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Ellis MA, Potter BA, Cresawn KO, Weisz OA. Polarized biosynthetic traffic in renal epithelial cells: sorting, sorting, everywhere. Am J Physiol Renal Physiol 2006; 291:F707-13. [PMID: 16788143 DOI: 10.1152/ajprenal.00161.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The maintenance of apical and basolateral membrane domains with distinct protein and lipid compositions is necessary for the proper function of polarized epithelial cells. Delivery of cargo to the basolateral surface is thought to be mediated by the interaction of cytoplasmically disposed sorting signals with sorting receptors, whereas apically destined cargoes are sorted via mechanisms dependent on cytoplasmic, glycan-mediated, or lipid-interacting sorting signals. Apical and basolateral cargo are delivered to the surface in discrete tubular and vesicular carriers that bud from the trans-Golgi network (TGN). While it has long been thought that the TGN is the primary compartment in which apical and basolateral cargoes are segregated, recent studies suggest that sorting may begin earlier along the biosynthetic pathway. Moreover, rather than being delivered directly from the TGN to the cell surface, at least a subset of biosynthetic cargo appears to transit recycling endosomes en route to the plasma membrane. The implications and limitations of these challenges to the conventional model for how proteins are sorted and trafficked along the biosynthetic pathway are discussed.
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Affiliation(s)
- Mark A Ellis
- Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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52
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Polishchuk RS, San Pietro E, Di Pentima A, Teté S, Bonifacino JS. Ultrastructure of long-range transport carriers moving from the trans Golgi network to peripheral endosomes. Traffic 2006; 7:1092-103. [PMID: 16787435 DOI: 10.1111/j.1600-0854.2006.00453.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The delivery of mannose 6-phosphate receptors carrying lysosomal hydrolases from the trans-Golgi network (TGN) to the endosomal system is mediated by selective incorporation of the receptor-hydrolase complexes into vesicular transport carriers (TCs) that are coated with clathrin and the adaptor proteins, GGA and AP-1. Previous electron microscopy (EM) and biochemical studies have shown that these TCs consist of spherical coated vesicles with a diameter of 60-100 nm. The use of fluorescent live cell imaging, however, has revealed that at least some of this transport relies on a subset of apparently larger and highly pleiomorphic carriers that detach from the TGN and translocate toward the peripheral cytoplasm until they meet with distally located endosomes. The ultrastructure of such long-range TCs has remained obscure because of the inability to examine by conventional EM the morphological details of rapidly moving organelles. The recent development of correlative light-EM has now allowed us to obtain ultrastructural 'snapshots' of these TCs immediately after their formation from the TGN in live cells. This approach has revealed that such carriers range from typical 60- to 100-nm clathrin-coated vesicles to larger, convoluted tubular-vesicular structures displaying several coated buds. We propose that this subset of TCs serve as vehicles for long-range distribution of biosynthetic or recycling cargo from the TGN to the peripheral endosomes.
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Affiliation(s)
- Roman S Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030, Santa Maria Imbaro (Chieti), Italy.
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53
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Potter BA, Weixel KM, Bruns JR, Ihrke G, Weisz OA. N-glycans mediate apical recycling of the sialomucin endolyn in polarized MDCK cells. Traffic 2006; 7:146-54. [PMID: 16420523 DOI: 10.1111/j.1600-0854.2005.00371.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Apical and basolateral proteins are maintained within distinct membrane subdomains in polarized epithelial cells by biosynthetic and postendocytic sorting processes. Sorting of basolateral proteins in these processes has been well studied; however, the sorting signals and mechanisms that direct proteins to the apical surface are less well understood. We previously demonstrated that an N-glycan-dependent sorting signal directs the sialomucin endolyn to the apical surface in polarized Madin-Darby canine kidney cells. Terminal processing of a subset of endolyn's N-glycans is key for polarized biosynthetic delivery to the apical membrane. Endolyn is subsequently internalized, and via a cytoplasmic tyrosine-based sorting motif is targeted to lysosomes from where it constitutively cycles to the cell surface. Here, we examine the polarized sorting of endolyn along the postendocytic pathway in polarized cells. Our results suggest that similar N-glycan sorting determinants are required for apical delivery of endolyn along both the biosynthetic and the postendocytic pathways.
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Affiliation(s)
- Beth A Potter
- Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
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54
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Luo H, Nakatsu F, Furuno A, Kato H, Yamamoto A, Ohno H. Visualization of the post-Golgi trafficking of multiphoton photoactivated transferrin receptors. Cell Struct Funct 2006; 31:63-75. [PMID: 17072087 DOI: 10.1247/csf.31.63] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Newly synthesized membrane proteins are sorted in the trans-Golgi network (TGN) on the basis of sorting signals carried in their cytoplasmic domains and delivered to their final destinations in the secretory and endocytic pathways. Although previous studies have suggested the involvement of early endosomes in the biosynthetic pathway of transmembrane proteins, the precise trafficking routes followed by the newly synthesized plasma membrane proteins, such as transferrin receptors (TfRs), after exit from the TGN remain unclear. In this report, first, we demonstrated the advantages of photoactivating PA-GFP, a variant of the Aequorea victoria green fluorescent protein (GFP), with multiphoton laser light rather than single-photon laser light, in terms of photoactivation efficiency and spatial resolution. We then applied the multiphoton photoactivation technique to selectively photoactivate the TfR tagged with PA-GFP (PA-GFP-TfR) at the TGN, and monitored the movement of the photoactivated PA-GFP-TfR in live cells. We observed that the PA-GFP-TfR photoactivated at the TGN are transported to the Tfn(+)EEA1(+) endosomal compartments after exiting the TGN. These data support the notion that early endosomes can serve as a sorting station for not only internalized plasma membrane proteins in the endocytic pathway but also newly synthesized membrane proteins in the post-Golgi secretory pathway.
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Affiliation(s)
- Hong Luo
- Laboratory for Epithelial Immunobiology, Research Center for Allergy and Immunology, RIKEN
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55
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Wasmeier C, Burgos PV, Trudeau T, Davidson HW, Hutton JC. An extended tyrosine-targeting motif for endocytosis and recycling of the dense-core vesicle membrane protein phogrin. Traffic 2005; 6:474-87. [PMID: 15882444 DOI: 10.1111/j.1600-0854.2005.00292.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Integral membrane proteins of neuroendocine dense-core vesicles (DCV) appear to undergo multiple rounds of exocytosis; however, their trafficking and site of incorporation into nascent DCVs is unclear. Previous studies with phogrin (IA-2beta) identified sorting signals in the luminal domain that is cleaved post-translationally; we now describe an independent DCV targeting motif in the cytosolic domain that may function at the level of endocytosis and recycling. Pulse-chase radiolabeling and cell surface biotinylation experiments in the pituitary corticotroph cell line AtT20 showed that the mature 60/65 kDa form that resides in the DCV is generated by limited proteolysis in a post-trans Golgi network compartment with similar kinetics to the formation of the principal cargo, ACTH. Phogrin is exposed on the cell surface in response to stimuli and progressively internalized to a perinuclear compartment that overlaps with recycling endosomes marked by transferrin. Chimeric molecules of phogrin transmembrane and cytosolic sequences with the interleukin-2 receptor alpha chain (Tac) were sorted to DCVs through the action of an extended tyrosine-based motif Y(654)QELCRQRMA located in a 27aa sequence adjacent to the membrane-spanning domain. A 36aa domain terminating in this sequence conferred DCV localization to Tac in the absence of any other cytosolic or luminal phogrin components. The endocytosis and DCV targeting of phogrin Y(654) > A mutants correlated with the impaired binding of the phogrin cytosolic tail to the micro-subunit of the AP2 adaptor complex in vitro.
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Affiliation(s)
- Christina Wasmeier
- Barbara Davis Center for Childhood Diabetes, University of Colorado at Denver and Health Sciences Center, 4200 East 9th Avenue, Box B140, Denver, CO 80262, USA
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56
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Janvier K, Bonifacino JS. Role of the endocytic machinery in the sorting of lysosome-associated membrane proteins. Mol Biol Cell 2005; 16:4231-42. [PMID: 15987739 PMCID: PMC1196333 DOI: 10.1091/mbc.e05-03-0213] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Accepted: 06/20/2005] [Indexed: 01/05/2023] Open
Abstract
The limiting membrane of the lysosome contains a group of transmembrane glycoproteins named lysosome-associated membrane proteins (Lamps). These proteins are targeted to lysosomes by virtue of tyrosine-based sorting signals in their cytosolic tails. Four adaptor protein (AP) complexes, AP-1, AP-2, AP-3, and AP-4, interact with such signals and are therefore candidates for mediating sorting of the Lamps to lysosomes. However, the role of these complexes and of the coat protein, clathrin, in sorting of the Lamps in vivo has either not been addressed or remains controversial. We have used RNA interference to show that AP-2 and clathrin-and to a lesser extent the other AP complexes-are required for efficient delivery of the Lamps to lysosomes. Because AP-2 is exclusively associated with plasma membrane clathrin coats, our observations imply that a significant population of Lamps traffic via the plasma membrane en route to lysosomes.
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Affiliation(s)
- Katy Janvier
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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57
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Yorikawa C, Shibata H, Waguri S, Hatta K, Horii M, Katoh K, Kobayashi T, Uchiyama Y, Maki M. Human CHMP6, a myristoylated ESCRT-III protein, interacts directly with an ESCRT-II component EAP20 and regulates endosomal cargo sorting. Biochem J 2005; 387:17-26. [PMID: 15511219 PMCID: PMC1134928 DOI: 10.1042/bj20041227] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
CHMP6 (charged multivesicular body protein 6) is a human orthologue of yeast Vps (vacuolar protein sorting) 20, a component of ESCRT (endosomal sorting complex required for transport)-III. Various CHMP6 orthologues in organisms ranging from yeast to humans contain the N-myristoylation consensus sequence at each N-terminus. Metabolic labelling of HEK-293 (human embryonic kidney) cells showed the incorporation of [3H]myristate into CHMP6 fused C-terminally to GFP (green fluorescent protein) (CHMP6-GFP). Interactions of CHMP6 with another ESCRT-III component CHMP4b/Shax [Snf7 (sucrose non-fermenting 7) homologue associated with Alix] 1, one of three paralogues of human Vps32/Snf7, and with EAP20 (ELL-associated protein 20), a human counterpart of yeast Vps25 and component of ESCRT-II, were observed by co-immunoprecipitation of epitope-tagged proteins expressed in HEK-293 cells. The in vitro pull-down assays using their recombinant proteins purified from Escherichia coli demonstrated direct physical interactions which were mediated by the N-terminal basic half of CHMP6. Overexpressed CHMP6-GFP in HeLa cells exhibited a punctate distribution throughout the cytoplasm especially in the perinuclear area, as revealed by fluorescence microscopic analysis. Accumulation of LBPA (lysobisphosphatidic acid), a major phospholipid in internal vesicles of an MVB (multivesicular body), was observed in the CHMP6-GFP-localizing area. FLAG-tagged EAP20 distributed diffusely, but exhibited a punctate distribution on co-expression with CHMP6-GFP. Overexpression of CHMP6-GFP caused reduction of transferrin receptors on the plasma membrane surface, but caused their accumulation in the cytoplasm. Ubiquitinated proteins and endocytosed EGF continuously accumulated in CHMP6-GFP-expressing cells. These results suggest that CHMP6 acts as an acceptor for ESCRT-II on endosomal membranes and regulates cargo sorting.
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Affiliation(s)
- Chiharu Yorikawa
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Hideki Shibata
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Satoshi Waguri
- †Department of Cell Biology and Neuroscience A1, Osaka University Graduate School of Medicine, Yamadaoka 2-2, Suita, Osaka 565-0871, Japan
| | - Kazumi Hatta
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Mio Horii
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Keiichi Katoh
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Toshihide Kobayashi
- ‡Supra-Biomolecular System Research Group, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Yasuo Uchiyama
- †Department of Cell Biology and Neuroscience A1, Osaka University Graduate School of Medicine, Yamadaoka 2-2, Suita, Osaka 565-0871, Japan
| | - Masatoshi Maki
- *Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- To whom correspondence should be addressed (email )
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58
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Rodriguez-Boulan E, Müsch A. Protein sorting in the Golgi complex: Shifting paradigms. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:455-64. [PMID: 15927284 DOI: 10.1016/j.bbamcr.2005.04.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Revised: 04/20/2005] [Accepted: 04/20/2005] [Indexed: 02/08/2023]
Abstract
The paradigms for transport along the biosynthetic route have changed dramatically over the past 15 years. Unlike the situation 15 years ago, the current paradigm involves sorting signals practically at every step of the pathway. In particular, at the exit from the Golgi complex, apical, basolateral and lysosomal targeting signals result in the generation of a variety of routes. Furthermore, it is now quite clear that not all sorting in the biosynthetic route occurs in the Golgi complex or the Trans Golgi Network (TGN). Sorting may occur distally to the Golgi, in recycling endosomes or in budded tubulosaccular structures, or it may occur proximally to the Golgi complex, at the exit from the ER. Several adaptors are candidates to sort apical and basolateral proteins but only AP1B and AP4 are currently involved. Progress is fast and future work should elucidate many of the open questions.
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Affiliation(s)
- Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Weill Medical College of Cornell University, LC-300, 1300 York Avenue, New York, NY 10021, USA.
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59
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Rodriguez-Boulan E, Kreitzer G, Müsch A. Organization of vesicular trafficking in epithelia. Nat Rev Mol Cell Biol 2005; 6:233-47. [PMID: 15738988 DOI: 10.1038/nrm1593] [Citation(s) in RCA: 490] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Experiments using mammalian epithelial cell lines have elucidated biosynthetic and recycling pathways for apical and basolateral plasma-membrane proteins, and have identified components that guide apical and basolateral proteins along these pathways. These components include apical and basolateral sorting signals, adaptors for basolateral signals, and docking and fusion proteins for vesicular trafficking. Recent live-cell-imaging studies provide a real-time view of sorting processes in epithelial cells, including key roles for actin, microtubules and motors in the organization of post-Golgi trafficking.
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Affiliation(s)
- Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York 10021, USA.
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60
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Dugast M, Toussaint H, Dousset C, Benaroch P. AP2 clathrin adaptor complex, but not AP1, controls the access of the major histocompatibility complex (MHC) class II to endosomes. J Biol Chem 2005; 280:19656-64. [PMID: 15749704 DOI: 10.1074/jbc.m501357200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Newly synthesized MHC II alpha- and beta-chains associated with the invariant chain chaperone (Ii) enter the endocytic pathway for Ii degradation and loading with peptides before transport to the cell surface. It is unclear how alphabetaIi complexes are sorted from the Golgi apparatus and directed to endosomes. However, indirect evidence tends to support direct transport involving the AP1 clathrin adaptor complex. Surprisingly, we show here that knocking down the production of AP1 by RNA interference did not affect the trafficking of alphabetaIi complexes. In contrast, AP2 depletion led to a large increase in surface levels of alphabetaIi complexes, inhibited their rapid internalization, and strongly delayed the appearance of mature MHC II in intracellular compartments. Thus, in the cell systems studied here, rapid internalization of alphabetaIi complexes via an AP2-dependent pathway represents a key step for MHC II delivery to endosomes and lysosomes.
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Affiliation(s)
- Marc Dugast
- INSERM U520 Institut Curie, Section de Recherche, Paris, France
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61
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Lock JG, Stow JL. Rab11 in recycling endosomes regulates the sorting and basolateral transport of E-cadherin. Mol Biol Cell 2005; 16:1744-55. [PMID: 15689490 PMCID: PMC1073657 DOI: 10.1091/mbc.e04-10-0867] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
E-cadherin plays an essential role in cell polarity and cell-cell adhesion; however, the pathway for delivery of E-cadherin to the basolateral membrane of epithelial cells has not been fully characterized. We first traced the post-Golgi, exocytic transport of GFP-tagged E-cadherin (Ecad-GFP) in unpolarized cells. In live cells, Ecad-GFP was found to exit the Golgi complex in pleiomorphic tubulovesicular carriers, which, instead of moving directly to the cell surface, most frequently fused with an intermediate compartment, subsequently identified as a Rab11-positive recycling endosome. In MDCK cells, basolateral targeting of E-cadherin relies on a dileucine motif. Both E-cadherin and a targeting mutant, DeltaS1-E-cadherin, colocalized with Rab11 and fused with the recycling endosome before diverging to basolateral or apical membranes, respectively. In polarized and unpolarized cells, coexpression of Rab11 mutants disrupted the cell surface delivery of E-cadherin and caused its mistargeting to the apical membrane, whereas apical DeltaS1-E-cadherin was unaffected. We thus demonstrate a novel pathway for Rab11 dependent, dileucine-mediated, mu1B-independent sorting and basolateral trafficking, exemplified by E-cadherin. The recycling endosome is identified as an intermediate compartment for the post-Golgi trafficking and exocytosis of E-cadherin, with a potentially important role in establishing and maintaining cadherin-based adhesion.
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Affiliation(s)
- John G Lock
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
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62
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Rodriguez-Boulan E, Müsch A, Le Bivic A. Epithelial trafficking: new routes to familiar places. Curr Opin Cell Biol 2005; 16:436-42. [PMID: 15261677 DOI: 10.1016/j.ceb.2004.06.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Research carried out in mammalian epithelial cell systems over the past 25 years has delineated pathways and sorting signals involved in polarized delivery of plasma membrane proteins. Recently some progress has been made in the identification of mechanisms underlying this polarized trafficking and in the visualization of trafficking routes in live cells. A promising area of research is the study of trafficking functions of novel polarity genes identified in Drosophila and Caenorhabditis elegans.
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Affiliation(s)
- Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Ave, New York, New York 10021, USA.
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63
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Ang AL, Taguchi T, Francis S, Fölsch H, Murrells LJ, Pypaert M, Warren G, Mellman I. Recycling endosomes can serve as intermediates during transport from the Golgi to the plasma membrane of MDCK cells. ACTA ACUST UNITED AC 2004; 167:531-43. [PMID: 15534004 PMCID: PMC2172492 DOI: 10.1083/jcb.200408165] [Citation(s) in RCA: 324] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The AP-1B clathrin adaptor complex is responsible for the polarized transport of many basolateral membrane proteins in epithelial cells. Localization of AP-1B to recycling endosomes (REs) along with other components (exocyst subunits and Rab8) involved in AP-1B-dependent transport suggested that RE might be an intermediate between the Golgi and the plasma membrane. Although the involvement of endosomes in the secretory pathway has long been suspected, we now present direct evidence using four independent methods that REs play a role in basolateral transport in MDCK cells. Newly synthesized AP-1B-dependent cargo, vesicular stomatitis virus glycoprotein G (VSV-G), was found by video microscopy, immunoelectron microscopy, and cell fractionation to enter transferrin-positive REs within a few minutes after exit from the trans-Golgi network. Although transient, RE entry appears essential because enzymatic inactivation of REs blocked VSV-G delivery to the cell surface. Because an apically targeted VSV-G mutant behaved similarly, these results suggest that REs not only serve as an intermediate but also as a common site for polarized sorting on the endocytic and secretory pathways.
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Affiliation(s)
- Agnes Lee Ang
- Department of Cell Biology, Ludwig Institute of Cancer Research, Yale University School of Medicine, New Haven, CT 06520, USA
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64
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Schuck S, Simons K. Polarized sorting in epithelial cells: raft clustering and the biogenesis of the apical membrane. J Cell Sci 2004; 117:5955-64. [PMID: 15564373 DOI: 10.1242/jcs.01596] [Citation(s) in RCA: 241] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polarized cells establish and maintain functionally distinct surface domains by an elaborate sorting process, which ensures accurate delivery of biosynthetic cargo to different parts of the plasma membrane. This is particularly evident in polarized epithelial cells, which have been used as a model system for studies of sorting mechanisms. The clustering of lipid rafts through the oligomerization of raft components could be utilized for segregating apical from basolateral cargo and for the generation of intracellular transport carriers. Besides functioning in polarized sorting in differentiated cells, raft clustering might also play an important role in the biogenesis of apical membrane domains during development.
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Affiliation(s)
- Sebastian Schuck
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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65
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Harhaj NS, Antonetti DA. Regulation of tight junctions and loss of barrier function in pathophysiology. Int J Biochem Cell Biol 2004; 36:1206-37. [PMID: 15109567 DOI: 10.1016/j.biocel.2003.08.007] [Citation(s) in RCA: 404] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Accepted: 08/21/2003] [Indexed: 12/16/2022]
Abstract
The mechanism by which epithelial and endothelial cells interact to form polarized tissue is of fundamental importance to multicellular organisms. Dysregulation of these barriers occurs in a variety of diseases, destroying the normal cellular environments and leading to organ failure. Increased levels of growth factors are a common characteristic of diseases exhibiting tissue permeability, suggesting that growth factors play a direct role in elevating permeability. Of particular concern for this laboratory, increased expression of vascular endothelial growth factor may enhance vascular permeability in diabetic retinopathy, leading to vision impairment and blindness. However, the mechanism by which growth factors increase permeability is unclear. Polarized cells form strong barriers through the development of tight junctions, which are specialized regions of the junctional complex. Tight junctions are composed of three types of transmembrane proteins, a number of peripheral membrane structural proteins, and are associated with a variety of regulatory proteins. Recent data suggest that growth factor-stimulated alterations in tight junctions contribute to permeability in a variety of disease states. The goal of this review was to elucidate potential mechanisms by which elevated growth factors elicit deregulated paracellular permeability via altered regulation of tight junctions, with particular emphasis on the tight junction proteins occludin and ZO-1, protein kinase C signaling, and endocytosis of junctional proteins. Understanding the molecular mechanisms underlying growth factor-mediated regulation of tight junctions will facilitate the development of novel treatments for diseases such as brain tumors, diabetic retinopathy and other diseases with compromised tight junction barriers.
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Affiliation(s)
- Nicole S Harhaj
- Penn State Retina Research Group, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA
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66
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67
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Cook NR, Row PE, Davidson HW. Lysosome associated membrane protein 1 (Lamp1) traffics directly from the TGN to early endosomes. Traffic 2004; 5:685-99. [PMID: 15296493 DOI: 10.1111/j.1600-0854.2004.00212.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The precise trafficking routes followed by newly synthesized lysosomal membrane proteins after exit from the Golgi are unclear. To study these events we created a novel chimera (YAL) having a lumenal domain comprising two tyrosine sulfation motifs fused to avidin, and the transmembrane and cytoplasmic domains of lysosome associated membrane protein 1 (Lamp1). The newly synthesized protein rapidly transited from the trans- Golgi Network (TGN) to lysosomes (t(1/2) approximately 30 min after a lag of 15-20 min). However, labeled chimera was captured by biotinylated probes endocytosed for only 5 min, indicating that the initial site of entry into the endocytic pathway was early endosomes. Capture required export of YAL from the TGN, and endocytosis of the biotinylated reagent, and was essentially quantitative within 2 h of chase, suggesting that all molecules were following an identical route. There was no evidence of YAL trafficking via the cell surface. Fusion of TGN-derived vesicles with 5 min endosomes could be recapitulated in vitro, but neither late endosomes nor lysosomes could serve as acceptor compartments. This suggests that contrary to previous conclusions, most if not all newly synthesized Lamp1 traffics from the TGN to early endosomes prior to delivery to late endosomes and lysosomes.
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Affiliation(s)
- Neil R Cook
- Cambridge Institute for Medical Research, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, CB2 2XY, UK
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68
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Kanaani J, Diacovo MJ, El-Husseini AED, Bredt DS, Baekkeskov S. Palmitoylation controls trafficking of GAD65 from Golgi membranes to axon-specific endosomes and a Rab5a-dependent pathway to presynaptic clusters. J Cell Sci 2004; 117:2001-13. [PMID: 15039456 DOI: 10.1242/jcs.01030] [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: 02/04/2023] Open
Abstract
The GABA-synthesizing enzyme GAD65 is synthesized as a soluble cytosolic protein but undergoes post-translational modification(s) to become anchored to the cytosolic face of Golgi membranes before targeting to synaptic vesicle membranes in neuroendocrine cells. Palmitoylation of cysteines 30 and 45 in GAD65 is not required for targeting to Golgi membranes but is crucial for post-Golgi trafficking to presynaptic clusters in neurons. Here, we show that palmitoylated GAD65 colocalizes with the small GTP-binding protein Rab5a in Golgi membranes and in axons but not in dendrites. In the presence of the constitutively positive mutant Rab5(Q79L) palmitoylation resulted in polarized targeting of GAD65 to giant Rab5a-positive axonal endosomes, characterized by the absence of the Rab5a-effector molecule EEA1 and the transferrin receptor. By contrast, Rab5a-positive/EEA1-positive somatodendritic giant endosomes containing the transferrin receptor were devoid of GAD65. Palmitoylation-deficient GAD65 was excluded from endosomal compartments. A dominant negative mutant of Rab5a, Rab5a(S34N), specifically blocked axonal trafficking and presynaptic clustering of palmitoylated GAD65, but did not affect axonal trafficking of mutants of GAD65 that fail to traffic to giant axonal endosomes containing Rab5a(Q79L). Two transmembrane synaptic vesicle proteins, VAMP2 and VGAT also localized to the axonal giant endosomes, and their axonal trafficking and presynaptic clustering was blocked by Rab5a(S34N). The results suggest that palmitoylation of GAD65 regulates the trafficking of the protein from Golgi membranes to an endosomal trafficking pathway in axons that is dependent on Rab5a and is required for the targeting of several synaptic vesicle proteins to presynaptic clusters.
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Affiliation(s)
- Jamil Kanaani
- Departments of Medicine, Microbiology/Immunology, and Diabetes Center, University of California San Francisco, CA 94143-0534, USA
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69
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70
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Ang AL, Fölsch H, Koivisto UM, Pypaert M, Mellman I. The Rab8 GTPase selectively regulates AP-1B-dependent basolateral transport in polarized Madin-Darby canine kidney cells. ACTA ACUST UNITED AC 2003; 163:339-50. [PMID: 14581456 PMCID: PMC2173525 DOI: 10.1083/jcb.200307046] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The AP-1B clathrin adaptor complex plays a key role in the recognition and intracellular transport of many membrane proteins destined for the basolateral surface of epithelial cells. However, little is known about other components that act in conjunction with AP-1B. We found that the Rab8 GTPase is one such component. Expression of a constitutively activated GTP hydrolysis mutant selectively inhibited basolateral (but not apical) transport of newly synthesized membrane proteins. Moreover, the effects were limited to AP-1B-dependent basolateral cargo; basolateral transport of proteins containing dileucine targeting motifs that do not interact with AP-1B were targeted normally despite overexpression of mutant Rab8. Similar results were obtained for a dominant-negative allele of the Rho GTPase Cdc42, previously implicated in basolateral transport but now shown to be selective for the AP-1B pathway. Rab8-GFP was localized to membranes in the TGN-recycling endosome, together with AP-1B complexes and the closely related but ubiquitously expressed AP-1A complex. However, expression of active Rab8 caused a selective dissociation of AP-1B complexes, reflecting the specificity of Rab8 for AP-1B-dependent transport.
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Affiliation(s)
- Agnes Lee Ang
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520-8002, USA
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71
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Abstract
Intracellular trafficking of membranes plays an essential role in the biogenesis and maintenance of myelin. The requisite proteins and lipids are transported from their sites of synthesis to myelin via vesicles. Vesicle transport is tightly coordinated with synthesis of lipids and proteins. To maintain the structural and functional organization of oligodendrocytes it is essential synchronize the various pathways of vesicle transport and to coordinate vesicle transport with reorganization of cytoskeleton. The systems that regulate the targeting of protein to myelin by vesicle transport are now being described. Here we review the current knowledge of these systems including those involved in (a) protein folding, (b) protein sorting and formation of carrier vesicles, (c) vesicle transport along elements of the cytoskeleton, and (d) vesicle targeting/fusion.
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Affiliation(s)
- J N Larocca
- Department of Neurology/Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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72
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Crottet P, Meyer DM, Rohrer J, Spiess M. ARF1.GTP, tyrosine-based signals, and phosphatidylinositol 4,5-bisphosphate constitute a minimal machinery to recruit the AP-1 clathrin adaptor to membranes. Mol Biol Cell 2002; 13:3672-82. [PMID: 12388765 PMCID: PMC129974 DOI: 10.1091/mbc.e02-05-0309] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2002] [Revised: 07/09/2002] [Accepted: 07/16/2002] [Indexed: 11/11/2022] Open
Abstract
At the trans-Golgi network, clathrin coats containing AP-1 adaptor complexes are formed in an ARF1-dependent manner, generating vesicles transporting cargo proteins to endosomes. The mechanism of site-specific targeting of AP-1 and the role of cargo are poorly understood. We have developed an in vitro assay to study the recruitment of purified AP-1 adaptors to chemically defined liposomes presenting peptides corresponding to tyrosine-based sorting motifs. AP-1 recruitment was found to be dependent on myristoylated ARF1, GTP or nonhydrolyzable GTP-analogs, tyrosine signals, and small amounts of phosphoinositides, most prominently phosphatidylinositol 4,5-bisphosphate, in the absence of any additional cytosolic or membrane bound proteins. AP-1 from cytosol could be recruited to a tyrosine signal independently of the lipid composition, but the rate of recruitment was increased by phosphatidylinositol 4,5-bisphosphate. The results thus indicate that cargo proteins are involved in coat recruitment and that the local lipid composition contributes to specifying the site of vesicle formation.
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Affiliation(s)
- Pascal Crottet
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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73
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Abstract
Functional analysis of exocytosis in yeast and animal cells has led to the identification of conserved elements and mechanisms of the trafficking machinery over the last decade. Although functional studies of protein secretion in plants are still fairly limited, the Arabidopsis genome sequence provides an opportunity to identify key players of vesicle trafficking that are conserved across the eukaryotic kingdoms. Here, we review and add to recent genome analyses of trafficking components and highlight some plant-specific modifications of the common eukaryotic machinery. Furthermore, we discuss the evidence for targeted, polarised secretion in plant cells, and speculate about possible underlying cargo sorting processes at the trans-Golgi network and endosomes, based on what is known in animals and yeast.
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Affiliation(s)
- Gerd Jürgens
- ZMBP, Entwicklungsgenetik, Universität Tübingen, Auf der Morgenstelle 3, D-72076 Tübingen, Federal Republic of Germany.
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74
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Burdett IDJ, Sullivan KH. Desmosome assembly in MDCK cells: transport of precursors to the cell surface occurs by two phases of vesicular traffic and involves major changes in centrosome and Golgi location during a Ca(2+) shift. Exp Cell Res 2002; 276:296-309. [PMID: 12027459 DOI: 10.1006/excr.2002.5509] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Desmosome formation in MDCK cells was investigated using a Ca(2+) shift. Following preliminary treatment with cycloheximide at 37 degrees C, continued surface transport and subsequent endocytosis were minimized by incubating cells at 19 degrees C to trap nascent glycoproteins within the Golgi body. Release into high Ca(2+) medium (HCM) at 37 degrees C resulted in junction formation as well as relocation of the Golgi body and centrosomes to a subapical location. Desmosome formation occurred in two stages over 2 h, the first occurring within 30 min of the shift to HCM, in 60-nm vesicles containing chiefly Dsc2 and lower concentrations of Dsg and E-cadherin distributed to the entire cell surface. Much of this material was subsequently endocytosed. The second stage involved transport of Dsg, E-cadherin, plakoglobin, and beta-catenin, in more complex vesicles some 200 nm in size, directed to possible nucleation sites on the developing basolateral surface. Plaque proteins such as desmoplakin I/II were added subsequently. Stage-two vesicles, but possibly not those of stage one, were accessible to endocytic markers via retrograde transport from multivesicular bodies prelabeled at 19 degrees C.
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Affiliation(s)
- Ian D J Burdett
- Division of Membrane Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom.
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75
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Gurunathan S, David D, Gerst JE. Dynamin and clathrin are required for the biogenesis of a distinct class of secretory vesicles in yeast. EMBO J 2002; 21:602-14. [PMID: 11847108 PMCID: PMC125853 DOI: 10.1093/emboj/21.4.602] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Yeast produce two classes of secretory vesicles (SVs) that differ in both density and cargo protein content. In late-acting secretory mutants (e.g. snc1(ala43) and sec6-4), both low- (LDSV) and high-density (HDSV) classes of vesicles accumulate at restrictive temperatures. Here, we have found that disruptions in the genes encoding a dynamin-related protein (VPS1) or clathrin heavy chain (CHC1) abolish HDSV production, yielding LDSVs that contain all secreted cargos. Interestingly, disruption of the PEP12 gene, which encodes the t-SNARE that mediates all Golgi to pre-vacuolar compartment (PVC) transport, also abolishes HDSV production. In contrast, deletions in genes that selectively confer vacuolar hydrolase sorting to the PVC or protein transport to the vacuole (i.e. VPS34 and VAM3, respectively) have no effect. Thus, one branch of the secretory pathway in yeast involves an intermediate sorting compartment and has a specific requirement for clathrin and a dynamin-related protein in SV biogenesis.
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76
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Abstract
Newly synthesized major histocompatibility complex class II needs to be directed to late endocytic compartments to combine with peptide antigens. Efficient transport requires complexes of major histocompatibility complex class II and invariant chain (alphabetaIi). Since such complexes have been detected on the plasma membrane in human cells, this compartment was proposed as the primary destination for alphabetaIi exiting the trans-Golgi network. Here, I have used density gradient electrophoresis and selective biotinylation to investigate the trafficking route of alphabetaIi quantitatively. Density gradient electrophoresis analysis showed that alphabetaIi was transported from the trans-Golgi network to endosomes at approximately 1.7% min-1. Surface delivery of alphabetaIi was delayed relative to endosome transport by approximately 10 min and showed slower kinetics ( approximately 0.4% min-1), suggesting that alphabetaIi reached the plasma membrane only after arrival in endosomes. A biotinylation assay revealed that 20-40% of endosomal alphabetaIi was delivered to the plasma membrane at steady state, suggesting that surface alphabetaIi was entirely derived from endosomes. Surface alphabetaIi was rapidly re-internalized and either returned to the cell surface or accessed degradative compartments. Peptide loading commenced approximately 30 min after delivery to endosomes. Thus alphabetaIi directly traffics from trans-Golgi network to endosomes and enters an endosome-plasma membrane 'carousel' until transport to peptide-loading compartments ensues.
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Affiliation(s)
- Robert Lindner
- Department of Cell Biology, Center of Anatomy, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
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77
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Simmen T, Höning S, Icking A, Tikkanen R, Hunziker W. AP-4 binds basolateral signals and participates in basolateral sorting in epithelial MDCK cells. Nat Cell Biol 2002; 4:154-9. [PMID: 11802162 DOI: 10.1038/ncb745] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Adaptors are heterotetrameric complexes that mediate the incorporation of cargo into transport vesicles by interacting with sorting signals present in the cytosolic domain of transmembrane proteins. Four adaptors, AP-1 (beta 1, gamma, mu 1A or mu 1B, sigma 1), AP-2 (beta 2, alpha, mu 2, sigma 2), AP-3 (beta 3 , delta, mu 3, sigma 3) or AP-4 (beta 4, epsilon, mu 4, sigma 4), have been characterized. AP-1 and AP-3 mediate sorting events at the level of the TGN and/or endosomes, whereas AP-2 functions in endocytic clathrin coated vesicle formation; no function is known so far for AP-4. Here, we show that AP-4 can bind different types of cytosolic signals known to mediate basolateral transport in epithelial cells. Furthermore, in MDCK cells with depleted mu 4 protein levels, several basolateral proteins are mis-sorted to the apical surface, showing that AP-4 participates in basolateral sorting in epithelial cells.
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Affiliation(s)
- Thomas Simmen
- Institute of Biochemistry, University of Lausanne, CH-1066 Epalinges, Switzerland
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78
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Harsay E, Schekman R. A subset of yeast vacuolar protein sorting mutants is blocked in one branch of the exocytic pathway. J Cell Biol 2002; 156:271-85. [PMID: 11807092 PMCID: PMC2199237 DOI: 10.1083/jcb.200109077] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exocytic vesicles that accumulate in a temperature-sensitive sec6 mutant at a restrictive temperature can be separated into at least two populations with different buoyant densities and unique cargo molecules. Using a sec6 mutant background to isolate vesicles, we have found that vacuolar protein sorting mutants that block an endosome-mediated route to the vacuole, including vps1, pep12, vps4, and a temperature-sensitive clathrin mutant, missort cargo normally transported by dense exocytic vesicles, such as invertase, into light exocytic vesicles, whereas transport of cargo specific to the light exocytic vesicles appears unaffected. Immunoisolation experiments confirm that missorting, rather than a changed property of the normally dense vesicles, is responsible for the altered density gradient fractionation profile. The vps41Delta and apl6Delta mutants, which block transport of only the subset of vacuolar proteins that bypasses endosomes, sort exocytic cargo normally. Furthermore, a vps10Delta sec6 mutant, which lacks the sorting receptor for carboxypeptidase Y (CPY), accumulates both invertase and CPY in dense vesicles. These results suggest that at least one branch of the yeast exocytic pathway transits through endosomes before reaching the cell surface. Consistent with this possibility, we show that immunoisolated clathrin-coated vesicles contain invertase.
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Affiliation(s)
- Edina Harsay
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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79
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Rodriguez-Gabin AG, Cammer M, Almazan G, Charron M, Larocca JN. Role of rRAB22b, an oligodendrocyte protein, in regulation of transport of vesicles from trans Golgi to endocytic compartments. J Neurosci Res 2001; 66:1149-60. [PMID: 11746448 DOI: 10.1002/jnr.1253] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Intracellular membrane trafficking plays an essential role in the biogenesis and maintenance of myelin. Members of the Rab protein family are important components of the systems that regulate intracellular vesicle transport. We examine the function of rRab22b, a novel rat Rab protein cloned from an oligodendrocyte cDNA library, by visualizing and identifying in living Hela cells the organelles that contain rRab22b. Our results show that rRab22b is present in the trans Golgi/TGN and endocytic compartments. Trafficking of membranes from trans Golgi to endocytic compartments takes place via small tubulo vesicular organelles containing rRab22b. The formation of vesicles in the trans Golgi also appears to be regulated by rRab22b. Additionally, our results suggest that rRab22b controls the transport of vesicles from the trans Golgi to endocytic compartments that localize in oligodendrocyte processes. That rRab22b is involved in the transport of certain proteins from trans Golgi to myelin is suggested by the evidence that certain proteins being targeted to the plasma membrane are first transported from trans Golgi to endocytic compartments.
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Affiliation(s)
- A G Rodriguez-Gabin
- Department of Neurology/Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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80
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Partridge CJ, Beech DJ, Sivaprasadarao A. Identification and pharmacological correction of a membrane trafficking defect associated with a mutation in the sulfonylurea receptor causing familial hyperinsulinism. J Biol Chem 2001; 276:35947-52. [PMID: 11457841 DOI: 10.1074/jbc.m104762200] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a genetic disorder characterized by excess secretion of insulin and hypoglycemia. In most patients, the disease is caused by mutations in sulfonylurea receptor-1 (SUR1), which, in association with Kir6.2, constitutes the functional ATP-sensitive potassium (K(ATP)) channel of the pancreatic beta-cell. Previous studies reported that coexpression of the PHHI mutant R1394H-SUR1 with Kir6.2 in COS cells produces no functional channels. To investigate if the loss of function could be due to impaired trafficking of mutant channels to the cell membrane, we have cotransfected wild-type and mutant SUR1 subunits with Kir6.2 into HEK293 cells and examined their cellular localization by immunofluorescent staining. Our results show that unlike the wild-type subunits, which showed fluorescence at the cell surface, the mutant subunits displayed fluorescence in punctate structures. Co-immunostaining with antibodies against organelle-specific marker proteins identified these structures as the trans-Golgi network. Limited localization in clathrin-positive, but transferrin receptor-negative vesicles was also observed. The post-endoplasmic reticulum localization suggests that the mutation does not impair the folding and assembly of the channels so as to cause its retention by the endoplasmic reticulum. Diazoxide, a K(ATP) channel opener drug that is used in the treatment of PHHI, restored the surface expression in a manner that could be prevented by the channel blocker glibenclamide. When expressed in Xenopus oocytes, R1394H-SUR1 formed functional channels with Kir6.2, indicating that the primary consequence of the mutation is impairment of trafficking rather than function. Thus, our data uncover a novel mechanism underlying the therapeutic action of diazoxide in the treatment of PHHI, i.e. its ability to recruit channels to the membrane. Furthermore, this is the first report to describe a trafficking disorder effecting retention of mutant proteins in the trans-Golgi network.
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Affiliation(s)
- C J Partridge
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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81
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Abstract
The trans-Golgi network (TGN) is a major secretory pathway sorting station that directs newly synthesized proteins to different subcellular destinations. The TGN also receives extracellular materials and recycled molecules from endocytic compartments. In this review, we summarize recent progress on understanding TGN structure and the dynamics of trafficking to and from this compartment. Protein sorting into different transport vesicles requires specific interactions between sorting motifs on the cargo molecules and vesicle coat components that recognize these motifs. Current understanding of the various targeting signals and vesicle coat components that are involved in TGN sorting are discussed, as well as the molecules that participate in retrieval to this compartment in both yeast and mammalian cells. Besides proteins, lipids and lipid-modifying enzymes also participate actively in the formation of secretory vesicles. The possible mechanisms of action of these lipid hydrolases and lipid kinases are discussed. Finally, we summarize the fundamentally different apical and basolateral cell surface delivery mechanisms and the current facts and hypotheses on protein sorting from the TGN into the regulated secretory pathway in neuroendocrine cells.
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Affiliation(s)
- F Gu
- Vollum Institute, Oregon Health Science University, Portland 97201, USA
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82
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Puertollano R, Martínez-Menárguez JA, Batista A, Ballesta J, Alonso MA. An intact dilysine-like motif in the carboxyl terminus of MAL is required for normal apical transport of the influenza virus hemagglutinin cargo protein in epithelial Madin-Darby canine kidney cells. Mol Biol Cell 2001; 12:1869-83. [PMID: 11408592 PMCID: PMC37348 DOI: 10.1091/mbc.12.6.1869] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2000] [Revised: 02/27/2001] [Accepted: 04/02/2001] [Indexed: 01/12/2023] Open
Abstract
The MAL proteolipid, a component of the integral protein sorting machinery, has been demonstrated as being necessary for normal apical transport of the influenza virus hemagglutinin (HA) and the overall apical membrane proteins in Madin-Darby canine kidney (MDCK) cells. The MAL carboxy terminus ends with the sequence Arg-Trp-Lys-Ser-Ser (RWKSS), which resembles dilysine-based motifs involved in protein sorting. To investigate whether the RWKSS pentapeptide plays a role in modulating the distribution of MAL and/or its function in apical transport, we have expressed MAL proteins with distinct carboxy terminus in MDCK cells whose apical transport was impaired by depletion of endogenous MAL. Apical transport of HA was restored to normal levels by expression of MAL with an intact but not with modified carboxyl terminal sequences bearing mutations that impair the functioning of dilysine-based sorting signals, although all the MAL proteins analyzed incorporated efficiently into lipid rafts. Ultrastructural analysis indicated that compared with MAL bearing an intact RWKSS sequence, a mutant with lysine -3 substituted by serine showed a twofold increased presence in clathrin-coated cytoplasmic structures and a reduced expression on the plasma membrane. These results indicate that the carboxyl-terminal RWKSS sequence modulates the distribution of MAL in clathrin-coated elements and is necessary for HA transport to the apical surface.
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Affiliation(s)
- R Puertollano
- Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Spain
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83
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Kleymenova E, Ibraghimov-Beskrovnaya O, Kugoh H, Everitt J, Xu H, Kiguchi K, Landes G, Harris P, Walker C. Tuberin-dependent membrane localization of polycystin-1: a functional link between polycystic kidney disease and the TSC2 tumor suppressor gene. Mol Cell 2001; 7:823-32. [PMID: 11336705 DOI: 10.1016/s1097-2765(01)00226-x] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The PKD1 gene accounts for 85% of autosomal dominant polycystic kidney disease (ADPKD), the most common human genetic disorder. Rats with a germline inactivation of one allele of the Tsc2 tumor suppressor gene developed early onset severe bilateral polycystic kidney disease, with similarities to the human contiguous gene syndrome caused by germline codeletion of PKD1 and TSC2 genes. Polycystic rat renal cells retained two normal Pkd1 alleles but were null for Tsc2 and exhibited loss of lateral membrane-localized polycystin-1. In tuberin-deficient cells, intracellular trafficking of polycystin-1 was disrupted, resulting in sequestration of polycystin-1 within the Golgi and reexpression of Tsc2 restored correct polycystin-1 membrane localization. These data identify tuberin as a determinant of polycystin-1 functional localization and, potentially, ADPKD severity.
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Affiliation(s)
- E Kleymenova
- Department of Carcinogenesis, University of Texas, MD Anderson Cancer Center, Science Park, Smithville, TX 78957, USA.
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84
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Maier O, Aït Slimane T, Hoekstra D. Membrane domains and polarized trafficking of sphingolipids. Semin Cell Dev Biol 2001; 12:149-61. [PMID: 11292381 DOI: 10.1006/scdb.2000.0232] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The plasma membrane of polarized cells consists of distinct domains, the apical and basolateral membrane, that are characterized by a distinct lipid and protein content. Apical protein transport is largely mediated by (glyco)sphingolipid--cholesterol enriched membrane microdomains, so called rafts. In addition changes in the direction of polarized sphingolipid transport appear instrumental in cell polarity development. Knowledge is therefore required of the mechanisms that mediate sphingolipid sorting and the complexity of the trafficking pathways that are involved in polarized transport of both sphingolipids and proteins. Here we summarize specific biophysical properties that underly mechanisms relevant to sphingolipid sorting, cargo recruitment and polarized trafficking, and discuss the central role of a subapical compartment, SAC or common endosome (CE), as a major intracellular site involved in polarized sorting of sphingolipids, and in development and maintenance of membrane polarity.
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Affiliation(s)
- O Maier
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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85
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Chen W, Wandinger-Ness A. Expression and functional analyses of Rab8 and Rab11a in exocytic transport from trans-Golgi network. Methods Enzymol 2001; 329:165-75. [PMID: 11210533 DOI: 10.1016/s0076-6879(01)29077-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- W Chen
- National Center for Genome Resources, Santa Fe, New Mexico 87505, USA
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86
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Keller P, Toomre D, Díaz E, White J, Simons K. Multicolour imaging of post-Golgi sorting and trafficking in live cells. Nat Cell Biol 2001; 3:140-9. [PMID: 11175746 DOI: 10.1038/35055042] [Citation(s) in RCA: 345] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The biogenesis and maintenance of asymmetry is crucial to many cellular functions including absorption and secretion, signalling, development and morphogenesis. Here we have directly visualized the segregation and trafficking of apical (glycosyl phosphatidyl inositol-anchored) and basolateral (vesicular stomatitis virus glycoprotein) cargo in living cells using multicolour imaging of green fluorescent protein variants. Apical and basolateral cargo segregate progressively into large domains in Golgi/trans-Golgi network structures, exclude resident proteins, and exit in separate transport containers. These remain distinct and do not merge with endocytic structures suggesting that lateral segregation in the trans-Golgi network is the primary sorting event. Fusion with the plasma membrane was detected by total internal reflection microscopy and reveals differences between apical and basolateral carriers as well as new 'hot spots' for exocytosis.
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Affiliation(s)
- P Keller
- Cell Biology/Biophysics Programme, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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87
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Ramalingam TS, West AP, Lebrón JA, Nangiana JS, Hogan TH, Enns CA, Bjorkman PJ. Binding to the transferrin receptor is required for endocytosis of HFE and regulation of iron homeostasis. Nat Cell Biol 2000; 2:953-7. [PMID: 11146662 DOI: 10.1038/35046611] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
HFE, the protein that is mutated in hereditary haemochromatosis, binds to the transferrin receptor (TfR). Here we show that wild-type HFE and TfR localize in endosomes and at the basolateral membrane of a polarized duodenal epithelial cell line, whereas the primary haemochromatosis HFE mutant, and another mutant with impaired TfR-binding ability accumulate in the ER/Golgi and at the basolateral membrane, respectively. Levels of the iron-storage protein ferritin are greatly reduced and those of TfR are slightly increased in cells expressing wild-type HFE, but not in cells expressing either mutant. Addition of an endosomal-targeting sequence derived from the human low-density lipoprotein receptor (LDLR) to the TfR-binding-impaired mutant restores its endosomal localization but not ferritin reduction or TfR elevation. Thus, binding to TfR is required for transport of HFE to endosomes and regulation of intracellular iron homeostasis, but not for basolateral surface expression of HFE.
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Affiliation(s)
- T S Ramalingam
- Division of Biology 156-29, California Institute of Technology, Pasadena, California 91125, USA
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88
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Laird V, Spiess M. A novel assay to demonstrate an intersection of the exocytic and endocytic pathways at early endosomes. Exp Cell Res 2000; 260:340-5. [PMID: 11035929 DOI: 10.1006/excr.2000.5006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The mechanism of transport of membrane proteins from the trans-Golgi to the cell surface is still poorly understood. Previous studies suggested that basolateral membrane proteins, such as the transferrin receptor and the asialoglycoprotein receptor H1, take an indirect route to the plasma membrane via an intracellular, most likely endosomal intermediate. To define this compartment we developed a biochemical assay based on the very definition of endosomes. The assay is based on internalizing anti-H1 antibodies via the endocytic cycle of the receptor itself. Internalized antibody formed immune complexes with newly synthesized H1, which had been pulse-labeled with [(35)S]sulfate and chased out of the trans-Golgi for a period of time that was insufficient for H1 to reach the surface. Hence, antibody capture occurred intracellularly. Double-immunofluorescence labeling demonstrated that antibody-containing compartments also contained transferrin and thus corresponded to early and recycling endosomes. The results therefore demonstrate an intracellular intersection of the exocytic and endocytic pathways with implications for basolateral sorting.
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Affiliation(s)
- V Laird
- Biozentrum, University of Basel, Klingelbergstrasse 70, Basel, CH-4056, Switzerland
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89
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Van IJzendoorn SC, Maier O, Van Der Wouden JM, Hoekstra D. The subapical compartment and its role in intracellular trafficking and cell polarity. J Cell Physiol 2000; 184:151-60. [PMID: 10867639 DOI: 10.1002/1097-4652(200008)184:2<151::aid-jcp2>3.0.co;2-r] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In polarized epithelial cells and hepatocytes, apical and basolateral plasma membrane surfaces are maintained, each displaying a distinct molecular composition. In recent years, it has become apparent that a subapical compartment, referred to as SAC, plays a prominent if not crucial role in the domain-specific sorting and targeting of proteins and lipids that are in dynamic transit between these plasma membrane domains. Although the molecular identity of the traffic-regulating devices is still obscure, the organization of SAC in distinct subcompartments and/or subdomains may well be instrumental to such functions. In this review, we will focus on the potential subcompartmentalization of the SAC in terms of regulation of membrane traffic, on how SAC relates to the endosomal system, and on how this compartment may operate in the context of other intracellular sorting organelles such as the Golgi complex, in generating and maintaining cell polarity.
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Affiliation(s)
- S C Van IJzendoorn
- Department of Physiological Chemistry, University of Groningen, Groningen, The Netherlands
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90
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Hirling H, Steiner P, Chaperon C, Marsault R, Regazzi R, Catsicas S. Syntaxin 13 is a developmentally regulated SNARE involved in neurite outgrowth and endosomal trafficking. Eur J Neurosci 2000; 12:1913-23. [PMID: 10886332 DOI: 10.1046/j.1460-9568.2000.00076.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In addition to its role in exocytosis, SNAP-25 is essential for axonal outgrowth. In order to identify SNARE proteins involved in neurite growth we have used SNAP-25 antibodies to affinity-purify protein complexes enriched in developing rat brain membrane extracts. We have identified a complex between SNAP-25 and syntaxin 13 predominantly present in brain at embryonic or early postnatal stages. We show that syntaxin 13 is developmentally regulated with a decrease in adult brain. In differentiated neuroendocrine PC12 cells as well as primary cortical neurons the protein is localized to a punctated and tubular staining in the perinuclear region and along processes with high levels in the central region of growth cones. Carboxy-terminally tagged syntaxin 13 was also detected on the plasma membrane by in vivo surface-labelling where it colocalized with SNAP-25. Syntaxin 13 has recently been shown to be implicated in early endosomal trafficking. In our study, colocalization with internalized transferrin in the cell body and along neurites confirmed endosomal location in both compartments. Finally, overexpression of full-length syntaxin 13 enhanced neurite outgrowth in NGF-stimulated PC12 cells, whilst it had no effect on regulated secretion. The data suggest that a syntaxin 13-dependent endocytic trafficking step plays a limiting role in membrane expansion during neuronal development.
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Affiliation(s)
- H Hirling
- Institut de Biologie Cellulaire et de Morphologie (IBCM), Rue du Bugnon 9, 1005 Lausanne, Switzerland.
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91
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Huber LA, Fialka I, Paiha K, Hunziker W, Sacks DB, Bähler M, Way M, Gagescu R, Gruenberg J. Both calmodulin and the unconventional myosin Myr4 regulate membrane trafficking along the recycling pathway of MDCK cells. Traffic 2000; 1:494-503. [PMID: 11208135 DOI: 10.1034/j.1600-0854.2000.010607.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In epithelial cells, endocytosed transferrin and its receptor, which cycle basolaterally, have been shown to transit through recycling endosomes which can also be accessed by markers internalized from the apical surface. In this work, we have used an in vitro assay to follow transfer of an endocytosed marker from apical or basolateral early endosomes to recycling endosomes labeled with transferrin. We show that calmodulin (CaM) function is necessary for transfer and identified myr4, a member of the unconventional myosin superfamily known to use CaM as a light chain, as a possible target protein for CaM. Since myr4 is believed to act as an actin-based mechanoenzyme, we tested the role of polymerized actin in the assay. Our data show that conditions which either prevent actin polymerization or induce the breakdown of existing filaments strongly inhibit interactions between recycling endosomes and either set of early endosomes. Altogether, our data indicate that trafficking at early steps of the endocytic pathway in Madin-Darby Canine Kidney cells depends on the actin-based mechanoenzyme myr4, its light chain CaM, and polymerized actin.
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Affiliation(s)
- L A Huber
- Research Institute of Molecular Pathology, I.M.P., Dr. Bohrgasse 7, A-1030 Wien, Austria.
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92
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Orzech E, Cohen S, Weiss A, Aroeti B. Interactions between the exocytic and endocytic pathways in polarized Madin-Darby canine kidney cells. J Biol Chem 2000; 275:15207-19. [PMID: 10809756 DOI: 10.1074/jbc.275.20.15207] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The compartments involved in polarized exocytosis of membrane proteins are not well defined. In this study we hypothesized that newly synthesized polymeric immunoglobulin receptors are targeted from the trans-Golgi network to endosomes prior to their appearance on the basolateral cell surface of polarized Madin-Darby canine kidney cells. To examine this hypothesis, we have used an assay designed to measure the meeting of newly synthesized receptors with a selective population of apical or basolateral endosomes loaded with horseradish peroxidase. We found that in the course of basolateral exocytosis, the wild-type polymeric immunoglobulin receptor is targeted from the trans-Golgi network to apical and basolateral endosomes. Phosphorylation of a Ser residue in the cytoplasmic tail of the receptor is implicated in this process. The biosynthetic pathway of apically sorted polymeric immunoglobulin receptor mutants similarly traversed apical endosomes, raising the possibility that apical receptors are segregated from basolateral receptors in apical endosomes. The post-endocytic pathway of transcytosing and recycling receptors also passed through apical endosomes. Together, these observations are consistent with the possibility that the biosynthetic and endocytic routes merge into endosomes and justify a model suggesting that endosomal recycling processes govern polarized trafficking of proteins traveling in both pathways.
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Affiliation(s)
- E Orzech
- Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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93
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Turner MD, Arvan P. Protein traffic from the secretory pathway to the endosomal system in pancreatic beta-cells. J Biol Chem 2000; 275:14025-30. [PMID: 10799475 DOI: 10.1074/jbc.275.19.14025] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Constitutive-like secretion involves vesicular trafficking corresponding kinetically and biochemically with a post-trans-Golgi network (TGN) origin. In pancreatic beta-cells, the budding of AP-1/clathrin-coated vesicles, a portion of which is derived from immature secretory granules, has been hypothesized to initiate constitutive-like trafficking. However, approximately 30 min after release of a 20 degrees C intracellular transport block in pancreatic beta-cells (to synchronize protein egress from the TGN), addition of brefeldin A (BFA) (which inhibits AP-1 recruitment) was reported not to block subsequent constitutive-like secretion. To further explore post-TGN trafficking in pancreatic beta-cell lines, we have followed the fate of pulse-labeled procathepsin B (ProB, a lysosomal proenyzme) after postpulse wortmannin treatment or the BFA treatment described above. We find that continuous wortmannin treatment allows ProB to reach immature secretory granules but inhibits its egress from maturing granules. Remarkably, BFA treatment causes augmented unstimulated secretion of newly synthesized ProB that is not paralleled by insulin. This effect requires a delay of 25-35 min after release from the 20 degrees C block. Further, when ProB delivery to endosomes is inhibited, its BFA-augmented secretion is eliminated. We hypothesize that the constitutive-like pathway involves an endosomal intermediate.
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Affiliation(s)
- M D Turner
- Diabetes Center, Division of Endocrinology and the Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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94
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Charron AJ, Nakamura S, Bacallao R, Wandinger-Ness A. Compromised cytoarchitecture and polarized trafficking in autosomal dominant polycystic kidney disease cells. J Cell Biol 2000; 149:111-24. [PMID: 10747091 PMCID: PMC2175108 DOI: 10.1083/jcb.149.1.111] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cystogenesis associated with autosomal dominant polycystic kidney disease (ADPKD) is characterized by perturbations in the polarized phenotype and function of cyst-lining epithelial cells. The polycystins, the protein products of the genes mutated in the majority of ADPKD cases, have been described recently, but the pathological mechanism by which causal mutations result in the mislocalization of cell membrane proteins has remained unclear. This report documents the dissociation from the ADPKD cell basolateral membrane of three molecules essential for spatial organization and exocytosis. The adherens junction protein E-cadherin, the subcellular disposition of which governs intercellular and intracellular architecture, was discovered sequestered in an internal ADPKD cell compartment. At the same time, sec6 and sec8, components of a complex critical for basolateral cargo delivery normally arrayed at the apico-lateral apex, were depleted from the ADPKD cell plasma membrane. An analysis of membrane transport revealed that basolateral trafficking of proteins and lipids was impaired as a result of delayed cargo exit from the ADPKD cell Golgi apparatus. Apical transport proceeded normally. Taken together with recent documentation of an association between polycystin-1 and E-cadherin (Huan and van Adelsberg 1999), the data suggest that causal mutations disrupt E-cadherin-dependent cytoarchitecture, adversely affecting protein assemblies crucial for basolateral trafficking.
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Affiliation(s)
- Audra J. Charron
- Integrated Graduate Program in the Life Sciences, Northwestern University Medical School, Chicago, Illinois 60611
| | - Sakie Nakamura
- Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611
| | - Robert Bacallao
- Department of Medicine, Indiana University Medical Center, Indianapolis, Indiana 46202
| | - Angela Wandinger-Ness
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
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95
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Renold A, Cescato R, Beuret N, Vogel LK, Wahlberg JM, Brown JL, Fiedler K, Spiess M. Basolateral sorting signals differ in their ability to redirect apical proteins to the basolateral cell surface. J Biol Chem 2000; 275:9290-5. [PMID: 10734069 DOI: 10.1074/jbc.275.13.9290] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polarized sorting of membrane proteins in epithelial cells is mediated by cytoplasmic basolateral signals or by apical signals in the transmembrane or exoplasmic domains. Basolateral signals were generally found to be dominant over apical determinants. We have generated chimeric proteins with the cytoplasmic domain of either the asialoglycoprotein receptor H1 or the transferrin receptor, two basolateral proteins, fused to the transmembrane and exoplasmic segments of aminopeptidase N, an apical protein, and analyzed them in Madin-Darby canine kidney cells. Whereas both cytoplasmic sequences induced endocytosis of the chimeras, only that of the transferrin receptor mediated basolateral expression in steady state. The H1 fusion protein, although still largely sorted to the basolateral side in biosynthetic surface transport, was subsequently resorted to the apical cell surface. We tested whether the difference in sorting between trimeric wild-type H1 and the dimeric aminopeptidase chimera was caused by the number of sorting signals presented in the oligomers. Consistent with this hypothesis, the H1 signal was fully functional in a tetrameric fusion protein with the transmembrane and exoplasmic domains of influenza neuraminidase. The results suggest that basolateral signals per se need not be dominant over apical determinants for steady-state polarity and emphasize an important contribution of the valence of signals in polarized sorting.
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Affiliation(s)
- A Renold
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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96
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Luo WJ, Chang A. An endosome-to-plasma membrane pathway involved in trafficking of a mutant plasma membrane ATPase in yeast. Mol Biol Cell 2000; 11:579-92. [PMID: 10679016 PMCID: PMC14795 DOI: 10.1091/mbc.11.2.579] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The plasma membrane ATPase, encoded by PMA1, is delivered to the cell surface via the secretory pathway. Previously, we characterized a temperature-sensitive pma1 mutant in which newly synthesized Pma1-7 is not delivered to the plasma membrane but is mislocalized instead to the vacuole at 37 degrees C. Several vps mutants, which are defective in vacuolar protein sorting, suppress targeting-defective pma1 by allowing mutant Pma1 to move once again to the plasma membrane. In this study, we have analyzed trafficking in the endosomal system by monitoring the movement of Pma1-7 in vps36, vps1, and vps8 mutants. Upon induction of expression, mutant Pma1 accumulates in the prevacuolar compartment in vps36 cells. After chase, a fraction of newly synthesized Pma1-7 is delivered to the plasma membrane. In both vps1 and vps8 cells, newly synthesized mutant Pma1 appears in small punctate structures before arrival at the cell surface. Nevertheless, biosynthetic membrane traffic appears to follow different routes in vps8 and vps1: the vacuolar protein-sorting receptor Vps10p is stable in vps8 but not in vps1. Furthermore, a defect in endocytic delivery to the vacuole was revealed in vps8 (and vps36) but not vps1 by endocytosis of the bulk membrane marker FM 4-64. Moreover, in vps8 cells, there is defective down-regulation from the cell surface of the mating receptor Ste3, consistent with persistent receptor recycling from an endosomal compartment to the plasma membrane. These data support a model in which mutant Pma1 is diverted from the Golgi to the surface in vps1 cells. We hypothesize that in vps8 and vps36, in contrast to vps1, mutant Pma1 moves to the surface via endosomal intermediates, implicating an endosome-to-surface traffic pathway.
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Affiliation(s)
- W j Luo
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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97
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Yoshimori T, Yamagata F, Yamamoto A, Mizushima N, Kabeya Y, Nara A, Miwako I, Ohashi M, Ohsumi M, Ohsumi Y. The mouse SKD1, a homologue of yeast Vps4p, is required for normal endosomal trafficking and morphology in mammalian cells. Mol Biol Cell 2000; 11:747-63. [PMID: 10679028 PMCID: PMC14807 DOI: 10.1091/mbc.11.2.747] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mouse SKD1 is an AAA-type ATPase homologous to the yeast Vps4p implicated in transport from endosomes to the vacuole. To elucidate a possible role of SKD1 in mammalian endocytosis, we generated a mutant SKD1, harboring a mutation (E235Q) that is equivalent to the dominant negative mutation (E233Q) in Vps4p. Overexpression of the mutant SKD1 in cultured mammalian cells caused defect in uptake of transferrin and low-density lipoprotein. This was due to loss of their receptors from the cell surface. The decrease of the surface transferrin receptor (TfR) was correlated with expression levels of the mutant protein. The mutant protein displayed a perinuclear punctate distribution in contrast to a diffuse pattern of the wild-type SKD1. TfR, the lysosomal protein lamp-1, endocytosed dextran, and epidermal growth factor but not markers for the secretory pathway were accumulated in the mutant SKD1-localized compartments. Degradation of epidermal growth factor was inhibited. Electron microscopy revealed that the compartments were exaggerated multivesicular vacuoles with numerous tubulo-vesicular extensions containing TfR and endocytosed horseradish peroxidase. The early endosome antigen EEA1 was also redistributed to these aberrant membranes. Taken together, our findings suggest that SKD1 regulates morphology of endosomes and membrane traffic through them.
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Affiliation(s)
- T Yoshimori
- Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan
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98
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Abstract
Synaptic vesicles, which have been a paradigm for the fusion of a vesicle with its target membrane, also serve as a model for understanding the formation of a vesicle from its donor membrane. Synaptic vesicles, which are formed and recycled at the periphery of the neuron, contain a highly restricted set of neuronal proteins. Insight into the trafficking of synaptic vesicle proteins has come from studying not only neurons but also neuroendocrine cells, which form synaptic-like microvesicles (SLMVs). Formation and recycling of synaptic vesicles/SLMVs takes place from the early endosome and the plasma membrane. The cytoplasmic machinery of synaptic vesicle/SLMV formation and recycling has been studied by a variety of experimental approaches, in particular using cell-free systems. This has revealed distinct machineries for membrane budding and fission. Budding is mediated by clathrin and clathrin adaptors, whereas fission is mediated by dynamin and its interacting protein SH3p4, a lysophosphatidic acid acyl transferase.
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Affiliation(s)
- M J Hannah
- MRC Laboratory for Molecular Cell Biology, University College London, UK
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99
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Trischler M, Stoorvogel W, Ullrich O. Biochemical analysis of distinct Rab5- and Rab11-positive endosomes along the transferrin pathway. J Cell Sci 1999; 112 ( Pt 24):4773-83. [PMID: 10574724 DOI: 10.1242/jcs.112.24.4773] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rab GTPases are associated with distinct cellular compartments and function as specific regulators of intracellular transport. In the endocytic pathway, it is well documented that Rab5 regulates transport from plasma membrane to early (sorting) endosomes. In contrast, little is known about the precise localization and function of Rab4 and Rab11, which are believed to control endocytic recycling. In the present study we have analysed the protein composition of Rab5- and Rab11-carrying endosomes to gain further insight into the compartmental organization of the endocytic and recycling pathway. Endosome populations of this transport route were purified by immunoadsorption from endosome-enriched subcellular fractions using antibodies directed against the cytoplasmic tail of the transferrin receptor, Rab5 or Rab11. Endocytosed transferrin moved sequentially through compartments that could be immunoadsorbed with anti-Rab5 and anti-Rab11, consistent with the theory that Rab5 and Rab11 localise to sorting and recycling endosomes, respectively. These compartments exhibited morphological differences, as determined by electron microscopy. Although their overall protein compositions were very similar, some proteins were found to be selectively enriched. While Rab4 was present on all endosome populations, Rab5 and Rab11 were strikingly segregated. Furthermore, the Rab11-positive endosomes were rich in annexin II, actin and the t-SNARE syntaxin 13, compared to Rab5-containing endosomes. In an in vitro assay, the Rab5 effector protein EEA1 was preferentially recruited by Rab5-positive endosomes. Taken together, our data suggest an organization of the transferrin pathway into distinct Rab5- and Rab11-positive compartments.
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Affiliation(s)
- M Trischler
- Institut f]ur Biochemie, Universit]at Mainz, Becherweg 30, D-55128 Mainz, Germany
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100
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Abstract
Sorting of membrane proteins is generally mediated by cytosolic coats, which create a scaffold to form coated buds and vesicles and to selectively concentrate cargo by interacting with cytosolic signals. The classical paradigm is the interaction between clathrin coats and associated adaptor proteins, which cluster receptors with characteristic tyrosine and dileucine motifs during endocytosis. Clathrin in association with different sets of adaptors is found in addition at the trans-Golgi network and endosomes. Sequences similar to internalization signals also direct lysosomal and basolateral sorting, which implicates related clathrinadaptor coats in the respective sorting pathways. This review concentrates on the recognition of sorting signals by clathrin-associated adaptor proteins, an area of significant recent progress due to new methodological and conceptual approaches.
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