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Rupawala H, Shah K, Davies C, Rose J, Colom-Cadena M, Peng X, Granat L, Aljuhani M, Mizuno K, Troakes C, Perez-Nievas BG, Morgan A, So PW, Hortobagyi T, Spires-Jones TL, Noble W, Giese KP. Cysteine string protein alpha accumulates with early pre-synaptic dysfunction in Alzheimer’s disease. Brain Commun 2022; 4:fcac192. [PMID: 35928052 PMCID: PMC9345313 DOI: 10.1093/braincomms/fcac192] [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: 11/10/2021] [Revised: 05/12/2022] [Accepted: 07/20/2022] [Indexed: 11/17/2022] Open
Abstract
In Alzheimer’s disease, synapse loss causes memory and cognitive impairment. However, the mechanisms underlying synaptic degeneration in Alzheimer’s disease are not well understood. In the hippocampus, alterations in the level of cysteine string protein alpha, a molecular co-chaperone at the pre-synaptic terminal, occur prior to reductions in synaptophysin, suggesting that it is a very sensitive marker of synapse degeneration in Alzheimer’s. Here, we identify putative extracellular accumulations of cysteine string alpha protein, which are proximal to beta-amyloid deposits in post-mortem human Alzheimer’s brain and in the brain of a transgenic mouse model of Alzheimer’s disease. Cysteine string protein alpha, at least some of which is phosphorylated at serine 10, accumulates near the core of beta-amyloid deposits and does not co-localize with hyperphosphorylated tau, dystrophic neurites or glial cells. Using super-resolution microscopy and array tomography, cysteine string protein alpha was found to accumulate to a greater extent than other pre-synaptic proteins and at a comparatively great distance from the plaque core. This indicates that cysteine string protein alpha is most sensitive to being released from pre-synapses at low concentrations of beta-amyloid oligomers. Cysteine string protein alpha accumulations were also evident in other neurodegenerative diseases, including some fronto-temporal lobar dementias and Lewy body diseases, but only in the presence of amyloid plaques. Our findings are consistent with suggestions that pre-synapses are affected early in Alzheimer’s disease, and they demonstrate that cysteine string protein alpha is a more sensitive marker for early pre-synaptic dysfunction than traditional synaptic markers. We suggest that cysteine string protein alpha should be used as a pathological marker for early synaptic disruption caused by beta-amyloid.
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Affiliation(s)
- Huzefa Rupawala
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Keshvi Shah
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Caitlin Davies
- Centre for Discovery Brain Sciences and the UK Dementia Research Institute, The University of Edinburgh , 1 George Square, Edinburgh EH8 9JZ , UK
| | - Jamie Rose
- Centre for Discovery Brain Sciences and the UK Dementia Research Institute, The University of Edinburgh , 1 George Square, Edinburgh EH8 9JZ , UK
| | - Marti Colom-Cadena
- Centre for Discovery Brain Sciences and the UK Dementia Research Institute, The University of Edinburgh , 1 George Square, Edinburgh EH8 9JZ , UK
| | - Xianhui Peng
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Lucy Granat
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Manal Aljuhani
- Department of Neuroimaging, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Keiko Mizuno
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Claire Troakes
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Beatriz Gomez Perez-Nievas
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool , Liverpool L69 3BX , UK
| | - Po-Wah So
- Department of Neuroimaging, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Tibor Hortobagyi
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
- Department of Neurology, ELKH-DE Cerebrovascular and Neurodegenerative Research Group, University of Debrecen , 4032 Debrecen , Hungary
| | - Tara L Spires-Jones
- Centre for Discovery Brain Sciences and the UK Dementia Research Institute, The University of Edinburgh , 1 George Square, Edinburgh EH8 9JZ , UK
| | - Wendy Noble
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
| | - Karl Peter Giese
- Department of Basic and Clinical Neuroscience, King’s College London, Institute of Psychiatry, Psychology and Neuroscience , 5 Cutcombe Road, London SE5 9RX , UK
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Gundersen CB. Cysteine string proteins. Prog Neurobiol 2020; 188:101758. [DOI: 10.1016/j.pneurobio.2020.101758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 01/06/2020] [Accepted: 01/13/2020] [Indexed: 12/17/2022]
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The Role of Cysteine String Protein α Phosphorylation at Serine 10 and 34 by Protein Kinase Cγ for Presynaptic Maintenance. J Neurosci 2017; 38:278-290. [PMID: 29167402 DOI: 10.1523/jneurosci.1649-17.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 10/23/2017] [Accepted: 11/12/2017] [Indexed: 01/05/2023] Open
Abstract
Protein kinase Cγ (PKCγ) knock-out (KO) animals exhibit symptoms of Parkinson's disease (PD), including dopaminergic neuronal loss in the substantia nigra. However, the PKCγ substrates responsible for the survival of dopaminergic neurons in vivo have not yet been elucidated. Previously, we found 10 potent substrates in the striatum of PKCγ-KO mice. Here, we focused on cysteine string protein α (CSPα), a protein from the heat shock protein (HSP) 40 cochaperone families localized on synaptic vesicles. We found that in cultured cells, PKCγ phosphorylates CSPα at serine (Ser) 10 and Ser34. Additionally, apoptosis was found to have been enhanced by the overexpression of a phosphorylation-null mutant of CSPα, CSPα(S10A/S34A). Compared with wild-type (WT) CSPα, the CSPα(S10A/S34A) mutant had a weaker interaction with HSP70. However, in sharp contrast, a phosphomimetic CSPα(S10D/S34D) mutant, compared with WT CSPα, had a stronger interaction with HSP70. In addition, total levels of synaptosomal-associated protein (SNAP) 25, a main downstream target of the HSC70/HSP70 chaperone complex, were found to have decreased by the CSPα(S10A/S34A) mutant through increased ubiquitination of SNAP25 in PC12 cells. In the striatum of 2-year-old male PKCγ-KO mice, decreased phosphorylation levels of CSPα and decreased SNAP25 protein levels were observed. These findings indicate the phosphorylation of CSPα by PKCγ may protect the presynaptic terminal from neurodegeneration. The PKCγ-CSPα-HSC70/HSP70-SNAP25 axis, because of its role in protecting the presynaptic terminal, may provide a new therapeutic target for the treatment of PD.SIGNIFICANCE STATEMENT Cysteine string protein α (CSPα) is a protein belonging to the heat shock protein (HSP) 40 cochaperone families localized on synaptic vesicles, which maintain the presynaptic terminal. However, the function of CSPα phosphorylation by protein kinase C (PKC) for neuronal cell survival remains unclear. The experiments presented here demonstrate that PKCγ phosphorylates CSPα at serine (Ser) 10 and Ser34. CSPα phosphorylation at Ser10 and Ser34 by PKCγ protects the presynaptic terminal by promoting HSP70 chaperone activity. This report suggests that CSPα phosphorylation, because of its role in modulating HSP70 chaperone activity, may be a target for the treatment of neurodegeneration.
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Patel P, Prescott GR, Burgoyne RD, Lian LY, Morgan A. Phosphorylation of Cysteine String Protein Triggers a Major Conformational Switch. Structure 2016; 24:1380-1386. [PMID: 27452402 PMCID: PMC4975591 DOI: 10.1016/j.str.2016.06.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/17/2016] [Accepted: 06/02/2016] [Indexed: 12/11/2022]
Abstract
Cysteine string protein (CSP) is a member of the DnaJ/Hsp40 chaperone family that localizes to neuronal synaptic vesicles. Impaired CSP function leads to neurodegeneration in humans and model organisms as a result of misfolding of client proteins involved in neurotransmission. Mammalian CSP is phosphorylated in vivo on Ser10, and this modulates its protein interactions and effects on neurotransmitter release. However, there are no data on the structural consequences of CSP phosphorylation to explain these functional effects. We show that Ser10 phosphorylation causes an order-to-disorder transition that disrupts CSP's extreme N-terminal α helix. This triggers the concomitant formation of a hairpin loop stabilized by ionic interactions between phosphoSer10 and the highly conserved J-domain residue, Lys58. These phosphorylation-induced effects result in significant changes to CSP conformation and surface charge distribution. The phospho-switch revealed here provides structural insight into how Ser10 phosphorylation modulates CSP function and also has potential implications for other DnaJ phosphoproteins. First structure of a phosphorylated DnaJ/Hsp40 protein Phosphorylation destabilizes CSP's N-terminal α helix Newly disordered, phosphorylated N-terminal loop binds to the J domain Phosphorylation causes significant changes to CSP conformation and surface charge
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Affiliation(s)
- Pryank Patel
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK; NMR Centre for Structural Biology, Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 3BX, UK; Department of Biological and Environmental Sciences, University of Hertfordshire, Hatfield AL10 9AB, UK
| | - Gerald R Prescott
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
| | - Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
| | - Lu-Yun Lian
- NMR Centre for Structural Biology, Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
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Burgoyne RD, Morgan A. Cysteine string protein (CSP) and its role in preventing neurodegeneration. Semin Cell Dev Biol 2015; 40:153-9. [PMID: 25800794 PMCID: PMC4447612 DOI: 10.1016/j.semcdb.2015.03.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 03/16/2015] [Indexed: 11/25/2022]
Abstract
Cysteine string protein (CSP) is a member of the DnaJ/Hsp40 family of co-chaperones that localises to neuronal synaptic vesicles. Its name derives from the possession of a string of 12–15 cysteine residues, palmitoylation of which is required for targeting to post-Golgi membranes. The DnaJ domain of CSP enables it to bind client proteins and recruit Hsc70 chaperones, thereby contributing to the maintenance of protein folding in the presynaptic compartment. Mutation of CSP in flies, worms and mice reduces lifespan and causes synaptic dysfunction and neurodegeneration. Furthermore, recent studies have revealed that the neurodegenerative disease, adult onset neuronal ceroid lipofuscinosis, is caused by mutations in the human CSPα-encoding DNAJC5 gene. Accumulating evidence suggests that the major mechanism by which CSP prevents neurodegeneration is by maintaining the conformation of SNAP-25, thereby facilitating its entry into the membrane-fusing SNARE complex. In this review, we focus on the role of CSP in preventing neurodegeneration and discuss how recent studies of this universal neuroprotective chaperone are being translated into potential novel therapeutics for neurodegenerative diseases.
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Affiliation(s)
- Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown St., Liverpool L69 3BX, UK
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown St., Liverpool L69 3BX, UK.
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Chiang N, Hsiao YT, Yang HJ, Lin YC, Lu JC, Wang CT. Phosphomimetic mutation of cysteine string protein-α increases the rate of regulated exocytosis by modulating fusion pore dynamics in PC12 cells. PLoS One 2014; 9:e99180. [PMID: 24956274 PMCID: PMC4067274 DOI: 10.1371/journal.pone.0099180] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 05/12/2014] [Indexed: 11/20/2022] Open
Abstract
Background Cysteine string protein-α (CSPα) is a chaperone to ensure protein folding. Loss of CSPα function associates with many neurological diseases. However, its function in modulating regulated exocytosis remains elusive. Although cspα-knockouts exhibit impaired synaptic transmission, overexpression of CSPα in neuroendocrine cells inhibits secretion. These seemingly conflicting results lead to a hypothesis that CSPα may undergo a modification that switches its function in regulating neurotransmitter and hormone secretion. Previous studies implied that CSPα undergoes phosphorylation at Ser10 that may influence exocytosis by altering fusion pore dynamics. However, direct evidence is missing up to date. Methodology/Principal Findings Using amperometry, we investigated how phosphorylation at Ser10 of CSPα (CSPα-Ser10) modulates regulated exocytosis and if this modulation involves regulating a specific kinetic step of fusion pore dynamics. The real-time exocytosis of single vesicles was detected in PC12 cells overexpressing control vector, wild-type CSPα (WT), the CSPα phosphodeficient mutant (S10A), or the CSPα phosphomimetic mutants (S10D and S10E). The shapes of amperometric signals were used to distinguish the full-fusion events (i.e., prespike feet followed by spikes) and the kiss-and-run events (i.e., square-shaped flickers). We found that the secretion rate was significantly increased in cells overexpressing S10D or S10E compared to WT or S10A. Further analysis showed that overexpression of S10D or S10E prolonged fusion pore lifetime compared to WT or S10A. The fraction of kiss-and-run events was significantly lower but the frequency of full-fusion events was higher in cells overexpressing S10D or S10E compared to WT or S10A. Advanced kinetic analysis suggests that overexpression of S10D or S10E may stabilize open fusion pores mainly by inhibiting them from closing. Conclusions/Significance CSPα may modulate fusion pore dynamics in a phosphorylation-dependent manner. Therefore, through changing its phosphorylated state influenced by diverse cellular signalings, CSPα may have a great capacity to modulate the rate of regulated exocytosis.
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Affiliation(s)
- Ning Chiang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
| | - Yu-Tien Hsiao
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Hui-Ju Yang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Yu-Chun Lin
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Juu-Chin Lu
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- * E-mail: (C-TW); (J-CL)
| | - Chih-Tien Wang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan
- * E-mail: (C-TW); (J-CL)
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7
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Abstract
Cysteine-string protein (CSP), a member of the DnaJ/Hsp40 family of cochaperones, is critical for maintaining neurotransmitter release and preventing neurodegeneration. CSP likely forms a chaperone complex on synaptic vesicles together with the 70-kDa heat shock cognate (Hsc70) and the small glutamine-rich tetratricopeptide repeat (TPR)-containing protein (SGT) that may control or protect the assembly and activity of SNARE proteins and various other protein substrates. Here, the author summarizes studies that elucidated CSP's neuroprotective role.
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Affiliation(s)
- Konrad E Zinsmaier
- Department of Neuroscience and Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721-0077, USA.
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Johnson JN, Ahrendt E, Braun JEA. CSPalpha: the neuroprotective J protein. Biochem Cell Biol 2010; 88:157-65. [PMID: 20453918 DOI: 10.1139/o09-124] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cysteine string protein (CSPalpha, also called DnaJC5) is unique among J proteins. Similar to other J proteins, CSPalpha interacts with and activates the ATPase of Hsc70s (heat shock proteins of 70 kDa), thereby harnessing the ATPase activity for conformational work on client proteins. In contrast to other J proteins, CSPalpha is anchored to synaptic vesicles, as well as to exocrine, endocrine and neuroendocrine secretory granules, and has been shown to have an essential anti-neurodegenerative role. CSPalpha-null organisms exhibit progressive neurodegeneration, behavioural deficits, and premature death, most likely due to the progressive misfolding of one or more client proteins. Here we highlight recent advances in our understanding of the critical role that CSPalpha plays in governing exocytotic secretory functions.
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Affiliation(s)
- Jadah N Johnson
- Department of Physiology and Pharmacology and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
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Prescott GR, Jenkins RE, Walsh CM, Morgan A. Phosphorylation of cysteine string protein on Serine 10 triggers 14-3-3 protein binding. Biochem Biophys Res Commun 2008; 377:809-14. [DOI: 10.1016/j.bbrc.2008.10.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 10/11/2008] [Indexed: 10/21/2022]
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10
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Liao L, McClatchy DB, Park SK, Xu T, Lu B, Yates JR. Quantitative analysis of brain nuclear phosphoproteins identifies developmentally regulated phosphorylation events. J Proteome Res 2008; 7:4743-55. [PMID: 18823140 DOI: 10.1021/pr8003198] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Protein phosphorylation is a globally adopted and tightly controlled post-translational modification, and represents one of the most important molecular switching mechanisms that govern the entire spectrum of biological processes. In the central nervous system, it has been demonstrated that phosphorylation of key proteins mediating chromatin remodeling and gene transcription plays an important role controlling brain development, synaptogenesis, learning and memory. Many studies have focused on large scale identification of phosphopeptides in brain tissue. These studies have identified phosphorylation site specific motifs useful for predicting protein kinase substrates. In this study, we applied a previously developed quantitative approach, stable isotope labeling of amino acids in mammals (SILAM), to quantify changes in the phosphorylation of nuclear proteins between a postnatal day one (p1) and a p45 rat brain cortex. Using a 15N labeled rat brain as an internal standard, we quantified 705 phosphopeptides in the p1 cortex and 1477 phosphopeptides in the p45 cortex, which translates to 380 and 585 phosphoproteins in p1 and p45 cortex, respectively. Bioinformatic analysis of the differentially modified phosphoproteins revealed that phosphorylation is upregulated on multiple components of chromatin remodeling complexes in the p1 cortex. Taken together, we demonstrated for the first time the usefulness of employing stable isotope labeled rat tissue for global quantitative phosphorylation analysis.
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Affiliation(s)
- Lujian Liao
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
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Bai L, Swayne LA, Braun JEA. The CSPα/G protein complex in PC12 cells. Biochem Biophys Res Commun 2007; 352:123-9. [PMID: 17113038 DOI: 10.1016/j.bbrc.2006.10.178] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 10/27/2006] [Indexed: 11/28/2022]
Abstract
Cysteine string proteinalpha (CSPalpha) is a regulated vesicle protein and molecular chaperone that has been found to be critical for continuous synaptic transmission and is implicated in the defense against neurodegeneration. Previous work has revealed links between CSPalpha and heterotrimeric GTP binding protein (G protein) signal transduction pathways. We have shown that CSPalpha is a guanine nucleotide exchange factor (GEF) for Galphas. In vitro Hsc70 (70 kDa heat shock cognate protein) and SGT (small glutamine-rich tetratricopeptide repeat domain protein) switch CSPalpha from an inactive GEF to an active GEF. Here we have examined the cellular distribution of the CSPalpha system in the PC12 neuroendocrine cell line. CSPalpha, an established secretory vesicle protein, was found to concentrate in the processes of NGF-differentiated PC12 cells as expected. Gbeta subunits co-localized and Galphas subunits partially co-localized with CSPalpha. However, under the conditions examined, the GEF activity of CSPalpha is expected to be inactive, in that Hsc70 was not found in PC12 processes. These results indicate that CSPalpha activity is subject to regulation by factors that alter Hsc70 distribution and translocation within the cell.
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Affiliation(s)
- Liping Bai
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, Alta., Canada T2N 4N1
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Beck KE, Kay JG, Braun JEA. Rdj2, a J protein family member, interacts with cellular prion PrP(C). Biochem Biophys Res Commun 2006; 346:866-71. [PMID: 16774738 DOI: 10.1016/j.bbrc.2006.05.185] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Accepted: 05/30/2006] [Indexed: 11/25/2022]
Abstract
PrP(C) is a glycosylphosphatidylinositol (GPI) anchored glycoprotein of unknown function. Misfolding of normal cellular PrP(C) to the pathogenic PrP(Sc) is the hallmark of prion diseases (transmissible spongiform encephalopathies). Prion diseases are characterized by extensive neurodegeneration and early death. Understanding how PrP(C) maintains its correct conformation is a major endeavor of current inquiry. Here we demonstrate a novel interaction between PrP(C) and the J protein family member, Rdj2 (DjA2; Dj3, Dnj3, Cpr3, and Hirip4). The importance of the J protein family in the cellular folding machinery has been recognized for many years. The PrP(C)/Rdj2 association was direct and concentration-dependent. Other J proteins such as CSPalpha and auxilin did not associate with PrP(C) in the absence of ATP, demonstrating the specificity of the PrP(C)/J protein interaction. These findings suggest that the J protein family serves as a 'folding catalyst' for PrP(C) and implicates Rdj2 as a factor in the protection against prion diseases.
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Affiliation(s)
- Katy E Beck
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, Alta., Canada T2N 4N1
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Evans GJO, Barclay JW, Prescott GR, Jo SR, Burgoyne RD, Birnbaum MJ, Morgan A. Protein kinase B/Akt is a novel cysteine string protein kinase that regulates exocytosis release kinetics and quantal size. J Biol Chem 2005; 281:1564-72. [PMID: 16243840 PMCID: PMC2423005 DOI: 10.1074/jbc.m503628200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase B/Akt has been implicated in the insulin-dependent exocytosis of GLUT4-containing vesicles, and, more recently, insulin secretion. To determine if Akt also regulates insulin-independent exocytosis, we used adrenal chromaffin cells, a popular neuronal model. Akt1 was the predominant isoform expressed in chromaffin cells, although lower levels of Akt2 and Akt3 were also found. Secretory stimuli in both intact and permeabilized cells induced Akt phosphorylation on serine 473, and the time course of Ca2+-induced Akt phosphorylation was similar to that of exocytosis in permeabilized cells. To determine if Akt modulated exocytosis, we transfected chromaffin cells with Akt constructs and monitored catecholamine release by amperometry. Wild-type Akt had no effect on the overall number of exocytotic events, but slowed the kinetics of catecholamine release from individual vesicles, resulting in an increased quantal size. This effect was due to phosphorylation by Akt, because it was not seen in cells transfected with kinase-dead mutant Akt. As overexpression of cysteine string protein (CSP) results in a similar alteration in release kinetics and quantal size, we determined if CSP was an Akt substrate. In vitro 32P-phosphorylation studies revealed that Akt phosphorylates CSP on serine 10. Using phospho-Ser10-specific antisera, we found that both transfected and endogenous cellular CSP is phosphorylated by Akt on this residue. Taken together, these findings reveal a novel role for Akt phosphorylation in regulating the late stages of exocytosis and suggest that this is achieved via the phosphorylation of CSP on serine 10.
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Affiliation(s)
- Gareth J. O. Evans
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - Jeff W. Barclay
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - Gerald R. Prescott
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - Sung-Ro Jo
- Howard Hughes Medical Institute, The Cox Institute, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Robert D. Burgoyne
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - Morris J. Birnbaum
- Howard Hughes Medical Institute, The Cox Institute, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Alan Morgan
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, L69 3BX, UK
- Corresponding author: Tel: 0151 794 5333, Fax: 0151 794 5337,
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