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Song J, Lee MH, Lee GJ, Yoo CM, Hwang I. Arabidopsis EPSIN1 plays an important role in vacuolar trafficking of soluble cargo proteins in plant cells via interactions with clathrin, AP-1, VTI11, and VSR1. THE PLANT CELL 2006; 18:2258-74. [PMID: 16905657 PMCID: PMC1560928 DOI: 10.1105/tpc.105.039123] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Epsin and related proteins play important roles in various steps of protein trafficking in animal and yeast cells. Many epsin homologs have been identified in plant cells from analysis of genome sequences. However, their roles have not been elucidated. Here, we investigate the expression, localization, and biological role in protein trafficking of an epsin homolog, Arabidopsis thaliana EPSIN1, which is expressed in most tissues we examined. In the cell, one pool of EPSIN1 is associated with actin filaments, producing a network pattern, and a second pool localizes primarily to the Golgi complex with a minor portion to the prevacuolar compartment, producing a punctate staining pattern. Protein pull-down and coimmunoprecipitation experiments reveal that Arabidopsis EPSIN1 interacts with clathrin, VTI11, gamma-adaptin-related protein (gamma-ADR), and vacuolar sorting receptor1 (VSR1). In addition, EPSIN1 colocalizes with clathrin and VTI11. The epsin1 mutant, which has a T-DNA insertion in EPSIN1, displays a defect in the vacuolar trafficking of sporamin:green fluorescent protein (GFP), but not in the secretion of invertase:GFP into the medium. Stably expressed HA:EPSIN1 complements this trafficking defect. Based on these data, we propose that EPSIN1 plays an important role in the vacuolar trafficking of soluble proteins at the trans-Golgi network via its interaction with gamma-ADR, VTI11, VSR1, and clathrin.
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Affiliation(s)
- Jinhee Song
- Division of Molecular and Life Sciences and Center for Plant Intracellular Trafficking, Pohang University of Science and Technology, Pohang 790-784, Korea
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52
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Costaguta G, Duncan MC, Fernández GE, Huang GH, Payne GS. Distinct roles for TGN/endosome epsin-like adaptors Ent3p and Ent5p. Mol Biol Cell 2006; 17:3907-20. [PMID: 16790491 PMCID: PMC1624859 DOI: 10.1091/mbc.e06-05-0410] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Clathrin adaptors are key factors in clathrin-coated vesicle formation, coupling clathrin to cargo and/or the lipid bilayer. A physically interacting network of three classes of adaptors participate in clathrin-mediated traffic between the trans-Golgi network (TGN) and endosomes: AP-1, Gga proteins, and epsin-like proteins. Here we investigate functional relationships within this network through transport assays and protein localization analysis in living yeast cells. We observed that epsin-like protein Ent3p preferentially localized with Gga2p, whereas Ent5p distributed equally between AP-1 and Gga2p. Ent3p was mislocalized in Gga-deficient but not in AP-1-deficient cells. In contrast, Ent5p retained localization in cells lacking either or both AP-1 and Gga proteins. The Ent proteins were dispensable for AP-1 or Gga localization. Synthetic genetic growth and alpha-factor maturation defects were observed when ent5Delta but not ent3Delta was introduced together with deletions of the GGA genes. In AP-1-deficient cells, ent3Delta and to a lesser extent ent5Delta caused minor alpha-factor maturation defects, but together resulted in a near-lethal phenotype. Deletions of ENT3 and ENT5 also displayed synthetic defects similar to, but less severe than, synthetic effects of AP-1 and Gga inactivation. These results differentiate Ent3p and Ent5p function in vivo, suggesting that Ent3p acts primarily with Gga proteins, whereas Ent5p acts with both AP-1 and Gga proteins but is more critical for AP-1-mediated transport. The data also support a model in which the Ent adaptors provide important accessory functions to AP-1 and Gga proteins in TGN/endosome traffic.
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Affiliation(s)
- Giancarlo Costaguta
- *Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095; and
| | - Mara C. Duncan
- *Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095; and
| | - G. Esteban Fernández
- *Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095; and
| | - Grace H. Huang
- Department of Biostatistics, School of Public Health, UCLA, Los Angeles, CA 90095
| | - Gregory S. Payne
- *Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095; and
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Liou YJ, Lai IC, Wang YC, Bai YM, Lin CC, Lin CY, Chen TT, Chen JY. Genetic analysis of the human ENTH (Epsin 4) gene and schizophrenia. Schizophr Res 2006; 84:236-43. [PMID: 16616458 DOI: 10.1016/j.schres.2006.02.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 02/25/2006] [Accepted: 02/26/2006] [Indexed: 11/24/2022]
Abstract
Numerous linkage studies suggest that chromosome 5q may be one of the important cytogenetic regions containing risk loci for schizophrenia susceptibility. Recently, genetic variations (rs254664 and rs10046055) in the intron 1 and 5' flanking regions of the ENTH (also known as Epsin 4) gene, which is located in 5q 33.3, have been demonstrated to be significantly associated with schizophrenia. The present study investigates whether this finding could be replicated in a population of Han Chinese, consisting of 269 patients with schizophrenia and 236 normal controls, by analyzing 9 single nucleotide polymorphisms (SNPs) ranging from the 5' upstream region to intron 8 of the ENTH gene and covering 96 kb. The results showed that we failed to identify the associations of rs1186922 and rs10046055 with schizophrenia. Although another genetic variation (rs1186922) showed a weak association with schizophrenia (uncorrected p value for alleles = 0.038), the significance did not survive after Bonferroni correction. This study thus fails to support an association of genetic variations in the ENTH gene and schizophrenia.
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Affiliation(s)
- Ying-Jay Liou
- Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
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54
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Kamikura DM, Cooper JA. Clathrin interaction and subcellular localization of Ce-DAB-1, an adaptor for protein secretion in Caenorhabditis elegans. Traffic 2006; 7:324-36. [PMID: 16497226 DOI: 10.1111/j.1600-0854.2006.00386.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Growth factors must be secreted appropriately to co-ordinate cell proliferation, specification and movement during development and to control cell numbers and migrations in adult animals. Previous results showed that the secretion of the Caenorhabditis elegans fibroblast growth factor homologue, EGL-17, from vulval precursor cells in vivo involves the cytoplasmic adaptor protein Ce-DAB-1 and two lipoprotein receptors that bind Ce-DAB-1 and EGL-17. Here, we confirm the Ce-DAB-1 requirement for EGL-17 secretion using mutant animals. In vitro, Ce-DAB-1 binds to clathrin and APT-4, the C. elegans homologue of the alpha-adaptin subunit of adaptor protein 2 (AP2), and weakly to the gamma-appendage domains of APT-1 (AP1gamma-adaptin) and APT-9 (GGA protein). In tissue-culture cells, Ce-DAB-1 localizes to various compartments, including AP2-containing vesicles near the cell surface and perinuclear vesicles that contain AP1. The latter also contain Rab8, but not Rab5 or Rab11, as well as proteins en route from the trans Golgi network (TGN) to the surface. In vivo, EGL-17 secretion was inhibited by depletion of apt-1, apt-9 or ce-rab-8 and partially inhibited by RNAi of ce-rab-5, consistent with an important role for these proteins in the secretion of EGL-17 in vivo. These results suggest that Ce-DAB-1 might co-ordinate the assembly of endocytic or secretory vesicles in vivo and may mediate EGL-17 secretion directly, by recruiting clathrin to lipoprotein receptors at the TGN, or indirectly, by affecting lipoprotein receptor endocytosis and recycling.
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Peracino B, Wagner C, Balest A, Balbo A, Pergolizzi B, Noegel AA, Steinert M, Bozzaro S. Function and mechanism of action of Dictyostelium Nramp1 (Slc11a1) in bacterial infection. Traffic 2006; 7:22-38. [PMID: 16445684 DOI: 10.1111/j.1600-0854.2005.00356.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dictyostelium amoebae are professional phagocytes, which ingest bacteria as the principal source of food. We have cloned the Dictyostelium homologue of human natural resistance-associated membrane protein 1 (Nramp1) [solute carrier family 11 member 1 (Slc11a1)], an endo-lysosomal membrane protein that confers on macrophages resistance to infection by a variety of intracellular bacteria and protozoa. The Dictyostelium Nramp1 gene encodes a protein of 53 kDa with 11 putative transmembrane domains. The Nramp1 gene is transcribed during the growth-phase and downregulated to barely detectable levels upon starvation. To gain insights into their intracellular localization, we fused Nramp1 or the vatB subunit of the V-H(+)ATPase with green fluorescent protein and expressed in cells. Green fluorescent protein-vatB was inserted in membranes of all acidic compartments and the contractile vacuole network and decorated macropinosomes and phagosomes. Green fluorescent protein-Nramp1 decorated macropinosomes and phagosomes, in addition to intracellular vesicular compartments positive for endosomal SNARE protein Vti1 or vacuolin, a marker of the exocytic pathway. Nramp1 disruption generated mutants that were more permissive hosts than wild-type cells for intracellular growth of Legionella pneumophila and Micobacterium avium. Nramp1 overexpression protected cells from L. pneumophila infection. Evidence is provided that Nramp1 transports metal cations out of the phagolysosome in an ATP-dependent process and that L. pneumophila and M. avium use different mechanisms to neutralize Nramp1 activity.
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Affiliation(s)
- Barbara Peracino
- Department of Clinical and Biological Sciences, University of Turin, Orbassano, Italy
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56
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Huse M, Lillemeier BF, Kuhns MS, Chen DS, Davis MM. T cells use two directionally distinct pathways for cytokine secretion. Nat Immunol 2006; 7:247-55. [PMID: 16444260 DOI: 10.1038/ni1304] [Citation(s) in RCA: 337] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Accepted: 12/22/2005] [Indexed: 11/09/2022]
Abstract
Activated T helper cells produce many cytokines, some of which are secreted through the immunological synapse toward the antigen-presenting cell. Here we have used immunocytochemistry, live-cell imaging and a surface-mediated secretion assay to show that there are two cytokine export pathways in T helper cells. Some cytokines, including interleukin 2 and interferon-gamma, were secreted into the synapse, whereas others, including tumor necrosis factor and the chemokine CCL3 (MIP-1alpha), were released multidirectionally. Each secretion pathway was associated with different trafficking proteins, indicating that they are molecularly distinct processes. These data suggest that T helper cells release some cytokines into the immunological synapse to impart specific communication and others multidirectionally to promote inflammation and to establish chemokine gradients.
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Affiliation(s)
- Morgan Huse
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, USA
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57
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Holstein SEH, Oliviusson P. Sequence analysis of Arabidopsis thaliana E/ANTH-domain-containing proteins: membrane tethers of the clathrin-dependent vesicle budding machinery. PROTOPLASMA 2005; 226:13-21. [PMID: 16231097 DOI: 10.1007/s00709-005-0105-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Accepted: 03/30/2005] [Indexed: 05/04/2023]
Abstract
The epsin N-terminal homology (ENTH) domain is a conserved protein module present in cytosolic proteins which are required in clathrin-mediated vesicle budding processes. A highly similar, yet unique module is the AP180 N-terminal homology (ANTH) domain, which is present in a set of proteins that also support clathrin-dependent endocytosis. Both ENTH and ANTH (E/ANTH) domains bind to phospholipids and proteins, in order to support the nucleation of clathrin coats on the plasma membrane or the trans-Golgi-network membrane. Therefore, E/ANTH proteins might be considered as universal tethering components of the clathrin-mediated vesicle budding machinery. Since the E/ANTH protein family appears to be crucial in the first steps of clathrin-coated vesicle budding, we performed data base searches of the Arabidopsis thaliana genome. Sequence analysis revealed three proteins containing the ENTH signature motif and eight proteins containing the ANTH signature motif. Another six proteins were found that do not contain either motif but seem to have the same domain structure and might therefore be seen as VHS-domain-containing plant proteins. Functional analysis of plant E/ANTH proteins are rather scarce, since only one ANTH homolog from A. thaliana, At-AP180, has been characterized so far. At-AP180 displays conserved functions as a clathrin assembly protein and as an alpha-adaptin binding partner, and in addition shows features at the molecular level that seem to be plant-specific.
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Affiliation(s)
- Susanne E H Holstein
- Heidelberg Institute for Plant Sciences, University of Heidelberg, Heidelberg, Federal Republic of Germany
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58
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Traub LM. Common principles in clathrin-mediated sorting at the Golgi and the plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:415-37. [PMID: 15922462 DOI: 10.1016/j.bbamcr.2005.04.005] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 04/17/2005] [Accepted: 04/19/2005] [Indexed: 12/12/2022]
Abstract
Clathrin-mediated vesicular trafficking events underpin the vectorial transfer of macromolecules between several eukaryotic membrane-bound compartments. Classical models for coat operation, focused principally on interactions between clathrin, the heterotetrameric adaptor complexes, and cargo molecules, fail to account for the full complexity of the coat assembly and sorting process. New data reveal that targeting of clathrin adaptor complexes is generally supported by phosphoinositides, that cargo recognition by heterotetrameric adaptors depends on phosphorylation-driven conformational alterations, and that dedicated clathrin-associated sorting proteins (CLASPs) exist to promote the selective trafficking of specific categories of cargo. A host of accessory factors also participate in coat polymerization events, and the independently folded appendage domains that project off the heterotetrameric adaptor core function as recruitment platforms that appear to oversee assembly operations. It is also now clear that focal polymerization of branched actin microfilaments contributes to clathrin-coated vesicle assembly and movement at both plasma membrane and Golgi sites. This improved appreciation of the complex mechanisms governing clathrin-dependent sorting events reveals several common principles of clathrin operation at the Golgi and the plasma membrane.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology University of Pittsburgh School of Medicine 3500 Terrace Street, S325BST Pittsburgh, PA 15206, USA.
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59
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Abstract
Clathrin-coated vesicles (CCVs) are responsible for the transport of proteins between various compartments of the secretory and endocytic systems. Clathrin forms a scaffold around these vesicles that is linked to membranes by clathrin adaptors. The adaptors simultaneously bind to clathrin and to transmembrane proteins and/or phospholipids and can also interact with each other and with other components of the CCV formation machinery. The result is a collection of proteins that can make multiple, moderate strength (microM Kd) interactions and thereby establish the dynamic regulatable networks to drive vesicle genesis at the correct time and place in the cell. This review focuses on the structure of clathrin adaptors and how these structures provide functional information on the mechanism of CCV formation.
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Affiliation(s)
- David J Owen
- Cambridge Institute for Medical Research, Department of Clinical Biochemistry, University of Cambridge, Cambridge CB2 2XY, UK.
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60
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Murray RZ, Wylie FG, Khromykh T, Hume DA, Stow JL. Syntaxin 6 and Vti1b form a novel SNARE complex, which is up-regulated in activated macrophages to facilitate exocytosis of tumor necrosis Factor-alpha. J Biol Chem 2005; 280:10478-83. [PMID: 15640147 DOI: 10.1074/jbc.m414420200] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A key function of activated macrophages is to secrete proinflammatory cytokines such as TNFalpha; however, the intracellular pathway and machinery responsible for cytokine trafficking and secretion is largely undefined. Here we show that individual SNARE proteins involved in vesicle docking and fusion are regulated at both gene and protein expression upon stimulation with the bacterial cell wall component lipopolysaccharide. Focusing on two intracellular SNARE proteins, Vti1b and syntaxin 6 (Stx6), we show that they are up-regulated in conjunction with increasing cytokine secretion in activated macrophages and that their levels are selectively titrated to accommodate the volume and timing of post-Golgi cytokine trafficking. In macrophages, Vti1b and syntaxin 6 are localized on intracellular membranes and are present on isolated Golgi membranes and on Golgi-derived TNFalpha vesicles budded in vitro. By immunoprecipitation, we find that Vti1b and syntaxin 6 interact to form a novel intracellular Q-SNARE complex. Functional studies using overexpression of full-length and truncated proteins show that both Vti1b and syntaxin 6 function and have rate-limiting roles in TNFalpha trafficking and secretion. This study shows how macrophages have uniquely adapted a novel Golgi-associated SNARE complex to accommodate their requirement for increased cytokine secretion.
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Affiliation(s)
- Rachael Z Murray
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia 4072
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61
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Szymkiewicz I, Shupliakov O, Dikic I. Cargo- and compartment-selective endocytic scaffold proteins. Biochem J 2004; 383:1-11. [PMID: 15219178 PMCID: PMC1134037 DOI: 10.1042/bj20040913] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Accepted: 06/24/2004] [Indexed: 01/05/2023]
Abstract
The endocytosis of membrane receptors is a complex and tightly controlled process that is essential for maintaining cellular homoeostasis. The removal of receptors from the cell surface can be constitutive or ligand-induced, and occurs in a clathrin-dependent or -independent manner. The recruitment of receptors into specialized membrane domains, the formation of vesicles and the trafficking of receptors together with their ligands within endocytic compartments are regulated by reversible protein modifications, and multiple protein-protein and protein-lipid interactions. Recent reports describe a variety of multidomain molecules that facilitate receptor endocytosis and function as platforms for the assembly of protein complexes. These scaffold proteins typically act in a cargo-specific manner, recognizing one or more receptor types, or function at the level of endocytic cellular microcompartments by controlling the movement of cargo molecules and linking endocytic machineries to signalling pathways. In the present review we summarize present knowledge on endocytic scaffold molecules and discuss their functions.
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Key Words
- cargo
- endocytosis
- microcompartment
- scaffold
- alix, alg-2 (apoptosis-linked gene 2)-interacting protein x
- anth domain, ap180 n-terminal homology domain
- ap-2, adaptor protein-2
- arh, autosomal recessive hypercholesterolaemia
- bar domain, bin/amphiphysin/rvs domain
- cd2ap, cd2-associated protein
- cin85, cbl-interacting protein of 85 kda
- dab2, disabled-2
- eea1, early endosome antigen 1
- egfr, epidermal growth factor receptor
- eh domain, eps15 homology domain
- enth domain, epsin n-terminal homology domain
- escrt, endosomal sorting complexes required for transport
- fyve, fab1p, yotb, vac1p and eea1
- gap, gtpase-activating protein
- gpcr, g-protein-coupled receptor
- hrs, hepatocyte growth factor-regulated tyrosine kinase substrate
- lbpa, lysobiphosphatidic acid
- ldl, low-density lipoprotein
- lnx, ligand of numb protein x
- mvb, multivesicular body
- nak, numb-associated kinase
- nsf, n-ethylmaleimide-sensitive fusion protein
- pon, partner of numb
- ptb domain, phosphotyrosine-binding domain
- rtk, receptor tyrosine kinase
- sh3, src homology 3
- snare, soluble nsf attachment protein receptor
- stam, signal-transducing adaptor molecule
- tcr, t-cell receptor
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Affiliation(s)
- Iwona Szymkiewicz
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
| | - Oleg Shupliakov
- †Department of Neuroscience, CEDB, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Ivan Dikic
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
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Hirst J, Miller SE, Taylor MJ, von Mollard GF, Robinson MS. EpsinR is an adaptor for the SNARE protein Vti1b. Mol Biol Cell 2004; 15:5593-602. [PMID: 15371541 PMCID: PMC532037 DOI: 10.1091/mbc.e04-06-0468] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
EpsinR is a clathrin-coated vesicle (CCV)-associated protein that binds to vti1b, suggesting that it may be a vti1b-selective adaptor. Depletion of epsinR to undetectable levels in HeLa cells using siRNA causes vti1b to redistribute from the perinuclear region to the cell periphery, but vti1a also redistributes in epsinR-depleted cells, and both vti isoforms redistribute in AP-1-depleted cells. As a more direct assay for epsinR function, we isolated CCVs from control and siRNA-treated cells and then looked for differences in cargo content. In clathrin-depleted cells, both coat and cargo proteins are greatly reduced in this preparation. Knocking down epsinR causes a approximately 50% reduction in the amount of AP-1 copurifying with CCVs and vice versa, indicating that the two proteins are dependent on each other for maximum incorporation into the coat. In addition, vti1b, but not vti1a, is reduced by >70% in CCVs from both epsinR- and AP-1-depleted cells. Because AP-1 knockdown reduces the amount of epsinR in CCVs, it is possible that its effect on vti1b may be indirect. These findings provide in vivo evidence that epsinR is an adaptor for vti1b, and they also show that CCV isolation can be used as an assay for adaptor function.
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Affiliation(s)
- Jennifer Hirst
- University of Cambridge, Cambridge Institute for Medical Research, Cambridge CB2 2XY, United Kingdom
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64
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Eugster A, Pécheur EI, Michel F, Winsor B, Letourneur F, Friant S. Ent5p is required with Ent3p and Vps27p for ubiquitin-dependent protein sorting into the multivesicular body. Mol Biol Cell 2004; 15:3031-41. [PMID: 15107463 PMCID: PMC452561 DOI: 10.1091/mbc.e03-11-0793] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
At the late endosomes, cargoes destined for the interior of the vacuole are sorted into invaginating vesicles of the multivesicular body. Both PtdIns(3,5)P(2) and ubiquitin are necessary for proper sorting of some of these cargoes. We show that Ent5p, a yeast protein of the epsin family homologous to Ent3p, localizes to endosomes and specifically binds to PtdIns(3,5)P(2) via its ENTH domain. In cells lacking Ent3p and Ent5p, ubiquitin-dependent sorting of biosynthetic and endocytic cargo into the multivesicular body is disrupted, whereas other trafficking routes to the vacuole are not affected. Ent3p and Ent5p are associated with Vps27p, a FYVE domain containing protein that interacts with ubiquitinated cargoes and is required for protein sorting into the multivesicular body. Therefore, Ent3p and Ent5p are the first proteins shown to be connectors between PtdIns(3,5)P(2)- and the Vps27p-ubiquitin-driven sorting machinery at the multivesicular body.
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Affiliation(s)
- Anne Eugster
- Laboratoire de Transport et Compartimentation Intracellulaire, Institut de Biologie et Chimie des Protéines, UMR5086 Centre National de la Recherche Scientifique, Institut Fédératif de Recherche 128 BioSciences Lyon-Gerland, 69367 Lyon, France
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65
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Saint-Pol A, Yélamos B, Amessou M, Mills IG, Dugast M, Tenza D, Schu P, Antony C, McMahon HT, Lamaze C, Johannes L. Clathrin Adaptor epsinR Is Required for Retrograde Sorting on Early Endosomal Membranes. Dev Cell 2004; 6:525-38. [PMID: 15068792 DOI: 10.1016/s1534-5807(04)00100-5] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Revised: 02/19/2004] [Accepted: 02/20/2004] [Indexed: 10/26/2022]
Abstract
Retrograde transport links early/recycling endosomes to the trans-Golgi network (TGN), thereby connecting the endocytic and the biosynthetic/secretory pathways. To determine how internalized molecules are targeted to the retrograde route, we have interfered with the function of clathrin and that of two proteins that interact with it, AP1 and epsinR. We found that the glycosphingolipid binding bacterial Shiga toxin entered cells efficiently when clathrin expression was inhibited. However, retrograde transport of Shiga toxin to the TGN was strongly inhibited. This allowed us to show that for Shiga toxin, retrograde sorting on early/recycling endosomes depends on clathrin and epsinR, but not AP1. EpsinR was also involved in retrograde transport of two endogenous proteins, TGN38/46 and mannose 6-phosphate receptor. In conclusion, our work reveals the existence of clathrin-independent and -dependent transport steps in the retrograde route, and establishes a function for clathrin and epsinR at the endosome-TGN interface.
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Affiliation(s)
- Agnès Saint-Pol
- Laboratoire Trafic et Signalisation, 75248 Paris Cedex 05, France
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