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Dr. Aiguader 88 08003, Barcelona, Spain
| | - Javier P Martinez
- Infection Biology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Dr. Aiguader 88 08003, Barcelona, Spain
| | - Bettina Hinkelmann
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Klaus Gerth
- Department of Microbial Drugs, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Peter Washausen
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Juana Diez
- Molecular Virology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Ronald Frank
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Florenz Sasse
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Andreas Meyerhans
- Infection Biology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Dr. Aiguader 88 08003, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| |
Collapse
|
32
|
Vostrikov VV, Mote KR, Verardi R, Veglia G. Structural dynamics and topology of phosphorylated phospholamban homopentamer reveal its role in the regulation of calcium transport. Structure 2013; 21:2119-30. [PMID: 24207128 DOI: 10.1016/j.str.2013.09.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/07/2013] [Accepted: 09/11/2013] [Indexed: 01/25/2023]
Abstract
Phospholamban (PLN) inhibits the sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA), thereby regulating cardiac diastole. In membranes, PLN assembles into homopentamers that in both the phosphorylated and nonphosphorylated states have been proposed to form ion-selective channels. Here, we determined the structure of the phosphorylated pentamer using a combination of solution and solid-state nuclear magnetic resonance methods. We found that the pinwheel architecture of the homopentamer is preserved upon phosphorylation, with each monomer having an L-shaped conformation. The TM domains form a hydrophobic pore approximately 24 Å long and 2 Å in diameter, which is inconsistent with canonical Ca²⁺-selective channels. Phosphorylation, however, enhances the conformational dynamics of the cytoplasmic region of PLN, causing partial unwinding of the amphipathic helix. We propose that PLN oligomers act as storage for active monomers, keeping SERCA function within a physiological window.
Collapse
Affiliation(s)
- Vitaly V Vostrikov
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | |
Collapse
|
33
|
Akin BL, Hurley TD, Chen Z, Jones LR. The structural basis for phospholamban inhibition of the calcium pump in sarcoplasmic reticulum. J Biol Chem 2013; 288:30181-30191. [PMID: 23996003 DOI: 10.1074/jbc.m113.501585] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
P-type ATPases are a large family of enzymes that actively transport ions across biological membranes by interconverting between high (E1) and low (E2) ion-affinity states; these transmembrane transporters carry out critical processes in nearly all forms of life. In striated muscle, the archetype P-type ATPase, SERCA (sarco(endo)plasmic reticulum Ca(2+)-ATPase), pumps contractile-dependent Ca(2+) ions into the lumen of sarcoplasmic reticulum, which initiates myocyte relaxation and refills the sarcoplasmic reticulum in preparation for the next contraction. In cardiac muscle, SERCA is regulated by phospholamban (PLB), a small inhibitory phosphoprotein that decreases the Ca(2+) affinity of SERCA and attenuates contractile strength. cAMP-dependent phosphorylation of PLB reverses Ca(2+)-ATPase inhibition with powerful contractile effects. Here we present the long sought crystal structure of the PLB-SERCA complex at 2.8-Å resolution. The structure was solved in the absence of Ca(2+) in a novel detergent system employing alkyl mannosides. The structure shows PLB bound to a previously undescribed conformation of SERCA in which the Ca(2+) binding sites are collapsed and devoid of divalent cations (E2-PLB). This new structure represents one of the key unsolved conformational states of SERCA and provides a structural explanation for how dephosphorylated PLB decreases Ca(2+) affinity and depresses cardiac contractility.
Collapse
Affiliation(s)
- Brandy L Akin
- From the Krannert Institute of Cardiology and the Departments of Medicine and.
| | - Thomas D Hurley
- Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Zhenhui Chen
- From the Krannert Institute of Cardiology and the Departments of Medicine and
| | - Larry R Jones
- From the Krannert Institute of Cardiology and the Departments of Medicine and.
| |
Collapse
|
34
|
Engineering plant alternative oxidase function in mammalian cells: substitution of the motif-like sequence ENV for QDT diminishes catalytic activity of Arum concinnatum AOX1a expressed in HeLa cells. Appl Biochem Biotechnol 2013; 170:1229-40. [PMID: 23653140 DOI: 10.1007/s12010-013-0235-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
Abstract
Alternative oxidase (AOX) is a nonproton motive quinol-oxygen oxidoreductase which is a component of the mitochondrial respiratory chain in higher plants. In this study, we have characterized the catalytic activity and regulatory behaviors of Arum concinnatum AOX isoforms, namely AcoAOX1a and AcoAOX1b, and their artificial mutants in HeLa cells. We demonstrated that substitution of the motif-like sequence ENV on the C-terminal half of AcoAOX1a for QDT diminishes its activity and proposed that the innate inactivity of AcoAOX1b in HeLa cells is, at least in part, attributable to its QDT motif. Furthermore, we show that introduction of F130L in the hydrophilic N-terminal extension of AcoAOX1a resulted in greater activity in the presence of pyruvate. This result indicates that functional significance of the N-terminal extension is not particular to the conventional regulatory cysteine. On the basis of these findings, we discuss new insights into the structural integrity of AOX in HeLa cells and the applicability of mammalian cells for functional analysis of this enzyme.
Collapse
|
35
|
Aschar-Sobbi R, Emmett TL, Kargacin GJ, Kargacin ME. Phospholamban phosphorylation increases the passive calcium leak from cardiac sarcoplasmic reticulum. Pflugers Arch 2012; 464:295-305. [DOI: 10.1007/s00424-012-1124-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/16/2012] [Accepted: 06/05/2012] [Indexed: 01/28/2023]
|
36
|
Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012; 205:9-25. [PMID: 22463608 DOI: 10.1111/j.1748-1716.2012.02389.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phospholamban (PLN) is a small phosphoprotein closely associated with the cardiac sarcoplasmic reticulum (SR). Dephosphorylated PLN tonically inhibits the SR Ca-ATPase (SERCA2a), while phosphorylation at Ser16 by PKA and Thr17 by Ca(2+) /calmodulin-dependent protein kinase (CaMKII) relieves the inhibition, and this increases SR Ca(2+) uptake. For this reason, PLN is one of the major determinants of cardiac contractility and relaxation. In this review, we attempted to highlight the functional significance of PLN in vertebrate cardiac physiology. We will refer to the huge literature on mammals in order to describe the molecular characteristics of this protein, its interaction with SERCA2a and its role in the regulation of the mechanic and the electric performance of the heart under basal conditions, in the presence of chemical and physical stresses, such as β-adrenergic stimulation, response to stretch, force-frequency relationship and intracellular acidosis. Our aim is to provide the basis to discuss the role of PLN also on the cardiac function of nonmammalian vertebrates, because so far this aspect has been almost neglected. Accordingly, when possible, the literature on PLN will be analysed taking into account the nonuniform cardiac structural and functional characteristics encountered in ectothermic vertebrates, such as the peculiar and variable organization of the SR, the large spectrum of response to stresses and the disaptive absence of crucial proteins (i.e. haemoglobinless and myoglobinless species).
Collapse
Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
| |
Collapse
|
37
|
Akin BL, Jones LR. Characterizing phospholamban to sarco(endo)plasmic reticulum Ca2+-ATPase 2a (SERCA2a) protein binding interactions in human cardiac sarcoplasmic reticulum vesicles using chemical cross-linking. J Biol Chem 2012; 287:7582-93. [PMID: 22247554 DOI: 10.1074/jbc.m111.334987] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Chemical cross-linking was used to study protein binding interactions between native phospholamban (PLB) and SERCA2a in sarcoplasmic reticulum (SR) vesicles prepared from normal and failed human hearts. Lys(27) of PLB was cross-linked to the Ca(2+) pump at the cytoplasmic extension of M4 (at or near Lys(328)) with the homobifunctional cross-linker, disuccinimidyl glutarate (7.7 Å). Cross-linking was augmented by ATP but abolished by Ca(2+) or thapsigargin, confirming in native SR vesicles that PLB binds preferentially to E2 (low Ca(2+) affinity conformation of the Ca(2+)-ATPase) stabilized by ATP. To assess the functional effects of PLB binding on SERCA2a activity, the anti-PLB antibody, 2D12, was used to disrupt the physical interactions between PLB and SERCA2a in SR vesicles. We observed a tight correlation between 2D12-induced inhibition of PLB cross-linking to SERCA2a and 2D12 stimulation of Ca(2+)-ATPase activity and Ca(2+) transport. The results suggest that the inhibitory effect of PLB on Ca(2+)-ATPase activity in SR vesicles results from mutually exclusive binding of PLB and Ca(2+) to the Ca(2+) pump, requiring PLB dissociation for catalytic activation. Importantly, the same result was obtained with SR vesicles prepared from normal and failed human hearts; therefore, we conclude that PLB binding interactions with the Ca(2+) pump are largely unchanged in failing myocardium.
Collapse
Affiliation(s)
- Brandy L Akin
- Krannert Institute of Cardiology and the Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | | |
Collapse
|
38
|
Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012. [DOI: 10.1111/j.1748-1716.2011.02389.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
| |
Collapse
|
39
|
Balasubramaniam D, Paul LN, Homan KT, Hall MC, Stauffacher CV. Specificity of HCPTP variants toward EphA2 tyrosines by quantitative selected reaction monitoring. Protein Sci 2011; 20:1172-81. [PMID: 21538645 DOI: 10.1002/pro.646] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 04/09/2011] [Accepted: 04/20/2011] [Indexed: 11/08/2022]
Abstract
EphA2 receptor tyrosine kinase and the human cytoplasmic protein tyrosine phosphatase (HCPTP) are overexpressed in a number of epithelial cancers. Overexpressed EphA2 in these cancers shows a significant decrease in phosphotyrosine content which results in suppression of receptor signaling and endocytosis and an increase in metastatic potential. The decreased phosphotyrosine content of EphA2 has been associated with decreased contact with its ligand, ephrin A1 and dephosphorylation by HCPTP. Potential specificity of the two HCPTP variants for tyrosines on EphA2 has not been investigated. We have used a mass spectrometry assay to measure relative rates of dephosphorylation for the two HCPTP variants at phosphotyrosine sites associated with control of the EphA2 kinase activity or interaction with downstream targets. Our results suggest that although both variants dephosphorylate the EphA2 receptor, the rate and specificity of dephosphorylation for specific tyrosines are different for HCPTP-A and HCPTP-B. The SAM domain tyrosine Y960 which has been implicated in downstream PI3K signaling is dephosphorylated exclusively by HCPTP-B. The activation loop tyrosine (Y772) which directly controls kinase activity is dephosphorylated about six times faster by HCPTP-A. In contrast, the juxtamembrane tyrosines (Y575, Y588 and Y594) which are implicated in both control of kinase activity and downstream signaling are dephosphorylated by both variants with similar rates. This difference in preference for dephosphorylation sites on EphA2 not only illuminates the different roles of the two variants of the phosphatase in EphA2 signaling, but also explains why both HCPTP variants are highly conserved in most mammals.
Collapse
Affiliation(s)
- Deepa Balasubramaniam
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
| | | | | | | | | |
Collapse
|
40
|
Tulumello DV, Deber CM. Positions of polar amino acids alter interactions between transmembrane segments and detergents. Biochemistry 2011; 50:3928-35. [PMID: 21473646 DOI: 10.1021/bi200238g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
α-Helical transmembrane (TM) segments in membrane proteins are comprised primarily of hydrophobic amino acids that accommodate insertion from water into the nonpolar membrane bilayer. In many such segments, however, polar residues are also present for structural or functional reasons. These latter residues impair the local favorable acyl interactions required for solvation by hydrophobic media such as phospholipids in native bilayers or detergents used for in vitro characterization. Using a series of Lys-tagged designed TM-like peptides (typified by KK-YAAAIAAIAWAIAAIAAAIAA-KKK) in which single-Asn residue substitutions (from Ile or Ala) were made successively from the center of the hydrophobic region toward the C-terminus, we demonstrate that polar residues strongly alter the nature of the interaction between TM segments and the solvating detergent. Through the application of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and tryptophan fluorescence, we observed drastic differences in the structures of the detergent-peptide complexes that contain relatively minor sequence differences. For example, the blue shift of the Trp fluorescence (indicating local detergent solvation at this location) differs by as much as ~10 nm depending upon the position of a single Asn substitution in an otherwise identical segment. The overall results suggest that polar point mutations occurring in a biological membrane will elicit comparable effects, placing a significant refolding burden on the local protein structure and potentially leading to disease states through altered protein--lipid interactions in membrane proteins.
Collapse
Affiliation(s)
- David V Tulumello
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | | |
Collapse
|
41
|
Brumbaugh K, Johnson W, Liao WC, Lin MS, Houchins JP, Cooper J, Stoesz S, Campos-Gonzalez R. Overview of the generation, validation, and application of phosphosite-specific antibodies. Methods Mol Biol 2011; 717:3-43. [PMID: 21370022 DOI: 10.1007/978-1-61779-024-9_1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Protein phosphorylation is a universal key posttranslational modification that affects the activity and other properties of intracellular proteins. Phosphosite-specific antibodies can be produced as polyclonals or monoclonals in different animal species, and each approach offers its own benefits and disadvantages. The validation of phosphosite-specific antibodies requires multiple techniques and tactics to demonstrate their specificity. These antibodies can be used in arrays, flow cytometry, and imaging platforms. The specificity of phosphosite-specific antibodies is key for their use in proteomics and profiling of disease.
Collapse
|
42
|
Hosokawa T, Saito T, Asada A, Fukunaga K, Hisanaga SI. Quantitative measurement of in vivo phosphorylation states of Cdk5 activator p35 by Phos-tag SDS-PAGE. Mol Cell Proteomics 2010; 9:1133-43. [PMID: 20097924 DOI: 10.1074/mcp.m900578-mcp200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Phosphorylation is a major post-translational modification widely used in the regulation of many cellular processes. Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase activated by activation subunit p35. Cdk5-p35 regulates various neuronal activities such as neuronal migration, spine formation, synaptic activity, and cell death. The kinase activity of Cdk5 is regulated by proteolysis of p35: proteasomal degradation causes down-regulation of Cdk5, whereas cleavage of p35 by calpain causes overactivation of Cdk5. Phosphorylation of p35 determines the proteolytic pathway. We have previously identified Ser(8) and Thr(138) as major phosphorylation sites using metabolic labeling of cultured cells followed by two-dimensional phosphopeptide mapping and phosphospecific antibodies. However, these approaches cannot determine the extent of p35 phosphorylation in vivo. Here we report the use of Phos-tag SDS-PAGE to reveal the phosphorylation states of p35 in neuronal culture and brain. Using Phos-tag acrylamide, the electrophoretic mobility of phosphorylated p35 was delayed because it is trapped at Phos-tag sites. We found a novel phosphorylation site at Ser(91), which was phosphorylated by Ca(2+)-calmodulin-dependent protein kinase II in vitro. We constructed phosphorylation-dependent banding profiles of p35 and Ala substitution mutants at phosphorylation sites co-expressed with Cdk5 in COS-7 cells. Using the standard banding profiles, we assigned respective bands of endogenous p35 with combinations of phosphorylation states and quantified Ser(8), Ser(91), and Thr(138) phosphorylation. The highest level of p35 phosphorylation was observed in embryonic brain; Ser(8) was phosphorylated in all p35 molecules, whereas Ser(91) was phosphorylated in 60% and Thr(138) was phosphorylated in approximately 12% of p35 molecules. These are the first quantitative and site-specific measurements of phosphorylation of p35, demonstrating the usefulness of Phos-tag SDS-PAGE for analysis of phosphorylation states of in vivo proteins.
Collapse
Affiliation(s)
- Tomohisa Hosokawa
- Department of Biological Sciences, Graduate School of Science and Technology, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
| | | | | | | | | |
Collapse
|
43
|
Chu S, Abu-Baker S, Lu J, Lorigan GA. (15)N Solid-state NMR spectroscopic studies on phospholamban at its phosphorylated form at ser-16 in aligned phospholipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:312-7. [PMID: 20044975 DOI: 10.1016/j.bbamem.2009.12.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 12/18/2009] [Accepted: 12/22/2009] [Indexed: 11/17/2022]
Abstract
Wild-type phospholamban (WT-PLB) is a pentameric transmembrane protein that regulates the cardiac cycle (contraction and relaxation). From a physiological prospective, unphosphorylated WT-PLB inhibits sarcoplasmic reticulum ATPase activity; whereas, its phosphorylated form relieves the inhibition in a mechanism that is not completely understood. In this study, site-specifically (15)N-Ala-11- and (15)N-Leu-7-labeled WT-PLB and the corresponding phosphorylated forms (P-PLB) were incorporated into 1,2-dioleoyl-sn-glycero-3-phosphocholine/2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPC/DOPE) mechanically oriented lipid bilayers. The aligned (15)N-labeled Ala-11 and Leu-7 WT-PLB samples show (15)N resonance peaks at approximately 71ppm and 75ppm, respectively, while the corresponding phosphorylated forms P-PLB show (15)N peaks at 92ppm and 99ppm, respectively. These (15)N chemical shift changes upon phosphorylation are significant and in agreement with previous reports, which indicate that phosphorylation of WT-PLB at Ser-16 alters the structural properties of the cytoplasmic domain with respect to the lipid bilayers.
Collapse
Affiliation(s)
- Shidong Chu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA
| | | | | | | |
Collapse
|
44
|
Tulumello DV, Deber CM. SDS Micelles as a Membrane-Mimetic Environment for Transmembrane Segments. Biochemistry 2009; 48:12096-103. [PMID: 19921933 DOI: 10.1021/bi9013819] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David V. Tulumello
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Charles M. Deber
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| |
Collapse
|
45
|
Solid-state (2)H and (15)N NMR studies of side-chain and backbone dynamics of phospholamban in lipid bilayers: investigation of the N27A mutation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:210-5. [PMID: 19840770 DOI: 10.1016/j.bbamem.2009.09.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 09/18/2009] [Accepted: 09/30/2009] [Indexed: 11/23/2022]
Abstract
Phospholamban (PLB) is an integral membrane protein regulating Ca(2+) transport through inhibitory interaction with sarco(endo)plasmic reticulum calcium ATPase (SERCA). The Asn27 to Ala (N27A) mutation of PLB has been shown to function as a superinhibitor of the affinity of SERCA for Ca(2+) and of cardiac contractility in vivo. The effects of this N27A mutation on the side-chain and backbone dynamics of PLB were investigated with (2)H and (15)N solid-state NMR spectroscopy in phospholipid multilamellar vesicles (MLVs). (2)H and (15)N NMR spectra indicate that the N27A mutation does not significantly change the side-chain or backbone dynamics of the transmembrane and cytoplasmic domains when compared to wild-type PLB. However, dynamic changes are observed for the hinge region, in which greater mobility is observed for the CD(3)-labeled Ala24 N27A-PLB. The increased dynamics in the hinge region of PLB upon N27A mutation may allow the cytoplasmic helix to more easily interact with the Ca(2+)-ATPase; thus, showing increased inhibition of Ca(2+)-ATPase.
Collapse
|
46
|
Detergent binding explains anomalous SDS-PAGE migration of membrane proteins. Proc Natl Acad Sci U S A 2009; 106:1760-5. [PMID: 19181854 DOI: 10.1073/pnas.0813167106] [Citation(s) in RCA: 602] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that does not correlate with formula molecular weights, termed "gel shifting," appears to be common for membrane proteins but has yet to be conclusively explained. In the present work, we investigate the anomalous gel mobility of helical membrane proteins using a library of wild-type and mutant helix-loop-helix ("hairpin") sequences derived from transmembrane segments 3 and 4 of the human cystic fibrosis transmembrane conductance regulator (CFTR), including disease-phenotypic residue substitutions. We find that these hairpins migrate at rates of -10% to +30% vs. their actual formula weights on SDS-PAGE and load detergent at ratios ranging from 3.4-10 g SDS/g protein. We additionally demonstrate that mutant gel shifts strongly correlate with changes in hairpin SDS loading capacity (R(2) = 0.8), and with hairpin helicity (R(2) = 0.9), indicating that gel shift behavior originates in altered detergent binding. In some cases, this differential solvation by SDS may result from replacing protein-detergent contacts with protein-protein contacts, implying that detergent binding and folding are intimately linked. The CF-phenotypic V232D mutant included in our library may thus disrupt CFTR function via altered protein-lipid interactions. The observed interdependence between hairpin migration, SDS aggregation number, and conformation additionally suggests that detergent binding may provide a rapid and economical screen for identifying membrane proteins with robust tertiary and/or quaternary structures.
Collapse
|
47
|
Miyazawa SI, Yoshimura S, Shinzaki Y, Maeshima M, Miyake C. Deactivation of aquaporins decreases internal conductance to CO 2 diffusion in tobacco leaves grown under long-term drought. FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:553-564. [PMID: 32688811 DOI: 10.1071/fp08117] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 06/03/2008] [Indexed: 06/11/2023]
Abstract
We compared the diffusion conductance to CO2 from the intercellular air space to the chloroplasts (internal conductance (g i)) between tobacco leaves acclimated to long-term drought (drought-acclimated (DA)) and those grown under sufficient irrigation (well-watered (WW)), and analysed the changes in g i in relation to the leaf anatomical characteristics and a possible CO2 transporter, aquaporin. The g i, which was estimated by combined analyses of CO2 gas exchange with chlorophyll fluorescence, in the DA plants was approximately half of that in the WW plants. The mesophyll and chloroplast surface areas exposing the intercellular air space, which potentially affect g i, were not significantly different between the WW and DA plants. The amounts of plasma membrane aquaporins (PIP), immunochemically determined using radish PIP antibodies, were unrelated to g i. After treatment with HgCl2, an aquaporin inhibitor, the water permeability of the leaf tissues (measured as the weight loss of fully-turgid leaf disks without the abaxial epidermis in 1 m sorbitol) in WW plants decreased with an increase in HgCl2 concentration. The g i in the WW plants decreased to similar levels to the DA plants when the detached leaflets were fed with 0.5 mm HgCl2. In contrast, both water permeability and g i were insensitive to HgCl2 treatments in DA plants. These results suggest that deactivation of aquaporins is responsible for the significant reduction in g i observed in plants growing under long-term drought.
Collapse
Affiliation(s)
- Shin-Ichi Miyazawa
- Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa City, Kyoto 619-0292, Japan
| | - Satomi Yoshimura
- Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa City, Kyoto 619-0292, Japan
| | - Yuki Shinzaki
- Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa City, Kyoto 619-0292, Japan
| | - Masayoshi Maeshima
- Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Chikahiro Miyake
- Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa City, Kyoto 619-0292, Japan
| |
Collapse
|
48
|
Hou Z, Kelly EM, Robia SL. Phosphomimetic mutations increase phospholamban oligomerization and alter the structure of its regulatory complex. J Biol Chem 2008; 283:28996-9003. [PMID: 18708665 DOI: 10.1074/jbc.m804782200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate the effect of phosphorylation on the interactions of phospholamban (PLB) with itself and its regulatory target, SERCA, we measured FRET from CFP-SERCA or CFP-PLB to YFP-PLB in live AAV-293 cells. Phosphorylation of PLB was mimicked by mutations S16E (PKA site) or S16E/T17E (PKA+CaMKII sites). FRET increased with protein concentration up to a maximum (FRET(max)) that was taken to represent the intrinsic FRET of the bound complex. The concentration dependence of FRET yielded dissociation constants (K(D)) for the PLB-PLB and PLB-SERCA interactions. PLB-PLB FRET data suggest pseudo-phosphorylation of PLB increased oligomerization of PLB but did not alter PLB pentamer quaternary structure. PLB-SERCA FRET experiments showed an apparent decrease in binding of PLB to SERCA and an increase in the apparent PLB-SERCA binding cooperativity. It is likely that these changes are secondary effects of increased oligomerization of PLB; a change in the inherent affinity of monomeric PLB for SERCA was not detected. In addition, PLB-SERCA complex FRET(max) was reduced by phosphomimetic mutations, suggesting the conformation of the regulatory complex is significantly altered by PLB phosphorylation.
Collapse
Affiliation(s)
- Zhanjia Hou
- Department of Physiology, Loyola University Chicago, Maywood, Illinois 60153, USA
| | | | | |
Collapse
|
49
|
Chen Z, Akin BL, Jones LR. Mechanism of reversal of phospholamban inhibition of the cardiac Ca2+-ATPase by protein kinase A and by anti-phospholamban monoclonal antibody 2D12. J Biol Chem 2007; 282:20968-76. [PMID: 17548345 DOI: 10.1074/jbc.m703516200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our model of phospholamban (PLB) regulation of the cardiac Ca(2+)-ATPase in sarcoplasmic reticulum (SERCA2a) states that PLB binds to the Ca(2+)-free, E2 conformation of SERCA2a and blocks it from transitioning from E2 to E1, the Ca(2+)-bound state. PLB and Ca(2+) binding to SERCA2a are mutually exclusive, and PLB inhibition of SERCA2a is manifested as a decreased apparent affinity of SERCA2a for Ca(2+). Here we extend this model to explain the reversal of SERCA2a inhibition that occurs after phosphorylation of PLB at Ser(16) by protein kinase A (PKA) and after binding of the anti-PLB monoclonal antibody 2D12, which recognizes residues 7-13 of PLB. Site-specific cysteine variants of PLB were co-expressed with SERCA2a, and the effects of PKA phosphorylation and 2D12 on Ca(2+)-ATPase activity and cross-linking to SERCA2a were monitored. In Ca(2+)-ATPase assays, PKA phosphorylation and 2D12 partially and completely reversed SERCA2a inhibition by decreasing K(Ca) values for enzyme activation, respectively. In cross-linking assays, cross-linking of PKA-phosphorylated PLB to SERCA2a was inhibited at only two of eight sites when conducted in the absence of Ca(2+) favoring E2. However, at a subsaturating Ca(2+) concentration supporting some E1, cross-linking of phosphorylated PLB to SERCA2a was attenuated at all eight sites. K(Ca) values for cross-linking inhibition were decreased nearly 2-fold at all sites by PLB phosphorylation, demonstrating that phosphorylated PLB binds more weakly to SERCA2a than dephosphorylated PLB. In parallel assays, 2D12 blocked PLB cross-linking to SERCA2a at all eight sites regardless of Ca(2+) concentration. Our results demonstrate that 2D12 restores maximal Ca(2+)-ATPase activity by physically disrupting the binding interaction between PLB and SERCA2a. Phosphorylation of PLB by PKA weakens the binding interaction between PLB and SERCA2a (yielding more PLB-free SERCA2a molecules at intermediate Ca(2+) concentrations), only partially restoring Ca(2+) affinity and Ca(2+)-ATPase activity.
Collapse
Affiliation(s)
- Zhenhui Chen
- Krannert Institute of Cardiology and the Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | | | | |
Collapse
|
50
|
Zhou YH, Chen Z, Purcell RH, Emerson SU. Positive reactions on Western blots do not necessarily indicate the epitopes on antigens are continuous. Immunol Cell Biol 2006; 85:73-8. [PMID: 17130902 DOI: 10.1038/sj.icb.7100004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epitope mapping (identification of an antigenic site recognized by an antibody) is an important component of vaccine development and immunological assays. It is widely accepted that in Western blots, antibodies react exclusively with continuous epitopes: discontinuous epitopes are assumed to be irreversibly destroyed by electrophoresis under the denaturing conditions used for sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Here, we demonstrate that the epitopes recognized by four different monoclonal antibodies were identified as discontinuous epitopes when characterized by radioimmunoprecipitation assays and enzyme-linked immunosorbent assays, yet each of these antibodies reacted with the corresponding antigen on Western blots. Reaction on Western blots may be due to epitope renaturation during or after the transfer of the protein to a membrane. Therefore, positive reactions on Western blots do not necessarily indicate that epitopes are continuous and this caveat should be kept in mind while characterizing them.
Collapse
Affiliation(s)
- Yi-Hua Zhou
- Laboratory of Infectious Diseases, Hepatitis Viruses and Molecular Hepatitis Sections, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | | | | |
Collapse
|