1
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Wang Y, Zhao X, Xiao M, Lin X, Chen Q, Qin S, Ti H, Yang Z. Network pharmacology associated anti-influenza mechanism research of Qingjie-Tuire Granule via STAT1/3 signaling pathway. Heliyon 2023; 9:e14649. [PMID: 37101493 PMCID: PMC10123184 DOI: 10.1016/j.heliyon.2023.e14649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 03/06/2023] [Accepted: 03/15/2023] [Indexed: 03/28/2023] Open
Abstract
Qingjie-Tuire (QT) granule was approved for clinical use and its combination was reported to treat influenza infection. To explore its active component and mechanism, the components of QT granule were retrieved from UPLC-UC-Q-TOF/MS analysis. The genes corresponding to the targets were retrieved using GeneCards and TTD database. The herb-compound-target network was constructed by Cytoscape. The target protein-protein interaction network was built using STRING database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of QT granule to IAV were performed for further study. The regulation to different signaling transduction events and cytokine/chemokine expression of QT granule was evaluated using Western blotting and real-time qPCR. Totally, 47 compounds were identified and effect of QT granule on cell STAT1/3 signaling pathways was confirmed by A549 cell model. The efficiency of QT granule on host cell contributes to its clinical application and mechanism research.
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2
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Flores-Montero K, Berberián MV, Mayorga LS, Tomes CN, Ruete MC. The molecular chaperone cysteine string protein is required for monomeric SNARE proteins to assemble in trans-complexes during human sperm acrosomal exocytosis†. Biol Reprod 2023; 108:229-240. [PMID: 36308432 DOI: 10.1093/biolre/ioac196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Revised: 10/06/2022] [Accepted: 10/24/2022] [Indexed: 11/13/2022] Open
Abstract
Membrane fusion in sperm cells is crucial for acrosomal exocytosis and must be preserved to ensure fertilizing capacity. Evolutionarily conserved protein machinery regulates acrosomal exocytosis. Molecular chaperones play a vital role in spermatogenesis and post-testicular maturation. Cysteine string protein (CSP) is a member of the Hsp40 co-chaperones, and the participation of molecular chaperones in acrosomal exocytosis is poorly understood. In particular, the role of CSP in acrosomal exocytosis has not been reported so far. Using western blot and indirect immunofluorescence, we show that CSP is present in human sperm, is palmitoylated, and predominantly bound to membranes. Moreover, using functional assays and transmission electron microscopy, we report that blocking the function of CSP avoided the assembly of trans-complexes and inhibited exocytosis. In summary, here, we describe the presence of CSP in human sperm and show that this protein has an essential role in membrane fusion during acrosomal exocytosis mediating the trans-SNARE complex assembly between the outer acrosomal and plasma membranes. In general, understanding CSP's role is critical in identifying new biomarkers and generating new rational-based approaches to treat male infertility.
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Affiliation(s)
- Karina Flores-Montero
- Instituto de Histología y Embriología de Mendoza - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - María Victoria Berberián
- Instituto de Histología y Embriología de Mendoza - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza, Argentina.,Instituto de Ciencias Básicas - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Luis Segundo Mayorga
- Instituto de Histología y Embriología de Mendoza - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Claudia Nora Tomes
- Instituto de Histología y Embriología de Mendoza - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - María Celeste Ruete
- Instituto de Histología y Embriología de Mendoza - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Cuyo, Mendoza, Argentina.,Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
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3
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Naseri N, Sharma M, Velinov M. Autosomal dominant neuronal ceroid lipofuscinosis: Clinical features and molecular basis. Clin Genet 2020; 99:111-118. [PMID: 32783189 DOI: 10.1111/cge.13829] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/04/2020] [Accepted: 08/05/2020] [Indexed: 11/26/2022]
Abstract
The neuronal ceroid lipofuscinoses (NCLs) are at least 13 distinct progressive neurodegenerative disorders unified by the accumulation of lysosomal auto-fluorescent material called lipofuscin. The only form that occurs via autosomal-dominant inheritance exhibits adult onset and is sometimes referred to as Parry type NCL. The manifestations may include behavioral symptoms followed by seizures, ataxia, dementia, and early death. Mutations in the gene DNAJC5 that codes for the presynaptic co-chaperone cysteine string protein-α (CSPα) were recently reported in sporadic adult-onset cases and in families with dominant inheritance. The mutant CSPα protein may lead to disease progression by both loss and gain of function mechanisms. Iron chelation therapy may be considered as a possible pharmaceutical intervention based on our recent mechanism-based proposal of CSPα oligomerization via ectopic Fe-S cluster-binding, summarized in this review.
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Affiliation(s)
- Nima Naseri
- Appel Institute for Alzheimer's Disease Research, and Brain & Mind Research Institute, Weill Cornell Medicine, New York City, New York, USA
| | - Manu Sharma
- Appel Institute for Alzheimer's Disease Research, and Brain & Mind Research Institute, Weill Cornell Medicine, New York City, New York, USA
| | - Milen Velinov
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, USA
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4
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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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5
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Abstract
Cell-to-cell transmission of misfolded proteins propagates proteotoxic stress in multicellular organisms when transmitted polypeptides serve as a seeding template to cause protein misfolding in recipient cells, but how misfolded proteins are released from cells to initiate this process is unclear. Misfolding-associated protein secretion (MAPS) is an unconventional protein-disposing mechanism that specifically exports misfolded cytosolic proteins including various neurodegenerative disease-causing proteins. Here we establish the HSC70 co-chaperone DNAJC5 as an essential mediator of MAPS. USP19, a previously uncovered MAPS regulator binds HSC70 and acts upstream of HSC70 and DNAJC5. We further show that as a membrane-associated protein localized preferentially to late endosomes and lysosomes, DNAJC5 can chaperone MAPS client proteins to the cell exterior. Intriguingly, upon secretion, misfolded proteins can be taken up through endocytosis and eventually degraded in the lysosome. Collectively, these findings suggest a transcellular protein quality control regulatory pathway in which a deubiquitinase-chaperone axis forms a “triaging hub”, transferring aberrant polypeptides from stressed cells to healthy ones for disposal.
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6
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Braga ACS, Carneiro BM, Batista MN, Akinaga MM, Bittar C, Rahal P. Heat shock proteins HSPB8 and DNAJC5B have HCV antiviral activity. PLoS One 2017; 12:e0188467. [PMID: 29182667 PMCID: PMC5705118 DOI: 10.1371/journal.pone.0188467] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 11/07/2017] [Indexed: 12/12/2022] Open
Abstract
Hepatitis C is a disease caused by the hepatitis C virus (HCV), and an estimated 3% of the world population is infected with the virus. During replication, HCV interacts with several cellular proteins. Studies have shown that several heat shock proteins (HSPs) have an altered expression profile in the presence of the virus, and some HSPs interact directly with HCV proteins. In the present study, we evaluated the expression levels of heat shock proteins in vitro in the presence and absence of HCV. The differential expression of 84 HSPs and chaperones was observed using a qPCR array, comparing HCV uninfected and infected Huh7.5 cells. To validate qPCR array, the differentially expressed genes were tested by real-time PCR in three different HCV models: subgenomic HCV replicon cells (SGR-JFH-1), JFH-1 infected cells (both genotype 2a) and subgenomic S52 cells (genotype 3). The HSPB8 gene showed increased expression in all three viral models. We silenced HSPB8 expression and observed an increase in viral replication. In contrast, when we increased the expression of HSPB8, a decrease in the HCV replication rate was observed. The same procedure was adopted for DNAJC5B, and HCV showed a similar replication pattern as that observed for HSPB8. These results suggest that HSPB8 may act as an intracellular factor against hepatitis C virus replication and that DNAJC5B has the same function, with more relevant results for genotype 3. We also evaluated the direct interactions between HCV and HSP proteins, and the IP experiments showed that the HCV NS4B protein interacts with HSPB8. These results contribute to a better understanding of the mechanisms involved in HCV replication.
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Affiliation(s)
- Ana Claudia Silva Braga
- Laboratório de Estudos Genômicos, UNESP/IBILCE, São José do Rio Preto, São Paulo, Brazil
- * E-mail:
| | - Bruno Moreira Carneiro
- Laboratório de Estudos Genômicos, UNESP/IBILCE, São José do Rio Preto, São Paulo, Brazil
- Instituto de Ciências Exatas e Naturais, UFMT/CUR, Rondonópolis, Mato Grosso, Brazil
| | | | - Mônica Mayumi Akinaga
- Laboratório de Estudos Genômicos, UNESP/IBILCE, São José do Rio Preto, São Paulo, Brazil
| | - Cíntia Bittar
- Laboratório de Estudos Genômicos, UNESP/IBILCE, São José do Rio Preto, São Paulo, Brazil
| | - Paula Rahal
- Laboratório de Estudos Genômicos, UNESP/IBILCE, São José do Rio Preto, São Paulo, Brazil
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7
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Carapito C, Duek P, Macron C, Seffals M, Rondel K, Delalande F, Lindskog C, Fréour T, Vandenbrouck Y, Lane L, Pineau C. Validating Missing Proteins in Human Sperm Cells by Targeted Mass-Spectrometry- and Antibody-based Methods. J Proteome Res 2017; 16:4340-4351. [DOI: 10.1021/acs.jproteome.7b00374] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Christine Carapito
- Laboratoire
de Spectrométrie de Masse BioOrganique (LSMBO), IPHC, Université de Strasbourg, CNRS UMR7178, 25 Rue Becquerel, Strasbourg F-67087, France
| | - Paula Duek
- CALIPHO
Group, SIB-Swiss Institute of Bioinformatics, CMU, rue Michel-Servet
1, CH-1211 Geneva
4, Switzerland
| | - Charlotte Macron
- Laboratoire
de Spectrométrie de Masse BioOrganique (LSMBO), IPHC, Université de Strasbourg, CNRS UMR7178, 25 Rue Becquerel, Strasbourg F-67087, France
| | - Marine Seffals
- H2P2
Core facility, UMS BioSit, University of Rennes 1, Rennes F-35040, France
| | - Karine Rondel
- Protim,
Inserm U1085, Irset, Campus de Beaulieu, Rennes F-35042, France
| | - François Delalande
- Laboratoire
de Spectrométrie de Masse BioOrganique (LSMBO), IPHC, Université de Strasbourg, CNRS UMR7178, 25 Rue Becquerel, Strasbourg F-67087, France
| | - Cecilia Lindskog
- Department
of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Thomas Fréour
- Service de
Médecine de la Reproduction, CHU de Nantes, 38 boulevard
Jean Monnet, Nantes F-44093, France
- Inserm UMR1064, Nantes F-44093, France
| | - Yves Vandenbrouck
- CEA, DRF, BIG,
Laboratoire de Biologie à Grande Echelle, 17, rue des Martyrs, Grenoble F-38054, France
- Inserm U1038, Grenoble F-38054, France
- Grenoble-Alpes University, Grenoble F-38054, France
| | - Lydie Lane
- CALIPHO
Group, SIB-Swiss Institute of Bioinformatics, CMU, rue Michel-Servet
1, CH-1211 Geneva
4, Switzerland
- Department
of Human Protein Sciences, Faculty of Medicine, University of Geneva, 1, rue Michel-Servet, 1211 Geneva 4, Switzerland
| | - Charles Pineau
- Protim,
Inserm U1085, Irset, Campus de Beaulieu, Rennes F-35042, France
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8
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Boal F, Hodgson LR, Reed SE, Yarwood SE, Just VJ, Stephens DJ, McCaffrey MW, Tavaré JM. Insulin promotes Rip11 accumulation at the plasma membrane by inhibiting a dynamin- and PI3-kinase-dependent, but Akt-independent, internalisation event. Cell Signal 2015; 28:74-82. [PMID: 26515129 PMCID: PMC4678287 DOI: 10.1016/j.cellsig.2015.10.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/23/2015] [Indexed: 12/11/2022]
Abstract
Rip11 is a Rab11 effector protein that has been shown to be important in controlling the trafficking of several intracellular cargoes, including the fatty acid transporter FAT/CD36, V-ATPase and the glucose transporter GLUT4. We have previously demonstrated that Rip11 translocates to the plasma membrane in response to insulin and here we examine the basis of this regulated phenomenon in more detail. We show that Rip11 rapidly recycles between the cell interior and surface, and that the ability of insulin to increase the appearance of Rip11 at the cell surface involves an inhibition of Rip11 internalisation from the plasma membrane. By contrast the hormone has no effect on the rate of Rip11 translocation towards the plasma membrane. The ability of insulin to inhibit Rip11 internalisation requires dynamin and class I PI3-kinases, but is independent of the activation of the protein kinase Akt; characteristics which are very similar to the mechanism by which insulin inhibits GLUT4 endocytosis.
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Affiliation(s)
- Frédéric Boal
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Lorna R Hodgson
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Sam E Reed
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Sophie E Yarwood
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Victoria J Just
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - David J Stephens
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Mary W McCaffrey
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Cork, Ireland
| | - Jeremy M Tavaré
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK.
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9
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Abstract
Synaptic vesicles release their vesicular contents to the extracellular space by Ca(2+)-triggered exocytosis. The Ca(2+)-triggered exocytotic process is regulated by synaptotagmin (Syt), a vesicular Ca(2+)-binding C2 domain protein. Synaptotagmin 1 (Syt1), the most studied major isoform among 16 Syt isoforms, mediates Ca(2+)-triggered synaptic vesicle exocytosis by interacting with the target membranes and SNARE/complexin complex. In synapses of the central nervous system, synaptobrevin 2, a major vesicular SNARE protein, forms a ternary SNARE complex with the plasma membrane SNARE proteins, syntaxin 1 and SNAP25. The affinities of Ca(2+)-dependent interactions between Syt1 and its targets (i.e., SNARE complexes and membranes) are well correlated with the efficacies of the corresponding exocytotic processes. Therefore, different SNARE protein isoforms and membrane lipids, which interact with Syt1 with various affinities, are capable of regulating the efficacy of Syt1-mediated exocytosis. Otoferlin, another type of vesicular C2 domain protein that binds to the membrane in a Ca(2+)-dependent manner, is also involved in the Ca(2+)-triggered synaptic vesicle exocytosis in auditory hair cells. However, the functions of otoferlin in the exocytotic process are not well understood. In addition, at least five different types of synaptic vesicle proteins such as synaptic vesicle protein 2, cysteine string protein α, rab3, synapsin, and a group of proteins containing four transmembrane regions, which includes synaptophysin, synaptogyrin, and secretory carrier membrane protein, are involved in modulating the exocytotic process by regulating the formation and trafficking of synaptic vesicles.
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Affiliation(s)
- Ok-Ho Shin
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas
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10
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Milochau A, Lagrée V, Benassy MN, Chaignepain S, Papin J, Garcia-Arcos I, Lajoix A, Monterrat C, Coudert L, Schmitter JM, Ochoa B, Lang J. Synaptotagmin 11 interacts with components of the RNA-induced silencing complex RISC in clonal pancreatic β-cells. FEBS Lett 2014; 588:2217-22. [PMID: 24882364 DOI: 10.1016/j.febslet.2014.05.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Revised: 05/08/2014] [Accepted: 05/14/2014] [Indexed: 01/06/2023]
Abstract
Synaptotagmins are two C2 domain-containing transmembrane proteins. The function of calcium-sensitive members in the regulation of post-Golgi traffic has been well established whereas little is known about the calcium-insensitive isoforms constituting half of the protein family. Novel binding partners of synaptotagmin 11 were identified in β-cells. A number of them had been assigned previously to ER/Golgi derived-vesicles or linked to RNA synthesis, translation and processing. Whereas the C2A domain interacted with the Q-SNARE Vti1a, the C2B domain of syt11 interacted with the SND1, Ago2 and FMRP, components of the RNA-induced silencing complex (RISC). Binding to SND was direct via its N-terminal tandem repeats. Our data indicate that syt11 may provide a link between gene regulation by microRNAs and membrane traffic.
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Affiliation(s)
| | - Valérie Lagrée
- Université de Bordeaux, UMR CNRS 5248, F-33607 Pessac, France
| | | | | | - Julien Papin
- Université de Bordeaux, UMR CNRS 5248, F-33607 Pessac, France
| | - Itsaso Garcia-Arcos
- University of the Basque Country, Faculty of Medicine and Dentistry, Department of Physiology, Bilbao, Spain
| | - Anne Lajoix
- Université Montpellier 1, CNRS FRE 3400, Faculté de Pharmacie, F-34093 Montpellier Cedex 5, France
| | | | | | | | - Begoña Ochoa
- University of the Basque Country, Faculty of Medicine and Dentistry, Department of Physiology, Bilbao, Spain
| | - Jochen Lang
- Université de Bordeaux, UMR CNRS 5248, F-33607 Pessac, France.
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11
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Boal F, Laguerre M, Milochau A, Lang J, Scotti PA. A charged prominence in the linker domain of the cysteine‐string protein Cspα mediates its regulated interaction with the calcium sensor synaptotagmin 9 during exocytosis. FASEB J 2010; 25:132-43. [DOI: 10.1096/fj.09-152033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Frédéric Boal
- Department of BiochemistrySchool of Medical SciencesUniversity of BristolBristolUK
| | - Michel Laguerre
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Alexandra Milochau
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Jochen Lang
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Pier A. Scotti
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
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12
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Gorleku OA, Chamberlain LH. Palmitoylation and Testis-Enriched Expression of the Cysteine-String Protein β Isoform. Biochemistry 2010; 49:5308-13. [DOI: 10.1021/bi100550h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Oforiwa A. Gorleku
- Centre for Integrative Physiology, School of Biomedical Sciences, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Luke H. Chamberlain
- Centre for Integrative Physiology, School of Biomedical Sciences, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
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13
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Gundersen CB, Kohan SA, Souda P, Whitelegge JP, Umbach JA. Cysteine string protein β is prominently associated with nerve terminals and secretory organelles in mouse brain. Brain Res 2010; 1332:1-11. [DOI: 10.1016/j.brainres.2010.03.044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 02/26/2010] [Accepted: 03/14/2010] [Indexed: 11/16/2022]
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14
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Greaves J, Salaun C, Fukata Y, Fukata M, Chamberlain LH. Palmitoylation and membrane interactions of the neuroprotective chaperone cysteine-string protein. J Biol Chem 2008; 283:25014-26. [PMID: 18596047 DOI: 10.1074/jbc.m802140200] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine-string protein (CSP) is an extensively palmitoylated DnaJ-family chaperone, which exerts an important neuroprotective function. Palmitoylation is required for the intracellular sorting and function of CSP, and thus it is important to understand how this essential modification of CSP is regulated. Recent work identified 23 putative palmitoyl transferases containing a conserved DHHC domain in mammalian cells, and here we show that palmitoylation of CSP is enhanced specifically by co-expression of the Golgi-localized palmitoyl transferases DHHC3, DHHC7, DHHC15, or DHHC17. Indeed, these DHHC proteins promote stable membrane attachment of CSP, which is otherwise cytosolic. An inverse correlation was identified between membrane affinity of unpalmitoylated CSP mutants and subsequent palmitoylation: mutants with an increased membrane affinity localize to the endoplasmic reticulum (ER) and are physically separated from the Golgi-localized DHHC proteins. Palmitoylation of an ER-localized mutant could be rescued by brefeldin A treatment, which promotes the mixing of ER and Golgi membranes. Interestingly though, the palmitoylated mutant remained at the ER following brefeldin A washout and did not traffic to more distal membrane compartments. We propose that CSP has a weak membrane affinity that allows the protein to locate its partner Golgi-localized DHHC proteins directly by membrane "sampling." Mutations that enhance membrane association prevent sampling and lead to accumulation of CSP on cellular membranes such as the ER. The coupling of CSP palmitoylation to Golgi membranes may thus be an important requirement for subsequent sorting.
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Affiliation(s)
- Jennifer Greaves
- Centre for Integrative Physiology, School of Biomedical Sciences, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
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15
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McHaffie GS, Graham C, Kohl B, Strunck-Warnecke U, Werner A. The role of an intracellular cysteine stretch in the sorting of the type II Na/phosphate cotransporter. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2099-106. [PMID: 17574207 DOI: 10.1016/j.bbamem.2007.05.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 05/11/2007] [Accepted: 05/15/2007] [Indexed: 01/04/2023]
Abstract
The type II Na/phosphate cotransporters (NaPi-II) are critical for the control of plasma phosphate levels in vertebrates. NaPi-IIb mediates phosphate uptake from the small intestine followed by glomerular filtration and selective reabsorption from the renal proximal tubule by NaPi-IIa and NaPi-IIc. A C-terminal stretch of cysteine residues represents the hallmark of the NaPi-IIb isoforms. This motif is well conserved among NaPi-IIb type transporters but not found in other membrane proteins. To investigate the role of this motif we analyzed NaPi-II constructs in transiently and stably transfected MDCK cells. This cell line targets the NaPi-IIb isoforms from flounder and mouse to the apical membrane whereas the mouse IIa isoform shows no plasma membrane preference. Different parts of mouse NaPi-IIa and NaPi-IIb C-termini were fused to GFP-tagged flounder NaPi-II. The constructs showed strong staining of the plasma membrane with NaPi-IIb related constructs sorted predominantly apically, the IIa constructs localized apically and basolaterally with slight intracellular retention. When the cysteine stretch was inserted into the NaPi-IIa C-terminus, the construct was retained in a cytoplasmic compartment. 2-bromopalmitate, a specific palmitoylation inhibitor, released the transporter to apical and basolateral membranes. The drug also leads to a redistribution of the NaPi-IIb construct to both plasma membrane compartments. Immunoprecipitation of tagged NaPi-II constructs from [(3)H]-palmitate labeled MDCK cells indicated that the cysteine stretch is palmitoylated. Our results suggest that the modified cysteine motif prevents the constructs from basolateral sorting. Additional sorting determinants located downstream of the cysteine stretch may release the cargo to the apical compartment.
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Affiliation(s)
- Gavin S McHaffie
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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16
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Grise F, Taib N, Monterrat C, Lagrée V, Lang J. Distinct roles of the C2A and the C2B domain of the vesicular Ca2+ sensor synaptotagmin 9 in endocrine beta-cells. Biochem J 2007; 403:483-92. [PMID: 17263688 PMCID: PMC1876385 DOI: 10.1042/bj20061182] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Synaptotagmins form a family of calcium-sensor proteins implicated in exocytosis, and these vesicular transmembrane proteins are endowed with two cytosolic calcium-binding C2 domains, C2A and C2B. Whereas the isoforms syt1 and syt2 have been studied in detail, less is known about syt9, the calcium sensor involved in endocrine secretion such as insulin release from large dense core vesicles in pancreatic beta-cells. Using cell-based assays to closely mimic physiological conditions, we observed SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor)-independent translocation of syt9C2AB to the plasma membrane at calcium levels corresponding to endocrine exocytosis, followed by internalization to endosomes. The use of point mutants and truncations revealed that initial translocation required only the C2A domain, whereas the C2B domain ensured partial pre-binding of syt9C2AB to the membrane and post-stimulatory localization to endosomes. In contrast with the known properties of neuronal and neuroendocrine syt1 or syt2, the C2B domain of syt9 did not undergo calcium-dependent membrane binding despite a high degree of structural homology as observed through molecular modelling. The present study demonstrates distinct intracellular properties of syt9 with different roles for each C2 domain in endocrine cells.
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Affiliation(s)
- Florence Grise
- *Jeune Equipe 2390, Institut Européen de Chimie et Biologie, Université de Bordeaux 1, 2 Av. Robert Escarpit, F-33607 Pessac, France
| | - Nada Taib
- †UMR 5144 CNRS Mobios, Institut Européen de Chimie et Biologie, Université de Bordeaux 1, 2 Av. Robert Escarpit, F-33607 Pessac, France
| | - Carole Monterrat
- *Jeune Equipe 2390, Institut Européen de Chimie et Biologie, Université de Bordeaux 1, 2 Av. Robert Escarpit, F-33607 Pessac, France
| | - Valérie Lagrée
- *Jeune Equipe 2390, Institut Européen de Chimie et Biologie, Université de Bordeaux 1, 2 Av. Robert Escarpit, F-33607 Pessac, France
| | - Jochen Lang
- *Jeune Equipe 2390, Institut Européen de Chimie et Biologie, Université de Bordeaux 1, 2 Av. Robert Escarpit, F-33607 Pessac, France
- To whom correspondence should be addressed (email )
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Monterrat C, Grise F, Benassy MN, Hémar A, Lang J. The calcium-sensing protein synaptotagmin 7 is expressed on different endosomal compartments in endocrine, neuroendocrine cells or neurons but not on large dense core vesicles. Histochem Cell Biol 2007; 127:625-32. [PMID: 17277932 DOI: 10.1007/s00418-007-0271-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2007] [Indexed: 11/24/2022]
Abstract
Synaptotagmin (syt) isoforms function as calcium sensor in post-Golgi transport although the precise transport step and compartment(s) concerned are still not fully resolved. As syt7 has been proposed to operate in lysosomal exocytosis and in exocytosis of large dense core vesicles (LDCVs), we have addressed the distribution of endogenous syt7 in insulin-secreting cells. These cells express different syt7 isoforms comparable to neurons. According to subcellular fractionation and quantitative confocal immunocytochemistry, syt7 is not found on LDCVs or on synaptic-like microvesicles but colocalizes with Rab7 on endosomes and to structures near to or at the plasma membrane. Similarly, endogenous syt7 was absent from LDCVs in pheochromocytoma PC12 cells. In contrast, syt7 localised to lysosomes in both, PC12 cells and hippocampal neurons. In conclusion, endogenous syt7 shows a wider distribution than previously reported but does not qualify as vesicular calcium sensor in SLMV or LDCV exocytosis according to its localisation.
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Affiliation(s)
- Carole Monterrat
- Institut Européen de Chimie et Biologie, Université de Bordeaux 1, JE 2390, 33607, Pessac/Bordeaux, France
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