1
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Zhang S, Wang H, Melick CH, Jeong MH, Curukovic A, Tiwary S, Lama-Sherpa TD, Meng D, Servage KA, James NG, Jewell JL. AKAP13 couples GPCR signaling to mTORC1 inhibition. PLoS Genet 2021; 17:e1009832. [PMID: 34673774 PMCID: PMC8570464 DOI: 10.1371/journal.pgen.1009832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 11/05/2021] [Accepted: 09/21/2021] [Indexed: 01/14/2023] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) senses multiple stimuli to regulate anabolic and catabolic processes. mTORC1 is typically hyperactivated in multiple human diseases such as cancer and type 2 diabetes. Extensive research has focused on signaling pathways that can activate mTORC1 such as growth factors and amino acids. However, less is known about signaling cues that can directly inhibit mTORC1 activity. Here, we identify A-kinase anchoring protein 13 (AKAP13) as an mTORC1 binding protein, and a crucial regulator of mTORC1 inhibition by G-protein coupled receptor (GPCR) signaling. GPCRs paired to Gαs proteins increase cyclic adenosine 3’5’ monophosphate (cAMP) to activate protein kinase A (PKA). Mechanistically, AKAP13 acts as a scaffold for PKA and mTORC1, where PKA inhibits mTORC1 through the phosphorylation of Raptor on Ser 791. Importantly, AKAP13 mediates mTORC1-induced cell proliferation, cell size, and colony formation. AKAP13 expression correlates with mTORC1 activation and overall lung adenocarcinoma patient survival, as well as lung cancer tumor growth in vivo. Our study identifies AKAP13 as an important player in mTORC1 inhibition by GPCRs, and targeting this pathway may be beneficial for human diseases with hyperactivated mTORC1. The mammalian target of rapamycin complex 1 (mTORC1) can sense multiple upstream stimuli to regulate cell growth and metabolism. Increased mTORC1 activation results in many human diseases such as cancer. Small molecules like rapamycin that target and inhibit mTORC1, are available in the clinic with limited success. Thus, decoding the mechanisms involved in mTORC1 regulation is crucial. Most of the research has focused on stimuli that activate mTORC1. Less is known about signaling pathways that can directly inhibit mTORC1 activity. G-protein coupled receptors (GPCRs) coupled to Gαs proteins signal to and potently inhibit mTORC1. In this study, we have identified AKAP13 to play a crucial role in mTORC1 inhibition by GPCR signaling. Importantly, GPCRs are the largest family of drug targets with many approved FDA compounds. Targeting this signaling pathway may be beneficial for human diseases with hyperactivated mTORC1.
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Affiliation(s)
- Shihai Zhang
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Provincial Key Laboratory of Animal Nutrition Control, College of Animal Science, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Huanyu Wang
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Chase H. Melick
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Mi-Hyeon Jeong
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Adna Curukovic
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Shweta Tiwary
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Tshering D. Lama-Sherpa
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Delong Meng
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Kelly A. Servage
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Nicholas G. James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Jenna L. Jewell
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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Tassin TC, Barylko B, Hedde PN, Chen Y, Binns DD, James NG, Mueller JD, Jameson DM, Taussig R, Albanesi JP. Gain-of-Function Properties of a Dynamin 2 Mutant Implicated in Charcot-Marie-Tooth Disease. Front Cell Neurosci 2021; 15:745940. [PMID: 34744632 PMCID: PMC8563704 DOI: 10.3389/fncel.2021.745940] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 09/29/2021] [Indexed: 11/29/2022] Open
Abstract
Mutations in the gene encoding dynamin 2 (DNM2), a GTPase that catalyzes membrane constriction and fission, are associated with two autosomal-dominant motor disorders, Charcot-Marie-Tooth disease (CMT) and centronuclear myopathy (CNM), which affect nerve and muscle, respectively. Many of these mutations affect the pleckstrin homology domain of DNM2, yet there is almost no overlap between the sets of mutations that cause CMT or CNM. A subset of CMT-linked mutations inhibit the interaction of DNM2 with phosphatidylinositol (4,5) bisphosphate, which is essential for DNM2 function in endocytosis. In contrast, CNM-linked mutations inhibit intramolecular interactions that normally suppress dynamin self-assembly and GTPase activation. Hence, CNM-linked DNM2 mutants form abnormally stable polymers and express enhanced assembly-dependent GTPase activation. These distinct effects of CMT and CNM mutations are consistent with current findings that DNM2-dependent CMT and CNM are loss-of-function and gain-of-function diseases, respectively. In this study, we present evidence that at least one CMT-causing DNM2 mutant (ΔDEE; lacking residues 555DEE557) forms polymers that, like the CNM mutants, are resistant to disassembly and display enhanced GTPase activation. We further show that the ΔDEE mutant undergoes 2-3-fold higher levels of tyrosine phosphorylation than wild-type DNM2. These results suggest that molecular mechanisms underlying the absence of pathogenic overlap between DNM2-dependent CMT and CNM should be re-examined.
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Affiliation(s)
- Tara C. Tassin
- Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, TX, United States
| | - Barbara Barylko
- Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, TX, United States
| | - Per Niklas Hedde
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States
- Laboratory for Fluorescence Dynamics, University of California, Irvine, Irvine, CA, United States
| | - Yan Chen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, United States
| | - Derk D. Binns
- Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, TX, United States
| | - Nicholas G. James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States
| | - Joachim D. Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, United States
| | - David M. Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States
| | - Ronald Taussig
- Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, TX, United States
| | - Joseph P. Albanesi
- Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, TX, United States
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3
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Meng D, Yang Q, Melick CH, Park BC, Hsieh T, Curukovic A, Jeong M, Zhang J, James NG, Jewell JL. ArfGAP1 inhibits mTORC1 lysosomal localization and activation. EMBO J 2021; 40:e106412. [PMID: 33988249 PMCID: PMC8204869 DOI: 10.15252/embj.2020106412] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 03/14/2021] [Accepted: 03/24/2021] [Indexed: 12/11/2022] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) integrates nutrients, growth factors, stress, and energy status to regulate cell growth and metabolism. Amino acids promote mTORC1 lysosomal localization and subsequent activation. However, the subcellular location or interacting proteins of mTORC1 under amino acid-deficient conditions is not completely understood. Here, we identify ADP-ribosylation factor GTPase-activating protein 1 (ArfGAP1) as a crucial regulator of mTORC1. ArfGAP1 interacts with mTORC1 in the absence of amino acids and inhibits mTORC1 lysosomal localization and activation. Mechanistically, the membrane curvature-sensing amphipathic lipid packing sensor (ALPS) motifs that bind to vesicle membranes are crucial for ArfGAP1 to interact with and regulate mTORC1 activity. Importantly, ArfGAP1 represses cell growth through mTORC1 and is an independent prognostic factor for the overall survival of pancreatic cancer patients. Our study identifies ArfGAP1 as a critical regulator of mTORC1 that functions by preventing the lysosomal transport and activation of mTORC1, with potential for cancer therapeutics.
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Affiliation(s)
- Delong Meng
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Qianmei Yang
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Chase H Melick
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Brenden C Park
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Ting‐Sung Hsieh
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Adna Curukovic
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Mi‐Hyeon Jeong
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Junmei Zhang
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Nicholas G James
- Department of Cell and Molecular BiologyJohn A. Burns School of MedicineUniversity of HawaiiHonoluluHIUSA
| | - Jenna L Jewell
- Department of Molecular BiologyUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Harold C. Simmons Comprehensive Cancer CenterUniversity of Texas Southwestern Medical CenterDallasTXUSA
- Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasTXUSA
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4
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Nguyen H, Ward WS, James NG. Spatial and temporal resolution of mORC4 fluorescent variants reveals structural requirements for achieving higher order self-association and pronuclei entry. Methods Appl Fluoresc 2019; 7:035002. [PMID: 30865939 PMCID: PMC6636821 DOI: 10.1088/2050-6120/ab0f57] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The Origin Replication Complex (ORC), which is a multi-subunit protein complex composed of six proteins ORC1-6, is essential for initiating licensing at DNA replication origins. We have previously reported that ORC4 has an alternative function wherein it forms a cage surrounding the extruded chromatin in female meiosis and is required for polar body extrusion (PBE). As this is a highly unexpected finding for protein that normally binds DNA, we tested whether ORC4 can actually form larger, higher order structures, which would be necessary to form a cage-like structure. We generated two fluorescent constructs of mouse ORC4, mORC4-EGFP and mORC4-FlAsH, to examine its spatial dynamics during oocyte activation in live cells. We show that both constructs were primarily monomeric throughout the embryo but self-association into larger units was detected with both probes. However, mORC4-FlAsH clearly showed higher order self-association and unique spatial distribution while mORC4-EGFP failed to form large structures during Anaphase II. Interestingly, both variants were found in the pronuclei suggesting that its role in DNA licensing is still functional. Our results with both constructs support the prediction that ORC4 can form higher order structures in the cytoplasm, suggesting that it is possible to form a cage-like structure. The finding that FlAsH labeled ORC4 formed demonstrably larger higher order structures than ORC4-GFP suggests that ORC4 oligomerization is sensitive to the bulky addition of GFP at its carboxy terminus.
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Affiliation(s)
- Hieu Nguyen
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, 1960 East-West Rd., University of Hawaii, Honolulu, HI 96822, United States of America
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5
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Gallea JI, Ambroggio EE, Vilcaes AA, James NG, Jameson DM, Celej MS. Amyloid oligomerization of the Parkinson's disease related protein α-synuclein impacts on its curvature-membrane sensitivity. J Neurochem 2018; 147:541-556. [PMID: 30142705 DOI: 10.1111/jnc.14573] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/28/2018] [Accepted: 08/17/2018] [Indexed: 11/28/2022]
Abstract
The amyloid aggregation of the presynaptic protein α-synuclein (AS) is pathognomonic of Parkinson's disease and other neurodegenerative disorders. Physiologically, AS contributes to synaptic homeostasis by participating in vesicle maintenance, trafficking, and release. Its avidity for highly curved acidic membranes has been related to the distinct chemistry of the N-terminal amphipathic helix adopted upon binding to appropriated lipid interfaces. Pathologically, AS populate a myriad of toxic aggregates ranging from soluble oligomers to insoluble amyloid fibrils. Different gain-of-toxic function mechanisms are linked to prefibrillar oligomers which are considered as the most neurotoxic species. Here, we investigated if amyloid oligomerization could hamper AS function as a membrane curvature sensor. We used fluorescence correlation spectroscopy to quantitatively evaluate the interaction of oligomeric species, produced using a popular method based on lyophilization and rehydration, to lipid vesicles of different curvatures and compositions. We found that AS oligomerization has a profound impact on protein-lipid interaction, altering binding affinity and/or curvature sensitivity depending on membrane composition. Our work provides novel insights into how the formation of prefibrillar intermediate species could contribute to neurodegeneration due to a loss-of-function mechanism. OPEN PRACTICES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- José Ignacio Gallea
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina
| | - Ernesto E Ambroggio
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina
| | - Aldo Alejandro Vilcaes
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - María Soledad Celej
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC, CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina
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6
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Goo BMSS, Sanstrum BJ, Holden DZY, Yu Y, James NG. Arc/Arg3.1 has an activity-regulated interaction with PICK1 that results in altered spatial dynamics. Sci Rep 2018; 8:14675. [PMID: 30279480 PMCID: PMC6168463 DOI: 10.1038/s41598-018-32821-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 05/25/2018] [Indexed: 01/28/2023] Open
Abstract
Activity-regulated cytoskeleton-associated protein (Arc; also known as Arg3.1) is an immediate early gene product that is transcribed in dendritic spines and, to date, has been best characterized as a positive regulator of AMPAR endocytosis during long-term depression (LTD) through interaction with endocytic proteins. Here, we show that protein interacting with C terminal kinase 1 (PICK1), a protein known to bind to the GluA2 subunit of AMPARs and associated with AMPAR trafficking, was pulled-down from brain homogenates and synaptosomes when using Arc as immobilized bait. Fluctuation and FLIM-FRET-Phasor analysis revealed direct interaction between these proteins when co-expressed that was increased under depolarizing conditions in live cells. At the plasma membrane, Arc-mCherry oligomerization was found to be concentration dependent. Additionally, co-expression of Arc-mCherry and EGFP-PICK1 followed by depolarizing conditions resulted in significant increases in the number and size of puncta containing both proteins. Furthermore, we identified the Arc binding region to be the first 126 amino acids of the PICK1 BAR domain. Overall, our data support a novel interaction and model where PICK1 mediates Arc regulation of AMPARs particularly under depolarizing conditions.
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Affiliation(s)
- Brandee M S S Goo
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, 651 Ilalo St., BSB 222, University of Hawaii, Honolulu, HI, 96813, USA
| | - Bethany J Sanstrum
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, 651 Ilalo St., BSB 222, University of Hawaii, Honolulu, HI, 96813, USA
| | - Diana Z Y Holden
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, 651 Ilalo St., BSB 222, University of Hawaii, Honolulu, HI, 96813, USA
| | | | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, 651 Ilalo St., BSB 222, University of Hawaii, Honolulu, HI, 96813, USA.
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7
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Barylko B, Wilkerson JR, Cavalier SH, Binns DD, James NG, Jameson DM, Huber KM, Albanesi JP. Palmitoylation and Membrane Binding of Arc/Arg3.1: A Potential Role in Synaptic Depression. Biochemistry 2017; 57:520-524. [PMID: 29264923 PMCID: PMC10370338 DOI: 10.1021/acs.biochem.7b00959] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Activity-regulated cytoskeletal-associated protein (Arc, also known as activity-regulated gene 3.1 or Arg3.1) is induced in neurons in response to salient experience and neural activity and is necessary for activity-induced forms of synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD), cellular substrates of learning and memory. The best-characterized function of Arc is enhancement of the endocytic internalization of AMPA receptors in dendritic spines, a process associated with LTD. Arc has also been implicated in the proteolytic processing of amyloid precursor protein on the surface of endosomes. To mediate these activities, Arc must associate with cellular membranes, but it is unclear whether Arc binds directly to the lipid bilayer or requires protein-protein interactions for membrane recruitment. In this study, we show that Arc associates with pure phospholipid vesicles in vitro and undergoes palmitoylation in neurons, a modification that allows it to insert directly into the hydrophobic core of the bilayer. The palmitoylated cysteines are clustered in a motif, 94CLCRC98, located in the N-terminal half of the protein, which has not yet been structurally characterized. Expression of Arc with three mutated cysteines in that motif cannot support synaptic depression induced by the activity-dependent transcription factor, MEF2 (myocyte enhancer factor 2), in contrast to wild-type Arc. Thus, it appears that palmitoylation regulates at least a subset of Arc functions in synaptic plasticity.
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Affiliation(s)
| | | | | | | | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii , Honolulu, Hawaii 96813, United States
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii , Honolulu, Hawaii 96813, United States
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8
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Nguyen H, James NG, Nguyen L, Nguyen TP, Vuong C, Ortega MA, Jameson DM, Ward WS. Higher Order Oligomerization of the Licensing ORC4 Protein Is Required for Polar Body Extrusion in Murine Meiosis. J Cell Biochem 2017; 118:2941-2949. [PMID: 28230328 DOI: 10.1002/jcb.25949] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 02/22/2017] [Indexed: 01/01/2023]
Abstract
We have previously shown that the DNA replication licensing factor ORC4 forms a cage around the chromosomes that are extruded in both polar bodies during murine oogenesis, but not around the chromosomes that are retained in the oocyte or around the sperm chromatin. We termed this structure the ORC4 cage. Here, we tested whether the formation of the ORC4 cage is necessary for polar body extrusion (PBE). We first experimentally forced oocytes to extrude sperm chromatin as a pseudo-polar body and found that under these conditions the sperm chromatin did become enclosed in an ORC4 cage. Next, we attempted to prevent the formation of the ORC4 cage by injecting peptides that contained sequences of different domains of the ORC4 protein into metaphase II (MII) oocytes just before the cage normally forms. Our rationale was that the ORC4 peptides would block protein-protein interactions required for cage formation. Two out of six tested peptides prevented the ORC4 cage formation and simultaneously inhibited PBE, resulting in the formation of two pronuclei (2 PN) that were retained in the oocyte. Together, these data demonstrate that ORC4 oligomerization is required to form the ORC4 cage and that it is required for PBE. J. Cell. Biochem. 118: 2941-2949, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Hieu Nguyen
- Department of Anatomy, Biochemistry and Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu
| | - Lynn Nguyen
- Department of Anatomy, Biochemistry and Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Thien P Nguyen
- Department of Anatomy, Biochemistry and Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Cindy Vuong
- Department of Anatomy, Biochemistry and Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Michael A Ortega
- University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, Hawaii
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu
| | - W Steven Ward
- Department of Anatomy, Biochemistry and Physiology, Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii.,Department of Obstetrics, Gynecology and Women's Health, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii
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9
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Jacky B, James NG, Jameson DM, Malik S, Broide RB, Brideau-Andersen A. Development of a receptor dimerization assay to study BoNT/A and FGFR interactions. Toxicon 2016. [DOI: 10.1016/j.toxicon.2016.11.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Berry MJ, Astern J, Bellinger F, Brampton C, Cann R, Gerschenson M, Haymer D, James NG, Jameson DM, LeSaux O, Hoffmann PR, Nichols R, Pitts M, Seale L, Seifried S, Stokes AJ, Todorovic C. Medical school hotline: the research mission of the cell and molecular biology department and program at the john a. Burns school of medicine. Hawaii J Med Public Health 2015; 74:150-3. [PMID: 25954603 PMCID: PMC4407459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Marla J Berry
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Joshua Astern
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Frederick Bellinger
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Christopher Brampton
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Rebecca Cann
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Mariana Gerschenson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - David Haymer
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Olivier LeSaux
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Peter R Hoffmann
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Robert Nichols
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Matthew Pitts
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Lucia Seale
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Steven Seifried
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Alexander J Stokes
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
| | - Cedomir Todorovic
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawai'i at Manoa, Honolulu HI
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11
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Byers CE, Barylko B, Ross JA, Southworth DR, James NG, Taylor CA, Wang L, Collins KA, Estrada A, Waung M, Tassin TC, Huber KM, Jameson DM, Albanesi JP. Enhancement of dynamin polymerization and GTPase activity by Arc/Arg3.1. Biochim Biophys Acta Gen Subj 2015; 1850:1310-8. [PMID: 25783003 DOI: 10.1016/j.bbagen.2015.03.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 02/17/2015] [Accepted: 03/09/2015] [Indexed: 01/28/2023]
Abstract
BACKGROUND The Activity-regulated cytoskeleton-associated protein, Arc, is an immediate-early gene product implicated in various forms of synaptic plasticity. Arc promotes endocytosis of AMPA type glutamate receptors and regulates cytoskeletal assembly in neuronal dendrites. Its role in endocytosis may be mediated by its reported interaction with dynamin 2, a 100 kDa GTPase that polymerizes around the necks of budding vesicles and catalyzes membrane scission. METHODS Enzymatic and turbidity assays are used in this study to monitor effects of Arc on dynamin activity and polymerization. Arc oligomerization is measured using a combination of approaches, including size exclusion chromatography, sedimentation analysis, dynamic light scattering, fluorescence correlation spectroscopy, and electron microscopy. RESULTS We present evidence that bacterially-expressed His6-Arc facilitates the polymerization of dynamin 2 and stimulates its GTPase activity under physiologic conditions (37°C and 100mM NaCl). At lower ionic strength Arc also stabilizes pre-formed dynamin 2 polymers against GTP-dependent disassembly, thereby prolonging assembly-dependent GTP hydrolysis catalyzed by dynamin 2. Arc also increases the GTPase activity of dynamin 3, an isoform of implicated in dendrite remodeling, but does not affect the activity of dynamin 1, a neuron-specific isoform involved in synaptic vesicle recycling. We further show in this study that Arc (either His6-tagged or untagged) has a tendency to form large soluble oligomers, which may function as a scaffold for dynamin assembly and activation. CONCLUSIONS AND GENERAL SIGNIFICANCE The ability of Arc to enhance dynamin polymerization and GTPase activation may provide a mechanism to explain Arc-mediated endocytosis of AMPA receptors and the accompanying effects on synaptic plasticity.
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Affiliation(s)
- Christopher E Byers
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Barbara Barylko
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Justin A Ross
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States
| | - Daniel R Southworth
- Department of Chemistry and Chemical Biology, University of California, San Francisco, CA 94158, United States
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States
| | - Clinton A Taylor
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Lei Wang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Katie A Collins
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Armando Estrada
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Maggie Waung
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Tara C Tassin
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Kimberly M Huber
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States
| | - Joseph P Albanesi
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
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12
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Montecinos-Franjola F, James NG, Concha-Marambio L, Brunet JE, Lagos R, Monasterio O, Jameson DM. Single tryptophan mutants of FtsZ: nucleotide binding/exchange and conformational transitions. Biochim Biophys Acta 2014; 1844:1193-200. [PMID: 24704635 DOI: 10.1016/j.bbapap.2014.03.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 03/24/2014] [Accepted: 03/26/2014] [Indexed: 11/27/2022]
Abstract
Cell division protein FtsZ cooperatively self-assembles into straight filaments when bound to GTP. A set of conformational changes that are linked to FtsZ GTPase activity are involved in the transition from straight to curved filaments that eventually disassemble. In this work, we characterized the fluorescence of single Trp mutants as a reporter of the predicted conformational changes between the GDP- and GTP-states of Escherichia coli FtsZ. Steady-state fluorescence characterization showed the Trp senses different environments and displays low solvent accessibility. Time-resolved fluorescence data indicated that the main conformational changes in FtsZ occur at the interaction surface between the N and C domains, but also minor rearrangements were detected in the bulk of the N domain. Surprisingly, despite its location near the bottom protofilament interface at the C domain, the Trp 275 fluorescence lifetime did not report changes between the GDP and GTP states. The equilibrium unfolding of FtsZ features an intermediate that is stabilized by the nucleotide bound in the N-domain as well as by quaternary protein-protein interactions. In this context, we characterized the unfolding of the Trp mutants using time-resolved fluorescence and phasor plot analysis. A novel picture of the structural transition from the native state in the absence of denaturant, to the solvent-exposed unfolded state is presented. Taken together our results show that conformational changes between the GDP and GTP states of FtsZ, such as those observed in FtsZ unfolding, are restricted to the interaction surface between the N and C domains.
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Affiliation(s)
- Felipe Montecinos-Franjola
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu 96813, HI, USA.
| | - Luis Concha-Marambio
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Juan E Brunet
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso 2373223, Chile.
| | - Rosalba Lagos
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Octavio Monasterio
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu 96813, HI, USA.
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13
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Abstract
Fluorescence methods are often employed for the characterization of molecular interactions. In particular, polarization/anisotropy studies are widely utilized in the life sciences as they allow quantification of protein interactions in the micro- and nanomolar concentration range. Herein we shall briefly describe the theoretical aspects of polarization/anisotropy and outline an experiment for determination of the dissociation constant for a protein-ligand complex.
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Affiliation(s)
- Nicholas G James
- Department Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
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14
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James NG, Digman MA, Ross JA, Barylko B, Wang L, Li J, Chen Y, Mueller JD, Gratton E, Albanesi JP, Jameson DM. A mutation associated with centronuclear myopathy enhances the size and stability of dynamin 2 complexes in cells. Biochim Biophys Acta Gen Subj 2013; 1840:315-21. [PMID: 24016602 DOI: 10.1016/j.bbagen.2013.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/31/2013] [Accepted: 09/03/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Dynamin 2 (Dyn2) is a ~100kDa GTPase that assembles around the necks of nascent endocytic and Golgi vesicles and catalyzes membrane scission. Mutations in Dyn2 that cause centronuclear myopathy (CNM) have been shown to stabilize Dyn2 polymers against GTP-dependent disassembly in vitro. Precisely timed regulation of assembly and disassembly is believed to be critical for Dyn2 function in membrane vesiculation, and the CNM mutations interfere with this regulation by shifting the equilibrium toward the assembled state. METHODS In this study we use two fluorescence fluctuation spectroscopy (FFS) approaches to show that a CNM mutant form of Dyn2 also has a greater propensity to self-assemble in the cytosol and on the plasma membrane of living cells. RESULTS Results obtained using brightness analysis indicate that unassembled wild-type Dyn2 is predominantly tetrameric in the cytosol, although different oligomeric species are observed, depending on the concentration of expressed protein. In contrast, an R369W mutant identified in CNM patients forms higher-order oligomers at concentrations above 1μM. Investigation of Dyn2-R369W by Total Internal Reflection Fluorescence (TIRF) FFS reveals that this mutant forms larger and more stable clathrin-containing structures on the plasma membrane than wild-type Dyn2. CONCLUSIONS AND GENERAL SIGNIFICANCE These observations may explain defects in membrane trafficking reported in CNM patient cells and in heterologous systems expressing CNM-associated Dyn2 mutants.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, HI 96813, USA
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15
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Jameson DM, Vetromile CM, James NG. Investigations of protein–protein interactions using time-resolved fluorescence and phasors. Methods 2013; 59:278-86. [DOI: 10.1016/j.ymeth.2013.01.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 01/10/2013] [Accepted: 01/11/2013] [Indexed: 11/28/2022] Open
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Abstract
Communication between cells and their environment, including other cells, is often mediated by cell surface receptors. Fluorescence methodologies are among the most important techniques used to study receptors and their interactions, and in the past decade, fluorescence fluctuation spectroscopy (FFS) approaches have been increasingly utilized. In this overview, we illustrate how diverse FFS approaches have been used to elucidate important aspects of receptor systems, including interactions of receptors with their ligands and receptor oligomerization and clustering. We also describe the most popular methods used to introduce fluorescent moieties into the biological systems. Finally, specific attention will be given to cell maintenance and transfection strategies especially as related to microscopy studies.
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Affiliation(s)
- David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
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17
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Garay PE, James NG, Ross JA, Jameson DM, Aoki KR, Fernández-Salas E. BoNT/A Trafficking with FGFR3 in Neuronal Cell Lines Studied with Cross-Correlation RICS. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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18
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James NG, Digman MA, Ross JA, Barylko B, Wang L, Chen Y, Müller JD, Gratton E, Albanesi JP, Jameson DM. Mutations Associated with Centronuclear Myopathy (CNM) Enhance the Size and Stability of Dynamin 2 Clusters in Cells. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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19
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James NG, Digman MA, Gratton E, Barylko B, Ding X, Albanesi JP, Goldberg MS, Jameson DM. Number and brightness analysis of LRRK2 oligomerization in live cells. Biophys J 2012; 102:L41-3. [PMID: 22713584 DOI: 10.1016/j.bpj.2012.04.046] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 04/16/2012] [Accepted: 04/24/2012] [Indexed: 10/28/2022] Open
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is a large multidomain protein that contains enzymatically functional GTPase and kinase domains. Several noncoding LRRK2 gene polymorphisms have been associated with susceptibility to Parkinson's disease (PD), Crohn's disease, and leprosy. Many LRRK2 coding polymorphisms have been associated with or causally linked to PD. The G2019S point mutation within the LRRK2 kinase domain is the most common cause of familial PD. The G2019S mutation appears to alter LRRK2 kinase activity. Some but not all studies have reported that LRRK2 kinase activity is dependent upon LRRK2 dimerization and membrane localization. It is important to define the oligomeric state(s) of LRRK2 in living cells, which to date have only been characterized in vitro. Here we use confocal and total internal reflection microscopy coupled with number and brightness analysis to study the oligomeric states of LRRK2 within the cytosol and on the plasma membrane of live CHO-K1 cells. Our results show, for the first time to our knowledge, that LRRK2 is predominantly monomeric throughout the cytosol of living cells, but attains predominately higher oligomeric states in the plasma membrane.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii, USA
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20
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Decarreau JA, James NG, Chrin LR, Berger CL. Switch I closure simultaneously promotes strong binding to actin and ADP in smooth muscle myosin. J Biol Chem 2011; 286:22300-7. [PMID: 21536675 DOI: 10.1074/jbc.m111.219014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The motor protein myosin uses energy derived from ATP hydrolysis to produce force and motion. Important conserved components (P-loop, switch I, and switch II) help propagate small conformational changes at the active site into large scale conformational changes in distal regions of the protein. Structural and biochemical studies have indicated that switch I may be directly responsible for the reciprocal opening and closing of the actin and nucleotide-binding pockets during the ATPase cycle, thereby aiding in the coordination of these important substrate-binding sites. Smooth muscle myosin has displayed the ability to simultaneously bind tightly to both actin and ADP, although it is unclear how both substrate-binding clefts could be closed if they are rigidly coupled to switch I. Here we use single tryptophan mutants of smooth muscle myosin to determine how conformational changes in switch I are correlated with structural changes in the nucleotide and actin-binding clefts in the presence of actin and ADP. Our results suggest that a closed switch I conformation in the strongly bound actomyosin-ADP complex is responsible for maintaining tight nucleotide binding despite an open nucleotide-binding pocket. This unique state is likely to be crucial for prolonged tension maintenance in smooth muscle.
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Affiliation(s)
- Justin A Decarreau
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, Vermont 05405, USA
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21
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Štefl M, James NG, Ross JA, Jameson DM. Applications of phasors to in vitro time-resolved fluorescence measurements. Anal Biochem 2011; 410:62-9. [PMID: 21078290 PMCID: PMC3065364 DOI: 10.1016/j.ab.2010.11.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/05/2010] [Accepted: 11/07/2010] [Indexed: 11/28/2022]
Abstract
The phasor method of treating fluorescence lifetime data provides a facile and convenient approach to characterize lifetime heterogeneity and to detect the presence of excited state reactions such as solvent relaxation and Förster resonance energy transfer. The method uses a plot of M sin(Φ) versus M cos(Φ), where M is the modulation ratio and Φ is the phase angle taken from frequency domain fluorometry. A principal advantage of the phasor method is that it provides a model-less approach to time-resolved data amenable to visual inspection. Although the phasor approach has been recently applied to fluorescence lifetime imaging microscopy, it has not been used extensively for cuvette studies. In the current study, we explore the applications of the method to in vitro samples. The phasors of binary and ternary mixtures of fluorescent dyes demonstrate the utility of the method for investigating complex mixtures. Data from excited state reactions, such as dipolar relaxation in membrane and protein systems and also energy transfer from the tryptophan residue to the chromophore in enhanced green fluorescent protein, are also presented.
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Affiliation(s)
- Martin Štefl
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Department of Biophysical Chemistry, Dolejškova 3, Prague 18223, Czech Republic
| | - Nicholas G. James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
| | - Justin A. Ross
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
| | - David M. Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
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22
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James NG, Ross JA, Stefl M, Jameson DM. Applications of phasor plots to in vitro protein studies. Anal Biochem 2010; 410:70-6. [PMID: 21078289 DOI: 10.1016/j.ab.2010.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/05/2010] [Accepted: 11/07/2010] [Indexed: 10/18/2022]
Abstract
In a recent article, we described the application of phasor analysis to fluorescence intensity decay data on in vitro samples. As detailed in that article, this method provides researchers with a simple graphical method for viewing lifetime data that can be used to quantify individual components of a mixture as well as to identify excited state reactions. In the current article, we extend the use of in vitro phasor analysis to intrinsic protein fluorescence. We show how alterations in the excited state properties of tryptophan residues are easily visualized using the phasor method. Specifically, we demonstrate that protein-ligand and protein-protein interactions can result in unique shifts in the location of phasor points, indicative of protein conformational changes. Application of the method to a rapid kinetic experiment is also shown. Finally, we show that the unfolding of lysozyme with either urea or guanidine hydrochloride results in different phasor trajectories, indicative of unique denaturation pathways.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA
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23
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James NG, Ross JA, Mason AB, Jameson DM. Excited-state lifetime studies of the three tryptophan residues in the N-lobe of human serum transferrin. Protein Sci 2010; 19:99-110. [PMID: 19916167 DOI: 10.1002/pro.287] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The energy transfer from the three Trp residues at positions 8, 128, and 264 within the human serum transferrin (hTF) N-lobe to the ligand to metal charge transfer band has been investigated by monitoring changes in Trp fluorescence emission and lifetimes. The fluorescence emission from hTF N-lobe is dominated by Trp264, as revealed by an 82% decrease in the quantum yield when this Trp residue is absent. Fluorescence lifetimes were determined by multifrequency phase fluorometry of mutants containing one or two Trp residues. Decays of these samples are best described by two or three discrete lifetimes or by a unimodal Lorentzian distribution. The discrete lifetimes and the center of the lifetime distribution for samples containing Trp128 and Trp264 are affected by iron. The distribution width narrows on iron removal and is consistent with a decrease in dynamic mobility of the dominant fluorophore, Trp264. Both the quantum yield and the lifetimes are lower when iron is present, however, not proportionally. The greater effect of iron on quantum yields is indicative of nonexcited state quenching, i.e., static quenching. The results of these experiments provide quantitative data strongly suggesting that Förster resonance energy transfer is not the sole source of Trp quenching in the N-lobe of hTF.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, USA.
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24
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James NG, Štefl M, Ross JA, Jameson DM. Application of Phasor Plots to Analysis of Fluorophore Heterogeneity, Excited State Reactions and Protein Conformations. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.4108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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25
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James NG, Byrne SL, Steere AN, Smith VC, MacGillivray RTA, Mason AB. Inequivalent contribution of the five tryptophan residues in the C-lobe of human serum transferrin to the fluorescence increase when iron is released. Biochemistry 2009; 48:2858-67. [PMID: 19281173 DOI: 10.1021/bi8022834] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human serum transferrin (hTF), with two Fe3+ binding lobes, transports iron into cells. Diferric hTF preferentially binds to a specific receptor (TFR) on the surface of cells, and the complex undergoes clathrin dependent receptor-mediated endocytosis. The clathrin-coated vesicle fuses with an endosome where the pH is lowered, facilitating iron release from hTF. On a biologically relevant time scale (2-3 min), the factors critical to iron release include pH, anions, a chelator, and the interaction of hTF with the TFR. Previous work, in which the increase in the intrinsic fluorescence signal was used to monitor iron release from the hTF/TFR complex, established that the TFR significantly enhances the rate of iron release from the C-lobe of hTF. In the current study, the role of the five C-lobe Trp residues in reporting the fluorescence change has been evaluated (+/-sTFR). Only four of the five recombinant Trp --> Phe mutants produced well. A single slow rate constant for iron release is found for the monoferric C-lobe (FeC hTF) and the four Trp mutants in the FeC hTF background. The three Trp residues equivalent to those in the N-lobe differed from the N-lobe and each other in their contributions to the fluorescent signal. Two rate constants are observed for the FeC hTF control and the four Trp mutants in complex with the TFR: k(obsC1) reports conformational changes in the C-lobe initiated by the TFR, and k(obsC2) is ascribed to iron release. Excitation at 295 nm (Trp only) and at 280 nm (Trp and Tyr) reveals interesting and significant differences in the rate constants for the complex.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington 05405, Vermont, USA
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James NG, Byrne SL, Mason AB. Incorporation of 5-hydroxytryptophan into transferrin and its receptor allows assignment of the pH induced changes in intrinsic fluorescence when iron is released. Biochim Biophys Acta 2008; 1794:532-40. [PMID: 19103311 DOI: 10.1016/j.bbapap.2008.11.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 11/11/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
Human serum transferrin (hTF) is a bilobal glycoprotein that transports iron to cells. At neutral pH, diferric hTF binds with nM affinity to the transferrin receptor (TFR) on the cell surface. The complex is taken into the cell where, at the acidic pH of the endosome ( approximately pH 5.6), iron is released. Since iron coordination strongly quenches the intrinsic tryptophan fluorescence of hTF, the increase in the fluorescent signal reports the rate constant(s) of iron release. At pH 5.6, the TFR considerably enhances iron release from the C-lobe (with little effect on iron release from the N-lobe). The recombinant soluble TFR is a dimer with 11 tryptophan residues per monomer. In the hTF/TFR complex these residues could contribute to and compromise the readout ascribed to iron release from hTF. We report that compared to Fe(C) hTF alone, the increase in the fluorescent signal from the preformed complex of Fe(C) hTF and the TFR at pH 5.6 is significantly quenched (75%). To dissect the contributions of hTF and the TFR to the change in fluorescence, 5-hydroxytryptophan was incorporated into each using our mammalian expression system. Selective excitation of the samples at 280 or 315 nm shows that the TFR contributes little or nothing to the increase in fluorescence when ferric iron is released from Fe(C) hTF. Quantum yield determinations of TFR, Fe(C) hTF and the Fe(C) hTF/TFR complex strongly support our interpretation of the kinetic data.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
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James NG, Mason AB. Corrigendum to “Protocol to determine accurate absorption coefficients for iron containing transferrins” [Anal. Biochem. 378 (2008) 202–207]. Anal Biochem 2008. [DOI: 10.1016/j.ab.2008.08.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Mason AB, Judson GL, Bravo MC, Edelstein A, Byrne SL, James NG, Roush ED, Fierke CA, Bobst CE, Kaltashov IA, Daughtery MA. Evolution reversed: the ability to bind iron restored to the N-lobe of the murine inhibitor of carbonic anhydrase by strategic mutagenesis. Biochemistry 2008; 47:9847-55. [PMID: 18712936 DOI: 10.1021/bi801133d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The murine inhibitor of carbonic anhydrase (mICA) is a member of the superfamily related to the bilobal iron transport protein transferrin (TF), which binds a ferric ion within a cleft in each lobe. Although the gene encoding ICA in humans is classified as a pseudogene, an apparently functional ICA gene has been annotated in mice, rats, cows, pigs, and dogs. All ICAs lack one (or more) of the amino acid ligands in each lobe essential for high-affinity coordination of iron and the requisite synergistic anion, carbonate. The reason why ICA family members have lost the ability to bind iron is potentially related to acquiring a new function(s), one of which is inhibition of certain carbonic anhydrase (CA) isoforms. A recombinant mutant of the mICA (W124R/S188Y) was created with the goal of restoring the ligands required for both anion (Arg124) and iron (Tyr188) binding in the N-lobe. Absorption and fluorescence spectra definitively show that the mutant binds ferric iron in the N-lobe. Electrospray ionization mass spectrometry confirms the presence of both ferric iron and carbonate. At the putative endosomal pH of 5.6, iron is released by two slow processes indicative of high-affinity coordination. Induction of specific iron binding implies that (1) the structure of mICA resembles those of other TF family members and (2) the N-lobe can adopt a conformation in which the cleft closes when iron binds. Because the conformational change in the N-lobe indicated by metal binding does not impact the inhibitory activity of mICA, inhibition of CA was tentatively assigned to the C-lobe. Proof of this assignment is provided by limited trypsin proteolysis of porcine ICA.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA.
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James NG, Mason AB. Protocol to determine accurate absorption coefficients for iron-containing transferrins. Anal Biochem 2008; 378:202-7. [PMID: 18471984 DOI: 10.1016/j.ab.2008.04.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 04/03/2008] [Accepted: 04/06/2008] [Indexed: 11/19/2022]
Abstract
An accurate protein concentration is an essential component of most biochemical experiments. The simplest method to determine a protein concentration is by measuring the A(280) using an absorption coefficient (epsilon) and applying the Beer-Lambert law. For some metalloproteins (including all transferrin family members), difficulties arise because metal binding contributes to the A(280) in a nonlinear manner. The Edelhoch method is based on the assumption that the epsilon of a denatured protein in 6 M guanidine-HCl can be calculated from the number of the tryptophan, tyrosine, and cystine residues. We extend this method to derive epsilon values for both apo- and iron-bound transferrins. The absorbance of an identical amount of iron-containing protein is measured in (i) 6 M guanidine-HCl (denatured, no iron), (ii) pH 7.4 buffer (nondenatured with iron), and (iii) pH 5.6 (or lower) buffer with a chelator (nondenatured without iron). Because the iron-free apoprotein has an identical A(280) under nondenaturing conditions, the difference between the reading at pH 7.4 and the lower pH directly reports the contribution of the iron. The method is fast and consumes approximately 1mg of sample. The ability to determine accurate epsilon values for transferrin mutants that bind iron with a wide range of affinities has proven to be very useful; furthermore, a similar approach could easily be followed to determine epsilon values for other metalloproteins in which metal binding contributes to the A(280).
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, College of Medicine, University of Vermont, Burlington, VT 05405, USA
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James NG, Berger CL, Byrne SL, Smith VC, MacGillivray RTA, Mason AB. Intrinsic Fluorescence Reports a Global Conformational Change in the N-Lobe of Human Serum Transferrin following Iron Release†. Biochemistry 2007; 46:10603-11. [PMID: 17711300 DOI: 10.1021/bi602425c] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transferrins have been extensively studied in order to understand how they reversibly bind and release iron. Human serum transferrin (hTF) is a single polypeptide chain that folds into two lobes (N- and C-lobe); each lobe binds a single ferric ion. Iron release induces a large conformational change in each lobe. At the putative endosomal pH of 5.6, measurement of the increase in intrinsic fluorescence upon iron release from the recombinant N-lobe yields two rate constants: 8.9 min-1 and 1.3 min-1. Direct monitoring of iron release from the N-lobe at pH 5.6 (by the decrease in absorbance at 470 nm) gives a single rate constant of 9.1 min-1, definitively establishing that the faster rate constant in the fluorescent studies is due to iron release. To further elucidate the molecular basis of the intrinsic fluorescence change (and the source of the slower rate constant), we examined the contributions of the three individual tryptophan residues in the N-lobe (Trp8, Trp128, and Trp264). Three double mutants, each containing the single remaining tryptophan residue, were produced. In the iron-bound N-lobe, Trp128 and Trp264 are quenched by iron and account for almost the entire fluorescent signal when iron is released. As for the wild-type N-lobe, the fluorescence increase for each of these mutants is best fit by a double-exponential function indicating two processes. Trp8 is severely quenched under all conditions, making virtually no contribution to the signal. Additionally, a mutant lacking all three Trp residues allows assignment of the fluorescent signal completely to the three tryptophan residues and observation of the presence of one (or more) tyrosinates in the N-lobe that have physiological significance in the uptake of iron.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, University of Vermont, Burlington, Vermont 05405, USA
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Mason AB, Halbrooks PJ, James NG, Connolly SA, Larouche JR, Smith VC, MacGillivray RTA, Chasteen ND. Mutational analysis of C-lobe ligands of human serum transferrin: insights into the mechanism of iron release. Biochemistry 2005; 44:8013-21. [PMID: 15924420 DOI: 10.1021/bi050015f] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Each homologous lobe of human serum transferrin (hTF) has one Fe(3+) ion bound by an aspartic acid, a histidine, two tyrosine residues, and two oxygens from the synergistic anion, carbonate. Extensive characterization of these ligands in the N-terminal lobe has been carried out. Despite sharing the same set of ligands, there is a substantial amount of evidence that the N- and C-lobes are inequivalent. Studies of full-length hTF have shown that iron release from each lobe is kinetically distinguishable. To simplify the assessment of mutations in the C-lobe, we have created mutant hTF molecules in which the N-lobe binds iron with high affinity or not at all. Mutations targeting the C-lobe liganding residues have been introduced into these hTF constructs. UV-visible spectral, kinetic, and EPR studies have been undertaken to assess the effects of each mutation and to allow direct comparison to the N-lobe. As found for the N-lobe, the presence of Y517 in the C-lobe (equivalent to Y188 in the N-lobe) is absolutely essential for the binding of iron. Unlike the N-lobe, however, mutation of Y426 (equivalent to Y95) does not produce a stable complex with iron. For the mutants that retain the ability to bind iron (D392S and H585A), the rates of release are considerably slower than those measured for equivalent mutations in the N-lobe at both pH 7.4 and pH 5.6. Equilibrium binding experiments with HeLa S(3) cells indicate that recombinant hTF, in which Y426 or H585 is mutated, favor a closed or nearly closed conformation while those with mutations of the D392 or Y517 ligands appear to promote an open conformation. The differences in the effects of mutating the liganding residues in the two lobes and the subtle indications of cooperativity between lobes point to the importance of the transferrin receptor in effecting iron release from the C-lobe. Significantly, the equilibrium binding experiments also indicate that, regardless of which lobe contains the iron, the free energy of binding is equivalent and not additive; each monoferric hTF has a free energy of binding that is 82% of diferric hTF.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA.
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