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Sagarika P, Yadav K, Sahi C. Volleying plasma membrane proteins from birth to death: Role of J-domain proteins. Front Mol Biosci 2022; 9:1072242. [PMID: 36589230 PMCID: PMC9798423 DOI: 10.3389/fmolb.2022.1072242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
The function, stability, and turnover of plasma membrane (PM) proteins are crucial for cellular homeostasis. Compared to soluble proteins, quality control of plasma membrane proteins is extremely challenging. Failure to meet the high quality control standards is detrimental to cellular and organismal health. J-domain proteins (JDPs) are among the most diverse group of chaperones that collaborate with other chaperones and protein degradation machinery to oversee cellular protein quality control (PQC). Although fragmented, the available literature from different models, including yeast, mammals, and plants, suggests that JDPs assist PM proteins with their synthesis, folding, and trafficking to their destination as well as their degradation, either through endocytic or proteasomal degradation pathways. Moreover, some JDPs interact directly with the membrane to regulate the stability and/or functionality of proteins at the PM. The deconvoluted picture emerging is that PM proteins are relayed from one JDP to another throughout their life cycle, further underscoring the versatility of the Hsp70:JDP machinery in the cell.
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Miller SC, Wegrzynowicz AK, Cole SJ, Hayward RE, Ganser SJ, Hines JK. Hsp40/JDP Requirements for the Propagation of Synthetic Yeast Prions. Viruses 2022; 14:v14102160. [PMID: 36298715 PMCID: PMC9611480 DOI: 10.3390/v14102160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/22/2022] [Accepted: 09/27/2022] [Indexed: 11/05/2022] Open
Abstract
Yeast prions are protein-based transmissible elements, most of which are amyloids. The chaperone protein network in yeast is inexorably linked to the spreading of prions during cell division by fragmentation of amyloid prion aggregates. Specifically, the core “prion fragmentation machinery” includes the proteins Hsp104, Hsp70 and the Hsp40/J-domain protein (JDP) Sis1. Numerous novel amyloid-forming proteins have been created and examined in the yeast system and occasionally these amyloids are also capable of continuous Hsp104-dependent propagation in cell populations, forming synthetic prions. However, additional chaperone requirements, if any, have not been determined. Here, we report the first instances of a JDP-Hsp70 system requirement for the propagation of synthetic prions. We utilized constructs from a system of engineered prions with prion-forming domains (PrDs) consisting of a polyQ stretch interrupted by a single heterologous amino acid interspersed every fifth residue. These “polyQX” PrDs are fused to the MC domains of Sup35, creating chimeric proteins of which a subset forms synthetic prions in yeast. For four of these prions, we show that SIS1 repression causes prion loss in a manner consistent with Sis1′s known role in prion fragmentation. PolyQX prions were sensitive to Sis1 expression levels to differing degrees, congruent with the variability observed among native prions. Our results expand the scope known Sis1 functionality, demonstrating that Sis1 acts on amyloids broadly, rather than through specific protein–protein interactions with individual yeast prion-forming proteins.
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Yamazaki Y, Kono K. Clathrin-mediated trafficking of phospholipid flippases is required for local plasma membrane/cell wall damage repair in budding yeast. Biochem Biophys Res Commun 2022; 606:156-162. [DOI: 10.1016/j.bbrc.2022.03.129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/09/2022] [Accepted: 03/23/2022] [Indexed: 11/02/2022]
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Roosen DA, Blauwendraat C, Cookson MR, Lewis PA. DNAJC
proteins and pathways to parkinsonism. FEBS J 2019; 286:3080-3094. [DOI: 10.1111/febs.14936] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 03/21/2019] [Accepted: 05/21/2019] [Indexed: 12/12/2022]
Affiliation(s)
- Dorien A. Roosen
- Laboratory of Neurogenetics National Institute on AgingNational Institutes of Health Bethesda MD USA
- School of Pharmacy University of Reading UK
| | - Cornelis Blauwendraat
- Laboratory of Neurogenetics National Institute on AgingNational Institutes of Health Bethesda MD USA
| | - Mark R. Cookson
- Laboratory of Neurogenetics National Institute on AgingNational Institutes of Health Bethesda MD USA
| | - Patrick A. Lewis
- School of Pharmacy University of Reading UK
- Department of Neurodegenerative Disease UCL Institute of Neurology London UK
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Boutchueng-Djidjou M, Belleau P, Bilodeau N, Fortier S, Bourassa S, Droit A, Elowe S, Faure RL. A type 2 diabetes disease module with a high collective influence for Cdk2 and PTPLAD1 is localized in endosomes. PLoS One 2018; 13:e0205180. [PMID: 30300385 PMCID: PMC6177195 DOI: 10.1371/journal.pone.0205180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 09/20/2018] [Indexed: 01/19/2023] Open
Abstract
Despite the identification of many susceptibility genes our knowledge of the underlying mechanisms responsible for complex disease remains limited. Here, we identified a type 2 diabetes disease module in endosomes, and validate it for functional relevance on selected nodes. Using hepatic Golgi/endosomes fractions, we established a proteome of insulin receptor-containing endosomes that allowed the study of physical protein interaction networks on a type 2 diabetes background. The resulting collated network is formed by 313 nodes and 1147 edges with a topology organized around a few major hubs with Cdk2 displaying the highest collective influence. Overall, 88% of the nodes are associated with the type 2 diabetes genetic risk, including 101 new candidates. The Type 2 diabetes module is enriched with cytoskeleton and luminal acidification–dependent processes that are shared with secretion-related mechanisms. We identified new signaling pathways driven by Cdk2 and PTPLAD1 whose expression affects the association of the insulin receptor with TUBA, TUBB, the actin component ACTB and the endosomal sorting markers Rab5c and Rab11a. Therefore, the interactome of internalized insulin receptors reveals the presence of a type 2 diabetes disease module enriched in new layers of feedback loops required for insulin signaling, clearance and islet biology.
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Affiliation(s)
- Martial Boutchueng-Djidjou
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Pascal Belleau
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Nicolas Bilodeau
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Suzanne Fortier
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Sylvie Bourassa
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Arnaud Droit
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Sabine Elowe
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Robert L. Faure
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
- * E-mail:
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Hermes Transposon Mutagenesis Shows [URE3] Prion Pathology Prevented by a Ubiquitin-Targeting Protein: Evidence for Carbon/Nitrogen Assimilation Cross Talk and a Second Function for Ure2p in Saccharomyces cerevisiae. Genetics 2018; 209:789-800. [PMID: 29769283 DOI: 10.1534/genetics.118.300981] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 05/01/2018] [Indexed: 11/18/2022] Open
Abstract
[URE3] is an amyloid-based prion of Ure2p, a regulator of nitrogen catabolism. While most "variants" of the [URE3] prion are toxic, mild variants that only slightly slow growth are more widely studied. The existence of several antiprion systems suggests that some components may be protecting cells from potential detrimental effects of mild [URE3] variants. Our extensive Hermes transposon mutagenesis showed that disruption of YLR352W dramatically slows the growth of [URE3-1] strains. Ylr352wp is an F-box protein, directing selection of substrates for ubiquitination by a "cullin"-containing E3 ligase. For efficient ubiquitylation, cullin-dependent E3 ubiquitin ligases must be NEDDylated, modified by a ubiquitin-related peptide called NEDD8 (Rub1p in yeast). Indeed, we find that disruption of NEDDylation-related genes RUB1, ULA1, UBA3, and UBC12 is also counterselected in our screen. We find that like ylr352wΔ [URE3] strains, ylr352wΔ ure2Δ strains do not grow on nonfermentable carbon sources. Overexpression of Hap4p, a transcription factor stimulating expression of mitochondrial proteins, or mutation of GLN1, encoding glutamine synthetase, allows growth of ylr352w∆ [URE3] strains on glycerol media. Supplying proline as a nitrogen source shuts off the nitrogen catabolite repression (NCR) function of Ure2p, but does not slow growth of ylr352wΔ strains, suggesting a distinct function of Ure2p in carbon catabolism. Also, gln1 mutations impair NCR, but actually relieve the growth defect of ylr352wΔ [URE3] and ylr352wΔ ure2Δ strains, again showing that loss of NCR is not producing the growth defect and suggesting that Ure2p has another function. YLR352W largely protects cells from the deleterious effects of otherwise mild [URE3] variants or of a ure2 mutation (the latter a rarer event), and we name it LUG1 (lets [URE3]/ure2 grow).
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Affiliation(s)
- Andrea N. Killian
- Department of Chemistry, Lafayette College, Easton, Pennsylvania, United States of America
| | - Justin K. Hines
- Department of Chemistry, Lafayette College, Easton, Pennsylvania, United States of America
- * E-mail:
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Oliver EE, Troisi EM, Hines JK. Prion-specific Hsp40 function: The role of the auxilin homolog Swa2. Prion 2017; 11:174-185. [PMID: 28574745 PMCID: PMC5480384 DOI: 10.1080/19336896.2017.1331810] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 05/09/2017] [Accepted: 05/10/2017] [Indexed: 01/14/2023] Open
Abstract
Yeast prions are protein-based genetic elements that propagate through cell populations via cytosolic transfer from mother to daughter cell. Molecular chaperone proteins including Hsp70, the Hsp40/J-protein Sis1, and Hsp104 are required for continued prion propagation, however the specific requirements of chaperone proteins differ for various prions. We recently reported that Swa2, the yeast homolog of the mammalian protein auxilin, is specifically required for the propagation of the prion [URE3]. 1 [URE3] propagation requires both a functional J-domain and the tetratricopeptide repeat (TPR) domain of Swa2, but does not require Swa2 clathrin binding. We concluded that the TPR domain determines the specificity of the genetic interaction between Swa2 and [URE3], and that this domain likely interacts with one or more proteins with a C-terminal EEVD motif. Here we extend that analysis to incorporate additional data that supports this hypothesis. We also present new data eliminating Hsp104 as the relevant Swa2 binding partner and discuss our findings in the context of other recent work involving Hsp90. Based on these findings, we propose a new model for Swa2's involvement in [URE3] propagation in which Swa2 and Hsp90 mediate the formation of a multi-protein complex that increases the number of sites available for Hsp104 disaggregation.
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9
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Effect of in vitro zinc supplementation on HSPs expression and Interleukin 10 production in heat treated peripheral blood mononuclear cells of transition Sahiwal and Karan Fries cows. J Therm Biol 2016; 56:68-76. [DOI: 10.1016/j.jtherbio.2016.01.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 01/01/2016] [Accepted: 01/04/2016] [Indexed: 12/12/2022]
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Ding J, Segarra VA, Chen S, Cai H, Lemmon SK, Ferro-Novick S. Auxilin facilitates membrane traffic in the early secretory pathway. Mol Biol Cell 2015; 27:127-36. [PMID: 26538028 PMCID: PMC4694752 DOI: 10.1091/mbc.e15-09-0631] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/27/2015] [Indexed: 12/01/2022] Open
Abstract
In this study, a proteomic approach links the J-domain chaperone auxilin, which uncoats clathrin-coated vesicles, to the other major coat complexes in the cell (COPII and COPI). Genetic and biochemical studies support the proposal that auxilin facilitates vesicle traffic in the early secretory pathway. Coat protein complexes contain an inner shell that sorts cargo and an outer shell that helps deform the membrane to give the vesicle its shape. There are three major types of coated vesicles in the cell: COPII, COPI, and clathrin. The COPII coat complex facilitates vesicle budding from the endoplasmic reticulum (ER), while the COPI coat complex performs an analogous function in the Golgi. Clathrin-coated vesicles mediate traffic from the cell surface and between the trans-Golgi and endosome. While the assembly and structure of these coat complexes has been extensively studied, the disassembly of COPII and COPI coats from membranes is less well understood. We describe a proteomic and genetic approach that connects the J-domain chaperone auxilin, which uncoats clathrin-coated vesicles, to COPII and COPI coat complexes. Consistent with a functional role for auxilin in the early secretory pathway, auxilin binds to COPII and COPI coat subunits. Furthermore, ER–Golgi and intra-Golgi traffic is delayed at 15°C in swa2Δ mutant cells, which lack auxilin. In the case of COPII vesicles, we link this delay to a defect in vesicle fusion. We propose that auxilin acts as a chaperone and/or uncoating factor for transport vesicles that act in the early secretory pathway.
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Affiliation(s)
- Jingzhen Ding
- Department of Cellular and Molecular Medicine, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093-0668
| | - Verónica A Segarra
- Department of Molecular and Cellular Pharmacology, University of Miami, Miami, FL 33136
| | - Shuliang Chen
- Department of Cellular and Molecular Medicine, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093-0668
| | - Huaqing Cai
- State Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Sandra K Lemmon
- Department of Molecular and Cellular Pharmacology, University of Miami, Miami, FL 33136
| | - Susan Ferro-Novick
- Department of Cellular and Molecular Medicine, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093-0668
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Troisi EM, Rockman ME, Nguyen PP, Oliver EE, Hines JK. Swa2, the yeast homolog of mammalian auxilin, is specifically required for the propagation of the prion variant [URE3-1]. Mol Microbiol 2015; 97:926-41. [PMID: 26031938 PMCID: PMC4689296 DOI: 10.1111/mmi.13076] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2015] [Indexed: 01/09/2023]
Abstract
Yeast prions require a core set of chaperone proteins including Sis1, Hsp70 and Hsp104 to generate new amyloid templates for stable propagation, yet emerging studies indicate that propagation of some prions requires additional chaperone activities, demonstrating chaperone specificity beyond the common amyloid requirements. To comprehensively assess such prion-specific requirements for the propagation of the [URE3] prion variant [URE3-1], we screened 12 yeast cytosolic J-proteins, and here we report a novel role for the J-protein Swa2/Aux1. Swa2 is the sole yeast homolog of the mammalian protein auxilin, which, like Swa2, functions in vesicle-mediated endocytosis by disassembling the structural lattice formed by the protein clathrin. We found that, in addition to Sis1, [URE3-1] is specifically dependent upon Swa2, but not on any of the 11 other J-proteins. Further, we show that [URE3-1] propagation requires both a functional J-domain and the tetratricopeptide repeat (TPR) domain, but surprisingly does not require Swa2-clathrin binding. Because the J-domain of Swa2 can be replaced with the J-domains of other proteins, our data strongly suggest that prion-chaperone specificity arises from the Swa2 TPR domain and supports a model where Swa2 acts through Hsp70, most likely to provide additional access points for Hsp104 to promote prion template generation.
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Affiliation(s)
| | | | - Phil P Nguyen
- Department of Chemistry, Lafayette College, Easton, PA, USA
| | - Emily E Oliver
- Department of Chemistry, Lafayette College, Easton, PA, USA
| | - Justin K Hines
- Department of Chemistry, Lafayette College, Easton, PA, USA
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12
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Sousa R, Lafer EM. The role of molecular chaperones in clathrin mediated vesicular trafficking. Front Mol Biosci 2015; 2:26. [PMID: 26042225 PMCID: PMC4436892 DOI: 10.3389/fmolb.2015.00026] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 05/05/2015] [Indexed: 12/04/2022] Open
Abstract
The discovery that the 70 kD “uncoating ATPase,” which removes clathrin coats from vesicles after endocytosis, is the constitutively expressed Hsc70 chaperone was a surprise. Subsequent work, however, revealed that uncoating is an archetypal Hsp70 reaction: the cochaperone auxilin, which contains a clathrin binding domain and an Hsc70 binding J domain, recruits Hsc70*ATP to the coat and, concomitant with ATP hydrolysis, transfers it to a hydrophobic Hsc70-binding element found on a flexible tail at the C-terminus of the clathrin heavy chain. Release of clathrin in association with Hsc70*ADP follows, and the subsequent, persistent association of clathrin with Hsc70 is important to prevent aberrant clathrin polymerization. Thus, the two canonical functions of Hsp70—dissociation of existing protein complexes or aggregates, and binding to a protein to inhibit its inappropriate aggregation—are recapitulated in uncoating. Association of clathrin with Hsc70 in vivo is regulated by Hsp110, an Hsp70 NEF that is itself a member of the Hsp70 family. How Hsp110 activity is itself regulated to make Hsc70-free clathrin available for endocytosis is unclear, though at synapses it's possible that the influx of calcium that accompanies depolarization activates the Ca++/calmodulin dependent calcineurin phosphatase which then dephosphorylates and activates Hsp110 to stimulate ADP/ATP exchange and release clathrin from Hsc70*ADP:clathrin complexes.
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Affiliation(s)
- Rui Sousa
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio San Antonio, TX, USA
| | - Eileen M Lafer
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio San Antonio, TX, USA
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13
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Control of Plasma Membrane Permeability by ABC Transporters. EUKARYOTIC CELL 2015; 14:442-53. [PMID: 25724885 DOI: 10.1128/ec.00021-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 02/19/2015] [Indexed: 12/13/2022]
Abstract
ATP-binding cassette transporters Pdr5 and Yor1 from Saccharomyces cerevisiae control the asymmetric distribution of phospholipids across the plasma membrane as well as serving as ATP-dependent drug efflux pumps. Mutant strains lacking these transporter proteins were found to exhibit very different resistance phenotypes to two inhibitors of sphingolipid biosynthesis that act either late (aureobasidin A [AbA]) or early (myriocin [Myr]) in the pathway leading to production of these important plasma membrane lipids. These pdr5Δ yor1 strains were highly AbA resistant but extremely sensitive to Myr. We provide evidence that these phenotypic changes are likely due to modulation of the plasma membrane flippase complexes, Dnf1/Lem3 and Dnf2/Lem3. Flippases act to move phospholipids from the outer to the inner leaflet of the plasma membrane. Genetic analyses indicate that lem3Δ mutant strains are highly AbA sensitive and Myr resistant. These phenotypes are fully epistatic to those seen in pdr5Δ yor1 strains. Direct analysis of AbA-induced signaling demonstrated that loss of Pdr5 and Yor1 inhibited the AbA-triggered phosphorylation of the AGC kinase Ypk1 and its substrate Orm1. Microarray experiments found that a pdr5Δ yor1 strain induced a Pdr1-dependent induction of the entire Pdr regulon. Our data support the view that Pdr5/Yor1 negatively regulate flippase function and activity of the nuclear Pdr1 transcription factor. Together, these data argue that the interaction of the ABC transporters Pdr5 and Yor1 with the Lem3-dependent flippases regulates permeability of AbA via control of plasma membrane protein function as seen for the high-affinity tryptophan permease Tat2.
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Abstract
Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed.
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Affiliation(s)
- Bruce L Goode
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Julian A Eskin
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Beverly Wendland
- The Johns Hopkins University, Department of Biology, Baltimore, Maryland 21218
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Wittinghofer A. Arf Proteins and Their Regulators: At the Interface Between Membrane Lipids and the Protein Trafficking Machinery. RAS SUPERFAMILY SMALL G PROTEINS: BIOLOGY AND MECHANISMS 2 2014. [PMCID: PMC7123483 DOI: 10.1007/978-3-319-07761-1_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The Arf small GTP-binding (G) proteins regulate membrane traffic and organelle structure in eukaryotic cells through a regulated cycle of GTP binding and hydrolysis. The first function identified for Arf proteins was recruitment of cytosolic coat complexes to membranes to mediate vesicle formation. However, subsequent studies have uncovered additional functions, including roles in plasma membrane signalling pathways, cytoskeleton regulation, lipid droplet function, and non-vesicular lipid transport. In contrast to other families of G proteins, there are only a few Arf proteins in each organism, yet they function specifically at many different cellular locations. Part of this specificity is achieved by formation of complexes with their guanine nucleotide-exchange factors (GEFs) and GTPase activating proteins (GAPs) that catalyse GTP binding and hydrolysis, respectively. Because these regulators outnumber their Arf substrates by at least 3-to-1, an important aspect of understanding Arf function is elucidating the mechanisms by which a single Arf protein is incorporated into different GEF, GAP, and effector complexes. New insights into these mechanisms have come from recent studies showing GEF–effector interactions, Arf activation cascades, and positive feedback loops. A unifying theme in the function of Arf proteins, carried out in conjunction with their regulators and effectors, is sensing and modulating the properties of the lipids that make up cellular membranes.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Dortmund, Nordrhein-Westfalen Germany
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Krantz KC, Puchalla J, Thapa R, Kobayashi C, Bisher M, Viehweg J, Carr CM, Rye HS. Clathrin coat disassembly by the yeast Hsc70/Ssa1p and auxilin/Swa2p proteins observed by single-particle burst analysis spectroscopy. J Biol Chem 2013; 288:26721-30. [PMID: 23913685 DOI: 10.1074/jbc.m113.491753] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of clathrin-coated vesicles in receptor-mediated endocytosis is conserved among eukaryotes, and many of the proteins required for clathrin coat assembly and disassembly have orthologs in yeast and mammals. In yeast, dozens of proteins have been identified as regulators of the multistep reaction required for endocytosis, including those that regulate disassembly of the clathrin coat. In mammalian systems, clathrin coat disassembly has been reconstituted using neuronal clathrin baskets mixed with the purified chaperone ATPase 70-kDa heat shock cognate (Hsc70), plus a clathrin-specific co-chaperone, such as the synaptic protein auxilin. Yet, despite previous characterization of the yeast Hsc70 ortholog, Ssa1p, and the auxilin-like ortholog, Swa2p, testing mechanistic models for disassembly of nonneuronal clathrin coats has been limited by the absence of a functional reconstitution assay. Here we use single-particle burst analysis spectroscopy, in combination with fluorescence correlation spectroscopy, to follow the population dynamics of fluorescently tagged yeast clathrin baskets in the presence of purified Ssa1p and Swa2p. An advantage of this combined approach for mechanistic studies is the ability to measure, as a function of time, changes in the number and size of objects from a starting population to the reaction products. Our results indicate that Ssa1p and Swa2p cooperatively disassemble yeast clathrin baskets into fragments larger than the individual triskelia, suggesting that disassembly of clathrin-coated vesicles may proceed through a partially uncoated intermediate.
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Affiliation(s)
- Kelly C Krantz
- From the Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
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Shen D, Yuan H, Hutagalung A, Verma A, Kümmel D, Wu X, Reinisch K, McNew JA, Novick P. The synaptobrevin homologue Snc2p recruits the exocyst to secretory vesicles by binding to Sec6p. ACTA ACUST UNITED AC 2013; 202:509-26. [PMID: 23897890 PMCID: PMC3734085 DOI: 10.1083/jcb.201211148] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The exocyst is recruited to secretory vesicles by the combinatorial signals of Sec4-GTP and the Snc proteins to confer both specificity and directionality to vesicular traffic. A screen for mutations that affect the recruitment of the exocyst to secretory vesicles identified genes encoding clathrin and proteins that associate or colocalize with clathrin at sites of endocytosis. However, no significant colocalization of the exocyst with clathrin was seen, arguing against a direct role in exocyst recruitment. Rather, these components are needed to recycle the exocytic vesicle SNAREs Snc1p and Snc2p from the plasma membrane into new secretory vesicles where they act to recruit the exocyst. We observe a direct interaction between the exocyst subunit Sec6p and the latter half of the SNARE motif of Snc2p. An snc2 mutation that specifically disrupts this interaction led to exocyst mislocalization and a block in exocytosis in vivo without affecting liposome fusion in vitro. Overexpression of Sec4p partially suppressed the exocyst localization defects of mutations in clathrin and clathrin-associated components. We propose that the exocyst is recruited to secretory vesicles by the combinatorial signals of Sec4-GTP and the Snc proteins. This could help to confer both specificity and directionality to vesicular traffic.
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Affiliation(s)
- David Shen
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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Evidence for recycling of invariant surface transmembrane domain proteins in African trypanosomes. EUKARYOTIC CELL 2012; 12:330-42. [PMID: 23264644 DOI: 10.1128/ec.00273-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intracellular trafficking is a vital component of both virulence mechanisms and drug interactions in Trypanosoma brucei, the causative agent of human African trypanosomiasis and n'agana of cattle. Both maintaining the surface proteome composition within a life stage and remodeling the composition when progressing between life stages are important features of immune evasion and development for trypanosomes. Our recent work implicates the abundant transmembrane invariant surface glycoproteins (ISGs) in the uptake of first-line therapeutic suramin, suggesting a potential therapeutic route into the cell. RME-8 is a mediator of recycling pathways in higher eukaryotes and is one of a small cohort of intracellular transport gene products upregulated in mammal-infective trypanosomes, suggesting a role in controlling the copy number of surface proteins in trypanosomes. Here we investigate RME-8 function and its contribution to intracellular trafficking and stability of ISGs. RME-8 is a highly conserved protein and is broadly distributed across multiple endocytic compartments. By knockdown we find that RME-8 is essential and mediates delivery of endocytic probes to late endosomal compartments. Further, we find ISG accumulation within endosomes, but that RME-8 knockdown also increases ISG turnover; combined with previous data, this suggests that it is most probable that ISGs are recycled, and that RME-8 is required to support recycling.
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19
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Gillies A, Taylor R, Gestwicki JE. Synthetic lethal interactions in yeast reveal functional roles of J protein co-chaperones. MOLECULAR BIOSYSTEMS 2012; 8:2901-8. [PMID: 22851130 PMCID: PMC3463740 DOI: 10.1039/c2mb25248a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
J proteins are a diverse family of co-chaperones that cooperate with heat shock protein 70 (Hsp70) to coordinate protein quality control, especially in response to cellular stress. Current models suggest that individual J proteins might play roles in recruiting Hsp70s to specific functions, such as maintaining cell wall integrity or promoting ribosome biogenesis. However, relatively few stresses have been used to test this model and, as a result, only a few specific activities have been identified. To expand our understanding of the J protein network, we used a synthetic lethal approach in which 11 Saccharomyces cerevisiae deletion strains were treated with 12 well-characterized chemical inhibitors. The results defined new roles for specific J proteins in major signaling pathways. For example, an important role for Swa2 in cell wall integrity was identified and activities of the under-explored Jjj1, Apj1, Jjj3 and Caj1 proteins were suggested. More generally, these findings support a model in which some J proteins, such as Ydj1 and Zuo1, play "generalist" roles, while others, such as Apj1 and Jjj2, are "specialists", having roles in relatively few pathways. Together, these results provide new insight into the network of J proteins.
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Affiliation(s)
- Anne Gillies
- Departments of Pathology and Biological Chemistry and the Life Sciences Institute University of Michigan, Ann Arbor, Michigan 48109
| | - Rebecca Taylor
- Departments of Pathology and Biological Chemistry and the Life Sciences Institute University of Michigan, Ann Arbor, Michigan 48109
| | - Jason E. Gestwicki
- Departments of Pathology and Biological Chemistry and the Life Sciences Institute University of Michigan, Ann Arbor, Michigan 48109
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20
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Biology of the heat shock response and protein chaperones: budding yeast (Saccharomyces cerevisiae) as a model system. Microbiol Mol Biol Rev 2012; 76:115-58. [PMID: 22688810 DOI: 10.1128/mmbr.05018-11] [Citation(s) in RCA: 372] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The eukaryotic heat shock response is an ancient and highly conserved transcriptional program that results in the immediate synthesis of a battery of cytoprotective genes in the presence of thermal and other environmental stresses. Many of these genes encode molecular chaperones, powerful protein remodelers with the capacity to shield, fold, or unfold substrates in a context-dependent manner. The budding yeast Saccharomyces cerevisiae continues to be an invaluable model for driving the discovery of regulatory features of this fundamental stress response. In addition, budding yeast has been an outstanding model system to elucidate the cell biology of protein chaperones and their organization into functional networks. In this review, we evaluate our understanding of the multifaceted response to heat shock. In addition, the chaperone complement of the cytosol is compared to those of mitochondria and the endoplasmic reticulum, organelles with their own unique protein homeostasis milieus. Finally, we examine recent advances in the understanding of the roles of protein chaperones and the heat shock response in pathogenic fungi, which is being accelerated by the wealth of information gained for budding yeast.
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21
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Lemmon SK, Traub LM. Getting in touch with the clathrin terminal domain. Traffic 2012; 13:511-9. [PMID: 22239657 DOI: 10.1111/j.1600-0854.2011.01321.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 12/14/2011] [Indexed: 12/16/2022]
Abstract
The N-terminal domain (TD) of the clathrin heavy chain is folded into a seven-bladed β-propeller that projects inward from the polyhedral outer clathrin coat. As the most membrane-proximal portion of assembled clathrin, the TD is a major protein-protein interaction node. Contact with the TD β-propeller occurs through short peptide sequences typically located within intrinsically disordered segments of coat components that usually are elements of the membrane-apposed, inner 'adaptor' coat layer. A huge variation in TD-binding motifs is known and now four spatially discrete interaction surfaces upon the β-propeller have been delineated. An important operational feature of the TD interaction sites in vivo is functional redundancy. The recent discovery that 'pitstop' chemical inhibitors apparently occupy only one of the four TD interaction surfaces, but potently block clathrin-mediated endocytosis, warrants careful consideration of the underlying molecular basis for this inhibition.
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Affiliation(s)
- Sandra K Lemmon
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
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22
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Sebastian TT, Baldridge RD, Xu P, Graham TR. Phospholipid flippases: building asymmetric membranes and transport vesicles. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:1068-77. [PMID: 22234261 DOI: 10.1016/j.bbalip.2011.12.007] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 12/14/2011] [Accepted: 12/16/2011] [Indexed: 01/25/2023]
Abstract
Phospholipid flippases in the type IV P-type ATPase family (P4-ATPases) are essential components of the Golgi, plasma membrane and endosomal system that play critical roles in membrane biogenesis. These pumps flip phospholipid across the bilayer to create an asymmetric membrane structure with substrate phospholipids, such as phosphatidylserine and phosphatidylethanolamine, enriched within the cytosolic leaflet. The P4-ATPases also help form transport vesicles that bud from Golgi and endosomal membranes, thereby impacting the sorting and localization of many different proteins in the secretory and endocytic pathways. At the organismal level, P4-ATPase deficiencies are linked to liver disease, obesity, diabetes, hearing loss, neurological deficits, immune deficiency and reduced fertility. Here, we review the biochemical, cellular and physiological functions of P4-ATPases, with an emphasis on their roles in vesicle-mediated protein transport. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Tessy T Sebastian
- Department of Biological Sciences, Vanderbilt University, Nashville TN 37235, USA
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23
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Abstract
A common need for microbial cells is the ability to respond to potentially toxic environmental insults. Here we review the progress in understanding the response of the yeast Saccharomyces cerevisiae to two important environmental stresses: heat shock and oxidative stress. Both of these stresses are fundamental challenges that microbes of all types will experience. The study of these environmental stress responses in S. cerevisiae has illuminated many of the features now viewed as central to our understanding of eukaryotic cell biology. Transcriptional activation plays an important role in driving the multifaceted reaction to elevated temperature and levels of reactive oxygen species. Advances provided by the development of whole genome analyses have led to an appreciation of the global reorganization of gene expression and its integration between different stress regimens. While the precise nature of the signal eliciting the heat shock response remains elusive, recent progress in the understanding of induction of the oxidative stress response is summarized here. Although these stress conditions represent ancient challenges to S. cerevisiae and other microbes, much remains to be learned about the mechanisms dedicated to dealing with these environmental parameters.
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Zhou X, Fabian L, Bayraktar JL, Ding HM, Brill JA, Chang HC. Auxilin is required for formation of Golgi-derived clathrin-coated vesicles during Drosophila spermatogenesis. Development 2011; 138:1111-20. [PMID: 21343365 DOI: 10.1242/dev.057422] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Clathrin has previously been implicated in Drosophila male fertility and spermatid individualization. To understand further the role of membrane transport in this process, we analyzed the phenotypes of mutations in Drosophila auxilin (aux), a regulator of clathrin function, in spermatogenesis. Like partial loss-of-function Clathrin heavy chain (Chc) mutants, aux mutant males are sterile and produce no mature sperm. The reproductive defects of aux males were rescued by male germ cell-specific expression of aux, indicating that auxilin function is required autonomously in the germ cells. Furthermore, this rescue depends on both the clathrin-binding and J domains, suggesting that the ability of Aux to bind clathrin and the Hsc70 ATPase is essential for sperm formation. aux mutant spermatids show a deficit in formation of the plasma membrane during elongation, which probably disrupts the subsequent coordinated migration of investment cones during individualization. In wild-type germ cells, GFP-tagged clathrin localized to clusters of vesicular structures near the Golgi. These structures also contained the Golgi-associated clathrin adaptor AP-1, suggesting that they were Golgi-derived. By contrast, in aux mutant cells, clathrin localized to abnormal patches surrounding the Golgi and its colocalization with AP-1 was disrupted. Based on these results, we propose that Golgi-derived clathrin-positive vesicles are normally required for sustaining the plasma membrane increase necessary for spermatid differentiation. Our data suggest that Aux participates in forming these Golgi-derived clathrin-positive vesicles and that Aux, therefore, has a role in the secretory pathway.
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Affiliation(s)
- Xin Zhou
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA
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25
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Banks SML, Cho B, Eun SH, Lee JH, Windler SL, Xie X, Bilder D, Fischer JA. The functions of auxilin and Rab11 in Drosophila suggest that the fundamental role of ligand endocytosis in notch signaling cells is not recycling. PLoS One 2011; 6:e18259. [PMID: 21448287 PMCID: PMC3063240 DOI: 10.1371/journal.pone.0018259] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 02/23/2011] [Indexed: 12/03/2022] Open
Abstract
Notch signaling requires ligand internalization by the signal sending cells. Two endocytic proteins, epsin and auxilin, are essential for ligand internalization and signaling. Epsin promotes clathrin-coated vesicle formation, and auxilin uncoats clathrin from newly internalized vesicles. Two hypotheses have been advanced to explain the requirement for ligand endocytosis. One idea is that after ligand/receptor binding, ligand endocytosis leads to receptor activation by pulling on the receptor, which either exposes a cleavage site on the extracellular domain, or dissociates two receptor subunits. Alternatively, ligand internalization prior to receptor binding, followed by trafficking through an endosomal pathway and recycling to the plasma membrane may enable ligand activation. Activation could mean ligand modification or ligand transcytosis to a membrane environment conducive to signaling. A key piece of evidence supporting the recycling model is the requirement in signaling cells for Rab11, which encodes a GTPase critical for endosomal recycling. Here, we use Drosophila Rab11 and auxilin mutants to test the ligand recycling hypothesis. First, we find that Rab11 is dispensable for several Notch signaling events in the eye disc. Second, we find that Drosophila female germline cells, the one cell type known to signal without clathrin, also do not require auxilin to signal. Third, we find that much of the requirement for auxilin in Notch signaling was bypassed by overexpression of both clathrin heavy chain and epsin. Thus, the main role of auxilin in Notch signaling is not to produce uncoated ligand-containing vesicles, but to maintain the pool of free clathrin. Taken together, these results argue strongly that at least in some cell types, the primary function of Notch ligand endocytosis is not for ligand recycling.
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Affiliation(s)
- Susan M. L. Banks
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Bomsoo Cho
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Suk Ho Eun
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Ji-Hoon Lee
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Sarah L. Windler
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Xuanhua Xie
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - David Bilder
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Janice A. Fischer
- Section of Molecular Cell and Developmental Biology and Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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26
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Suetsugu N, Takano A, Kohda D, Wada M. Structure and activity of JAC1 J-domain implicate the involvement of the cochaperone activity with HSC70 in chloroplast photorelocation movement. PLANT SIGNALING & BEHAVIOR 2010; 5:1602-6. [PMID: 21139434 PMCID: PMC3115112 DOI: 10.4161/psb.5.12.13915] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 10/11/2010] [Indexed: 05/20/2023]
Abstract
Chloroplast photorelocation movement towards weak light and away from strong light is essential for plants to adapt to the fluctuation of ambient light conditions. In the previous study, we showed that blue light receptor phototropins mediated blue light-induced chloroplast movement in Arabidopsis by regulating short actin filaments localized at the chloroplast periphery (cp-actin filaments) rather than actin cables in the cytoplasm. However, the signaling pathway for the chloroplast photorelocation movement is still unclear. We also identified JAC1 (J-domain protein required for chloroplast accumulation response 1) as an essential component for the accumulation response and dark positioning in Arabidopsis. We recently determined the crystal structure of the J-domain of JAC1. The JAC1 J-domain has a positively charged surface, which forms a putative interface with the Hsc70 chaperone by analogy to that of bovine auxilin. Furthermore, the mutation of the highly conserved HPD motif in the JAC1 J-domain impaired the in vivo activity of JAC1. These data suggest that JAC1 cochaperone activity with HSC70 is essential for chloroplast photorelocation movement.
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Affiliation(s)
- Noriyuki Suetsugu
- Department of Biology; Faculty of Sciences; Kyushu University; Fukuoka, Japan
| | - Akira Takano
- Division of Structural Biology; Medical Institute of Bioregulation; Kyushu University; Fukuoka, Japan
| | - Daisuke Kohda
- Division of Structural Biology; Medical Institute of Bioregulation; Kyushu University; Fukuoka, Japan
| | - Masamitsu Wada
- Department of Biology; Faculty of Sciences; Kyushu University; Fukuoka, Japan
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27
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Susa M, Choy E, Liu X, Schwab J, Hornicek FJ, Mankin H, Duan Z. Cyclin G-associated kinase is necessary for osteosarcoma cell proliferation and receptor trafficking. Mol Cancer Ther 2010; 9:3342-50. [PMID: 20881269 DOI: 10.1158/1535-7163.mct-10-0637] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Osteosarcoma is the most frequent primary malignant bone tumor among the children. The advent of neoadjuvant chemotherapy significantly improved the prognosis of patients with osteosarcoma in the 1980s, but it has since plateaued in the past decades. Recently, one of the most researched areas in sarcoma treatment is tyrosine kinases. Here, we describe research on a serine/threonine kinase, cyclin G-associated kinase (GAK), which has not been reported in osteosarcoma previously. In this study, a lentiviral based human shRNA library was utilized to screen for kinases in KHOS and U-2OS osteosarcoma cells. The expression of GAK was examined in osteosarcoma and the effect on cell proliferation was analyzed by GAK siRNA knockdown. The level of GAK expression and its correlation to prognosis was analyzed in osteosarcoma tissue microarray. The effect of GAK depletion on insulin-like growth factor and epidermal growth factor receptor-mediated signal transduction was analyzed by Western blot. We observed that GAK was overexpressed in both osteosarcoma cell lines and tissue samples when compared with human osteoblasts. GAK knockdown by siRNA decreased cell proliferation in both drug-sensitive and multidrug-resistant osteosarcoma cell lines. Immunohistochemistry of osteosarcoma tissue microarray revealed that overexpression of GAK was associated with poor prognosis. Finally, knockdown of GAK resulted in alterations of receptor trafficking and several downstream proteins. In conclusion, our results suggest that osteosarcoma cell proliferation and survival are dependent on GAK. These findings may lead to the development of new therapeutic options for osteosarcoma.
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Affiliation(s)
- Michiro Susa
- Department of Orthopaedic Surgery, and SarcomaBiology Laboratory, Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Boston, MA 02114, USA
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28
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Abstract
Numerous studies have shown that the clinical antidepressant sertraline (Zoloft) is biologically active in model systems, including fungi, which do not express its putative protein target, the serotonin/5-HT transporter, thus demonstrating the existence of one or more secondary targets. Here we show that in the absence of its putative protein target, sertraline targets phospholipid membranes that comprise the acidic organelles of the intracellular vesicle transport system by a mechanism consistent with the bilayer couple hypothesis. On the basis of a combination of drug-resistance selection and chemical-genomic screening, we hypothesize that loss of vacuolar ATPase activity reduces uptake of sertraline into cells, whereas dysregulation of clathrin function reduces the affinity of membranes for sertraline. Remarkably, sublethal doses of sertraline stimulate growth of mutants with impaired clathrin function. Ultrastructural studies of sertraline-treated cells revealed a phenotype that resembles phospholipidosis induced by cationic amphiphilic drugs in mammalian cells. Using reconstituted enzyme assays, we also demonstrated that sertraline inhibits phospholipase A(1) and phospholipase D, exhibits mixed effects on phospholipase C, and activates phospholipase A(2). Overall, our study identifies two evolutionarily conserved membrane--active processes-vacuolar acidification and clathrin-coat formation--as modulators of sertraline's action at membranes.
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29
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Martineau CN, Melki R, Kabani M. Swa2p-dependent clathrin dynamics is critical for Flo11p processing and ‘Mat’ formation in the yeastSaccharomyces cerevisiae. FEBS Lett 2010; 584:1149-55. [DOI: 10.1016/j.febslet.2010.02.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 01/26/2010] [Accepted: 02/02/2010] [Indexed: 11/26/2022]
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Vembar SS, Jin Y, Brodsky JL, Hendershot LM. The mammalian Hsp40 ERdj3 requires its Hsp70 interaction and substrate-binding properties to complement various yeast Hsp40-dependent functions. J Biol Chem 2009; 284:32462-71. [PMID: 19748898 DOI: 10.1074/jbc.m109.000729] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Heat shock proteins of 70 kDa (Hsp70s) and their J domain-containing Hsp40 cofactors are highly conserved chaperone pairs that facilitate a large number of cellular processes. The observation that each Hsp70 partners with many J domain-containing proteins (JDPs) has led to the hypothesis that Hsp70 function is dictated by cognate JDPs. If this is true, one might expect highly divergent Hsp70-JDP pairs to be unable to function in vivo. However, we discovered that, when a yeast cytosolic JDP, Ydj1, was targeted to the mammalian endoplasmic reticulum (ER), it interacted with the ER-lumenal Hsp70, BiP, and bound to BiP substrates. Conversely, when a mammalian ER-lumenal JDP, ERdj3, was directed to the yeast cytosol, it rescued the temperature-sensitive growth phenotype of yeast-containing mutant alleles in two cytosolic JDPs, HLJ1 and YDJ1, and activated the ATP hydrolysis rate of Ssa1, the yeast cytosolic Hsp70 that partners with Hlj1 and Ydj1. Surprisingly, ERdj3 mutants that were compromised for substrate binding were unable to rescue the hlj1ydj1 growth defect even though they stimulated the ATPase activity of Ssa1. Yet, J domain mutants of ERdj3 that were defective for interaction with Ssa1 restored the growth of hlj1ydj1 yeast. Taken together, these data suggest that the substrate binding properties of certain JDPs, not simply the formation of unique Hsp70-JDP pairs, are critical to specify in vivo function.
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Affiliation(s)
- Shruthi S Vembar
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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31
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Muthusamy BP, Raychaudhuri S, Natarajan P, Abe F, Liu K, Prinz WA, Graham TR. Control of protein and sterol trafficking by antagonistic activities of a type IV P-type ATPase and oxysterol binding protein homologue. Mol Biol Cell 2009; 20:2920-31. [PMID: 19403696 DOI: 10.1091/mbc.e08-10-1036] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The oxysterol binding protein homologue Kes1p has been implicated in nonvesicular sterol transport in Saccharomyces cerevisiae. Kes1p also represses formation of protein transport vesicles from the trans-Golgi network (TGN) through an unknown mechanism. Here, we show that potential phospholipid translocases in the Drs2/Dnf family (type IV P-type ATPases [P4-ATPases]) are downstream targets of Kes1p repression. Disruption of KES1 suppresses the cold-sensitive (cs) growth defect of drs2Delta, which correlates with an enhanced ability of Dnf P4-ATPases to functionally substitute for Drs2p. Loss of Kes1p also suppresses a drs2-ts allele in a strain deficient for Dnf P4-ATPases, suggesting that Kes1p antagonizes Drs2p activity in vivo. Indeed, Drs2-dependent phosphatidylserine translocase (flippase) activity is hyperactive in TGN membranes from kes1Delta cells and is potently attenuated by addition of recombinant Kes1p. Surprisingly, Drs2p also antagonizes Kes1p activity in vivo. Drs2p deficiency causes a markedly increased rate of cholesterol transport from the plasma membrane to the endoplasmic reticulum (ER) and redistribution of endogenous ergosterol to intracellular membranes, phenotypes that are Kes1p dependent. These data suggest a homeostatic feedback mechanism in which appropriately regulated flippase activity in the Golgi complex helps establish a plasma membrane phospholipid organization that resists sterol extraction by a sterol binding protein.
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32
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Muthusamy BP, Natarajan P, Zhou X, Graham TR. Linking phospholipid flippases to vesicle-mediated protein transport. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:612-9. [PMID: 19286470 DOI: 10.1016/j.bbalip.2009.03.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Revised: 03/03/2009] [Accepted: 03/04/2009] [Indexed: 11/16/2022]
Abstract
Type IV P-type ATPases (P4-ATPases) are a large family of putative phospholipid translocases (flippases) implicated in the generation of phospholipid asymmetry in biological membranes. P4-ATPases are typically the largest P-type ATPase subgroup found in eukaryotic cells, with five members in Saccharomyces cerevisiae, six members in Caenorhabditis elegans, 12 members in Arabidopsis thaliana and 14 members in humans. In addition, many of the P4-ATPases require interaction with a noncatalytic subunit from the CDC50 gene family for their transport out of the endoplasmic reticulum (ER). Deficiency of a P4-ATPase (Atp8b1) causes liver disease in humans, and studies in a variety of model systems indicate that P4-ATPases play diverse and essential roles in membrane biogenesis. In addition to their proposed role in establishing and maintaining plasma membrane asymmetry, P4-ATPases are linked to vesicle-mediated protein transport in the exocytic and endocytic pathways. Recent studies have also suggested a role for P4-ATPases in the nonvesicular intracellular trafficking of sterols. Here, we discuss the physiological requirements for yeast P4-ATPases in phospholipid translocase activity, transport vesicle budding and ergosterol metabolism, with an emphasis on Drs2p and its noncatalytic subunit, Cdc50p.
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33
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Matta-Camacho E, Kozlov G, Trempe JF, Gehring K. Atypical Binding of the Swa2p UBA Domain to Ubiquitin. J Mol Biol 2009; 386:569-77. [DOI: 10.1016/j.jmb.2008.09.086] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 09/30/2008] [Accepted: 09/30/2008] [Indexed: 10/21/2022]
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Hirst J, Sahlender DA, Li S, Lubben NB, Borner GHH, Robinson MS. Auxilin depletion causes self-assembly of clathrin into membraneless cages in vivo. Traffic 2008; 9:1354-71. [PMID: 18489706 PMCID: PMC2628426 DOI: 10.1111/j.1600-0854.2008.00764.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Auxilin is a cofactor for Hsc70-mediated uncoating of clathrin-coated vesicles (CCVs). However, small interfering RNA (siRNA) knockdown of the ubiquitous auxilin 2 in HeLa cells only moderately impairs clathrin-dependent trafficking. In this study, we show that HeLa cells also express auxilin 1, previously thought to be neuron specific, and that both auxilins need to be depleted for inhibition of clathrin-mediated endocytosis and intracellular sorting. Depleting both auxilins cause an ∼50% reduction in the number of clathrin-coated pits at the plasma membrane but enhances the association of clathrin and adaptors with intracellular membranes. CCV fractions isolated from auxilin-depleted cells have an ∼1.5-fold increase in clathrin content and more than fivefold increase in the amount of AP-2 adaptor complex and other endocytic machinery, with no concomitant increase in cargo. In addition, the structures isolated from auxilin-depleted cells are on average smaller than CCVs from control cells and are largely devoid of membrane, indicating that they are not CCVs but membraneless clathrin cages. Similar structures are observed by electron microscopy in intact auxilin-depleted HeLa cells. Together, these findings indicate that the two auxilins have overlapping functions and that they not only facilitate the uncoating of CCVs but also prevent the formation of nonproductive clathrin cages in the cytosol.
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Affiliation(s)
- Jennifer Hirst
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust, Addenbrooke's Hospital, Cambridge, UK.
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35
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Kandachar V, Bai T, Chang HC. The clathrin-binding motif and the J-domain of Drosophila Auxilin are essential for facilitating Notch ligand endocytosis. BMC DEVELOPMENTAL BIOLOGY 2008; 8:50. [PMID: 18466624 PMCID: PMC2391152 DOI: 10.1186/1471-213x-8-50] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 05/08/2008] [Indexed: 11/24/2022]
Abstract
Background Ligand endocytosis plays a critical role in regulating the activity of the Notch pathway. The Drosophila homolog of auxilin (dAux), a J-domain-containing protein best known for its role in the disassembly of clathrin coats from clathrin-coated vesicles, has recently been implicated in Notch signaling, although its exact mechanism remains poorly understood. Results To understand the role of auxilin in Notch ligand endocytosis, we have analyzed several point mutations affecting specific domains of dAux. In agreement with previous work, analysis using these stronger dAux alleles shows that dAux is required for several Notch-dependent processes, and its function during Notch signaling is required in the signaling cells. In support of the genetic evidences, the level of Delta appears elevated in dAux deficient cells, suggesting that the endocytosis of Notch ligand is disrupted. Deletion analysis shows that the clathrin-binding motif and the J-domain, when over-expressed, are sufficient for rescuing dAux phenotypes, implying that the recruitment of Hsc70 to clathrin is a critical role for dAux. However, surface labeling experiment shows that, in dAux mutant cells, Delta accumulates at the cell surface. In dAux mutant cells, clathrin appears to form large aggregates, although Delta is not enriched in these aberrant clathrin-positive structures. Conclusion Our data suggest that dAux mutations inhibit Notch ligand internalization at an early step during clathrin-mediated endocytosis, before the disassembly of clathrin-coated vesicles. Further, the inhibition of ligand endocytosis in dAux mutant cells possibly occurs due to depletion of cytosolic pools of clathrin via the formation of clathrin aggregates. Together, our observations argue that ligand endocytosis is critical for Notch signaling and auxilin participates in Notch signaling by facilitating ligand internalization.
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Affiliation(s)
- Vasundhara Kandachar
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907-2054, USA.
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36
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Lee DW, Zhao X, Yim YI, Eisenberg E, Greene LE. Essential role of cyclin-G-associated kinase (Auxilin-2) in developing and mature mice. Mol Biol Cell 2008; 19:2766-76. [PMID: 18434600 DOI: 10.1091/mbc.e07-11-1115] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Hsc70 with its cochaperone, either auxilin or GAK, not only uncoats clathrin-coated vesicles but also acts as a chaperone during clathrin-mediated endocytosis. However, because synaptojanin is also involved in uncoating, it is not clear whether GAK is an essential gene. To answer this question, GAK conditional knockout mice were generated and then mated to mice expressing Cre recombinase under the control of the nestin, albumin, or keratin-14 promoters, all of which turn on during embryonic development. Deletion of GAK from brain, liver, or skin dramatically altered the histology of these tissues, causing the mice to die shortly after birth. Furthermore, by expressing a tamoxifen-inducible promoter to express Cre recombinase we showed that deletion of GAK caused lethality in adult mice. Mouse embryonic fibroblasts in which the GAK was disrupted showed a lack of clathrin-coated pits and a complete block in clathrin-mediated endocytosis. We conclude that GAK deletion blocks development and causes lethality in adult animals by disrupting clathrin-mediated endocytosis.
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Affiliation(s)
- Dong-Won Lee
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-0301, USA
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37
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Abstract
Endocytosis regulates Notch signaling in both signaling and receiving cells. A puzzling observation is that endocytosis of transmembrane ligand by the signaling cells is required for Notch activation in adjacent receiving cells. A key to understanding why signaling depends on ligand endocytosis lies in identifying and understanding the functions of crucial endocytic proteins. One such protein is Epsin, an endocytic factor first identified in vertebrate cells. Here, we show in Drosophila that Auxilin, an endocytic factor that regulates Clathrin dynamics, is also essential for Notch signaling. Auxilin, a co-factor for the ATPase Hsc70, brings Hsc70 to Clathrin cages. Hsc70/Auxilin functions in vesicle scission and also in uncoating Clathrin-coated vesicles. We find that like Epsin, Auxilin is required in Notch signaling cells for ligand internalization and signaling. Results of several experiments suggest that the crucial role of Auxilin in signaling is, at least in part, the generation of free Clathrin. We discuss these observations in the light of current models for the role of Epsin in ligand endocytosis and the role of ligand endocytosis in Notch signaling.
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Affiliation(s)
- Suk Ho Eun
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA
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38
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Rapoport I, Boll W, Yu A, Böcking T, Kirchhausen T. A motif in the clathrin heavy chain required for the Hsc70/auxilin uncoating reaction. Mol Biol Cell 2007; 19:405-13. [PMID: 17978091 DOI: 10.1091/mbc.e07-09-0870] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The 70-kDa heat-shock cognate protein (Hsc70) chaperone is an ATP-dependent "disassembly enzyme" for many subcellular structures, including clathrin-coated vesicles where it functions as an uncoating ATPase. Hsc70, and its cochaperone auxilin together catalyze coat disassembly. Like other members of the Hsp70 chaperone family, it is thought that ATP-bound Hsc70 recognizes the clathrin triskelion through an unfolded exposed hydrophobic segment. The best candidate is the unstructured C terminus (residues 1631-1675) of the heavy chain at the foot of the tripod below the hub, containing the sequence motif QLMLT, closely related to the sequence bound preferentially by the substrate groove of Hsc70 (Fotin et al., 2004b). To test this hypothesis, we generated in insect cells recombinant mammalian triskelions that in vitro form clathrin cages and clathrin/AP-2 coats exactly like those assembled from native clathrin. We show that coats assembled from recombinant clathrin are good substrates for ATP- and auxilin-dependent, Hsc70-catalyzed uncoating. Finally, we show that this uncoating reaction proceeds normally when the coats contain recombinant heavy chains truncated C-terminal to the QLMLT motif, but very inefficiently when the motif is absent. Thus, the QLMLT motif is required for Hsc-70-facilitated uncoating, consistent with the proposal that this sequence is a specific target of the chaperone.
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Affiliation(s)
- Iris Rapoport
- Department of Cell Biology and Immune Disease Institute, Harvard Medical School, Boston, MA 02115, USA
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39
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Abstract
The ATP-dependent dissociation of clathrin from clathrin-coated vesicles (CCVs) by the molecular chaperone Hsc70 requires J-domain cofactor proteins, either auxilin or cyclin-G-associated kinase (GAK). Both the nerve-specific auxilin and the ubiquitous GAK induce CCVs to bind to Hsc70. The removal of auxilin or GAK from various organisms and cells has provided definitive evidence that Hsc70 uncoats CCVs in vivo. In addition, evidence from various studies has suggested that Hsc70 and auxilin are involved in several other key processes that occur during clathrin-mediated endocytosis. First, Hsc70 and auxilin are required for the clathrin exchange that occurs during coated-pit invagination and constriction; this clathrin exchange may catalyze any rearrangement of the clathrin-coated pit (CCP) structure that is required during invagination and constriction. Second, Hsc70 and auxilin may chaperone clathrin after it dissociates from CCPs so that it does not aggregate in the cytosol. Third, auxilin and Hsc70 may be involved in the rebinding of clathrin to the plasma membrane to form new CCPs and independently appear to chaperone adaptor proteins so that they can also rebind to membranes to nucleate the formation of new CCPs. Finally, if formation of the curved clathrin coat induces membrane curvature, then Hsc70 and auxilin provide the energy for this curvature by inducing ATP-dependent clathrin exchange and rearrangement during endocytosis and ATP-dependent dissociation of clathrin at the end of the cycle so that it is energetically primed to rebind to the plasma membrane.
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Affiliation(s)
- Evan Eisenberg
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD 20892-0301, USA
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40
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Eun SH, Lea K, Overstreet E, Stevens S, Lee JH, Fischer JA. Identification of genes that interact with Drosophila liquid facets. Genetics 2006; 175:1163-74. [PMID: 17179082 PMCID: PMC1840095 DOI: 10.1534/genetics.106.067959] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have performed mutagenesis screens of the Drosophila X chromosome and the autosomes for dominant enhancers of the rough eye resulting from overexpression of liquid facets. The liquid facets gene encodes the homolog of vertebrate endocytic Epsin, an endocytic adapter protein. In Drosophila, Liquid facets is a core component of the Notch signaling pathway required in the signaling cells for ligand endocytosis and signaling. Why ligand internalization by the signaling cells is essential for signaling is a mystery. The requirement for Liquid facets is a hint at the answer, and the genes identified in this screen provide further clues. Mutant alleles of clathrin heavy chain, Rala, split ends, and auxilin were identified as enhancers. We describe the mutant alleles and mutant phenotypes of Rala and aux. We discuss the relevance of all of these genetic interactions to the function of Liquid facets in Notch signaling.
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Affiliation(s)
- Suk Ho Eun
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA
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41
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Han C, Chen T, Li N, Yang M, Wan T, Cao X. HDJC9, a novel human type C DnaJ/HSP40 member interacts with and cochaperones HSP70 through the J domain. Biochem Biophys Res Commun 2006; 353:280-5. [PMID: 17182002 DOI: 10.1016/j.bbrc.2006.12.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 12/02/2006] [Indexed: 11/29/2022]
Abstract
HSP40s are a subfamily of heat shock proteins (HSPs) and play important roles in regulation of cell proliferation, survival and apoptosis by serving as chaperones for HSP70s. Up to date hundreds of HSP40 proteins derived from various species ranging from Escherichia coli to homo sapiens have been identified. Here we report the cloning and characterization of a novel human type C DnaJ homologue, HDJC9, containing a typical N-terminal J domain. HDJC9 is upregulated at both mRNA and protein levels upon various stress and mitogenic stimulations. HDJC9 is mainly localized in cell nuclei under normal culture conditions while it is transported into cytoplasm and plasma membrane upon heat shock stress through a non-classical and lipid-dependent pathway. HDJC9 can interact with HSP70s and activate the ATPase activity of HSP70s, both of which are dependent on the J domain. Our data suggest that HDJC9 is a novel cochaperone for HSP70s.
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Affiliation(s)
- Chaofeng Han
- Institute of Immunology, Tsinghua University, Beijing 100084, PR China
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42
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Du Y, Walker L, Novick P, Ferro-Novick S. Ptc1p regulates cortical ER inheritance via Slt2p. EMBO J 2006; 25:4413-22. [PMID: 16977319 PMCID: PMC1589985 DOI: 10.1038/sj.emboj.7601319] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Accepted: 08/09/2006] [Indexed: 01/28/2023] Open
Abstract
Studies in the yeast Saccharomyces cerevisiae have shown that the inheritance of endoplasmic reticulum (ER), mitochondria, and vacuoles involves the capture of a tubular structure at the bud tip. Ptc1p, a serine/threonine phosphatase, has previously been shown to regulate mitochondrial inheritance by an unknown mechanism. Ptc1p regulates the high osmolarity glycerol mitogen-activated protein kinase (MAPK) pathway and has also been implicated in the cell wall integrity (CWI) MAPK pathway. Here we show that the loss of Ptc1p or the Ptc1p binding protein, Nbp2p, causes a prominent delay in the delivery of ER tubules to the periphery of daughter cells and results in a dramatic increase in the level of phosphorylated Slt2p, the MAPK in the CWI pathway. Either loss of Slt2p or inhibition of the CWI pathway by addition of sorbitol, suppresses the ER inheritance defect in the ptc1Delta and nbp2Delta mutants. Our findings indicate that Ptc1p and Nbp2p regulate ER inheritance through the CWI MAPK pathway by modulating the MAPK, Slt2p.
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Affiliation(s)
- Yunrui Du
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA
| | - Lee Walker
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA
| | - Peter Novick
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Susan Ferro-Novick
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Cell Biology, Yale University School of Medicine, Boyer Center for Molecular Medicine, Howard Hughes Medical Institute, 295 Congress Avenue, Room 254B, New Haven, CT 06519-1418, USA. Tel.: +1 203 737 5207; Fax: +1 203 737 5746; E-mail:
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43
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Chen S, Wang J, Muthusamy BP, Liu K, Zare S, Andersen RJ, Graham TR. Roles for the Drs2p-Cdc50p Complex in Protein Transport and Phosphatidylserine Asymmetry of the Yeast Plasma Membrane. Traffic 2006; 7:1503-17. [PMID: 16956384 DOI: 10.1111/j.1600-0854.2006.00485.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Drs2p, a P-type adenosine triphosphatase required for a phosphatidylserine (PS) flippase activity in the yeast trans Golgi network (TGN), was first implicated in protein trafficking by a screen for mutations synthetically lethal with arf1 (swa). Here, we show that SWA4 is allelic to CDC50, encoding a membrane protein previously shown to chaperone Drs2p from the endoplasmic reticulum to the Golgi complex. We find that cdc50Delta exhibits the same clathrin-deficient phenotypes as drs2Delta, including delayed transport of carboxypeptidase Y to the vacuole, mislocalization of resident TGN enzymes and the accumulation of aberrant membrane structures. These trafficking defects precede appearance of cell polarity defects in cdc50Delta, suggesting that the latter are a secondary consequence of disrupting Golgi function. Involvement of Drs2p-Cdc50p in PS translocation suggests a role in restricting PS to the cytosolic leaflet of the Golgi and plasma membrane. Annexin V binding and papuamide B hypersensitivity indicate that drs2Delta or cdc50Delta causes a loss of plasma membrane PS asymmetry. However, clathrin and other endocytosis null mutants also exhibit a comparable loss of PS asymmetry, and studies with drs2-ts and clathrin (chc1-ts) conditional mutants suggest that loss of plasma membrane asymmetry is a secondary consequence of disrupting protein trafficking.
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Affiliation(s)
- Sophie Chen
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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44
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Hagedorn EJ, Bayraktar JL, Kandachar VR, Bai T, Englert DM, Chang HC. Drosophila melanogaster auxilin regulates the internalization of Delta to control activity of the Notch signaling pathway. ACTA ACUST UNITED AC 2006; 173:443-52. [PMID: 16682530 PMCID: PMC2063844 DOI: 10.1083/jcb.200602054] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have isolated mutations in the Drosophila melanogaster homologue of auxilin, a J-domain-containing protein known to cooperate with Hsc70 in the disassembly of clathrin coats from clathrin-coated vesicles in vitro. Consistent with this biochemical role, animals with reduced auxilin function exhibit genetic interactions with Hsc70 and clathrin. Interestingly, the auxilin mutations interact specifically with Notch and disrupt several Notch-mediated processes. Genetic evidence places auxilin function in the signal-sending cells, upstream of Notch receptor activation, suggesting that the relevant cargo for this auxilin-mediated endocytosis is the Notch ligand Delta. Indeed, the localization of Delta protein is disrupted in auxilin mutant tissues. Thus, our data suggest that auxilin is an integral component of the Notch signaling pathway, participating in the ubiquitin-dependent endocytosis of Delta. Furthermore, the fact that auxilin is required for Notch signaling suggests that ligand endocytosis in the signal-sending cells needs to proceed past coat disassembly to activate Notch.
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MESH Headings
- Animals
- Auxilins/genetics
- Auxilins/physiology
- Body Patterning/genetics
- Body Patterning/physiology
- Clathrin/genetics
- Clathrin/metabolism
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/physiology
- Endocytosis/genetics
- Endocytosis/physiology
- ErbB Receptors/genetics
- ErbB Receptors/physiology
- Eye Abnormalities/genetics
- Eye Abnormalities/ultrastructure
- Gene Expression Regulation, Developmental
- Genotype
- HSC70 Heat-Shock Proteins/genetics
- HSC70 Heat-Shock Proteins/metabolism
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Microscopy, Electron, Scanning
- Mutation/genetics
- Nervous System/embryology
- Nervous System/metabolism
- Phenotype
- Photoreceptor Cells, Invertebrate/embryology
- Photoreceptor Cells, Invertebrate/metabolism
- RNA, Small Interfering/genetics
- Receptors, Notch/genetics
- Receptors, Notch/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Wings, Animal/embryology
- Wings, Animal/metabolism
- Wings, Animal/ultrastructure
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Affiliation(s)
- Elliott J Hagedorn
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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45
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Xiao J, Kim LS, Graham TR. Dissection of Swa2p/auxilin domain requirements for cochaperoning Hsp70 clathrin-uncoating activity in vivo. Mol Biol Cell 2006; 17:3281-90. [PMID: 16687570 PMCID: PMC1483056 DOI: 10.1091/mbc.e06-02-0106] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 04/17/2006] [Accepted: 04/27/2006] [Indexed: 11/11/2022] Open
Abstract
The auxilin family of J-domain proteins load Hsp70 onto clathrin-coated vesicles (CCVs) to drive uncoating. In vitro, auxilin function requires its ability to bind clathrin and stimulate Hsp70 ATPase activity via its J-domain. To test these requirements in vivo, we performed a mutational analysis of Swa2p, the yeast auxilin ortholog. Swa2p is a modular protein with three N-terminal clathrin-binding (CB) motifs, a ubiquitin association (UBA) domain, a tetratricopeptide repeat (TPR) domain, and a C-terminal J-domain. In vitro, clathrin binding is mediated by multiple weak interactions, but a Swa2p truncation lacking two CB motifs and the UBA domain retains nearly full function in vivo. Deletion of all CB motifs strongly abrogates clathrin disassembly but does not eliminate Swa2p function in vivo. Surprisingly, mutation of the invariant HPD motif within the J-domain to AAA only partially affects Swa2p function. Similarly, a TPR point mutation (G388R) causes a modest phenotype. However, Swa2p function is abolished when these TPR and J mutations are combined. The TPR and J-domains are not functionally redundant because deletion of either domain renders Swa2p nonfunctional. These data suggest that the TPR and J-domains collaborate in a bipartite interaction with Hsp70 to regulate its activity in clathrin disassembly.
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Affiliation(s)
- Jing Xiao
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235-1634
| | - Leslie S. Kim
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235-1634
| | - Todd R. Graham
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235-1634
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46
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Fernández GE, Payne GS. Laa1p, a conserved AP-1 accessory protein important for AP-1 localization in yeast. Mol Biol Cell 2006; 17:3304-17. [PMID: 16687571 PMCID: PMC1483057 DOI: 10.1091/mbc.e06-02-0096] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
AP-1 and Gga adaptors participate in clathrin-mediated protein transport between the trans-Golgi network and endosomes. Both adaptors contain homologous domains that act to recruit accessory proteins involved in clathrin-coated vesicle formation, but the spectrum of known adaptor-binding partners is limited. This study describes an evolutionarily conserved protein of Saccharomyces cerevisiae, Laa1p (Yjl207cp), that interacts and functions specifically with AP-1. Deletion of LAA1, when combined with a conditional mutation in clathrin heavy chain or deletion of GGA genes, accentuated growth defects and increased disruption of clathrin-dependent alpha-factor maturation and transport of carboxypeptidase Y to the vacuole. In contrast, such genetic interactions were not observed between deletions of LAA1 and AP-1 subunit genes. Laa1p preferentially interacted with AP-1 compared with Gga proteins by glutathione S-transferase-fusion affinity binding and coimmunoprecipitations. Localization of AP-1 and Laa1p, but not Gga proteins, was highly sensitive to brefeldin A, an inhibitor of ADP-ribosylation factor (Arf) activation. Importantly, deletion of LAA1 caused mislocalization of AP-1, especially in cells at high density (postdiauxic shift), but it did not affect Gga protein distribution. Our results identify Laa1p as a new determinant of AP-1 localization, suggesting a model in which Laa1p and Arf cooperate to direct stable association of AP-1 with appropriate intracellular membranes.
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Affiliation(s)
- G. Esteban Fernández
- Department of Biological Chemistry, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Gregory S. Payne
- Department of Biological Chemistry, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
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47
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Estrada de Martin P, Novick P, Ferro-Novick S. The organization, structure, and inheritance of the ER in higher and lower eukaryotes. Biochem Cell Biol 2006; 83:752-61. [PMID: 16333327 DOI: 10.1139/o05-159] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The endoplasmic reticulum (ER) is a fundamental organelle required for protein assembly, lipid biosynthesis, and vesicular traffic, as well as calcium storage and the controlled release of calcium from the ER lumen into the cytosol. Membranes functionally linked to the ER by vesicle-mediated transport, such as the Golgi complex, endosomes, vacuoles-lysosomes, secretory vesicles, and the plasma membrane, originate largely from proteins and lipids synthesized in the ER. In this review we will discuss the structural organization of the ER and its inheritance.
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Affiliation(s)
- Paula Estrada de Martin
- Department of Cell Biology, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT 06519, USA
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48
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Zhang CX, Engqvist-Goldstein AEY, Carreno S, Owen DJ, Smythe E, Drubin DG. Multiple roles for cyclin G-associated kinase in clathrin-mediated sorting events. Traffic 2006; 6:1103-13. [PMID: 16262722 DOI: 10.1111/j.1600-0854.2005.00346.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Cyclin G-associated kinase (GAK), also known as auxilin 2, is a potential regulator of clathrin-mediated membrane trafficking. It possesses a kinase domain at its N-terminus that can phosphorylate the clathrin adaptors AP-1 and AP-2 in vitro. The GAK C-terminus can act as a cochaperaone in vitro for Hsc70, a heat-shock protein required for clathrin uncoating. Here we show that the specificity of GAK is very similar to that of adaptor-associated kinase 1, another mammalian adaptor kinase. We used siRNA to investigate GAK's in vivo function. We discovered that early stages of clathrin-mediated endocytosis (CME) were partially inhibited when GAK expression was knocked down. This defect was specifically caused by GAK knockdown because it could be rescued by expressing a rat GAK gene that could not be silenced by one of the siRNAs. To identify the GAK activity required during CME, we mutated the kinase domain and the J domain of the rat gene. Only GAK with a functional J domain could rescue the defect, suggesting that GAK is important for clathrin uncoating. Furthermore, we demonstrated that GAK plays a role in the clathrin-dependent trafficking from the trans Golgi network.
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Affiliation(s)
- Claire X Zhang
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
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49
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Lee DW, Zhao X, Zhang F, Eisenberg E, Greene LE. Depletion of GAK/auxilin 2 inhibits receptor-mediated endocytosis and recruitment of both clathrin and clathrin adaptors. J Cell Sci 2006; 118:4311-21. [PMID: 16155256 DOI: 10.1242/jcs.02548] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cyclin G-associated kinase (GAK/auxilin 2), the ubiquitous form of the neuronal-specific protein auxilin 1, is an essential cofactor for the Hsc70-dependent uncoating of clathrin-coated vesicles. We have now investigated the effect of knocking down GAK in HeLa cells by vector-based small hairpin RNA. Functionally, depletion of GAK caused a marked decrease in internalization of both transferrin and epidermal growth factor and altered mannose 6-phosphate receptor trafficking, but had little effect on the recycling of transferrin receptor back to the plasma membrane. Structurally, depletion of GAK caused a marked reduction in perinuclear clathrin associated with the trans-Golgi network and in the number of clathrin-coated pits on the plasma membrane, and reduced clathrin exchange on the few clathrin-coated pits that remained. Surprisingly, while clathrin depletion does not prevent adaptors from assembling on the membrane, depletion of GAK caused a dramatic reduction in AP2 and epsin on the plasma membrane and AP1 and GGA at the trans-Golgi network. A similar effect was caused by expression of a dominant negative Hsp70 mutant. These results suggest that GAK, in conjunction with Hsc70, not only uncoats clathrin-coated vesicles and induces clathrin exchange on clathrin-coated pits, but also mediates binding of clathrin and adaptors to the plasma membrane and the trans-Golgi network.
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Affiliation(s)
- Dong-won Lee
- Laboratory of Cell Biology, NHLBI, 50 South Drive, Rm 2537, MSC 8017, NIH, Bethesda, MD 20892-0301, USA
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50
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Craig EA, Huang P, Aron R, Andrew A. The diverse roles of J-proteins, the obligate Hsp70 co-chaperone. Rev Physiol Biochem Pharmacol 2006; 156:1-21. [PMID: 16634144 DOI: 10.1007/s10254-005-0001-0] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Hsp70s and J-proteins, which constitute one of the most ubiquitous types of molecular chaperone machineries, function in a wide variety of cellular processes. J-proteins play a central role by stimulating an Hsp70's ATPase activity, thereby stabilizing its interaction with client proteins. However, while all J-proteins serve this core purpose, individual proteins are both structurally and functionally diverse. Some, but not all, J-proteins interact with client polypeptides themselves, facilitating their binding to an Hsp70. Some J-proteins have many client proteins, others only one. Certain J-proteins, while not others, are tethered to particular locations within a cellular compartment, thus "recruiting" Hsp70s to the vicinity of their clients. Here we review recent work on the diverse family of J-proteins, outlining emerging themes concerning their function.
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Affiliation(s)
- E A Craig
- University of Wisconsin-Madison, 441E Biochemistry Addition, Department of Biochemistry, 433 Babcock Drive, Madison, 53706 WI, USA.
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