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de Caestecker C, Macara IG. A size filter at the Golgi regulates apical membrane protein sorting. Nat Cell Biol 2024:10.1038/s41556-024-01500-0. [PMID: 39237743 DOI: 10.1038/s41556-024-01500-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 08/12/2024] [Indexed: 09/07/2024]
Abstract
Despite decades of research, apical sorting of epithelial membrane proteins remains incompletely understood. We noted that apical cytoplasmic domains are smaller than those of basolateral proteins; however, the reason for this discrepancy is unknown. Here we used a synthetic biology approach to investigate whether a size barrier at the Golgi apparatus might hinder apical sorting of proteins with large cytoplasmic tails. We focused on Crb3, Ace2 and Muc1 as representative apical proteins with short cytoplasmic tails. By incorporating a streptavidin-binding peptide, these proteins can be trapped in the endoplasmic reticulum until addition of biotin, which triggers synchronous release to the Golgi and subsequent transport to the apical cortex. Strikingly, increasing the size of their cytoplasmic domains caused partial mislocalization to the basolateral cortex and significantly delayed Golgi departure. Moreover, N-glycosylation of 'large' Crb3 was delayed, and 'small' Crb3 segregated into spatially distinct Golgi regions. Biologically, Crb3 forms a complex through its cytoplasmic tail with the Pals1 protein, which could also delay departure, but although associated at the endoplasmic reticulum and Golgi, Pals1 disassociated before Crb3 departure. Notably, a non-dissociable mutant Pals1 hampered the exit of Crb3. We conclude that, unexpectedly, a size filter at the Golgi facilitates apical sorting of proteins with small cytoplasmic domains and that timely release of Pals1, to reduce cytoplasmic domain size, is essential for normal Crb3 sorting.
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Affiliation(s)
- Christian de Caestecker
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ian G Macara
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA.
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2
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Ma M, Kler S, Pan YA. Structural Neural Connectivity Analysis in Zebrafish With Restricted Anterograde Transneuronal Viral Labeling and Quantitative Brain Mapping. Front Neural Circuits 2020; 13:85. [PMID: 32038180 PMCID: PMC6989443 DOI: 10.3389/fncir.2019.00085] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 12/30/2019] [Indexed: 12/13/2022] Open
Abstract
The unique combination of small size, translucency, and powerful genetic tools makes larval zebrafish a uniquely useful vertebrate system to investigate normal and pathological brain structure and function. While functional connectivity can now be assessed by optical imaging (via fluorescent calcium or voltage reporters) at the whole-brain scale, it remains challenging to systematically determine structural connections and identify connectivity changes during development or disease. To address this, we developed Tracer with Restricted Anterograde Spread (TRAS), a novel vesicular stomatitis virus (VSV)-based neural circuit labeling approach. TRAS makes use of replication-incompetent VSV (VSVΔG) and a helper virus (lentivirus) to enable anterograde transneuronal spread between efferent axons and their direct postsynaptic targets but restricts further spread to downstream areas. We integrated TRAS with the Z-Brain zebrafish 3D atlas for quantitative connectivity analysis and identified targets of the retinal and habenular efferent projections, in patterns consistent with previous reports. We compared retinofugal connectivity patterns between wild-type and down syndrome cell adhesion molecule-like 1 (dscaml1) mutant zebrafish and revealed differences in topographical distribution. These results demonstrate the utility of TRAS for quantitative structural connectivity analysis that would be valuable for detecting novel efferent targets and mapping connectivity changes underlying neurological or behavioral deficits.
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Affiliation(s)
- Manxiu Ma
- Center for Neurobiology Research, Fralin Biomedical Research Institute at VTC, Virginia Tech, Roanoke, VA, United States.,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States
| | - Stanislav Kler
- Center for Neurobiology Research, Fralin Biomedical Research Institute at VTC, Virginia Tech, Roanoke, VA, United States.,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States
| | - Y Albert Pan
- Center for Neurobiology Research, Fralin Biomedical Research Institute at VTC, Virginia Tech, Roanoke, VA, United States.,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States.,Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States.,Department of Psychiatry and Behavioral Medicine, Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
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3
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Caceres PS, Benedicto I, Lehmann GL, Rodriguez-Boulan EJ. Directional Fluid Transport across Organ-Blood Barriers: Physiology and Cell Biology. Cold Spring Harb Perspect Biol 2017; 9:a027847. [PMID: 28003183 PMCID: PMC5334253 DOI: 10.1101/cshperspect.a027847] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Directional fluid flow is an essential process for embryo development as well as for organ and organism homeostasis. Here, we review the diverse structure of various organ-blood barriers, the driving forces, transporters, and polarity mechanisms that regulate fluid transport across them, focusing on kidney-, eye-, and brain-blood barriers. We end by discussing how cross talk between barrier epithelial and endothelial cells, perivascular cells, and basement membrane signaling contribute to generate and maintain organ-blood barriers.
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Affiliation(s)
- Paulo S Caceres
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, New York 10065
| | - Ignacio Benedicto
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, New York 10065
| | - Guillermo L Lehmann
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, New York 10065
| | - Enrique J Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, New York 10065
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4
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Preferential Budding of Vesicular Stomatitis Virus from the Basolateral Surface of Polarized Epithelial Cells Is Not Solely Directed by Matrix Protein or Glycoprotein. J Virol 2015; 89:11718-22. [PMID: 26339064 PMCID: PMC4645653 DOI: 10.1128/jvi.01658-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 08/28/2015] [Indexed: 11/20/2022] Open
Abstract
Vesicular stomatitis virus has been shown to bud basolaterally, and the matrix protein, but not glycoprotein, was proposed to mediate this asymmetry. Using polarized T84 monolayers, we demonstrate that no single viral protein is sufficient for polarized budding. Particles are released from the apical and basolateral surfaces and are indistinguishable, indicating that there is no apical assembly defect. We propose that aspects of host cell polarity create a more efficient budding process at the basolateral surface.
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5
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Fölsch H. Role of the epithelial cell-specific clathrin adaptor complex AP-1B in cell polarity. CELLULAR LOGISTICS 2015; 5:e1074331. [PMID: 27057418 DOI: 10.1080/21592799.2015.1074331] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/07/2015] [Accepted: 07/09/2015] [Indexed: 10/23/2022]
Abstract
Epithelial cells are important for organ development and function. To this end, they polarize their plasma membrane into biochemically and physically distinct membrane domains. The apical membrane faces the luminal site of an organ and the basolateral domain is in contact with the basement membrane and neighboring cells. To establish and maintain this polarity it is important that newly synthesized and endocytic cargos are correctly sorted according to their final destinations at either membrane. Sorting takes place at one of 2 major sorting stations in the cells, the trans-Golgi network (TGN) and recycling endosomes (REs). Polarized sorting may involve epithelial cell-specific sorting adaptors like the AP-1B clathrin adaptor complex. AP-1B facilitates basolateral sorting from REs. This review will discuss various aspects of basolateral sorting in epithelial cells with a special emphasis on AP-1B.
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Affiliation(s)
- Heike Fölsch
- Department of Cell and Molecular Biology; Northwestern University; Feinberg School of Medicine ; Chicago, IL USA
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Yaffe Y, Hugger I, Yassaf IN, Shepshelovitch J, Sklan EH, Elkabetz Y, Yeheskel A, Pasmanik-Chor M, Benzing C, Macmillan A, Gaus K, Eshed-Eisenbach Y, Peles E, Hirschberg K. The myelin proteolipid plasmolipin forms oligomers and induces liquid-ordered membranes in the Golgi complex. J Cell Sci 2015; 128:2293-302. [DOI: 10.1242/jcs.166249] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 05/18/2015] [Indexed: 01/27/2023] Open
Abstract
ABSTRACT
Myelin comprises a compactly stacked massive surface area of protein-poor thick membrane that insulates axons to allow fast signal propagation. Increasing levels of the myelin protein plasmolipin (PLLP) were correlated with post-natal myelination; however, its function is unknown. Here, the intracellular localization and dynamics of PLLP were characterized in primary glial and cultured cells using fluorescently labeled PLLP and antibodies against PLLP. PLLP localized to and recycled between the plasma membrane and the Golgi complex. In the Golgi complex, PLLP forms oligomers based on fluorescence resonance energy transfer (FRET) analyses. PLLP oligomers blocked Golgi to plasma membrane transport of the secretory protein vesicular stomatitis virus G protein (VSVG), but not of a VSVG mutant with an elongated transmembrane domain. Laurdan staining analysis showed that this block is associated with PLLP-induced proliferation of liquid-ordered membranes. These findings show the capacity of PLLP to assemble potential myelin membrane precursor domains at the Golgi complex through its oligomerization and ability to attract liquid-ordered lipids. These data support a model in which PLLP functions in myelin biogenesis through organization of myelin liquid-ordered membranes in the Golgi complex.
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Affiliation(s)
- Yakey Yaffe
- Department of Pathology, Sackler School of Medicine, Tel-Aviv 69978, Israel
| | - Ilan Hugger
- Department of Pathology, Sackler School of Medicine, Tel-Aviv 69978, Israel
| | - Inbar Nevo Yassaf
- Department of Pathology, Sackler School of Medicine, Tel-Aviv 69978, Israel
| | | | - Ella H. Sklan
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel-Aviv 69978, Israel
| | - Yechiel Elkabetz
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel-Aviv 69978, Israel
| | - Adva Yeheskel
- Bioinformatics Unit, G.S.W. Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Metsada Pasmanik-Chor
- Bioinformatics Unit, G.S.W. Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Carola Benzing
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, Centre for Vascular Research University of New South Wales, Sydney, Australia 2033
| | - Alexander Macmillan
- Biomedical Imaging Facility, University of New South Wales, Sydney, Australia 2033
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, Centre for Vascular Research University of New South Wales, Sydney, Australia 2033
| | - Yael Eshed-Eisenbach
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel 76100
| | - Elior Peles
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel 76100
| | - Koret Hirschberg
- Department of Pathology, Sackler School of Medicine, Tel-Aviv 69978, Israel
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Fossati M, Colombo SF, Borgese N. A positive signal prevents secretory membrane cargo from recycling between the Golgi and the ER. EMBO J 2014; 33:2080-97. [PMID: 25063674 DOI: 10.15252/embj.201488367] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The Golgi complex and ER are dynamically connected by anterograde and retrograde trafficking pathways. To what extent and by what mechanism outward-bound cargo proteins escape retrograde trafficking has been poorly investigated. Here, we analysed the behaviour of several membrane proteins at the ER/Golgi interface in live cells. When Golgi-to-plasma membrane transport was blocked, vesicular stomatitis virus glycoprotein (VSVG), which bears an ER export signal, accumulated in the Golgi, whereas an export signal-deleted version of VSVG attained a steady state determined by the balance of retrograde and anterograde traffic. A similar behaviour was displayed by EGF receptor and by a model tail-anchored protein, whose retrograde traffic was slowed by addition of VSVG's export signal. Retrograde trafficking was energy- and Rab6-dependent, and Rab6 inhibition accelerated signal-deleted VSVG's transport to the cell surface. Our results extend the dynamic bi-directional relationship between the Golgi and ER to include surface-directed proteins, uncover an unanticipated role for export signals at the Golgi complex, and identify recycling as a novel factor that regulates cargo transport out of the early secretory pathway.
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Affiliation(s)
- Matteo Fossati
- BIOMETRA Department, CNR Institute of Neuroscience, Università degli Studi di Milano, Milano, Italy
| | - Sara F Colombo
- BIOMETRA Department, CNR Institute of Neuroscience, Università degli Studi di Milano, Milano, Italy
| | - Nica Borgese
- BIOMETRA Department, CNR Institute of Neuroscience, Università degli Studi di Milano, Milano, Italy Department of Health Science, Magna Graecia University of Catanzaro, Catanzaro, Italy
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Stoops EH, Caplan MJ. Trafficking to the apical and basolateral membranes in polarized epithelial cells. J Am Soc Nephrol 2014; 25:1375-86. [PMID: 24652803 DOI: 10.1681/asn.2013080883] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Renal epithelial cells must maintain distinct protein compositions in their apical and basolateral membranes in order to perform their transport functions. The creation of these polarized protein distributions depends on sorting signals that designate the trafficking route and site of ultimate functional residence for each protein. Segregation of newly synthesized apical and basolateral proteins into distinct carrier vesicles can occur at the trans-Golgi network, recycling endosomes, or a growing assortment of stations along the cellular trafficking pathway. The nature of the specific sorting signal and the mechanism through which it is interpreted can influence the route a protein takes through the cell. Cell type-specific variations in the targeting motifs of a protein, as are evident for Na,K-ATPase, demonstrate a remarkable capacity to adapt sorting pathways to different developmental states or physiologic requirements. This review summarizes our current understanding of apical and basolateral trafficking routes in polarized epithelial cells.
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Affiliation(s)
- Emily H Stoops
- Departments of Cellular & Molecular Physiology and Cell Biology, Yale University School of Medicine, New Haven, Connecticut
| | - Michael J Caplan
- Departments of Cellular & Molecular Physiology and Cell Biology, Yale University School of Medicine, New Haven, Connecticut
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10
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Gravotta D, Carvajal-Gonzalez JM, Mattera R, Deborde S, Banfelder JR, Bonifacino JS, Rodriguez-Boulan E. The clathrin adaptor AP-1A mediates basolateral polarity. Dev Cell 2012; 22:811-23. [PMID: 22516199 DOI: 10.1016/j.devcel.2012.02.004] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 12/29/2011] [Accepted: 02/06/2012] [Indexed: 12/16/2022]
Abstract
Clathrin and the epithelial-specific clathrin adaptor AP-1B mediate basolateral trafficking in epithelia. However, several epithelia lack AP-1B, and mice knocked out for AP-1B are viable, suggesting the existence of additional mechanisms that control basolateral polarity. Here, we demonstrate a distinct role of the ubiquitous clathrin adaptor AP-1A in basolateral protein sorting. Knockdown of AP-1A causes missorting of basolateral proteins in MDCK cells, but only after knockdown of AP-1B, suggesting that AP-1B can compensate for lack of AP-1A. AP-1A localizes predominantly to the TGN, and its knockdown promotes spillover of basolateral proteins into common recycling endosomes, the site of function of AP-1B, suggesting complementary roles of both adaptors in basolateral sorting. Yeast two-hybrid assays detect interactions between the basolateral signal of transferrin receptor and the medium subunits of both AP-1A and AP-1B. The basolateral sorting function of AP-1A reported here establishes AP-1 as a major regulator of epithelial polarity.
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Affiliation(s)
- Diego Gravotta
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065, USA.
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11
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Polarised apical-like intracellular sorting and trafficking regulates invadopodia formation and degradation of the extracellular matrix in cancer cells. Eur J Cell Biol 2012; 91:961-8. [PMID: 22564726 DOI: 10.1016/j.ejcb.2012.03.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 03/23/2012] [Accepted: 03/26/2012] [Indexed: 01/07/2023] Open
Abstract
Invadopodia are proteolytically active protrusions formed by invasive tumoral cells when grown on an extracellular matrix (ECM) substratum. A current challenge is to understand how proteolytic activity is so precisely localised at discrete sites of the plasma membrane to produce focalised ECM degradation at invadopodia. Indeed, a number of components including metalloproteases need to be directed to invadopodia to ensure proper segregation of proteolytic activities. We recently found invadopodia to feature the properties of cholesterol-rich membrane domains (a.k.a. lipid drafts) and that ECM degradation depends on the tight control of cholesterol homeostasis. Since apically directed polarised sorting and transport in epithelial cells relies on segregation of proteins into lipid rafts at the Golgi complex, we hypothesised that invadopodia-dependent ECM degradation might also rely on lipid raft-dependent polarised transport routes. To investigate this issue we undertook a three-pronged approach. First, we found that microtubule depolymerisation, which is known to disrupt polarised transport in polarised cells, strongly inhibited invadopodia formation, while not affecting overall protein transport. In the second approach we found that glycosylphosphatidylinositol-anchored green fluorescent protein (an apical model protein), but not vesicular stomatitis virus G-protein or influenza virus hemagglutinin (both model basolateral model cargoes), was transported to sites of ECM degradation. Finally, RNAi-mediated knock-down of proteins known to specifically regulate polarised apical or basolateral transport in epithelial cells, such as caveolin 1 and annexin XIIIB or clathrin, respectively, demonstrated that the selective inhibition of the apical, but not the basolateral, transport route impairs invadopodia formation and ECM degradation. Taken together, our findings suggest that invadopodia are apical-like membrane domains, where signal transduction and local membrane remodelling events might be temporally and spatially confined via selective raft-dependent apical transport routes.
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13
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Cereijido M, Contreras RG, Shoshani L, Larre I. The Na+-K+-ATPase as self-adhesion molecule and hormone receptor. Am J Physiol Cell Physiol 2011; 302:C473-81. [PMID: 22049208 DOI: 10.1152/ajpcell.00083.2011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Thanks to the homeostasis of the internal milieu, metazoan cells can enormously simplify their housekeeping efforts and engage instead in differentiation and multiple forms of organization (tissues, organs, systems) that enable them to produce an astonishing diversity of mammals. The stability of the internal milieu despite drastic variations of the external environment (air, fresh or seawater, gastrointestinal fluids, glomerular filtrate, bile) is due to transporting epithelia that can adjust their specific permeability to H(2)O, H(+), Na(+), K(+), Ca(2+), and Cl(-) over several orders of magnitude and exchange substances with the outer milieu with exquisite precision. This exchange is due to the polarized expression of membrane proteins, among them Na(+)-K(+)-ATPase, an oligomeric enzyme that uses chemical energy from ATP molecules to translocate ions across the plasma membrane of epithelial cells. Na(+)-K(+)-ATPase presents two types of asymmetries: the arrangement of its subunits, and its expression in one pole of the epithelial cell ("polarity"). In most epithelia, polarity consists of the expression of Na(+)-K(+)-ATPase towards the intercellular space and arises in part from the interaction of the extracellular segment of the β-subunit with another β-subunit present in a Na(+)-K(+)-ATPase molecule expressed by a neighboring cell. In addition to enabling the Na(+)-K(+)-ATPase to transport ions and water vectorially, this position exposes its receptors to ouabain and analogous cardiotonic steroids, which are present in the internal milieu because these were secreted by endocrine cells.
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Affiliation(s)
- M Cereijido
- CINVESTAV, Col. San Pedro Zacatenco, Del. Gustavo A. Madero, México, D.F., México.
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Anterograde or retrograde transsynaptic labeling of CNS neurons with vesicular stomatitis virus vectors. Proc Natl Acad Sci U S A 2011; 108:15414-9. [PMID: 21825165 DOI: 10.1073/pnas.1110854108] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To understand how the nervous system processes information, a map of the connections among neurons would be of great benefit. Here we describe the use of vesicular stomatitis virus (VSV) for tracing neuronal connections in vivo. We made VSV vectors that used glycoprotein (G) genes from several other viruses. The G protein from lymphocytic choriomeningitis virus endowed VSV with the ability to spread transsynaptically, specifically in an anterograde direction, whereas the rabies virus glycoprotein gave a specifically retrograde transsynaptic pattern. The use of an avian G protein fusion allowed specific targeting of cells expressing an avian receptor, which allowed a demonstration of monosynaptic anterograde tracing from defined cells. Synaptic connectivity of pairs of virally labeled cells was demonstrated by using slice cultures and electrophysiology. In vivo infections of several areas in the mouse brain led to the predicted patterns of spread for anterograde or retrograde tracers.
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Castorino JJ, Deborde S, Deora A, Schreiner R, Gallagher-Colombo SM, Rodriguez-Boulan E, Philp NJ. Basolateral sorting signals regulating tissue-specific polarity of heteromeric monocarboxylate transporters in epithelia. Traffic 2011; 12:483-98. [PMID: 21199217 DOI: 10.1111/j.1600-0854.2010.01155.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Many solute transporters are heterodimers composed of non-glycosylated catalytic and glycosylated accessory subunits. These transporters are specifically polarized to the apical or basolateral membranes of epithelia, but this polarity may vary to fulfill tissue-specific functions. To date, the mechanisms regulating the tissue-specific polarity of heteromeric transporters remain largely unknown. Here, we investigated the sorting signals that determine the polarity of three members of the proton-coupled monocarboxylate transporter (MCT) family, MCT1, MCT3 and MCT4, and their accessory subunit CD147. We show that MCT3 and MCT4 harbor strong redundant basolateral sorting signals (BLSS) in their C-terminal cytoplasmic tails that can direct fusion proteins with the apical marker p75 to the basolateral membrane. In contrast, MCT1 lacks a BLSS and its polarity is dictated by CD147, which contains a weak BLSS that can direct Tac, but not p75 to the basolateral membrane. Knockdown experiments in MDCK cells indicated that basolateral sorting of MCTs was clathrin-dependent but clathrin adaptor AP1B-independent. Our results explain the consistently basolateral localization of MCT3 and MCT4 and the variable localization of MCT1 in different epithelia. They introduce a new paradigm for the sorting of heterodimeric transporters in which a hierarchy of apical and BLSS in the catalytic and/or accessory subunits regulates their tissue-specific polarity.
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Affiliation(s)
- John J Castorino
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Subach FV, Patterson GH, Renz M, Lippincott-Schwartz J, Verkhusha VV. Bright monomeric photoactivatable red fluorescent protein for two-color super-resolution sptPALM of live cells. J Am Chem Soc 2010; 132:6481-91. [PMID: 20394363 PMCID: PMC2866019 DOI: 10.1021/ja100906g] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Rapidly emerging techniques of super-resolution single-molecule microscopy of living cells rely on the continued development of genetically encoded photoactivatable fluorescent proteins. On the basis of monomeric TagRFP, we have developed a photoactivatable TagRFP protein that is initially dark but becomes red fluorescent after violet light irradiation. Compared to other monomeric dark-to-red photoactivatable proteins including PAmCherry, PATagRFP has substantially higher molecular brightness, better pH stability, substantially less sensitivity to blue light, and better photostability in both ensemble and single-molecule modes. Spectroscopic analysis suggests that PATagRFP photoactivation is a two-step photochemical process involving sequential one-photon absorbance by two distinct chromophore forms. True monomeric behavior, absence of green fluorescence, and single-molecule performance in live cells make PATagRFP an excellent protein tag for two-color imaging techniques, including conventional diffraction-limited photoactivation microscopy, super-resolution photoactivated localization microscopy (PALM), and single particle tracking PALM (sptPALM) of living cells. Two-color sptPALM imaging was demonstrated using several PATagRFP tagged transmembrane proteins together with PAGFP-tagged clathrin light chain. Analysis of the resulting sptPALM images revealed that single-molecule transmembrane proteins, which are internalized into a cell via endocytosis, colocalize in space and time with plasma membrane domains enriched in clathrin light-chain molecules.
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Affiliation(s)
- Fedor V. Subach
- Department of Anatomy and Structural Biology and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
| | - George H. Patterson
- Biophotonics Section, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892
| | - Malte Renz
- Section on Organelle Biology, Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892
| | - Jennifer Lippincott-Schwartz
- Section on Organelle Biology, Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892
| | - Vladislav V. Verkhusha
- Department of Anatomy and Structural Biology and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
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Caldieri G, Buccione R. Aiming for invadopodia: organizing polarized delivery at sites of invasion. Trends Cell Biol 2009; 20:64-70. [PMID: 19931459 DOI: 10.1016/j.tcb.2009.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 10/22/2009] [Accepted: 10/26/2009] [Indexed: 01/05/2023]
Abstract
Recent years have witnessed growing interest in the biology of invadopodia, proteolytically active protrusions formed by invasive tumor cells when cultured on an extracellular matrix (ECM). Although substantial progress has been made towards defining their basic elements and features, the need remains to understand how these components are recruited and, ultimately, how ECM degradation is so precisely localized. According to recent evidence, invadopodia are raft-like membrane domains where cholesterol levels are tightly regulated, and active transport of protease-delivering carriers is required for their function. On this basis we hypothesize that the correct delivery of cargo to invadopodia is ensured by a polarized, cholesterol-dependent trafficking mechanism, similar to that of the apical domain of epithelial cells.
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Affiliation(s)
- Giusi Caldieri
- Tumor Cell Invasion Laboratory, Consorzio Mario Negri Sud, S. Maria Imbaro (Chieti), 66030 Italy
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Gonzalez A, Rodriguez-Boulan E. Clathrin and AP1B: key roles in basolateral trafficking through trans-endosomal routes. FEBS Lett 2009; 583:3784-95. [PMID: 19854182 DOI: 10.1016/j.febslet.2009.10.050] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 10/15/2009] [Accepted: 10/20/2009] [Indexed: 12/12/2022]
Abstract
Research following introduction of the MDCK model system to study epithelial polarity (1978) led to an initial paradigm that posited independent roles of the trans Golgi network (TGN) and recycling endosomes (RE) in the generation of, respectively, biosynthetic and recycling routes of plasma membrane (PM) proteins to apical and basolateral PM domains. This model dominated the field for 20 years. However, studies over the past decade and the discovery of the involvement of clathrin and clathrin adaptors in protein trafficking to the basolateral PM has led to a new paradigm. TGN and RE are now believed to cooperate closely in both biosynthetic and recycling trafficking routes. Here, we critically review these recent advances and the questions that remain unanswered.
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Affiliation(s)
- Alfonso Gonzalez
- Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina, Centro de Regulación Celular y Patología and Centro de Envejecimiento y Regeneración, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 6510260 Santiago, Chile.
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19
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Sequence- or Position-Specific Mutations in the Carboxyl-Terminal FL Motif of the Kidney Sodium Bicarbonate Cotransporter (NBC1) Disrupt Its Basolateral Targeting and α-Helical Structure. J Membr Biol 2009; 228:111-24. [DOI: 10.1007/s00232-009-9164-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 02/18/2009] [Indexed: 12/22/2022]
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20
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Martelli AM, Baldini G, Tabellini G, Koticha D, Bareggi R, Baldini G. Rab3A and Rab3D Control the Total Granule Number and the Fraction of Granules Docked at the Plasma Membrane in PC12 Cells. Traffic 2008. [DOI: 10.1111/j.1600-0854.2000.11207.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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21
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Clathrin is a key regulator of basolateral polarity. Nature 2008; 452:719-23. [PMID: 18401403 DOI: 10.1038/nature06828] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 02/07/2008] [Indexed: 12/20/2022]
Abstract
Clathrin-coated vesicles are vehicles for intracellular trafficking in all nucleated cells, from yeasts to humans. Many studies have demonstrated their essential roles in endocytosis and cellular signalling processes at the plasma membrane. By contrast, very few of their non-endocytic trafficking roles are known, the best characterized being the transport of hydrolases from the Golgi complex to the lysosome. Here we show that clathrin is required for polarity of the basolateral plasma membrane proteins in the epithelial cell line MDCK. Clathrin knockdown depolarized most basolateral proteins, by interfering with their biosynthetic delivery and recycling, but did not affect the polarity of apical proteins. Quantitative live imaging showed that chronic and acute clathrin knockdown selectively slowed down the exit of basolateral proteins from the Golgi complex, and promoted their mis-sorting into apical carrier vesicles. Our results demonstrate a broad requirement for clathrin in basolateral protein trafficking in epithelial cells.
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22
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Klunder B, Baron W, Schrage C, de Jonge J, de Vries H, Hoekstra D. Sorting signals and regulation of cognate basolateral trafficking in myelin biogenesis. J Neurosci Res 2008; 86:1007-16. [DOI: 10.1002/jnr.21556] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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23
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Cellular localization of Nicastrin affects amyloid β species production. FEBS Lett 2008; 582:427-33. [DOI: 10.1016/j.febslet.2008.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 12/20/2007] [Accepted: 01/02/2008] [Indexed: 11/23/2022]
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24
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Duffield A, Caplan MJ, Muth TR. Chapter 4 Protein Trafficking in Polarized Cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 270:145-79. [DOI: 10.1016/s1937-6448(08)01404-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Murphy SJ, Shapira KE, Henis YI, Leof EB. A unique element in the cytoplasmic tail of the type II transforming growth factor-beta receptor controls basolateral delivery. Mol Biol Cell 2007; 18:3788-99. [PMID: 17634290 PMCID: PMC1995729 DOI: 10.1091/mbc.e06-10-0930] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Transforming growth factor (TGF)-beta receptors stimulate diverse signaling processes that control a wide range of biological responses. In polarized epithelia, the TGFbeta type II receptor (T2R) is localized at the basolateral membranes. Sequential cytoplasmic truncations resulted in receptor missorting to apical surfaces, and they indicated an essential targeting element(s) near the receptor's C terminus. Point mutations in the full-length receptor confirmed this prediction, and a unique basolateral-targeting region was elucidated between residues 529 and 538 (LTAxxVAxxR) that was distinct, but colocalized within a clinically significant signaling domain essential for TGFbeta-dependent activation of the Smad2/3 cascade. Transfer of a terminal 84 amino-acid fragment, containing the LTAxxVAxxR element, to the apically sorted influenza hemagglutinin (HA) protein was dominant and directed basolateral HA expression. Although delivery to the basolateral surfaces was direct and independent of any detectable transient apical localization, fluorescence recovery after photobleaching demonstrated similar mobility for the wild-type receptor and a missorted mutant lacking the targeting motif. This latter finding excludes the possibility that the domain acts as a cell membrane retention signal, and it supports the hypothesis that T2R sorting occurs from an intracellular compartment.
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Affiliation(s)
- Stephen J. Murphy
- *Thoracic Diseases Research Unit, Department of Biochemistry and Molecular Biology and Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, MN 55905; and
| | - Keren E. Shapira
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I. Henis
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Edward B. Leof
- *Thoracic Diseases Research Unit, Department of Biochemistry and Molecular Biology and Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, MN 55905; and
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26
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Fields IC, Shteyn E, Pypaert M, Proux-Gillardeaux V, Kang RS, Galli T, Fölsch H. v-SNARE cellubrevin is required for basolateral sorting of AP-1B-dependent cargo in polarized epithelial cells. ACTA ACUST UNITED AC 2007; 177:477-88. [PMID: 17485489 PMCID: PMC2034334 DOI: 10.1083/jcb.200610047] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The epithelial cell–specific adaptor complex AP-1B is crucial for correct delivery of many transmembrane proteins from recycling endosomes to the basolateral plasma membrane. Subsequently, membrane fusion is dependent on the formation of complexes between SNARE proteins located at the target membrane and on transport vesicles. Although the t-SNARE syntaxin 4 has been localized to the basolateral membrane, the v-SNARE operative in the AP-1B pathway remained unknown. We show that the ubiquitously expressed v-SNARE cellubrevin localizes to the basolateral membrane and to recycling endosomes, where it colocalizes with AP-1B. Furthermore, we demonstrate that cellubrevin coimmunoprecipitates preferentially with syntaxin 4, implicating this v-SNARE in basolateral fusion events. Cleavage of cellubrevin with tetanus neurotoxin (TeNT) results in scattering of AP-1B localization and missorting of AP-1B–dependent cargos, such as transferrin receptor and a truncated low-density lipoprotein receptor, LDLR-CT27. These data suggest that cellubrevin and AP-1B cooperate in basolateral membrane trafficking.
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Affiliation(s)
- Ian C Fields
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA
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27
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Au JSY, Puri C, Ihrke G, Kendrick-Jones J, Buss F. Myosin VI is required for sorting of AP-1B-dependent cargo to the basolateral domain in polarized MDCK cells. ACTA ACUST UNITED AC 2007; 177:103-14. [PMID: 17403927 PMCID: PMC2064115 DOI: 10.1083/jcb.200608126] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In polarized epithelial cells, newly synthesized membrane proteins are delivered on specific pathways to either the apical or basolateral domains, depending on the sorting motifs present in these proteins. Because myosin VI has been shown to facilitate secretory traffic in nonpolarized cells, we investigated its role in biosynthetic trafficking pathways in polarized MDCK cells. We observed that a specific splice isoform of myosin VI with no insert in the tail domain is required for the polarized transport of tyrosine motif containing basolateral membrane proteins. Sorting of other basolateral or apical cargo, however, does not involve myosin VI. Site-directed mutagenesis indicates that a functional complex consisting of myosin VI, optineurin, and probably the GTPase Rab8 plays a role in the basolateral delivery of membrane proteins, whose sorting is mediated by the clathrin adaptor protein complex (AP) AP-1B. Our results suggest that myosin VI is a crucial component in the AP-1B–dependent biosynthetic sorting pathway to the basolateral surface in polarized epithelial cells.
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Affiliation(s)
- Josephine Sui-Yan Au
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, England, UK
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28
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Abstract
Many viruses express membrane proteins. For enveloped viruses in particular, membrane proteins are frequently structural components of the virus that mediate the essential tasks of receptor recognition and membrane fusion. The functional activities of these proteins require that they are sorted correctly in infected cells. These sorting events often depend on the ability of the virus to mimic cellular protein trafficking signals and to interact with the cellular trafficking machinery. Importantly, loss or modification of these signals can influence virus infectivity and pathogenesis.
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Affiliation(s)
- R Byland
- MRC-LMCB and Department of Biochemistry and Molecular Biology, University College London, London, WC1E 6BT, UK
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29
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Heine M, Cramm-Behrens CI, Ansari A, Chu HP, Ryazanov AG, Naim HY, Jacob R. Alpha-kinase 1, a new component in apical protein transport. J Biol Chem 2005; 280:25637-43. [PMID: 15883161 DOI: 10.1074/jbc.m502265200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A key aspect in the structure of epithelial cells is the maintenance of a polarized organization based on a highly specific sorting machinery for cargo destined for the apical or the basolateral membrane domain at the exit site of the trans-Golgi network. We could recently identify two distinct post-trans-Golgi network vesicle populations that travel along separate routes to the plasma membrane, a lipid raft-dependent and a lipid raft-independent pathway. A new component of raft-carrying apical vesicles is alpha-kinase 1 (ALPK1), which was identified in immunoisolated vesicles carrying raft-associated sucrase-isomaltase (SI). This kinase was absent from vesicles carrying raft-non-associated lactase-phlorizin hydrolase. The expression of ALPK1 increases by the time of epithelial cell differentiation, whereas the intracellular localization of ALPK1 on apical transport vesicles was confirmed by confocal analysis. A phosphorylation assay on isolated SI-carrying vesicles revealed the phosphorylation of a protein band of about 105 kDa, which could be identified as the motor protein myosin I. Finally, a specific reduction of ALPK1-expression by RNA interference results in a significant decrease in the apical delivery of SI. Taken together, our data suggest that the phosphorylation of myosin I by ALPK1 is an essential process in the apical trafficking of raft-associated SI.
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Affiliation(s)
- Martin Heine
- Department of Cell Biology and Cell Pathology, Philipps-University Marburg, D-35033 Marburg, Germany
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30
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Abstract
Rhabdoviruses are a diverse, widely-distributed group of enveloped viruses that assemble and bud from the plasma membrane of host cells. Recent advances in the identification of domains on both the envelope glycoprotein and the matrix protein of rhabdoviruses that contribute to virus assembly and release have allowed us to refine current models of rhabdovirus budding and to describe in better detail the interplay between both viral and cellular components involved in the budding process. In this review we discuss the steps involved in rhabdovirus assembly beginning with genome encapsidation and the association of nucleocapsid-matrix protein pre-assembly complexes with the inner leaflet of the plasma membrane, how condensation of these complexes may occur, how microdomains containing the envelope glycoprotein facilitate bud site formation, and how multiple forms of the matrix protein may participate in virion extrusion and release.
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Affiliation(s)
- Himangi R Jayakar
- GTx Inc., 3 N. Dunlap, Van Vleet Research Building, Memphis, TN 38163, USA
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31
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Campo C, Mason A, Maouyo D, Olsen O, Yoo D, Welling PA. Molecular mechanisms of membrane polarity in renal epithelial cells. Rev Physiol Biochem Pharmacol 2004; 153:47-99. [PMID: 15674648 DOI: 10.1007/s10254-004-0037-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Exciting discoveries in the last decade have cast light onto the fundamental mechanisms that underlie polarized trafficking in epithelial cells. It is now clear that epithelial cell membrane asymmetry is achieved by a combination of intracellular sorting operations, vectorial delivery mechanisms and plasmalemma-specific fusion and retention processes. Several well-defined signals that specify polarized segregation, sorting, or retention processes have, now, been described in a number of proteins. The intracellular machineries that decode and act on these signals are beginning to be described. In addition, the nature of the molecules that associate with intracellular trafficking vesicles to coordinate polarized delivery, tethering, docking, and fusion are also becoming understood. Combined with direct visualization of polarized sorting processes with new technologies in live-cell fluorescent microscopy, new and surprising insights into these once-elusive trafficking processes are emerging. Here we provide a review of these recent advances within an historically relevant context.
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Affiliation(s)
- C Campo
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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32
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Soza A, Norambuena A, Cancino J, de la Fuente E, Henklein P, González A. Sorting Competition with Membrane-permeable Peptides in Intact Epithelial Cells Revealed Discrimination of Transmembrane Proteins Not Only at the trans-Golgi Network but Also at Pre-Golgi Stages. J Biol Chem 2004; 279:17376-83. [PMID: 14764609 DOI: 10.1074/jbc.m313197200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Transmembrane proteins destined to the basolateral cell surface of epithelial cells contain in their cytosolic domain at least two classes of sorting signals: one class promotes exit from the endoplasmic reticulum (ER) and transport to the Golgi complex, and the other class operates at the trans-Golgi network (TGN) specifying segregation into basolateral exocytic pathways. Both kinds of addressing motifs are quite diverse among different proteins. It is unclear to what extent this feature reflects alternative decoding mechanisms or variations in motifs recognized by the same sorting factor. Here we applied a novel strategy based on permeable peptide technology and temperature-sensitive model proteins to study competition between cytosolic sorting motifs in the context of mammalian living cells. We used the transduction domain of HIV-1 Tat protein to make a membrane-permeable peptide of the cytosolic tail of GtsO45, which contains a well characterized ER exit di-acidic (DIE) motif and a tyrosine-based basolateral sorting signal (YTDI). This peptide added to the media inhibited transport of GtsO45 from both ER-to-Golgi and TGN-to-basolateral cell surface in transfected Madin-Darby canine kidney cells. Instead, it did not affect the exocytic trafficking of a GtsO45-derived chimeric protein bearing 30 juxtamembrane residues from the cytosolic domain of the epidermal growth factor receptor that contains a variant ER exit motif (ERE) and an unconventional proline-based basolateral sorting signal. These results not only proved the feasibility of competing for sorting events in intact cells but also showed that distinct plasma membrane proteins can be discriminated at pre-TGN stages, and that basolateral sorting involves different recognition elements for tyrosine-based motifs and an unconventional basolateral motif.
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Affiliation(s)
- Andrea Soza
- Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina, and Centro de Regulación Celular y Patología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 6510260 Santiago, Chile
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33
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Abstract
In order to carry out their physiological functions, ion transport proteins must be targeted to the appropriate domains of cell membranes. Regulation of ion transport activity frequently involves the tightly controlled delivery of intracellular populations of transport proteins to the plasma membrane or the endocytic retrieval of transport proteins from the cell surface. Transport proteins carry signals embedded within their structures that specify their subcellular distributions and endow them with the capacity to participate in regulated membrane trafficking processes. Recently, a great deal has been learned about the biochemical nature of these signals, as well as about the cellular machinery that interprets them and acts upon their messages.
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Affiliation(s)
- Theodore R Muth
- Department of Biology, CUNY Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11231, USA.
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34
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Jacob R, Heine M, Eikemeyer J, Frerker N, Zimmer KP, Rescher U, Gerke V, Naim HY. Annexin II Is Required for Apical Transport in Polarized Epithelial Cells. J Biol Chem 2004; 279:3680-4. [PMID: 14670963 DOI: 10.1074/jbc.c300503200] [Citation(s) in RCA: 69] [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
The sorting of apical proteins comprises an initial recognition step in the trans Golgi network and a final partitioning of the apical pool of proteins into at least two different types of vesicular carriers. One criteria of these carriers is the association or non-association of the protein content with lipid rafts. We have previously characterized a population containing the raft-associated sucrase-isomaltase-carrying vesicles (SAVs) and another one, the non-raft-associated lactase-phlorizin hydrolase-carrrying vesicles (LAVs) that are targeted separately to the apical membrane. Here, we demonstrate biochemically and by employing confocal laser microscopy that the annexin II-S100A10 complex is a component of SAVs and is absent from LAVs. The unequivocal role of annexin II in the apical targeting of SI is clearly demonstrated when down-regulation of this protein by annexin II-specific small interfering RNA drastically decreases the apical delivery of SI in the epithelial cell line Madin-Darby canine kidney. The annexin II-S100A10 complex plays therefore a crucial role in routing SAVs to the apical membrane of epithelial cells.
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Affiliation(s)
- Ralf Jacob
- Department of Physiological Chemistry, School of Veterinary Medicine Hannover, Germany.
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35
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Brown A, Muth T, Caplan M. The COOH-terminal tail of the GAT-2 GABA transporter contains a novel motif that plays a role in basolateral targeting. Am J Physiol Cell Physiol 2003; 286:C1071-7. [PMID: 15075206 DOI: 10.1152/ajpcell.00291.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability of polarized epithelia to perform vectorial transport depends on the asymmetrical distribution of transmembrane proteins among their plasma membrane domains. The establishment and maintenance of these polar distributions relies on molecular signals embedded in the proteins themselves and the interpretation of these signals by cellular sorting machinery. Using Madin-Darby canine kidney (MDCK) cells as an in vitro model of polarized epithelia, our laboratory has previously shown that the COOH-terminal cytoplasmic 22 amino acids of the GAT-2 isoform of the gamma-amino butyric acid (GABA) transporter are necessary for its basolateral distribution. We demonstrate that the COOH-terminal tail of the transporter can function as an autonomous basolateral distribution signal, independently of the rest of the transporter. We find that the three-amino acid PDZ domain-interacting motif at the COOH-terminus of GAT-2 is not necessary for its basolateral distribution. Instead, the more proximal seven amino acids are necessary both for targeting and for steady-state distribution. Because this sequence resembles no other known basolateral sorting information, we conclude that these seven amino acids contain a novel basolateral targeting and distribution motif.
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Affiliation(s)
- Andrea Brown
- Yale Univ. School of Medicine, 333 Cedar St., New Haven, CT 06511, USA.
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36
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Fölsch H, Pypaert M, Maday S, Pelletier L, Mellman I. The AP-1A and AP-1B clathrin adaptor complexes define biochemically and functionally distinct membrane domains. ACTA ACUST UNITED AC 2003; 163:351-62. [PMID: 14581457 PMCID: PMC2173537 DOI: 10.1083/jcb.200309020] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Most epithelial cells contain two AP-1 clathrin adaptor complexes. AP-1A is ubiquitously expressed and involved in transport between the TGN and endosomes. AP-1B is expressed only in epithelia and mediates the polarized targeting of membrane proteins to the basolateral surface. Both AP-1 complexes are heterotetramers and differ only in their 50-kD μ1A or μ1B subunits. Here, we show that AP-1A and AP-1B, together with their respective cargoes, define physically and functionally distinct membrane domains in the perinuclear region. Expression of AP-1B (but not AP-1A) enhanced the recruitment of at least two subunits of the exocyst complex (Sec8 and Exo70) required for basolateral transport. By immunofluorescence and cell fractionation, the exocyst subunits were found to selectively associate with AP-1B–containing membranes that were both distinct from AP-1A–positive TGN elements and more closely apposed to transferrin receptor–positive recycling endosomes. Thus, despite the similarity of the two AP-1 complexes, AP-1A and AP-1B exhibit great specificity for endosomal transport versus cell polarity.
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Affiliation(s)
- Heike Fölsch
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520, USA.
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37
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Dempsey PJ, Meise KS, Coffey RJ. Basolateral sorting of transforming growth factor-alpha precursor in polarized epithelial cells: characterization of cytoplasmic domain determinants. Exp Cell Res 2003; 285:159-74. [PMID: 12706112 DOI: 10.1016/s0014-4827(03)00035-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In polarized Madin-Darby canine kidney (MDCK) cells, newly synthesized transforming growth factor-alpha precursor (proTGFalpha) is directly sorted to the basolateral cell surface where it is sequentially cleaved and released into the basolateral conditioned medium (Dempsey, P.J., Coffey, R.J., J. Biol. Chem. 269 (1994) 16878-16889). In the present study, the role of the proTGFalpha cytoplasmic domain in basolateral sorting has been investigated using deletional and site-directed mutagenesis, as well as chimeric analyses of different TGFalpha constructs stably expressed in MDCK cells. The loss of polarized secretion of a proTGFalpha secretory mutant (TGFsec88) indicated that the proTGFalpha transmembrane and/or cytoplasmic domains contain essential basolateral sorting information. Using reporter chimeras with two apically sorted membrane proteins, p75 neurotrophin growth factor receptor and placental alkaline phosphatase, we show that the proTGFalpha cytoplasmic domain contains dominant basolateral sorting information. Analysis of proTGFalpha cytoplasmic domain truncation and internal deletion mutants, together with site-directed mutagenesis studies within the full-length proTGFalpha cytoplasmic domain, revealed redundant basolateral sorting motifs. Importantly, the C-terminal type I PDZ-binding motif was not required for basolateral sorting as determined by the integrity of basolateral sorting in deletion mutants lacking this motif. ProTGFalpha basolateral sorting may have important consequences for ligand presentation and spatial compartmentalization of epidermal growth factor receptor signaling networks in polarized epithelial cells.
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Affiliation(s)
- Peter J Dempsey
- Department of Medicine, Vanderbilt University School of Medicine and Veterans Affairs Medical Center, Nashville, TN 37232-2279, USA
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38
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Cereijido M, Contreras RG, Shoshani L, García-Villegas MR. Membrane targeting. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 81:81-115. [PMID: 12565697 DOI: 10.1016/s0079-6107(02)00047-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- M Cereijido
- Center for Research and Advanced Studies (CINVESTAV), Av. Instituto Politécnico Nacional 2508, San Pedro Zacatenco, México D.F. 07300, Mexico.
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39
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Barman S, Adhikary L, Kawaoka Y, Nayak DP. Influenza A virus hemagglutinin containing basolateral localization signal does not alter the apical budding of a recombinant influenza A virus in polarized MDCK cells. Virology 2003; 305:138-52. [PMID: 12504548 DOI: 10.1006/viro.2002.1731] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Morphogenesis of influenza virus is a complex multistep process involving transport of all viral components as either individual or subviral components to the specified assembly site and interaction among the viral components in an ordered fashion to initiate the budding process. Envelope glycoprotein(s) is believed to be the major determinant in selecting the viral budding site since the majority of the viral glycoproteins are directed to the budding site independent of other viral components. Influenza viruses bud from the apical surface of polarized epithelial cells and all three envelope proteins, hemagglutinin (HA), neuraminidase (NA), and M2, are also targeted independently to the apical surface. Since HA is the major viral envelope protein, we decided to test whether basolaterally expressed HA can make the virus bud from the basolateral surface. Accordingly, we introduced the tyrosine-based basolateral-sorting signal to the cytoplasmic tail of HA by changing Cys561 --> Tyr561 and generated a transfectant virus by reverse genetics. Compared to the parent WSN virus, the mutant virus (HAtyr virus) contained less HA on its envelope. While the wild-type (wt) HA was >95% apical, the mutated HA (HAtyr) was approximately 60% basolateral in both transfected and virus-infected polarized MDCK cells. Also, HAtyr protein exhibited a much higher rate of endocytosis than the wt HA, in both apical and basolateral surface of transfected as well as virus-infected cells. However, the HAtyr virus, similar to wt WSN virus, was seen to bud almost exclusively (>99%) from the apical side of polarized MDCK cells. This finding was confirmed by using neuraminidase to facilitate virus release, by treating the collected virus particles with trypsin to cleave HA0 --> HA1 and HA2, by protein analysis of released virus particles, and finally, by electron microscopy. Therefore HA, the major glycoprotein alone, does not determine the budding site, and other factor(s), possibly both viral and host, is responsible for selecting the budding site of influenza virus.
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Affiliation(s)
- Subrata Barman
- Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, UCLA School of Medicine, Los Angeles, California 90095-1747, USA
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Ledesma MD, Dotti CG. Membrane and cytoskeleton dynamics during axonal elongation and stabilization. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 227:183-219. [PMID: 14518552 DOI: 10.1016/s0074-7696(03)01010-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Proper nervous activities are gradually developing events. Reflecting this, embryonic neurons start differentiation by sprouting multiple extensions, neurites, which do not bear clear axonal or dendritic structural and molecular characteristics. Later in development one of these multiple neurites elongates further, generating a morphologically polarized neuron with a single long axon and many short dendrites. Still, despite such morphological differences these processes can switch destiny, further reflecting their immaturity. Final and irreversible axonal and dendritic commitment occurs after both axons and dendrites have elongated considerably. Recent evidence suggests that the transition from axonal immaturity to maturity reflects changes in the mechanisms used by neurons to control the precise membrane and cytoskeleton polarization. This chapter provides an overview of how these mechanisms contribute to the formation of an axon.
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Affiliation(s)
- Maria Dolores Ledesma
- Cavalieri Ottolenghi Scientific Institute, Universita degli Studi di Torino, Orbassano, Turin, Italy
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41
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Hamilton VT, Stone DM, Pritchard SM, Cantor GH. Bovine leukemia virus gp30 transmembrane (TM) protein is not tyrosine phosphorylated: examining potential interactions with host tyrosine-mediated signaling. Virus Res 2002; 90:155-69. [PMID: 12457971 DOI: 10.1016/s0168-1702(02)00149-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Bovine leukemia virus (BLV) causes persistent lymphocytosis, a preneoplastic, polyclonal expansion of B lymphocytes. The expansion increases viral transmission to new hosts, but the mechanisms of this expansion have not been determined. We hypothesized that BLV infection contributes to B-cell expansion by signaling initiated via viral transmembrane protein motifs undergoing tyrosine phosphorylation. Viral mimicry of host cell proteins is a well-demonstrated mechanism by which viruses may increase propagation or decrease recognition by the host immune system. The cytoplasmic tail of BLV transmembrane protein gp30 (TM) has multiple areas of homology to motifs of host cell signaling proteins, including two immunoreceptor tyrosine-based activation motifs (ITAMs) and two immunoreceptor tyrosine-based inhibition motifs (ITIMs), which are homologous to B-cell receptor and inhibitory co-receptor motifs. Signaling by these motifs in B cells typically relies on tyrosine phosphorylation, followed by interactions with Src-homology-2 (SH2) domains of nonreceptor protein tyrosine kinases or phosphatases. Phosphorylation of tyrosine residues in the cytoplasmic tail of TM was tested in four systems including ex vivo cultured peripheral blood mononuclear cells from BLV infected cows, BLV-expressing fetal lamb kidney cell and bat lung cell lines, and DT40 B cells transfected with a fusion of mouse extracellular CD8alpha and cytoplasmic TM. No phosphorylation of TM was detected in our experiments in any of the cell types utilized, or with various stimulation methods. Detection was attempted by immunoblotting for phosphotyrosines, or by metabolic labeling of cells. Thus BLV TM is not likely to modify host signal pathways through interactions between phosphorylated tyrosines of the ITAM or ITIM motifs and host-cell tyrosine kinases or phosphatases.
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MESH Headings
- Amino Acid Sequence
- Animals
- B-Lymphocytes/immunology
- Cattle
- Cell Line
- Enzootic Bovine Leukosis/virology
- Leukemia Virus, Bovine/pathogenicity
- Lymphocyte Activation
- Mice
- Molecular Sequence Data
- Phosphorylation
- Receptors, Amino Acid/chemistry
- Receptors, Amino Acid/metabolism
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/metabolism
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/metabolism
- Retroviridae Proteins, Oncogenic/chemistry
- Retroviridae Proteins, Oncogenic/metabolism
- Signal Transduction
- Tyrosine/metabolism
- Viral Envelope Proteins/chemistry
- Viral Envelope Proteins/metabolism
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Affiliation(s)
- Valerie T Hamilton
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA
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42
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He C, Hobert M, Friend L, Carlin C. The epidermal growth factor receptor juxtamembrane domain has multiple basolateral plasma membrane localization determinants, including a dominant signal with a polyproline core. J Biol Chem 2002; 277:38284-93. [PMID: 12161422 DOI: 10.1074/jbc.m104646200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The epidermal growth factor (EGF) receptor is located predominantly in the basolateral membrane of polarized epithelia, where it plays a pivotal role during organogenesis and tissue homeostasis. We have shown previously that a 22-amino acid sequence in the EGF receptor juxtamembrane domain contains autonomous sorting information necessary for basolateral localization using the Madin-Darby canine kidney epithelial cell model. The goal of this study was to determine the molecular basis of EGF receptor basolateral membrane expression using site-directed mutagenesis to modify specific residues in this region. We now show that this sequence has two different, functionally redundant basolateral sorting signals with distinct amino acid requirements: one dependent on residues (658)LL(659) conforming to well-characterized leucine-based sorting signals, and a second containing a polyproline core comprising residues Pro(667) and Pro(670) ((667)PXXP(670)). Our data also suggest that Arg(662) contributes to the function of the proline-based signal. (667)PXXP(670) was the dominant signal when both motifs were present and was more effective than (658)LL(659) at overriding strong apical sorting signals located in the same molecule. Site-directed mutations at Arg(662), Pro(667), and Pro(670) were also associated with increased apical expression of full-length EGF receptors, demonstrating for the first time that the juxtamembrane region is necessary for accurate polarized expression of the native molecule.
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Affiliation(s)
- Cheng He
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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43
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Dillon C, Creer A, Kerr K, Kümin A, Dickson C. Basolateral targeting of ERBB2 is dependent on a novel bipartite juxtamembrane sorting signal but independent of the C-terminal ERBIN-binding domain. Mol Cell Biol 2002; 22:6553-63. [PMID: 12192053 PMCID: PMC135631 DOI: 10.1128/mcb.22.18.6553-6563.2002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
ERBB2 is a receptor tyrosine kinase present on the basolateral membrane of polarized epithelia and has important functions in organ development and tumorigenesis. Using mutagenic analyses and Madin-Darby canine kidney (MDCK) cells, we have investigated the signals that regulate basolateral targeting of ERBB2. We show that basolateral delivery of ERBB2 is dependent on a novel bipartite juxtamembrane sorting signal residing between Gln-692 and Thr-701. The signal shows only limited sequence homology to known basolateral targeting signals and is both necessary and sufficient for correct sorting of ERBB2. In addition we demonstrate that this motif can function as a dominant basolateral targeting signal by its ability to redirect the apically localized P75 neurotrophin receptor to the basolateral membrane domain of polarized epithelial cells. Interestingly, LLC-PK1 cells, which are deficient for the micro 1B subunit of the AP1B adaptor complex, missort a large proportion of ERBB2 to the apical membrane domain. This missorting can be partially corrected by the introduction of micro 1B, suggesting a possible role for AP1B in ERBB2 endosomal trafficking. Furthermore, we find that the C-terminal ERBIN binding domain of ERBB2 is not necessary for its basolateral targeting in MDCK cells.
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44
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Nishimura N, Plutner H, Hahn K, Balch WE. The delta subunit of AP-3 is required for efficient transport of VSV-G from the trans-Golgi network to the cell surface. Proc Natl Acad Sci U S A 2002; 99:6755-60. [PMID: 11997454 PMCID: PMC124475 DOI: 10.1073/pnas.092150699] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2001] [Accepted: 03/14/2002] [Indexed: 11/18/2022] Open
Abstract
Vesicular stomatitis virus glycoprotein (VSV-G) is a transmembrane protein that functions as the surface coat of enveloped viral particles. We report the surprising result that VSV-G uses the tyrosine-based di-acidic motif (-YTDIE-) found in its cytoplasmic tail to recruit adaptor protein complex 3 for export from the trans-Golgi network. The same sorting code is used to recruit coat complex II to direct efficient transport from the endoplasmic reticulum to the Golgi apparatus. These results demonstrate that a single sorting sequence can interact with sequential coat machineries to direct transport through the secretory pathway. We propose that use of this compact sorting domain reflects a need for both efficient endoplasmic reticulum export and concentration of VSV-G into specialized post-trans-Golgi network secretory-lysosome type transport containers to facilitate formation of viral coats at the cell surface.
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Affiliation(s)
- Noriyuki Nishimura
- Department of Cell Biology and the Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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45
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Mora R, Rodriguez-Boulan E, Palese P, García-Sastre A. Apical budding of a recombinant influenza A virus expressing a hemagglutinin protein with a basolateral localization signal. J Virol 2002; 76:3544-53. [PMID: 11884578 PMCID: PMC136015 DOI: 10.1128/jvi.76.7.3544-3553.2002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Accepted: 12/26/2001] [Indexed: 12/15/2022] Open
Abstract
Influenza virions bud preferentially from the apical plasma membrane of infected epithelial cells, by enveloping viral nucleocapsids located in the cytosol with its viral integral membrane proteins, i.e., hemagglutinin (HA), neuraminidase (NA), and M2 proteins, located at the plasma membrane. Because individually expressed HA, NA, and M2 proteins are targeted to the apical surface of the cell, guided by apical sorting signals in their transmembrane or cytoplasmic domains, it has been proposed that the polarized budding of influenza virions depends on the interaction of nucleocapsids and matrix proteins with the cytoplasmic domains of HA, NA, and/or M2 proteins. Since HA is the major protein component of the viral envelope, its polarized surface delivery may be a major force that drives polarized viral budding. We investigated this hypothesis by infecting MDCK cells with a transfectant influenza virus carrying a mutant form of HA (C560Y) with a basolateral sorting signal in its cytoplasmic domain. C560Y HA was expressed nonpolarly on the surface of infected MDCK cells. Interestingly, viral budding remained apical in C560Y virus-infected cells, and so did the location of NP and M1 proteins at late times of infection. These results are consistent with a model in which apical viral budding is a shared function of various viral components rather than a role of the major viral envelope glycoprotein HA.
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Affiliation(s)
- Rosalia Mora
- Dyson Vision Research Institute, Departments of Ophthalmology and Cell Biology, Joan and Sanford Weill Medical College of Cornell University, New York, New York 10021, USA
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46
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West JT, Weldon SK, Wyss S, Lin X, Yu Q, Thali M, Hunter E. Mutation of the dominant endocytosis motif in human immunodeficiency virus type 1 gp41 can complement matrix mutations without increasing Env incorporation. J Virol 2002; 76:3338-49. [PMID: 11884559 PMCID: PMC136014 DOI: 10.1128/jvi.76.7.3338-3349.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The human immunodeficiency virus type 1 transmembrane glycoprotein (TM) is efficiently endocytosed in a clathrin-dependent manner. Internalization is mediated by a tyrosine-containing motif within the cytoplasmic domain, and replacement of the cytoplasmic tyrosine by cysteine or phenylalanine increased expression of mutant glycoprotein on the surface of transfected cells by as much as 2.5-fold. Because interactions between the cytoplasmic domain of Env and the matrix protein (MA) have been suggested to mediate incorporation of Env in virus particles, we examined whether perturbation of endocytosis would alter incorporation. Proviruses were constructed to contain the wild-type or mutant Env in conjunction with point mutations in MA that had previously been shown to block Env incorporation. These constructs were used to evaluate the effect of glycoprotein endocytosis on incorporation into virus particles and to test the necessity for a specific interaction between Env and MA to mediate incorporation. Viruses produced from transfected 293T cells were used to infect various cell lines, including MAGI, H9, and CEMx174. Viruses encoding both a disrupted endocytosis motif signal and mutations within MA were significantly more infectious in MAGI cells than their counterparts encoding a mutant MA and wild-type Env. This complementation of infectivity for the MA incorporation mutant viruses was not due to increased glycoprotein incorporation into particles but instead reflected an enhanced fusogenicity of the mutated Env proteins. Our findings further support the concept that a specific interaction between the long cytoplasmic domain of TM and MA is required for efficient incorporation of Env into assembling virions. Alteration of the endocytosis signal of Env, and the resulting increase in cell surface glycoprotein, has no effect on incorporation despite demonstrable effects on fusion, virus entry, and infectivity.
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Affiliation(s)
- John T West
- Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama 35294-2170, USA
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47
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Alfalah M, Jacob R, Naim HY. Intestinal dipeptidyl peptidase IV is efficiently sorted to the apical membrane through the concerted action of N- and O-glycans as well as association with lipid microdomains. J Biol Chem 2002; 277:10683-90. [PMID: 11773049 DOI: 10.1074/jbc.m109357200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The apical sorting of human intestinal dipeptidyl peptidase IV (DPPIV) occurs through complex N-linked and O-linked carbohydrates. Inhibition of O-linked glycosylation by benzyl-N-acetyl-alpha-d-galactosaminide affects significantly the sorting behavior of DPPIV in intestinal Caco-2 and HT-29 cells. However, random delivery to the apical and basolateral membranes and hence a more drastic effect on the sorting of DPPIV in both cell types is only observed when, in addition to O-glycans, the processing of N-glycans is affected by swainsonine, an inhibitor of mannosidase II. Together the data indicate that both types of glycosylation are critical components of the apical sorting signal of DPPIV. The sorting mechanism of DPPIV implicates its association with detergent-insoluble membrane microdomains containing cholesterol and sphingolipids, whereas an efficient association largely depends on the presence of a fully complex N- and O-linked glycosylated DPPIV. Interestingly, cholesterol is a more critical component in this context than sphingolipids, because cholesterol depletion by beta-cyclodextrin affects the detergent solubility and the sorting behavior of DPPIV more strongly than fumonisin, an inhibitor of sphingolipid synthesis.
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Affiliation(s)
- Marwan Alfalah
- Department of Physiological Chemistry, School of Veterinary Medicine Hannover, Hannover D-30559, Germany
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48
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Spodsberg N, Alfalah M, Naim HY. Characteristics and structural requirements of apical sorting of the rat growth hormone through the O-glycosylated stalk region of intestinal sucrase-isomaltase. J Biol Chem 2001; 276:46597-604. [PMID: 11577111 DOI: 10.1074/jbc.m108187200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The apical sorting of the small intestinal membrane glycoprotein sucrase-isomaltase (SI) depends on the presence of O-linked glycans and the transmembrane domain. Here, we investigate the role of O-glycans carried by the Ser/Thr-rich stalk region of SI as an apical sorting signal and evaluate the spatial requirements for an efficient recognition of this signal. Several hybrid proteins are generated comprising the unsorted and unglycosylated protein, the rat growth hormone (rGH), fused to either the transmembrane domain of SI (GH-SI(TM)), or the transmembrane and the stalk domains (GH-SI(SR/TM)). Both constructs are randomly distributed over the apical and basolateral membranes of MDCK cells indicating that neither the transmembrane domain nor the O-glycans are sufficient per se for an apical delivery. Only when a polyglycine spacer is inserted between the stalk region of SI and the luminal part of rGH in the GH-SI(Gly/SR/TM) fusion protein does efficient apical sorting of an O-glycosylated protein as well as a time-dependent association with detergent-insoluble lipid microdomains occur. Obviously, the polyglycine spacer facilitates the accessibility of the O-glycans in GH-SI(Gly/SR/TM) to a putative sorting receptor, whereas these glycans are inadequately recognized in GH-SI(SR/TM). We conclude that the O-glycans in the stalk region of SI act as an apical sorting signal within a sorting machinery that comprises at least a carbohydrate-binding protein and fulfills specific spatial requirements provided, for example by a polyglycine spacer in the context of rGH or the P-domain within the SI enzyme complex.
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Affiliation(s)
- N Spodsberg
- Department of Physiological Chemistry, School of Veterinary Medicine Hanover, Bünteweg 17, Hanover D-30559, Germany
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49
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Bello V, Goding JW, Greengrass V, Sali A, Dubljevic V, Lenoir C, Trugnan G, Maurice M. Characterization of a di-leucine-based signal in the cytoplasmic tail of the nucleotide-pyrophosphatase NPP1 that mediates basolateral targeting but not endocytosis. Mol Biol Cell 2001; 12:3004-15. [PMID: 11598187 PMCID: PMC60151 DOI: 10.1091/mbc.12.10.3004] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Enzymes of the nucleotide pyrophosphatase/phosphodiesterase (NPPase) family are expressed at opposite surfaces in polarized epithelial cells. We investigated the targeting signal of NPP1, which is exclusively expressed at the basolateral surface. Full-length NPP1 and different constructs and mutants were transfected into the polarized MDCK cell line. Expression of the proteins was analyzed by confocal microscopy and surface biotinylation. The basolateral signal of NPP1 was identified as a di-leucine motif located in the cytoplasmic tail. Mutation of either or both leucines largely redirected NPP1 to the apical surface. Furthermore, addition of the conserved sequence AAASLLAP redirected the apical nucleotide pyrophosphatase/phosphodiesterase NPP3 to the basolateral surface. Full-length NPP1 was not significantly internalized. However, when the cytoplasmic tail was deleted upstream the di-leucine motif or when the six upstream flanking amino acids were deleted, the protein was mainly found intracellularly. Endocytosis experiments indicated that these mutants were endocytosed from the basolateral surface. These results identify the basolateral signal of NPP1 as a short sequence including a di-leucine motif that is dominant over apical determinants and point to the importance of surrounding amino acids in determining whether the signal will function as a basolateral signal only or as an endocytotic signal as well.
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Affiliation(s)
- V Bello
- U538 INSERM, CHU St-Antoine, 75571 Paris Cedex 12, France
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50
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Sevier CS, Machamer CE. p38: A novel protein that associates with the vesicular stomatitis virus glycoprotein. Biochem Biophys Res Commun 2001; 287:574-82. [PMID: 11554768 DOI: 10.1006/bbrc.2001.5621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The vesicular stomatitis virus glycoprotein (VSV G) is a model transmembrane glycoprotein that has been extensively used to study the exocytotic pathway. The cytoplasmic domain of VSV G contains information for several intracellular sorting steps including efficient export from the ER, basolateral delivery, and endocytosis. In order to identify proteins that potentially interact with the polypeptide sorting motifs in the VSV G tail, the carboxy-terminal 27 amino acids of VSV G were used as bait in a yeast two-hybrid system. The protein identified most frequently in the screen is a novel protein of 38 kDa, p38. In the present work, the initial molecular and biochemical characterization of p38 is described. Preliminary evidence suggests that p38 may interact transiently with endoplasmic reticulum (ER) membranes, and thus may affect VSV G and other cargo movement at the step of ER to Golgi traffic.
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Affiliation(s)
- C S Sevier
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205, USA
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