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Fu D, Wakabayashi Y, Ido Y, Lippincott-Schwartz J, Arias IM. Regulation of bile canalicular network formation and maintenance by AMP-activated protein kinase and LKB1. J Cell Sci 2010; 123:3294-302. [PMID: 20826460 DOI: 10.1242/jcs.068098] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AMP-activated protein kinase (AMPK), a cellular metabolic sensor, is essential in energy regulation and metabolism. Hepatocyte polarization during liver development and regeneration parallels increased metabolism. The current study investigates the effects of AMPK and its upstream activator LKB1 on polarity and bile canalicular network formation and maintenance in collagen sandwich cultures of rat hepatocytes. Immunostaining for the apical protein ABCB1 and the tight junction marker occludin demonstrated that canalicular network formation is sequential and is associated with activation of AMPK and LKB1. AMPK and LKB1 activators accelerated canalicular network formation. Inhibition of AMPK or LKB1 by dominant-negative AMPK or kinase-dead LKB1 constructs blocked canalicular network formation. AICAR and 2-deoxyglucose, which activate AMPK, circumvented the inhibitory effect of kinase-dead LKB1 on canalicular formation, indicating that AMPK directly affects canalicular network formation. After the canalicular network was formed, inhibition of AMPK and LKB1 by dominant-negative AMPK or kinase-dead LKB1 constructs resulted in loss of canalicular network, indicating that AMPK and LKB1 also participate in network maintenance. In addition, activation of AMPK and LKB1 prevented low-Ca(2+)-mediated disruption of the canalicular network and tight junctions. These studies reveal that AMPK and its upstream kinase, LKB1, regulate canalicular network formation and maintenance.
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Affiliation(s)
- Dong Fu
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Health, Bethesda, MD 20892, USA
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52
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Purvanov V, Koval A, Katanaev VL. A Direct and Functional Interaction Between Go and Rab5 During G Protein-Coupled Receptor Signaling. Sci Signal 2010; 3:ra65. [DOI: 10.1126/scisignal.2000877] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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53
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Su L, Mruk DD, Lee WM, Cheng CY. Differential effects of testosterone and TGF-β3 on endocytic vesicle-mediated protein trafficking events at the blood-testis barrier. Exp Cell Res 2010; 316:2945-60. [PMID: 20682309 DOI: 10.1016/j.yexcr.2010.07.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 06/22/2010] [Accepted: 07/25/2010] [Indexed: 01/17/2023]
Abstract
The intricate interaction between protein endocytosis, transcytosis, recycling and endosome- or ubiquitin-mediated protein degradation determines the junction integrity in epithelial cells including Sertoli cells at the blood-testis barrier (BTB). Studies have shown that androgens and cytokines (e.g., TGF-β3) that are known to promote and disrupt BTB integrity, respectively, accelerate protein endocytosis at the BTB. We hypothesized that testosterone-induced endocytosed proteins are transcytosed and recycled back to the Sertoli cell surface, whereas cytokine-induced endocytosed proteins are degraded so that androgens and cytokines have opposing effects on BTB integrity. Herein, we report that both testosterone and TGF-β3 induced the steady-state level of clathrin, an endocytic vesicle protein. Testosterone and TGF-β3 also induced the association between internalized occludin (a BTB integral membrane protein) and clathrin, as well as early endosome antigen-1 (EEA-1). Interestingly, testosterone, but not TGF-β3, also induced the levels of proteins that regulate protein transcytosis (e.g., caveolin-1) and recycling (e.g., Rab11), and their association with internalized occludin and N-cadherin from the cell surface. In contrast, TGF-β3, but not testosterone, induced the level of ubiquitin-conjugating enzyme E2 J1 (Ube2j1), a protein crucial to the intracellular protein degradation pathway, and its association with internalized occludin. Based on these findings and recent reports in the field, we hypothesize that the concerted effects of testosterone and TGF-β3 likely facilitate the transit of preleptotene spermatocytes at the BTB while maintaining the immunological barrier in that testosterone induces the assembly of "new" tight junction (TJ)-fibrils below migrating spermatocytes via protein transcytosis and recycling before cytokines induce the disassembly of "old" TJ-fibrils above spermatocytes via endocytic vesicle-mediated degradation of internalized proteins. This thus provides a unique mechanism in the testis to facilitate the transit of preleptotene spermatocytes, many of which are connected in "clones" via cytoplasmic bridges, at the BTB while maintaining the immunological barrier during stage VIII of the seminiferous epithelial cycle of spermatogenesis.
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Affiliation(s)
- Linlin Su
- Center for Biomedical Research, Population Council, New York, NY 10065, USA
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54
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Ryan S, Verghese S, Cianciola NL, Cotton CU, Carlin CR. Autosomal recessive polycystic kidney disease epithelial cell model reveals multiple basolateral epidermal growth factor receptor sorting pathways. Mol Biol Cell 2010; 21:2732-45. [PMID: 20519437 PMCID: PMC2912358 DOI: 10.1091/mbc.e09-12-1059] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have discovered that multiple basolateral pathways mediate EGF receptor sorting in renal epithelial cells. The polycystic kidney disease allele in the BPK mouse model, Bicc1, interferes with one specific EGF receptor pathway, causing nonpolar delivery of the receptor without affecting overall cell polarity. Sorting and maintenance of the EGF receptor on the basolateral surface of renal epithelial cells is perturbed in polycystic kidney disease and apical expression of receptors contributes to severity of disease. The goal of these studies was to understand the molecular basis for EGF receptor missorting using a well-established mouse model for the autosomal recessive form of the disease. We have discovered that multiple basolateral pathways mediate EGF receptor sorting in renal epithelial cells. The polycystic kidney disease allele in this model, Bicc1, interferes with one specific EGF receptor pathway without affecting overall cell polarity. Furthermore one of the pathways is regulated by a latent basolateral sorting signal that restores EGF receptor polarity in cystic renal epithelial cells via passage through a Rab11-positive subapical compartment. These studies give new insights to possible therapies to reconstitute EGF receptor polarity and function in order to curb disease progression. They also indicate for the first time that the Bicc1 gene that is defective in the mouse model used in these studies regulates cargo-specific protein sorting mediated by the epithelial cell specific clathrin adaptor AP-1B.
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Affiliation(s)
- Sean Ryan
- Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
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55
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Norum M, Tång E, Chavoshi T, Schwarz H, Linke D, Uv A, Moussian B. Trafficking through COPII stabilises cell polarity and drives secretion during Drosophila epidermal differentiation. PLoS One 2010; 5:e10802. [PMID: 20520821 PMCID: PMC2875407 DOI: 10.1371/journal.pone.0010802] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 05/01/2010] [Indexed: 11/23/2022] Open
Abstract
Background The differentiation of an extracellular matrix (ECM) at the apical side of epithelial cells implies massive polarised secretion and membrane trafficking. An epithelial cell is hence engaged in coordinating secretion and cell polarity for a correct and efficient ECM formation. Principal Findings We are studying the molecular mechanisms that Drosophila tracheal and epidermal cells deploy to form their specific apical ECM during differentiation. In this work we demonstrate that the two genetically identified factors haunted and ghost are essential for polarity maintenance, membrane topology as well as for secretion of the tracheal luminal matrix and the cuticle. We show that they code for the Drosophila COPII vesicle-coating components Sec23 and Sec24, respectively, that organise vesicle transport from the ER to the Golgi apparatus. Conclusion Taken together, epithelial differentiation during Drosophila embryogenesis is a concerted action of ECM formation, plasma membrane remodelling and maintenance of cell polarity that all three rely mainly, if not absolutely, on the canonical secretory pathway from the ER over the Golgi apparatus to the plasma membrane. Our results indicate that COPII vesicles constitute a central hub for these processes.
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Affiliation(s)
- Michaela Norum
- Interfaculty Institute for Cell Biology, University of Tübingen, Tübingen, Germany
| | - Erika Tång
- Institute of Biomedicine, Göteborg University, Göteborg, Sweden
| | - Tina Chavoshi
- Institute of Biomedicine, Göteborg University, Göteborg, Sweden
| | - Heinz Schwarz
- Max-Planck Institute for Developmental Biology, Tübingen, Germany
| | - Dirk Linke
- Max-Planck Institute for Developmental Biology, Tübingen, Germany
| | - Anne Uv
- Institute of Biomedicine, Göteborg University, Göteborg, Sweden
| | - Bernard Moussian
- Interfaculty Institute for Cell Biology, University of Tübingen, Tübingen, Germany
- * E-mail:
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56
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Boehlke C, Bashkurov M, Buescher A, Krick T, John AK, Nitschke R, Walz G, Kuehn EW. Differential role of Rab proteins in ciliary trafficking: Rab23 regulates Smoothened levels. J Cell Sci 2010; 123:1460-7. [DOI: 10.1242/jcs.058883] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The structure and function of the primary cilium as a sensory organelle depends on a motor-protein-powered intraflagellar transport system (IFT); defective IFT results in retinal degeneration and pleiotropic disorders such as the Bardet Biedl syndrome (BBS) and defective hedgehog (HH) signaling. Protein transport to the cilium involves Rab GTPases. Rab8, together with a multi protein complex of BBS proteins, recruits cargo to the basal body for transport to the cilium. Loss of Rab23 in mice recapitulates the HH phenotype but its function in HH signaling is unknown. Here we established a novel protocol, based on fluorescence recovery after photo-bleaching (FRAP), allowing the quantitative analysis of protein transport into the cilium of MDCK cells. We compared the effect of Rab8, Rab5 and Rab23 on the ciliary transport of the HH-associated transmembrane receptor Smoothened, the microtubular tip protein EB1, and the receptor protein Kim1. Ciliary FRAP confirmed the role of Rab8 in protein entry to the cilium. Dominant negative Rab5 had no impact on the ciliary transport of Smoothened or EB1, but slowed the recovery of the apical protein Kim1 in the cilium. Depletion of Rab23 or expression of dominant-negative Rab23 decreased the ciliary steady state specifically of Smoothened but not EB1 or Kim1, suggesting a role of Rab23 in protein turnover in the cilium.
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Affiliation(s)
- Christopher Boehlke
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
| | - Mikhail Bashkurov
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
| | - Andrea Buescher
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
| | - Theda Krick
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
| | - Anne-Katharina John
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
| | - Roland Nitschke
- Life Imaging Center, Center for Biological Systems Analysis, Albert-Ludwig-University of Freiburg, Habsburgerstrasse 49, 79104 Freiburg, Germany
- Center for Biological Signalling Studies (bioss), Albertstrasse 94, 79104 Freiburg, Germany
| | - Gerd Walz
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
- Center for Biological Signalling Studies (bioss), Albertstrasse 94, 79104 Freiburg, Germany
| | - E. Wolfgang Kuehn
- Renal Unit, University Medical Center, University of Freiburg, Hugstetter Strasse 55, Freiburg, 79106 Germany
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57
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Ohgaki R, Matsushita M, Kanazawa H, Ogihara S, Hoekstra D, van Ijzendoorn SCD. The Na+/H+ exchanger NHE6 in the endosomal recycling system is involved in the development of apical bile canalicular surface domains in HepG2 cells. Mol Biol Cell 2010; 21:1293-304. [PMID: 20130086 PMCID: PMC2847532 DOI: 10.1091/mbc.e09-09-0767] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
This study underscores the emerging role of NHE6 as a novel regulatory protein in the apical surface development of human hepatoma HepG2 cells. A limited range of endosomal pH facilitated by NHE6.1 is suggested to be important for securing the polarized distribution of membrane lipids and proteins and maintenance of apical bile canaliculi. Polarized epithelial cells develop and maintain distinct apical and basolateral surface domains despite a continuous flux of membranes between these domains. The Na+/H+exchanger NHE6 localizes to endosomes but its function is unknown. Here, we demonstrate that polarized hepatoma HepG2 cells express an NHE6.1 variant that localizes to recycling endosomes and colocalizes with transcytosing bulk membrane lipids. NHE6.1 knockdown or overexpression decreases or increases recycling endosome pH, respectively, and inhibits the maintenance of apical, bile canalicular plasma membranes and, concomitantly, apical lumens. NHE6.1 knockdown or overexpression has little effect on the de novo biogenesis of apical surface domains. NHE6.1 knockdown does not inhibit basolateral-to-apical transcytosis of bulk membrane lipids, but it does promote their progressive loss from the apical surface, leaving cells unable to efficiently retain bulk membrane and bile canalicular proteins at the apical surface. The data suggest that a limited range of endosome pH mediated by NHE6.1 is important for securing the polarized distribution of membrane lipids at the apical surface and maintenance of apical bile canaliculi in HepG2 cells and hence cell polarity. This study underscores the emerging role of the endosomal recycling system in apical surface development and identifies NHE6 as a novel regulatory protein in this process.
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Affiliation(s)
- Ryuichi Ohgaki
- Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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58
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Weisz OA, Rodriguez-Boulan E. Apical trafficking in epithelial cells: signals, clusters and motors. J Cell Sci 2010; 122:4253-66. [PMID: 19923269 DOI: 10.1242/jcs.032615] [Citation(s) in RCA: 228] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In the early days of epithelial cell biology, researchers working with kidney and/or intestinal epithelial cell lines and with hepatocytes described the biosynthetic and recycling routes followed by apical and basolateral plasma membrane (PM) proteins. They identified the trans-Golgi network and recycling endosomes as the compartments that carried out apical-basolateral sorting. They described complex apical sorting signals that promoted association with lipid rafts, and simpler basolateral sorting signals resembling clathrin-coated-pit endocytic motifs. They also noticed that different epithelial cell types routed their apical PM proteins very differently, using either a vectorial (direct) route or a transcytotic (indirect) route. Although these original observations have generally held up, recent studies have revealed interesting complexities in the routes taken by apically destined proteins and have extended our understanding of the machinery required to sustain these elaborate sorting pathways. Here, we critically review the current status of apical trafficking mechanisms and discuss a model in which clustering is required to recruit apical trafficking machineries. Uncovering the mechanisms responsible for polarized trafficking and their epithelial-specific variations will help understand how epithelial functional diversity is generated and the pathogenesis of many human diseases.
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Affiliation(s)
- Ora A Weisz
- Department of Medicine and Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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59
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Feliciangeli S, Tardy MP, Sandoz G, Chatelain FC, Warth R, Barhanin J, Bendahhou S, Lesage F. Potassium channel silencing by constitutive endocytosis and intracellular sequestration. J Biol Chem 2009; 285:4798-805. [PMID: 19959478 DOI: 10.1074/jbc.m109.078535] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Tandem of P domains in a weak inwardly rectifying K(+) channel 1 (TWIK1) is a K(+) channel that produces unusually low levels of current. Replacement of lysine 274 by a glutamic acid (K274E) is associated with stronger currents. This mutation would prevent conjugation of a small ubiquitin modifier peptide to Lys-274, a mechanism proposed to be responsible for channel silencing. However, we found no biochemical evidence of TWIK1 sumoylation, and we showed that the conservative change K274R did not increase current, suggesting that K274E modifies TWIK1 gating through a charge effect. Now we rule out an eventual effect of K274E on TWIK1 trafficking, and we provide convincing evidence that TWIK1 silencing results from its rapid retrieval from the cell surface. TWIK1 is internalized via a dynamin-dependent mechanism and addressed to the recycling endosomal compartment. Mutation of a diisoleucine repeat located in its cytoplasmic C terminus (I293A,I294A) stabilizes TWIK1 at the plasma membrane, resulting in robust currents. The effects of I293A,I294A on channel trafficking and of K274E on channel activity are cumulative, promoting even more currents. Activation of serotoninergic receptor 5-HT(1)R or adrenoreceptor alpha2A-AR stimulates TWIK1 but has no effect on TWIK1I293A,I294A, suggesting that G(i) protein activation is a physiological signal for increasing the number of active channels at the plasma membrane.
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Affiliation(s)
- Sylvain Feliciangeli
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia-Antipolis, Sophia-Antipolis, 06560 Valbonne, France
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60
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Chua CEL, Lim YS, Tang BL. Rab35 - A vesicular traffic-regulating small GTPase with actin modulating roles. FEBS Lett 2009; 584:1-6. [DOI: 10.1016/j.febslet.2009.11.051] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 11/09/2009] [Accepted: 11/15/2009] [Indexed: 12/25/2022]
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61
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On the biogenesis of myelin membranes: sorting, trafficking and cell polarity. FEBS Lett 2009; 584:1760-70. [PMID: 19896485 DOI: 10.1016/j.febslet.2009.10.085] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 10/29/2009] [Accepted: 10/30/2009] [Indexed: 11/22/2022]
Abstract
In the central nervous system, a multilayered membrane layer known as the myelin sheath enwraps axons, and is required for optimal saltatory signal conductance. The sheath develops from membrane processes that extend from the plasma membrane of oligodendrocytes and displays a unique lipid and protein composition. Myelin biogenesis is carefully regulated, and multiple transport pathways involving a variety of endosomal compartments are involved. Here we briefly summarize how the major myelin proteins proteolipid protein and myelin basic protein reach the sheath, and highlight potential mechanisms involved, including the role of myelin specific lipids and cell polarity related transport pathways.
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62
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Characterization of the MAL2-positive compartment in oligodendrocytes. Exp Cell Res 2009; 315:3453-65. [DOI: 10.1016/j.yexcr.2009.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 07/21/2009] [Accepted: 08/02/2009] [Indexed: 01/13/2023]
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63
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Abstract
RAB25, a member of the rat sarcoma (RAS) family of small GTPase, has been implicated in the pathophysiology of ovarian, breast and other cancers. Its role in endosomal transport and recycling of cell-surface receptors and signaling proteins presents a novel paradigm for the disruption of cellular pathways and promotion of tumor development and aggressiveness. Variations in structure and post-translational modifications control the localization of RAS superfamily proteins to specific subcellular compartments and recruitment of downstream effectors, allowing these small GTPases to function as sophisticated modulators of a complex and diverse range of cellular processes. Here, we review the link between RAB25 and tumor development and current knowledge regarding its possible roles in cancer.
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Affiliation(s)
- Roshan Agarwal
- Department of Systems Biology, Unit 950, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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64
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Tzaban S, Massol RH, Yen E, Hamman W, Frank SR, Lapierre LA, Hansen SH, Goldenring JR, Blumberg RS, Lencer WI. The recycling and transcytotic pathways for IgG transport by FcRn are distinct and display an inherent polarity. ACTA ACUST UNITED AC 2009; 185:673-84. [PMID: 19451275 PMCID: PMC2711563 DOI: 10.1083/jcb.200809122] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Fc receptor FcRn traffics immunoglobulin G (IgG) in both directions across polarized epithelial cells that line mucosal surfaces, contributing to host defense. We show that FcRn traffics IgG from either apical or basolateral membranes into the recycling endosome (RE), after which the actin motor myosin Vb and the GTPase Rab25 regulate a sorting step that specifies transcytosis without affecting recycling. Another regulatory component of the RE, Rab11a, is dispensable for transcytosis, but regulates recycling to the basolateral membrane only. None of these proteins affect FcRn trafficking away from lysosomes. Thus, FcRn transcytotic and recycling sorting steps are distinct. These results are consistent with a single structurally and functionally heterogeneous RE compartment that traffics FcRn to both cell surfaces while discriminating between recycling and transcytosis pathways polarized in their direction of transport.
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Affiliation(s)
- Salit Tzaban
- Children's Hospital, Gastroenterology Division, Harvard Digestive Diseases Center, Harvard Medical School, Boston, MA 02115, USA
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65
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Cheshire AM, Kerman BE, Zipfel WR, Spector AA, Andrew DJ. Kinetic and mechanical analysis of live tube morphogenesis. Dev Dyn 2008; 237:2874-88. [PMID: 18816822 DOI: 10.1002/dvdy.21709] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Ribbon is a nuclear Broad Tramtrack Bric-a-brac (BTB) -domain protein required for morphogenesis of the salivary gland and trachea. We recently showed that ribbon mutants exhibit decreased Crumbs and Rab11-coincident apical vesicles and increased apical Moesin activity and microvillar structure during tube elongation. To learn how these molecular and morphological changes affect the dynamics of tubulogenesis, we optimized an advanced two-photon microscope to enable high-resolution live imaging of the salivary gland and trachea. Live imaging revealed that ribbon mutant tissues exhibit slowed and incomplete lumenal morphogenesis, consistent with previously described apical defects. Because Moesin activity correlates with cortical stiffness, we hypothesize that ribbon mutants suffer from increased apical stiffness during morphogenesis. We develop this hypothesis through mechanical analysis, using the advantages of live imaging to construct computational elastic and analytical viscoelastic models of tube elongation, which suggest that ribbon mutant tubes exhibit three- to fivefold increased apical stiffness and twofold increased effective apical viscosity.
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Affiliation(s)
- Alan M Cheshire
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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66
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Seebohm G, Strutz-Seebohm N, Ureche ON, Henrion U, Baltaev R, Mack AF, Korniychuk G, Steinke K, Tapken D, Pfeufer A, Kääb S, Bucci C, Attali B, Merot J, Tavare JM, Hoppe UC, Sanguinetti MC, Lang F. Long QT syndrome-associated mutations in KCNQ1 and KCNE1 subunits disrupt normal endosomal recycling of IKs channels. Circ Res 2008; 103:1451-7. [PMID: 19008479 DOI: 10.1161/circresaha.108.177360] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Physical and emotional stress is accompanied by release of stress hormones such as the glucocorticoid cortisol. This hormone upregulates the serum- and glucocorticoid-inducible kinase (SGK)1, which in turn stimulates I(Ks), a slow delayed rectifier potassium current that mediates cardiac action potential repolarization. Mutations in I(Ks) channel alpha (KCNQ1, KvLQT1, Kv7.1) or beta (KCNE1, IsK, minK) subunits cause long QT syndrome (LQTS), an inherited cardiac arrhythmia associated with increased risk of sudden death. Together with the GTPases RAB5 and RAB11, SGK1 facilitates membrane recycling of KCNQ1 channels. Here, we show altered SGK1-dependent regulation of LQTS-associated mutant I(Ks) channels. Whereas some mutant KCNQ1 channels had reduced basal activity but were still activated by SGK1, currents mediated by KCNQ1(Y111C) or KCNQ1(L114P) were paradoxically reduced by SGK1. Heteromeric channels coassembled of wild-type KCNQ1 and the LQTS-associated KCNE1(D76N) mutant were similarly downregulated by SGK1 because of a disrupted RAB11-dependent recycling. Mutagenesis experiments indicate that stimulation of I(Ks) channels by SGK1 depends on residues H73, N75, D76, and P77 in KCNE1. Identification of the I(Ks) recycling pathway and its modulation by stress-stimulated SGK1 provides novel mechanistic insight into potentially fatal cardiac arrhythmias triggered by physical or psychological stress.
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67
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Schonteich E, Wilson GM, Burden J, Hopkins CR, Anderson K, Goldenring JR, Prekeris R. The Rip11/Rab11-FIP5 and kinesin II complex regulates endocytic protein recycling. J Cell Sci 2008; 121:3824-33. [PMID: 18957512 DOI: 10.1242/jcs.032441] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Sorting and recycling of endocytosed proteins are required for proper cellular function and growth. Internalized receptors either follow a fast constitutive recycling pathway, returning to the cell surface directly from the early endosomes, or a slow pathway that involves transport via perinuclear recycling endosomes. Slow recycling pathways are thought to play a key role in directing recycling proteins to specific locations on cell surfaces, such as the leading edges of motile cells. These pathways are regulated by various Rab GTPases, such as Rab4 and Rab11. Here we characterize the role of Rip11/FIP5, a known Rab11-binding protein, in regulating endocytic recycling. We use a combination of electron and fluorescent microscopy with siRNA-based protein knockdown to show that Rip11/FIP5 is present at the peripheral endosomes, where it regulates the sorting of internalized receptors to a slow recycling pathway. We also identify kinesin II as a Rip11/FIP5-binding protein and show that it is required for directing endocytosed proteins into the same recycling pathway. Thus, we propose that the Rip11/FIP5-kinesin-II complex has a key role in the routing of internalized receptors through the perinuclear recycling endosomes.
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Affiliation(s)
- Eric Schonteich
- Department of Cellular and Developmental Biology, School of Medicine, University of Colorado Health Sciences Center, 12801 E. 17th Avenue, Aurora, CO 80045, USA
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68
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Kerman BE, Cheshire AM, Myat MM, Andrew DJ. Ribbon modulates apical membrane during tube elongation through Crumbs and Moesin. Dev Biol 2008; 320:278-88. [PMID: 18585700 PMCID: PMC2562552 DOI: 10.1016/j.ydbio.2008.05.541] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Revised: 05/13/2008] [Accepted: 05/14/2008] [Indexed: 01/23/2023]
Abstract
Although the formation and maintenance of epithelial tubes are essential for the viability of multicellular organisms, our understanding of the molecular and cellular events coordinating tubulogenesis is relatively limited. Here, we focus on the activities of Ribbon, a novel BTB-domain containing nuclear protein, in the elongation of two epithelial tubes: the Drosophila salivary gland and trachea. We show that Ribbon interacts with Lola Like, another BTB-domain containing protein required for robust nuclear localization of Ribbon, to upregulate crumbs expression and downregulate Moesin activity. Our ultrastructural analysis of ribbon null salivary glands by TEM reveals a diminished pool of subapical vesicles and an increase in microvillar structure, cellular changes consistent with the known role of Crumbs in apical membrane generation and of Moesin in the cross-linking of the apical membrane to the subapical cytoskeleton. Furthermore, the subapical localization of Rab11, a small GTPase associated with apical membrane delivery and rearrangement, is significantly diminished in ribbon mutant salivary glands and tracheae. These findings suggest that Ribbon and Lola Like function as a novel transcriptional cassette coordinating molecular changes at the apical membrane of epithelial cells to facilitate tube elongation.
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Affiliation(s)
- Bilal E. Kerman
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alan M. Cheshire
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Monn Monn Myat
- Department of Cell and Developmental Biology, Weill Medical College, Cornell University, New York, NY 10021, USA
| | - Deborah J. Andrew
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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69
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Kim E, Lee JW, Baek DC, Lee SR, Kim MS, Kim SH, Imakawa K, Chang KT. Identification of novel retromer complexes in the mouse testis. Biochem Biophys Res Commun 2008; 375:16-21. [PMID: 18656452 DOI: 10.1016/j.bbrc.2008.07.067] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 07/16/2008] [Indexed: 11/19/2022]
Abstract
A family of vacuolar protein sorting (Vps) proteins, which are components of mammalian retromer complex, has been studied in the mouse. Vps26a is known as a retromer component that plays an important role in embryonic development: however, its cell-type expression and precise role remain to be elucidated. In this study, we identified a new isoform of Vps26a, called Vps26aT, which was expressed specifically in the mouse testis. Diverse expression patterns of Vps26 variants in mouse tissues were determined by Western blot and RT-PCR analyses, and the direct interaction of Vps26aT with Vps35 was also demonstrated by immunoprecipitation and pull-down assay using antibodies raised against each Vps component. Our results revealed that the retromer complex could be formed from different Vps26 isoforms in a tissue-specific manner, resulting in more than two types of the retromer complex, including the Vps26a-Vps29-Vps35, Vps26aT-Vps29-Vps35, and Vps26b-Vps29-Vps35 complexes in mouse tissues.
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Affiliation(s)
- Ekyune Kim
- National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology, 685-1 Yangcheong-ri, Ochang-eup, Chung-buk 363-883, Republic of Korea
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70
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Petersen NH, Faergeman NJ, Faegeman NJ, Yu L, Wüstner D. Kinetic imaging of NPC1L1 and sterol trafficking between plasma membrane and recycling endosomes in hepatoma cells. J Lipid Res 2008; 49:2023-37. [PMID: 18523240 DOI: 10.1194/jlr.m800145-jlr200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Niemann-Pick C1-like 1 (NPC1L1) is a recently identified protein that mediates intestinal cholesterol absorption and regulates biliary cholesterol excretion. The itineraries and kinetics of NPC1L1 trafficking remain uncertain. In this study, we have visualized movement of NPC1L1-enhanced green fluorescent protein (NPC1L1-EGFP) and cholesterol analogs in hepatoma cells. At steady state, about 42% of NPC1L1 resided in the transferrin (Tf)-positive, sterol-enriched endocytic recycling compartment (ERC), whereas time-lapse microscopy demonstrated NPC1L1 traffic between the plasma membrane and the ERC. Fluorescence recovery after photobleaching revealed rapid recovery (half-time approximately 2.5 min) of about 35% of NPC1L1 in the ERC, probably replenished from peripheral sorting endosomes. Acute cholesterol depletion blocked internalization of NPC1L1-EGFP and Tf and stimulated recycling of NPC1L1-EGFP from the ERC to the plasma membrane. NPC1L1-EGFP facilitated transport of fluorescent sterols from the plasma membrane to the ERC. Insulin induced translocation of vesicles containing NPC1L1 and fluorescent sterol from the ERC to the cell membrane. Upon polarization of hepatoma cells, NPC1L1 resided almost exclusively in the canalicular membrane, where the protein is highly mobile. Our study demonstrates dynamic trafficking of NPC1L1 between the cell surface and intracellular compartments and suggests that this transport is involved in NPC1L1-mediated cellular sterol uptake.
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Affiliation(s)
- Nicole Hartwig Petersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, Denmark
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71
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Wojtal KA, Hoekstra D, van Ijzendoorn SCD. cAMP-dependent protein kinase A and the dynamics of epithelial cell surface domains: moving membranes to keep in shape. Bioessays 2008; 30:146-55. [PMID: 18200529 DOI: 10.1002/bies.20705] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) and cAMP-dependent protein kinase A (PKA) are evolutionary conserved molecules with a well-established position in the complex network of signal transduction pathways. cAMP/PKA-mediated signaling pathways are implicated in many biological processes that cooperate in organ development including the motility, survival, proliferation and differentiation of epithelial cells. Cell surface polarity, here defined as the anisotropic organisation of cellular membranes, is a critical parameter for most of these processes. Changes in the activity of cAMP/PKA elicit a variety of effects on intracellular membrane dynamics, including membrane sorting and trafficking. One of the most intriguing aspects of cAMP/PKA signaling is its evolutionary conserved abundance on the one hand and its precise spatial-temporal actions on the other. Here, we review recent developments with regard to the role of cAMP/PKA in the regulation of intracellular membrane trafficking in relation to the dynamics of epithelial surface domains.
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Affiliation(s)
- Kacper A Wojtal
- Division of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
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72
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Bilan F, Nacfer M, Fresquet F, Norez C, Melin P, Martin-Berge A, Costa de Beauregard MA, Becq F, Kitzis A, Thoreau V. Endosomal SNARE proteins regulate CFTR activity and trafficking in epithelial cells. Exp Cell Res 2008; 314:2199-211. [PMID: 18570918 DOI: 10.1016/j.yexcr.2008.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 04/04/2008] [Accepted: 04/22/2008] [Indexed: 01/20/2023]
Abstract
The Cystic Fibrosis Transmembrane conductance Regulator (CFTR) protein is a chloride channel localized at the apical plasma membrane of epithelial cells. We previously described that syntaxin 8, an endosomal SNARE (Soluble N-ethylmaleimide-sensitive factor Attachment protein REceptor) protein, interacts with CFTR and regulates its trafficking to the plasma membrane and hence its channel activity. Syntaxin 8 belongs to the endosomal SNARE complex which also contains syntaxin 7, vti1b and VAMP8. Here, we report that these four endosomal SNARE proteins physically and functionally interact with CFTR. In LLC-PK1 cells transfected with CFTR and in Caco-2 cells endogenously expressing CFTR, we demonstrated that endosomal SNARE protein overexpression inhibits CFTR activity but not swelling- or calcium-activated iodide efflux, indicating a specific effect upon CFTR activity. Moreover, co-immunoprecipitation experiments in LLC-PK1-CFTR cells showed that CFTR and SNARE proteins belong to a same complex and pull-down assays showed that VAMP8 and vti1b preferentially interact with CFTR N-terminus tail. By cell surface biotinylation and immunofluorescence experiments, we evidenced that endosomal SNARE overexpression disturbs CFTR apical targeting. Finally, we found a colocalization of CFTR and endosomal SNARE proteins in Rab11-positive recycling endosomes, suggesting a new role for endosomal SNARE proteins in CFTR trafficking in epithelial cells.
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Affiliation(s)
- Frédéric Bilan
- Institut de Physiologie et de Biologie Cellulaires, CNRS UMR6187, Université de Poitiers, France; CHU de Poitiers, BP577, 86021 Poitiers cedex, France
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73
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Lighthouse DV, Buszczak M, Spradling AC. New components of the Drosophila fusome suggest it plays novel roles in signaling and transport. Dev Biol 2008; 317:59-71. [PMID: 18355804 PMCID: PMC2410214 DOI: 10.1016/j.ydbio.2008.02.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Accepted: 02/02/2008] [Indexed: 12/18/2022]
Abstract
The fusome plays an essential role in prefollicular germ cell development within insects such as Drosophila melanogaster. Alpha-spectrin and the adducin-like protein Hu-li tai shao (Hts) are required to maintain fusome integrity, synchronize asymmetric cystocyte mitoses, form interconnected 16-cell germline cysts, and specify the initial cell as the oocyte. By screening a library of protein trap lines, we identified 14 new fusome-enriched proteins, including many associated with its characteristic vesicles. Our studies reveal that fusomes change during development and contain recycling endosomal and lysosomal compartments in females but not males. A significant number of fusome components are dispensable, because genetic disruption of tropomodulin, ferritin-1 heavy chain, or scribble, does not alter fusome structure or female fertility. In contrast, rab11 is required to maintain the germline stem cells, and to maintain the vesicle content of the spectrosome, suggesting that the fusome mediates intercellular signals that depend on the recycling endosome.
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Affiliation(s)
- Daniel V Lighthouse
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution, Baltimore, MD 21218, USA
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74
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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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75
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Priolo C, Tang D, Brahamandan M, Benassi B, Sicinska E, Ogino S, Farsetti A, Porrello A, Finn S, Zimmermann J, Febbo P, Loda M. The isopeptidase USP2a protects human prostate cancer from apoptosis. Cancer Res 2007; 66:8625-32. [PMID: 16951176 DOI: 10.1158/0008-5472.can-06-1374] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Deubiquitinating enzymes can prevent the destruction of protein substrates prior to proteasomal degradation. The ubiquitin-specific protease 2a (USP2a) deubiquitinates the antiapoptotic proteins Fatty Acid Synthase and Mdm2. Here, we show that when USP2a is overexpressed in nontransformed cells, it exhibits oncogenic behavior both in vitro and in vivo and prevents apoptosis induced by chemotherapeutic agents. Notably, USP2a silencing in several human cancer cell lines results in apoptosis. Gene set enrichment analysis, which focuses on groups of genes sharing biological function or regulatory pathways, was done on microarray expression data from human prostate cancers. The cell death-related gene set, as well as a selected cluster of validated p53 target genes, were significantly enriched in the low USP2a expression group of tumors. Conversely, genes implicated in fatty acid metabolism were significantly associated with tumors expressing high USP2a (44%). The expression profile analysis is consistent with the effects of USP2a on its known targets, i.e., Fatty Acid Synthase and Mdm2, defining a subset of prostate tumors resistant to apoptosis. USP2a thus represents a therapeutic target in prostate cancer.
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Affiliation(s)
- Carmen Priolo
- Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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76
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Mettlen M, Platek A, Van Der Smissen P, Carpentier S, Amyere M, Lanzetti L, de Diesbach P, Tyteca D, Courtoy PJ. Src triggers circular ruffling and macropinocytosis at the apical surface of polarized MDCK cells. Traffic 2007; 7:589-603. [PMID: 16643281 DOI: 10.1111/j.1600-0854.2006.00412.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We addressed the role of Src on cortical actin dynamics and polarized endocytosis in MDCK cells harboring a thermosensitive v-src mutant. Shifting monolayers established at 40 degrees C (non-permissive temperature) to 34 degrees C (permissive temperature) rapidly reactivated v-Src kinase, but tight junctions and cell polarity resisted for >6 h. At this interval, activated v-src was recruited on apical vesicles, induced cortactin-associated apical circular ruffles productive of macropinosomes, thereby accelerating apical pinocytosis by approximately fivefold. Ruffling and macropinosome formation were selectively abrogated by inhibitors of actin polymerization, phosphoinositide 3-kinase, phospholipase C, and phospholipase D, which all returned apical pinocytosis to the level observed at 40 degrees C, underscoring the distinct control of apical micropinocytosis and macropinocytosis. Src promoted microtubule-dependent fusion of macropinosomes to the apical recycling endosome (ARE), causing its strong vacuolation. However, preservation of tubulation and apical polarity indicated that its function was not affected. The ARE was labeled for v-src, Rab11, and rabankyrin-5 but not early endosome antigen 1, thus distinguishing two separate Rab5-dependent apical pathways. The mechanisms of Src-induced apical ruffling and macropinocytosis could shed light on the triggered apical enteroinvasive pathogens entry and on the apical differentiation of osteoclasts.
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Affiliation(s)
- Marcel Mettlen
- CELL Unit, Université catholique de Louvain and Christian de Duve Institute of Cellular Pathology, 1200 Brussels, Belgium
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77
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Brown J, Rudel L, Yu L. NPC1L1 (Niemann-Pick C1-like 1) mediates sterol-specific unidirectional transport of non-esterified cholesterol in McArdle-RH7777 hepatoma cells. Biochem J 2007; 406:273-83. [PMID: 17523925 PMCID: PMC1948962 DOI: 10.1042/bj20070168] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Recent evidence suggests that NPC1L1 (Niemann-Pick C1-like 1) is critical for intestinal sterol absorption in mice, yet mechanisms by which NPC1L1 regulates cellular sterol transport are lacking. In the study we used a McArdle-RH7777 rat hepatoma cell line stably expressing NPC1L1 to examine the sterol-specificity and directionality of NPC1L1-mediated sterol transport. As previously described, cholesterol-depletion-driven recycling of NPC1L1 to the cell surface facilitates cellular uptake of non-esterified (free) cholesterol. However, it has no impact on the uptake of esterified cholesterol, indicating free sterol specificity. Interestingly, the endocytic recycling of NPC1L1 was also without effect on beta-sitosterol uptake, indicating that NPC1L1 can differentiate between free sterols of animal and plant origin in hepatoma cells. Furthermore, NPC1L1-driven free cholesterol transport was unidirectional, since cellular cholesterol efflux to apolipoprotein A-I, high-density lipoprotein or serum was unaffected by NPC1L1 expression or localization. Additionally, NPC1L1 facilitates mass non-esterified-cholesterol uptake only when it is located on the cell surface and not when it resides intracellularly. Finally, NPC1L1-dependent cholesterol uptake required adequate intracellular K(+), yet did not rely on intracellular Ca(2+), the cytoskeleton or signalling downstream of protein kinase A, protein kinase C or pertussis-toxin-sensitive G-protein-coupled receptors. Collectively, these findings support the notion that NPC1L1 can selectively recognize non-esterified cholesterol and promote its unidirectional transport into hepatoma cells.
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Affiliation(s)
- J. Mark Brown
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1040, U.S.A
| | - Lawrence L. Rudel
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1040, U.S.A
| | - Liqing Yu
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1040, U.S.A
- To whom correspondence should be addressed (email )
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78
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Ishida-Yamamoto A, Kishibe M, Takahashi H, Iizuka H. Rab11 Is Associated with Epidermal Lamellar Granules. J Invest Dermatol 2007; 127:2166-70. [PMID: 17476295 DOI: 10.1038/sj.jid.5700850] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Epidermal lamellar granules (LGs) are specialized organelles that transport and secrete various molecules, including lipids, proteases, protease inhibitors, and structural proteins, thereby providing a protective barrier against the environment. Abnormalities in LG-related molecules result in severe skin diseases, but their transport mechanisms are poorly understood. We studied the distribution of Rab11, a common GTPase in recycling endosomes, in normal human epidermis. Confocal laser scanning microscopy detected Rab11 immunoreactivity in differentiated epidermal keratinocytes. Staining was strong at the apical side of each cell, a pattern commonly seen in LG-associated molecules. Around the nuclei, Rab11 was colocalized with TGN46, a trans-Golgi network marker. Rab11 was also colocalized with known LG-molecules, namely lymphoepithelial Kazal-type-related inhibitor, corneodesmosine, cathepsin D, and glucosylceramides. Immunoelectron microscopy revealed that Rab11 was widely distributed along TGN and tubular-vesicular structures containing different LG molecules. The present results suggest that Rab11 plays a role in the intracellular trafficking of various types of LG-molecule from the TGN to the cell surface.
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79
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Miserey-Lenkei S, Waharte F, Boulet A, Cuif MH, Tenza D, El Marjou A, Raposo G, Salamero J, Héliot L, Goud B, Monier S. Rab6-interacting protein 1 links Rab6 and Rab11 function. Traffic 2007; 8:1385-403. [PMID: 17725553 DOI: 10.1111/j.1600-0854.2007.00612.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Rab11 and Rab6 guanosine triphosphatases are associated with membranes of the recycling endosomes (REs) and Golgi complex, respectively. Evidence indicates that they sequentially regulate a retrograde transport pathway between these two compartments, suggesting the existence of proteins that must co-ordinate their functions. Here, we report the characterization of two isoforms of a protein, Rab6-interacting protein 1 (R6IP1), originally identified as a Rab6-binding protein. R6IP1 also binds to Rab11A in its GTP-bound conformation. In interphase cells, R6IP1 is targeted to the Golgi in a Rab6-dependent manner but can associate with Rab11-positive compartments when the level of Rab11A is increased within the cells. Fluorescence resonance energy transfer analysis using fluorescence lifetime imaging shows that the overexpression of R6IP1 promotes an interaction between Rab11A and Rab6 in living cells. Accordingly, the REs marked by Rab11 and transferrin receptor are depleted from the cell periphery and accumulate in the pericentriolar area. However, endosomal and Golgi membranes do not appear to fuse with each other. We also show that R6IP1 function is required during metaphase and cytokinesis, two mitotic steps in which a role of Rab6 and Rab11 has been previously documented. We propose that R6IP1 may couple Rab6 and Rab11 function throughout the cell cycle.
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80
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Cresawn KO, Potter BA, Oztan A, Guerriero CJ, Ihrke G, Goldenring JR, Apodaca G, Weisz OA. Differential involvement of endocytic compartments in the biosynthetic traffic of apical proteins. EMBO J 2007; 26:3737-48. [PMID: 17673908 PMCID: PMC1952228 DOI: 10.1038/sj.emboj.7601813] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Accepted: 07/04/2007] [Indexed: 12/21/2022] Open
Abstract
Newly synthesized basolateral markers can traverse recycling endosomes en route to the surface of Madin-Darby canine kidney cells; however, the routes used by apical proteins are less clear. Here, we functionally inactivated subsets of endocytic compartments and examined the effect on surface delivery of the basolateral marker vesicular stomatitis virus glycoprotein (VSV-G), the raft-associated apical marker influenza hemagglutinin (HA), and the non-raft-associated protein endolyn. Inactivation of transferrin-positive endosomes after internalization of horseradish peroxidase (HRP)-containing conjugates inhibited VSV-G delivery, but did not disrupt apical delivery. In contrast, inhibition of protein export from apical recycling endosomes upon expression of dominant-negative constructs of myosin Vb or Sec15 selectively perturbed apical delivery of endolyn. Ablation of apical endocytic components accessible to HRP-conjugated wheat germ agglutinin (WGA) disrupted delivery of HA but not endolyn. However, delivery of glycosylphosphatidylinositol-anchored endolyn was inhibited by >50% under these conditions, suggesting that the biosynthetic itinerary of a protein is dependent on its targeting mechanism. Our studies demonstrate that apical and basolateral proteins traverse distinct endocytic intermediates en route to the cell surface, and that multiple routes exist for delivery of newly synthesized apical proteins.
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Affiliation(s)
- Kerry O Cresawn
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
| | - Beth A Potter
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
| | - Asli Oztan
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Gudrun Ihrke
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - James R Goldenring
- Department of Surgery, Vanderbilt University School of Medicine and Nashville Veterans Affairs Medical Center, Nashville, TN, USA
| | - Gerard Apodaca
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ora A Weisz
- Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA, USA
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81
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Bhat P, Anderson DA. Hepatitis B virus translocates across a trophoblastic barrier. J Virol 2007; 81:7200-7. [PMID: 17442714 PMCID: PMC1933314 DOI: 10.1128/jvi.02371-06] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 04/08/2007] [Indexed: 12/20/2022] Open
Abstract
Mother-infant transmission of hepatitis B virus (HBV) accounts for up to 30% of worldwide chronic infections. The mechanism and high-risk period of HBV transmission from mother to infant are unknown. Although largely prevented by neonatal vaccination, significant transmission continues to occur in high-risk populations. It is unclear whether HBV can traverse an intact epithelial barrier to infect a new host. Transplacental transmission of a number of viruses relies on transcytotic pathways across placental cells. We wished to determine whether infectious HBV can traverse a polarized trophoblast monolayer. We used a human placenta-derived cell line, BeWo, cultured on membranes as polarized monolayers, to model the maternal-fetal barrier. We assessed the effects of placental maturity and maternal immunoglobulin on viral transport. Intracellular viral trafficking pathways were investigated by confocal microscopy. Free HBV (and infectious duck hepatitis B virus) transcytosed across trophoblastic cells at a rate of 5% in 30 min. Viral transport occurred in microtubule-dependent endosomal vesicles. Additionally, confocal microscopy showed that the internalized virus traverses a monensin-sensitive endosomal compartment. Differentiation of the cytotrophoblasts to syncytiotrophoblasts resulted in a 25% reduction in viral transcytosis, suggesting that placental maturity may protect the fetus. Virus translocation was also reduced in the presence of HBV immunoglobulin. We show for the first time that transcytosis of infectious hepadnavirus can occur across a trophoblastic barrier early in gestation, with the risk of transmission being reduced by placental maturity and specific maternal antibody. This study suggests a mechanism by which mother-infant transmission may occur.
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Affiliation(s)
- Purnima Bhat
- School of Biomedical Sciences, The University of Queensland, St. Lucia 4072, Australia.
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82
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Da Silva N, Shum WWC, Breton S. Regulation of vacuolar proton pumping ATPase-dependent luminal acidification in the epididymis. Asian J Androl 2007; 9:476-82. [PMID: 17589784 DOI: 10.1111/j.1745-7262.2007.00299.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Luminal acidification in the epididymis is an important process for the regulation of male fertility. Low pH and low bicarbonate concentration are among key factors that keep spermatozoa in a dormant state while they mature and are stored in this organ. Although significant bicarbonate reabsorption is achieved by principal cells in the proximal regions of the epididymis, clear and narrow cells are specialized for net proton secretion. Clear cells express very high levels of the vacuolar proton pumping ATPase (V-ATPase) in their apical membrane and are responsible for the bulk of proton secretion. In the present paper, selected aspects of V-ATPase regulation in clear cells are described and potential pathologies associated with mutations of some of the V-ATPase subunits are discussed.
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Affiliation(s)
- Nicolas Da Silva
- Program in Membrane Biology/Nephrology Division, Massachusetts General Hospital, Boston, MA 02114, USA
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83
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Wojtal KA, Hoekstra D, van IJzendoorn SC. Anchoring of protein kinase A-regulatory subunit IIalpha to subapically positioned centrosomes mediates apical bile canalicular lumen development in response to oncostatin M but not cAMP. Mol Biol Cell 2007; 18:2745-54. [PMID: 17494870 PMCID: PMC1924835 DOI: 10.1091/mbc.e06-08-0732] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Oncostatin M and cAMP signaling stimulate apical surface-directed membrane trafficking and apical lumen development in hepatocytes, both in a protein kinase A (PKA)-dependent manner. Here, we show that oncostatin M, but not cAMP, promotes the A-kinase anchoring protein (AKAP)-dependent anchoring of the PKA regulatory subunit (R)IIalpha to subapical centrosomes and that this requires extracellular signal-regulated kinase 2 activation. Stable expression of the RII-displacing peptide AKAP-IS, but not a scrambled peptide, inhibits the association of RIIalpha with centrosomal AKAPs and results in the repositioning of the centrosome from a subapical to a perinuclear location. Concomitantly, common endosomes, but not apical recycling endosomes, are repositioned from a subapical to a perinuclear location, without significant effects on constitutive or oncostatin M-stimulated basolateral-to-apical transcytosis. Importantly, however, the expression of the AKAP-IS peptide completely blocks oncostatin M-, but not cAMP-stimulated apical lumen development. Together, the data suggest that centrosomal anchoring of RIIalpha and the interrelated subapical positioning of these centrosomes is required for oncostatin M-, but not cAMP-mediated, bile canalicular lumen development in a manner that is uncoupled from oncostatin M-stimulated apical lumen-directed membrane trafficking. The results also imply that multiple PKA-mediated signaling pathways control apical lumen development and that subapical centrosome positioning is important in some of these pathways.
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Affiliation(s)
- Kacper A. Wojtal
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Dick Hoekstra
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Sven C.D. van IJzendoorn
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
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84
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Thompson A, Nessler R, Wisco D, Anderson E, Winckler B, Sheff D. Recycling endosomes of polarized epithelial cells actively sort apical and basolateral cargos into separate subdomains. Mol Biol Cell 2007; 18:2687-97. [PMID: 17494872 PMCID: PMC1924834 DOI: 10.1091/mbc.e05-09-0873] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The plasma membranes of epithelial cells plasma membranes contain distinct apical and basolateral domains that are critical for their polarized functions. However, both domains are continuously internalized, with proteins and lipids from each intermixing in supranuclear recycling endosomes (REs). To maintain polarity, REs must faithfully recycle membrane proteins back to the correct plasma membrane domains. We examined sorting within REs and found that apical and basolateral proteins were laterally segregated into subdomains of individual REs. Subdomains were absent in unpolarized cells and developed along with polarization. Subdomains were formed by an active sorting process within REs, which precedes the formation of AP-1B-dependent basolateral transport vesicles. Both the formation of subdomains and the fidelity of basolateral trafficking were dependent on PI3 kinase activity. This suggests that subdomain and transport vesicle formation occur as separate sorting steps and that both processes may contribute to sorting fidelity.
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Affiliation(s)
| | - Randy Nessler
- Imaging Core Facility, University of Iowa Carver College of Medicine, Iowa City, IA 52242
| | - Dolora Wisco
- Department of Neuroscience, University of Virginia Medical School, Charlottesville, VA 22908; and
| | - Eric Anderson
- Department of Cell Biology, Yale School of Medicine and Ludwig Institute for Cancer Research, New Haven, CT 06520
| | - Bettina Winckler
- Department of Neuroscience, University of Virginia Medical School, Charlottesville, VA 22908; and
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85
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Reynolds A, Parris A, Evans LA, Lindqvist S, Sharp P, Lewis M, Tighe R, Williams MR. Dynamic and differential regulation of NKCC1 by calcium and cAMP in the native human colonic epithelium. J Physiol 2007; 582:507-24. [PMID: 17478539 PMCID: PMC2075325 DOI: 10.1113/jphysiol.2007.129718] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The capacity of the intestine to secrete fluid is dependent on the basolateral Na(+)-K(+)-2Cl(-) co-transporter (NKCC1). Given that cAMP and Ca(2+) signals promote sustained and transient episodes of fluid secretion, respectively, this study investigated the differential regulation of functional NKCC1 membrane expression in the native human colonic epithelium. Tissue sections and colonic crypts were obtained from sigmoid rectal biopsy tissue samples. Cellular location of NKCC1, Na(+)-K(+)-ATPase, M3 muscarinic acetylcholine receptor (M(3)AChR) and lysosomes was examined by immunolabelling techniques. NKCC1 activity (i.e. bumetanide-sensitive uptake), intracellular Ca(2+) and cell volume were assessed by 2',7'-bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), Fura-2 and differential interference contrast/calcein imaging. Unstimulated NKCC1 was expressed on basolateral membranes and exhibited a topological expression gradient, predominant at the crypt base. Cholinergic Ca(2+) signals initiated at the crypt base and spread along the crypt axis. In response, NKCC1 underwent a Ca(2+)-dependent 4 h cycle of recruitment to basolateral membranes, activation, internalization, degradation and re-expression. Internalization was prevented by the epidermal growth factor receptor kinase inhibitor tyrphostin-AG1478, and re-expression was prohibited by the protein synthesis inhibitor cylcoheximide; the lysosome inhibitor chloroquine promoted accumulation of NKCC1 vesicles. NKCC1 internalization and re-expression were accompanied by secretory volume decrease and bumetanide-sensitive regulatory volume increase, respectively. In contrast, forskolin (i.e. cAMP elevation)-stimulated NKCC1 activity was sustained, and membrane expression and cell volume remained constant. Co-stimulation with forskolin and acetylcholine promoted dramatic recruitment of NKCC1 to basolateral membranes and prolonged the cycle of co-transporter activation, internalization and re-expression. In conclusion, persistent NKCC1 activation by cAMP is constrained by a Ca(2+)-dependent cycle of co-transporter internalization, degradation and re-expression; this is a novel mechanism to limit intestinal fluid loss.
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Affiliation(s)
- Amy Reynolds
- School of Biological Sciences, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
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86
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Wallrabe H, Bonamy G, Periasamy A, Barroso M. Receptor complexes cotransported via polarized endocytic pathways form clusters with distinct organizations. Mol Biol Cell 2007; 18:2226-43. [PMID: 17409357 PMCID: PMC1877110 DOI: 10.1091/mbc.e06-08-0700] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Previously, FRET confocal microscopy has shown that polymeric IgA-receptor (pIgA-R) is distributed in a clustered manner in apical endosomes. To test whether different membrane-bound components form clusters during membrane trafficking, live-cell quantitative FRET was used to characterize the organization of pIgA-R and transferrin receptor (TFR) in endocytic membranes of polarized MDCK cells upon internalization of donor- and acceptor-labeled ligands. We show that pIgA-R and TFR complexes form increasingly organized clusters during cotransport from basolateral to perinuclear endosomes. The organization of these receptor clusters in basolateral versus perinuclear/apical endosomes is significantly different; the former showing a mixed random/clustered distribution while the latter highly organized clusters. Our results indicate that although both perinuclear and apical endosomes comprise pIgA-R and TFR clusters, their E% levels are significantly different suggesting that these receptors are packed into clusters in a distinct manner. The quantitative FRET-based assay presented here suggests that different receptor complexes form clusters, with diverse levels of organization, while being cotransported via the polarized endocytic pathways.
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Affiliation(s)
- H Wallrabe
- Department of Biology, W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, VA 22904, USA
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87
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Affiliation(s)
- Sven C D van Ijzendoorn
- Department of Cell Biology, section Membrane Cell Biology, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands.
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88
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Coutelis JB, Ephrussi A. Rab6 mediates membrane organization and determinant localization during Drosophila oogenesis. Development 2007; 134:1419-30. [PMID: 17329360 DOI: 10.1242/dev.02821] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The Drosophila melanogaster body axes are defined by the precise localization and the restriction of molecular determinants in the oocyte. Polarization of the oocyte during oogenesis is vital for this process. The directed traffic of membranes and proteins is a crucial component of polarity establishment in various cell types and organisms. Here, we investigate the role of the small GTPase Rab6 in the organization of the egg chamber and in asymmetric determinant localization during oogenesis. We show that exocytosis is affected in rab6-null egg chambers, which display a loss of nurse cell plasma membranes. Rab6 is also required for the polarization of the oocyte microtubule cytoskeleton and for the posterior localization of oskar mRNA. We show that, in vivo, Rab6 is found in a complex with Bicaudal-D, and that Rab6 and Bicaudal-D cooperate in oskar mRNA localization. Thus, during Drosophila oogenesis, Rab6-dependent membrane trafficking is doubly required; first, for the general organization and growth of the egg chamber, and second, more specifically, for the polarization of the microtubule cytoskeleton and localization of oskar mRNA. These findings highlight the central role of vesicular trafficking in the establishment of polarity and in determinant localization in Drosophila.
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Affiliation(s)
- Jean-Baptiste Coutelis
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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89
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de Souza N, Vallier LG, Fares H, Greenwald I. SEL-2, theC. elegansneurobeachin/LRBA homolog, is a negative regulator oflin-12/Notchactivity and affects endosomal traffic in polarized epithelial cells. Development 2007; 134:691-702. [PMID: 17215302 DOI: 10.1242/dev.02767] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The vulval precursor cells (VPCs) of Caenorhabditis elegans are polarized epithelial cells that adopt a precise pattern of fates through regulated activity of basolateral LET-23/EGF receptor and apical LIN-12/Notch. During VPC patterning, there is reciprocal modulation of endocytosis and trafficking of both LET-23 and LIN-12. We identified sel-2 as a negative regulator of lin-12/Notch activity in the VPCs, and found that SEL-2 is the homolog of two closely related human proteins, neurobeachin(also known as BCL8B) and LPS-responsive, beige-like anchor protein (LRBA). SEL-2, neurobeachin and LRBA belong to a distinct subfamily of BEACH-WD40 domain-containing proteins. Loss of sel-2 activity leads to basolateral mislocalization and increased accumulation of LIN-12 in VPCs in which LET-23 is not active, and to impaired downregulation of basolateral LET-23 in VPCs in which LIN-12 is active. Downregulation of apical LIN-12 in the VPC in which LET-23 is active is not affected. In addition, in sel-2 mutants, the polarized cells of the intestinal epithelium display an aberrant accumulation of the lipophilic dye FM4-64 when the dye is presented to the basolateral surface. Our observations indicate that SEL-2/neurobeachin/LRBA is involved in endosomal traffic and may be involved in efficient delivery of cell surface proteins to the lysosome. Our results also suggest that sel-2 activity may contribute to the appropriate steady-state level of LIN-12 or to trafficking events that affect receptor activation.
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Affiliation(s)
- Natalie de Souza
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, 701 W. 168th Street, Hammer Health Sciences, New York, NY 10032, USA
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90
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Seebohm G, Strutz-Seebohm N, Birkin R, Dell G, Bucci C, Spinosa MR, Baltaev R, Mack AF, Korniychuk G, Choudhury A, Marks D, Pagano RE, Attali B, Pfeufer A, Kass RS, Sanguinetti MC, Tavare JM, Lang F. Regulation of endocytic recycling of KCNQ1/KCNE1 potassium channels. Circ Res 2007; 100:686-92. [PMID: 17293474 DOI: 10.1161/01.res.0000260250.83824.8f] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Stress-dependent regulation of cardiac action potential duration is mediated by the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis. It is accompanied by an increased magnitude of the slow outward potassium ion current, I(Ks). KCNQ1 and KCNE1 subunits coassemble to form the I(Ks) channel. Mutations in either subunit cause long QT syndrome, an inherited cardiac arrhythmia associated with an increased risk of sudden cardiac death. Here we demonstrate that exocytosis of KCNQ1 proteins to the plasma membrane requires the small GTPase RAB11, whereas endocytosis is dependent on RAB5. We further demonstrate that RAB-dependent KCNQ1/KCNE1 exocytosis is enhanced by the serum- and glucocorticoid-inducible kinase 1, and requires phosphorylation and activation of phosphoinositide 3-phosphate 5-kinase and the generation of PI(3,5)P(2). Identification of KCNQ1/KCNE1 recycling and its modulation by serum- and glucocorticoid-inducible kinase 1-phosphoinositide 3-phosphate 5-kinase -PI(3,5)P(2) provides a mechanistic insight into stress-induced acceleration of cardiac repolarization.
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Affiliation(s)
- Guiscard Seebohm
- Department of Physiology I, University of Tuebingen, Gmelinstrasse 5, D-72076 Tuebingen, Germany.
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91
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Abstract
In higher eukaryotic cells pleiomorphic compartments composed of vacuoles, tubules and vesicles move from the endoplasmic reticulum (ER) and the plasma membrane to the cell center, operating in early biosynthetic trafficking and endocytosis, respectively. Besides transporting cargo to the Golgi apparatus and lysosomes, a major task of these compartments is to promote extensive membrane recycling. The endocytic membrane system is traditionally divided into early (sorting) endosomes, late endosomes and the endocytic recycling compartment (ERC). Recent studies on the intermediate compartment (IC) between the ER and the Golgi apparatus suggest that it also consists of peripheral ("early") and centralized ("late") structures, as well as a third component, designated here as the biosynthetic recycling compartment (BRC). We propose that the ERC and the BRC exist as long-lived "mirror compartments" at the cell center that also share the ability to expand and become mobilized during cell activation. These considerations emphasize the functional symmetry of endomembrane compartments, which provides a basis for the membrane rearrangements taking place during cell division, polarization, and differentiation.
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Affiliation(s)
- Jaakko Saraste
- *Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, N-5009 Bergen, Norway; and
| | - Bruno Goud
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 144, Institut Curie, Section de Recherche, 75248 Paris Cedex 05, France
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92
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Breton S, Brown D. New insights into the regulation of V-ATPase-dependent proton secretion. Am J Physiol Renal Physiol 2006; 292:F1-10. [PMID: 17032935 DOI: 10.1152/ajprenal.00340.2006] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The vacuolar H(+)-ATPase (V-ATPase) is a key player in several aspects of cellular function, including acidification of intracellular organelles and regulation of extracellular pH. In specialized cells of the kidney, male reproductive tract and osteoclasts, proton secretion via the V-ATPase represents a major process for the regulation of systemic acid/base status, sperm maturation and bone resorption, respectively. These processes are regulated via modulation of the plasma membrane expression and activity of the V-ATPase. The present review describes selected aspects of V-ATPase regulation, including recycling of V-ATPase-containing vesicles to and from the plasma membrane, assembly/disassembly of the two domains (V(0) and V(1)) of the holoenzyme, and the coupling ratio between ATP hydrolysis and proton pumping. Modulation of the V-ATPase-rich cell phenotype and the pathophysiology of the V-ATPase in humans and experimental animals are also discussed.
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Affiliation(s)
- Sylvie Breton
- Program in Membrane Biology, Nephrology Division, Massachusetts General Hospital, and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114-2790, USA.
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93
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Wakabayashi Y, Kipp H, Arias IM. Transporters on Demand: Intracellular Reservoirs and Cycling of Bile Canalicular ABC Transporters. J Biol Chem 2006; 281:27669-73. [PMID: 16737964 DOI: 10.1074/jbc.r600013200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Yoshiyuki Wakabayashi
- Unit on Cellular Polarity, Cell Biology and Metabolism Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA
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94
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Liégeois S, Benedetto A, Garnier JM, Schwab Y, Labouesse M. The V0-ATPase mediates apical secretion of exosomes containing Hedgehog-related proteins in Caenorhabditis elegans. ACTA ACUST UNITED AC 2006; 173:949-61. [PMID: 16785323 PMCID: PMC2063919 DOI: 10.1083/jcb.200511072] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polarized intracellular trafficking in epithelia is critical in development, immunity, and physiology to deliver morphogens, defensins, or ion pumps to the appropriate membrane domain. The mechanisms that control apical trafficking remain poorly defined. Using Caenorhabditis elegans, we characterize a novel apical secretion pathway involving multivesicularbodies and the release of exosomes at the apical plasma membrane. By means of two different genetic approaches, we show that the membrane-bound V0 sector of the vacuolar H+-ATPase (V-ATPase) acts in this pathway, independent of its contribution to the V-ATPase proton pump activity. Specifically, we identified mutations in the V0 “a” subunit VHA-5 that affect either the V0-specific function or the V0+V1 function of the V-ATPase. These mutations allowed us to establish that the V0 sector mediates secretion of Hedgehog-related proteins. Our data raise the possibility that the V0 sector mediates exosome and morphogen release in mammals.
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Affiliation(s)
- Samuel Liégeois
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Universite Louis Pasteur, 67400 Illkirch, France
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95
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Hodson CA, Ambrogi IG, Scott RO, Mohler PJ, Milgram SL. Polarized apical sorting of guanylyl cyclase C is specified by a cytosolic signal. Traffic 2006; 7:456-64. [PMID: 16536743 DOI: 10.1111/j.1600-0854.2006.00398.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Receptor guanylyl cyclases respond to ligand stimulation by increasing intracellular cGMP, thereby initiating a variety of cell-signaling pathways. Furthermore, these proteins are differentially localized at the apical and basolateral membranes of epithelial cells. We have identified a region of 11 amino acids in the cytosolic COOH terminus of guanylyl cyclase C (GCC) required for normal apical localization in Madin-Darby canine kidney (MDCK) cells. These amino acids share no significant sequence homology with previously identified cytosolic apical sorting determinants. However, these amino acids are highly conserved and are sufficient to confer apical polarity to the interleukin-2 receptor alpha-chain (Tac). Additionally, we find two molecular weight species of GCC in lysates prepared from MDCK cells over-expressing GCC but observe only the fully mature species on the cell surface. Using pulse-chase analysis in polarized MDCK cells, we followed the generation of this mature species over time finding it to be detectable only at the apical cell surface. These data support the hypothesis that selective apical sorting can be determined using short, cytosolic amino acid motifs and argue for the existence of apical sorting machinery comparable with the machinery identified for basolateral protein traffic.
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Affiliation(s)
- Caleb A Hodson
- Graduate Program in Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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96
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Herrema H, Czajkowska D, Théard D, van der Wouden JM, Kalicharan D, Zolghadr B, Hoekstra D, van IJzendoorn SC. Rho kinase, myosin-II, and p42/44 MAPK control extracellular matrix-mediated apical bile canalicular lumen morphogenesis in HepG2 cells. Mol Biol Cell 2006; 17:3291-303. [PMID: 16687572 PMCID: PMC1552049 DOI: 10.1091/mbc.e06-01-0067] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 04/18/2006] [Accepted: 04/27/2006] [Indexed: 12/29/2022] Open
Abstract
The molecular mechanisms that regulate multicellular architecture and the development of extended apical bile canalicular lumens in hepatocytes are poorly understood. Here, we show that hepatic HepG2 cells cultured on glass coverslips first develop intercellular apical lumens typically formed by a pair of cells. Prolonged cell culture results in extensive organizational changes, including cell clustering, multilayering, and apical lumen morphogenesis. The latter includes the development of large acinar structures and subsequent elongated canalicular lumens that span multiple cells. These morphological changes closely resemble the early organizational pattern during development, regeneration, and neoplasia of the liver and are rapidly induced when cells are cultured on predeposited extracellular matrix (ECM). Inhibition of Rho kinase or its target myosin-II ATPase in cells cultured on glass coverslips mimics the morphogenic response to ECM. Consistently, stimulation of Rho kinase and subsequent myosin-II ATPase activity by lipoxygenase-controlled eicosatetranoic acid metabolism inhibits ECM-mediated cell multilayering and apical lumen morphogenesis but not initial apical lumen formation. Furthermore, apical lumen remodeling but not cell multilayering requires basal p42/44 MAPK activity. Together, the data suggest a role for hepatocyte-derived ECM in the spatial organization of hepatocytes and apical lumen morphogenesis and identify Rho kinase, myosin-II, and MAPK as potentially important players in different aspects of bile canalicular lumen morphogenesis.
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Affiliation(s)
| | | | | | | | - Dharamdajal Kalicharan
- Electron Microscopy, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
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97
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Babbey CM, Ahktar N, Wang E, Chen CCH, Grant BD, Dunn KW. Rab10 regulates membrane transport through early endosomes of polarized Madin-Darby canine kidney cells. Mol Biol Cell 2006; 17:3156-75. [PMID: 16641372 PMCID: PMC1483048 DOI: 10.1091/mbc.e05-08-0799] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Rab10, a protein originally isolated from Madin-Darby Canine Kidney (MDCK) epithelial cells, belongs to a family of Rab proteins that includes Rab8 and Rab13. Although both Rab8 and Rab13 have been found to mediate polarized membrane transport, the function of Rab10 in mammalian cells has not yet been established. We have used quantitative confocal microscopy of polarized MDCK cells expressing GFP chimeras of wild-type and mutant forms of Rab10 to analyze the function of Rab10 in polarized cells. These studies demonstrate that Rab10 is specifically associated with the common endosomes of MDCK cells, accessible to endocytic probes internalized from either the apical or basolateral plasma membrane domains. Expression of mutant Rab10 defective for either GTP hydrolysis or GTP binding increased recycling from early compartments on the basolateral endocytic pathway without affecting recycling from later compartments or the apical recycling pathway. These results suggest that Rab10 mediates transport from basolateral sorting endosomes to common endosomes.
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Affiliation(s)
- Clifford M. Babbey
- *Department of Medicine, Division of Nephrology, Indiana University Medical Center, Indianapolis, IN 46202; and
| | - Nahid Ahktar
- *Department of Medicine, Division of Nephrology, Indiana University Medical Center, Indianapolis, IN 46202; and
| | - Exing Wang
- *Department of Medicine, Division of Nephrology, Indiana University Medical Center, Indianapolis, IN 46202; and
| | | | - Barth D. Grant
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854
| | - Kenneth W. Dunn
- *Department of Medicine, Division of Nephrology, Indiana University Medical Center, Indianapolis, IN 46202; and
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98
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Bruewer M, Utech M, Ivanov AI, Hopkins AM, Parkos CA, Nusrat A. Interferon-gamma induces internalization of epithelial tight junction proteins via a macropinocytosis-like process. FASEB J 2006; 19:923-33. [PMID: 15923402 DOI: 10.1096/fj.04-3260com] [Citation(s) in RCA: 286] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Increased epithelial permeability is observed in inflammatory states. However, the mechanism by which inflammatory mediators such as IFN-gamma increase epithelial permeability is unknown. We recently observed that IFN-gamma induces disassembly of tight junctions (TJ); in this study we asked whether such TJ disassembly is mediated by endocytosis of junctional proteins. The role of three major internalization pathways in disruption of TJ in IFN-gamma-treated intestinal epithelial cells was analyzed using selective inhibitors and markers of the pathways. No role for the clathrin- and caveolar-mediated endocytosis in the IFN-gamma-induced internalization of TJ proteins was observed. However, inhibitors of macropinocytosis blocked internalization of TJ proteins and junctional proteins colocalized with macropinocytosis markers, dextran and phosphatidylinositol-3,4,5-trisphosphate. Internalized TJ proteins were identified in early and recycling endosomes but not in late endosomes/lysosomes. These results for the first time suggest that IFN-gamma produces a leaky epithelial barrier by inducing macropinoytosis of TJ proteins.
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Affiliation(s)
- Matthias Bruewer
- Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30322, USA
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99
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Pastor-Soler N, Piétrement C, Breton S. Role of acid/base transporters in the male reproductive tract and potential consequences of their malfunction. Physiology (Bethesda) 2006; 20:417-28. [PMID: 16287991 DOI: 10.1152/physiol.00036.2005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Acid/base transporters play a key role in establishing an acidic luminal environment for sperm maturation and storage in the male reproductive tract. Impairment of the acidification capacity of the epididymis, via either genetic mutations or exposure to environmental factors, may have profound consequences on male fertility.
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Affiliation(s)
- Nuria Pastor-Soler
- Program in Membrane Biology/Nephrology Division, Massachusetts General Hospital and Harvard Medical School, Boston, USA
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100
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Chen CCH, Schweinsberg PJ, Vashist S, Mareiniss DP, Lambie EJ, Grant BD. RAB-10 is required for endocytic recycling in the Caenorhabditis elegans intestine. Mol Biol Cell 2006; 17:1286-97. [PMID: 16394106 PMCID: PMC1382317 DOI: 10.1091/mbc.e05-08-0787] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The endocytic pathway of eukaryotes is essential for the internalization and trafficking of macromolecules, fluid, membranes, and membrane proteins. One of the most enigmatic aspects of this process is endocytic recycling, the return of macromolecules (often receptors) and fluid from endosomes to the plasma membrane. We have previously shown that the EH-domain protein RME-1 is a critical regulator of endocytic recycling in worms and mammals. Here we identify the RAB-10 protein as a key regulator of endocytic recycling upstream of RME-1 in polarized epithelial cells of the Caenorhabditis elegans intestine. rab-10 null mutant intestinal cells accumulate abnormally abundant RAB-5-positive early endosomes, some of which are enlarged by more than 10-fold. Conversely most RME-1-positive recycling endosomes are lost in rab-10 mutants. The abnormal early endosomes in rab-10 mutants accumulate basolaterally recycling transmembrane cargo molecules and basolaterally recycling fluid, consistent with a block in basolateral transport. These results indicate a role for RAB-10 in basolateral recycling upstream of RME-1. We found that a functional GFP-RAB-10 reporter protein is localized to endosomes and Golgi in wild-type intestinal cells consistent with a direct role for RAB-10 in this transport pathway.
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Affiliation(s)
- Carlos Chih-Hsiung Chen
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854, USA
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