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Sun X, Whittaker GR. Role of the actin cytoskeleton during influenza virus internalization into polarized epithelial cells. Cell Microbiol 2007; 9:1672-82. [PMID: 17578407 DOI: 10.1111/j.1462-5822.2007.00900.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The in vivo site of influenza virus infection is a polarized epithelium, and it is well established that the virus preferentially enters from the apical surface of polarized epithelial cells; however, many of the molecular events involved during the endocytosis of the virus into polarized epithelia remain unclear. Here we examined the role of actin microfilaments and the myosin VI motor protein during influenza entry into a panel of polarized and non-polarized cells. By treatment of cells with cytochalasin D and jasplakinolide, we show that influenza virus entry into all the polarized epithelial cells tested requires actin dynamics, with a specific role for the actin cytoskeleton in the process of virus internalization from the plasma membrane. In contrast, influenza could still could efficiently enter and infect all non-polarized cells tested after disruption or stabilization of the actin cytoskeleton. To examine the role of the actin motor protein, myosin VI, we expressed a dominant-negative construct in both polarized and non-polarized cells. Influenza virus infectivity in myosin VI tail mutant-transfected cells was significantly decreased in polarized epithelial cells, but not in non-polarized cells. As a whole, our data suggest indispensable roles of a dynamic actin cytoskeleton for influenza virus entry into polarized epithelial cells, a feature not shared with non-polarized cells.
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Affiliation(s)
- Xiangjie Sun
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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102
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Akimova OA, Hamet P, Orlov SN. [Na+]i/[K+]i -independent death of ouabain-treated renal epithelial cells is not mediated by Na+,K+ -ATPase internalization and de novo gene expression. Pflugers Arch 2007; 455:711-9. [PMID: 17622553 DOI: 10.1007/s00424-007-0283-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Accepted: 05/02/2007] [Indexed: 10/23/2022]
Abstract
The cytotoxic effect of long-term exposure of renal epithelial cells to ouabain and other cardiotonic steroids (CTS) is mediated by the interaction of these compounds with Na(+),K(+)-ATPase but is independent of the inhibition of Na(+),K(+)-ATPase-mediated ion fluxes. Sustained application of CTS also leads to Na(+),K(+)-ATPase endocytosis and its translocation into the nuclei that might trigger the cell death machinery via the regulation of gene expression. This study examines the role of Na(+),K(+)-ATPase internalization and de novo gene expression in the death of ouabain-treated C7-Madin-Darby canine kidney (MDCK) cells derived from distal tubules of the MDCK. In these cells, 6-h exposure to 3 microM ouabain led to the internalization of approximately 50% of plasmalemmal Na(+),K(+)-ATPase. Prolonged incubation in a K(+)-free medium abolished ouabain-induced Na(+),K(+)-ATPase internalization but did not affect the cytotoxic action of ouabain seen after 18-h incubation. Previously, it was shown that CTS-induced Na(+),K(+)-ATPase internalization is mediated by its interaction with Src within caveolae. Neither caveolae damage by cholesterol depletion with methyl-beta-cyclodextrin nor Src inhibition with 4-amino-5(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]pyridine affected the death of ouabain-treated C7-MDCK cells. Actinomycin D at the 0.1-microg/ml concentration almost completely abolished ribonucleic acid synthesis but did not protect C7-MDCK cells from the cytotoxic action of ouabain. Our results show that neither Na(+),K(+)-ATPase endocytosis nor de novo gene expression contributes to Na(+)(i), K(+)(i)-independent cell death signaling evoked by prolonged exposure to CTS.
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Affiliation(s)
- Olga A Akimova
- Research Centre, Centre Hospitalier de l'Université de Montréal, Technôpole Angus, 2901 Rachel East, Montreal, Quebec H1W 4A4, Canada
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103
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Casartelli M, Corti P, Cermenati G, Grimaldi A, Fiandra L, Santo N, Pennacchio F, Giordana B. Absorption of horseradish peroxidase in Bombyx mori larval midgut. JOURNAL OF INSECT PHYSIOLOGY 2007; 53:517-25. [PMID: 17391693 DOI: 10.1016/j.jinsphys.2007.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Revised: 02/07/2007] [Accepted: 02/07/2007] [Indexed: 05/14/2023]
Abstract
Increasing experimental evidence indicates that ingested proteins can in part reach the haemocoel undegraded, but information on the mechanisms involved in protein transport across the insect gut is very limited, in spite of the implications that this may have on the development of novel delivery strategies of insecticide proteins targeting haemocoelic receptors. Here we contribute to this field of study, by focusing on horseradish peroxidase (HRP) transport through Bombyx mori larval midgut, isolated and perfused in vitro. The protein crossed the intestinal barrier in a time-dependent manner and the influx was linearly related to time between 30 and 90 min of incubation. HRP absorption was strongly affected by temperature and inhibition of cell metabolism: protein influx at 4 degrees C was reduced to 27% of that measured at 25 degrees C and was similarly inhibited by the metabolic inhibitor DNP. Transmission electron microscopy analysis of midgut columnar cells exposed to HRP showed the presence of the protein both in vesicular structures inside the cytoplasm and in the space between two adjacent absorptive cells, indicating the occurrence of both a transcellular and a paracellular permeation route. The analysis of HRP influx as a function of increasing protein concentration in the lumen supported this morphological indication. The J(max) relative to the HRP transcellular transport component was 121+/-24 pmol/cm(2)/h and the K(d) of the passage through the paracellular route was 1.9+/-0.3 microl/cm(2)/h. The paracellular electrical resistance decreased in midguts exposed to HRP, indicating that its passage through this pathway was likely due to an alteration exerted on the junctional complex by the protein itself. The role of the cytoskeleton in HRP transport was investigated by assessing the impact of drugs affecting microtubules and actin filaments.
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Affiliation(s)
- Morena Casartelli
- Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, 20133 Milan, Italy.
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104
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Srisawang P, Chatsudthipong A, Chatsudthipong V. Modulation of succinate transport in Hep G2 cell line by PKC. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1378-88. [PMID: 17395152 DOI: 10.1016/j.bbamem.2007.02.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 02/16/2007] [Accepted: 02/20/2007] [Indexed: 01/18/2023]
Abstract
The cellular uptake of the tricarboxylic acid cycle (TCA) intermediates is very important for cellular metabolism. However, the transport pathways for these intermediates in liver cells are not well characterized. We have examined the transport of succinate and citrate in the human hepatoma cell line Hep G2 and found that it exhibited a higher rate of succinate compared to citrate transport, which was sodium dependent. Comparison of the transport properties of Hep G2 to that of human retinal pigment epithelial (HRPE) cells transfected with human sodium dicarboxylate transporters, hNaDC-1, hNaDC-3, and hNaCT indicated that Hep G2 cells express a combination of hNaDC-3 and hNaCT. Short period activation of protein kinase C (PKC) by phorbol 12-myristate, 13-acetate (PMA) and alpha-adrenergic receptor agonist, phenylephrine (PE), downregulated sodium-dependent succinate transport presumably via hNaDC-3. The inhibition by PMA was partially prevented by cytochalasin D, suggesting that PKC reduces the hNaDC-3 activity, at least in part, by increased endocytosis. In contrast, activation of PKA by both forskolin and epidermal growth factor (EGF) had no effect on succinate transport. Our results suggest that Hep G2 cells provide a useful model for studies of di- and tricarboxylate regulation of human liver.
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Affiliation(s)
- Piyarat Srisawang
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
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105
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Mae M, Iyori M, Yasuda M, Shamsul HM, Kataoka H, Kiura K, Hasebe A, Totsuka Y, Shibata KI. The diacylated lipopeptide FSL-1 enhances phagocytosis of bacteria by macrophages through a Toll-like receptor 2-mediated signalling pathway. ACTA ACUST UNITED AC 2007; 49:398-409. [PMID: 17316370 DOI: 10.1111/j.1574-695x.2007.00218.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A significant amount of evidence has been accumulated to show that Toll-like receptors (TLRs) function as sensors for microbial invasion. However, little is known about how signalling triggered by TLRs leads to the phagocytosis of pathogens. This study was designed to determine whether stimulation of TLR2 mainly with the lipopeptide FSL-1 plays a role in the phagocytosis of pathogens by macrophages. FSL-1 enhanced the phagocytosis of Escherichia coli to a markedly greater extent than it did that of Staphylococcus aureus, but did not enhance the phagocytosis of latex beads. FSL-1 stimulation resulted in enhanced phagocytosis of bacteria by macrophages from TLR2(+/+) mice but not by those from TLR2(-/-) mice. Chinese hamster ovary cells stably expressing TLR2 failed to phagocytose these bacteria, but the cells expressing CD14 did. FSL-1 induced upregulation of the expression of phagocytic receptors, including MSR1, CD36, DC-SIGN and Dectin-1 in THP-1 cells. Human embryonic kidney 293 cells transfected with DC-SIGN and MSR1 phagocytosed these bacteria. These results suggest that the FSL-1-induced enhancement of phagocytosis of bacteria by macrophages may be explained partly by the upregulation of scavenger receptors and the C-type lectins through TLR2-mediated signalling pathways, and that TLR2 by itself does not function as a phagocytic receptor.
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Affiliation(s)
- Masako Mae
- Laboratory of Oral Molecular Microbiology, Department of Oral Pathobiological Science, Hokkaido University Graduate School of Dental Medicine, Kita, Sapporo, Japan
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106
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Clement C, Tiwari V, Scanlan PM, Valyi-Nagy T, Yue BYJT, Shukla D. A novel role for phagocytosis-like uptake in herpes simplex virus entry. ACTA ACUST UNITED AC 2006; 174:1009-21. [PMID: 17000878 PMCID: PMC2064392 DOI: 10.1083/jcb.200509155] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
It is becoming increasingly clear that herpesviruses can exploit the endocytic pathway to infect cells, yet several important features of this process remain poorly defined. Using herpes simplex virus-1 (HSV-1) as a model, we demonstrate that endocytosis of the virions mimic many features of phagocytosis. During entry, HSV-1 virions associated with plasma membrane protrusions followed by a phagocytosis-like uptake involving rearrangement of actin cytoskeleton and trafficking of the virions in large phagosome-like vesicles. RhoA GTPase was activated during this process and the mode of entry was cell type-specific. Clathrin-coated vesicles had no detectable role in virion trafficking as Eps15 dominant-negative mutants failed to affect HSV-1 uptake. Binding and fusion of the virion envelope with the phagosomal membrane is likely facilitated by clustering of nectin-1 (or HVEM) in phagosomes, which was observed in infected cells. Collectively, our data suggests a novel mode of uptake by which the virus can infect both professional and nonprofessional phagocytes.
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Affiliation(s)
- Christian Clement
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA
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107
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Kaksonen M, Toret CP, Drubin DG. Harnessing actin dynamics for clathrin-mediated endocytosis. Nat Rev Mol Cell Biol 2006; 7:404-14. [PMID: 16723976 DOI: 10.1038/nrm1940] [Citation(s) in RCA: 548] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Actin polymerization often occurs at the plasma membrane to drive the protrusion of lamellipodia and filopodia at the leading edge of migrating cells. A role for actin polymerization in another cellular process that involves the reshaping of the plasma membrane--namely endocytosis--has recently been established. Live-cell imaging studies are shedding light on the order and timing of the molecular events and mechanisms of actin function during endocytosis.
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Affiliation(s)
- Marko Kaksonen
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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108
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Carvou N, Norden AGW, Unwin RJ, Cockcroft S. Signalling through phospholipase C interferes with clathrin-mediated endocytosis. Cell Signal 2006; 19:42-51. [PMID: 16843639 DOI: 10.1016/j.cellsig.2006.05.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 05/23/2006] [Accepted: 05/24/2006] [Indexed: 11/23/2022]
Abstract
We investigated if phosphatidylinositol(4,5)bisphosphate (PtdIns(4,5)P2) hydrolysis by phospholipase C activation through cell surface receptors would interfere with clathrin-mediated endocytosis as recruitment of clathrin assembly proteins is PtdIns(4,5)P2-dependent. In the WKPT renal epithelial cell line, endocytosed insulin and beta2-glycoprotein I (beta2gpI) were observed in separate compartments, although endocytosis of both ligands was clathrin-dependent as demonstrated by expression of the clathrin-binding C-terminal domain of AP180 (AP180-C). The two uptake mechanisms were different as only insulin uptake was reduced when the mu2-subunit of the adaptor complex AP-2 was silenced by RNA interference. ATP receptors are expressed at the apical surface of renal cells and, thus, we examined the effect of extracellular ATP on insulin and beta2gpI uptake. ATP stimulated phospholipase C activity, and also suppressed uptake of insulin, but not beta2gpI. This effect was reversed by the PLC inhibitor U-73122. In polarized cell cultures, insulin uptake was apical, whereas beta2gpI uptake was through the basolateral membrane, thus providing an explanation for selective inhibition of insulin endocytosis by ATP. Taken together, these results demonstrate that stimulation of apical G-protein-coupled P2Y receptors, which are coupled to phospholipase C activation diminishes clathrin-mediated endocytosis without interfering with basolateral endocytic mechanisms.
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Affiliation(s)
- Nicolas Carvou
- Department of Physiology, University College London, London WC1E 6JJ UK
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109
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Lundberg P, Langel Ü. Uptake Mechanisms of Cell-Penetrating Peptides Derived from the Alzheimer’s Disease Associated Gamma-Secretase Complex. Int J Pept Res Ther 2006. [DOI: 10.1007/s10989-005-9007-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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110
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Sutherland MSK, Sanderson RJ, Gordon KA, Andreyka J, Cerveny CG, Yu C, Lewis TS, Meyer DL, Zabinski RF, Doronina SO, Senter PD, Law CL, Wahl AF. Lysosomal trafficking and cysteine protease metabolism confer target-specific cytotoxicity by peptide-linked anti-CD30-auristatin conjugates. J Biol Chem 2006; 281:10540-7. [PMID: 16484228 DOI: 10.1074/jbc.m510026200] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chimeric anti-CD30 monoclonal antibody cAC10, linked to the antimitotic agents monomethyl auristatin E (MMAE) or F (MMAF), produces potent and highly CD30-selective anti-tumor activity in vitro and in vivo. These drugs are appended via a valine-citrulline (vc) dipeptide linkage designed for high stability in serum and conditional cleavage and putative release of fully active drugs by lysosomal cathepsins. To characterize the biochemical processes leading to effective drug delivery, we examined the intracellular trafficking, internalization, and metabolism of the parent antibody and two antibody-drug conjugates, cAC10vc-MMAE and cAC10vc-MMAF, following CD30 surface antigen interaction with target cells. Both cAC10 and its conjugates bound to target cells and internalized in a similar manner. Subcellular fractionation and immunofluorescence studies demonstrated that the antibody and antibody-drug conjugates entering target cells migrated to the lysosomes. Trafficking of both species was blocked by inhibitors of clathrin-mediated endocytosis, suggesting that drug conjugation does not alter the fate of antibody-antigen complexes. Incubation of cAC10vc-MMAE or cAC10vc-MMAF with purified cathepsin B or with enriched lysosomal fractions prepared by subcellular fractionation resulted in the release of active, free drug. Cysteine protease inhibitors, but not aspartic or serine protease inhibitors, blocked antibody-drug conjugate metabolism and the ensuing cytotoxicity of target cells and yielded enhanced intracellular levels of the intact conjugates. These findings suggest that in addition to trafficking to the lysosomes, cathepsin B and perhaps other lysosomal cysteine proteases are requisite for drug release and provide a mechanistic basis for developing antibody-drug conjugates cleavable by intracellular proteases for the targeted delivery of anti-cancer therapeutics.
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Affiliation(s)
- May S Kung Sutherland
- Department of Molecular Oncology & Immunology, Seattle Genetics Inc., 21823-30th Drive SE, Bothell, WA 98021, USA
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111
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Argüeso P, Tisdale A, Spurr-Michaud S, Sumiyoshi M, Gipson IK. Mucin characteristics of human corneal-limbal epithelial cells that exclude the rose bengal anionic dye. Invest Ophthalmol Vis Sci 2006; 47:113-9. [PMID: 16384952 PMCID: PMC1351157 DOI: 10.1167/iovs.05-0735] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Rose bengal is an organic anionic dye used to assess damage of the ocular surface epithelium in ocular surface disease. It has been proposed that mucins have a protective role, preventing rose bengal staining of normal ocular surface epithelial cells. The current study was undertaken to evaluate rose bengal staining in a human corneal-limbal epithelial (HCLE) cell line known to produce and glycosylate membrane-associated mucins. METHODS HCLE cells were grown to confluence in serum-free medium and switched to DMEM/F12 with 10% serum to promote differentiation. Immunolocalization of the membrane-associated mucins MUC1 and MUC16 and the T-antigen carbohydrate epitope was performed with the monoclonal antibodies HMFG-2 and OC125 and jacalin lectin, respectively. To assess dye uptake, cultures were incubated for 5 minutes with 0.1% rose bengal and photographed. To determine whether exclusion of negatively charged rose bengal requires a negative charge at the cell surface, cells were incubated with fluoresceinated cationized ferritin. The effect of hyperosmotic stress on rose bengal staining in vitro was evaluated by increasing the ion concentration (Ca+2 and Mg+2) in the rose bengal uptake assay. RESULTS The cytoplasm and nucleus of confluent HCLE cells cultured in media without serum, lacking the expression of MUC16 but not MUC1, as well as human corneal fibroblasts, which do not express mucins, stained with rose bengal. Culture of HCLE cells in medium containing serum resulted in the formation of islands of stratified cells that excluded rose bengal. Apical cells of the stratified islands produced MUC16 and the T-antigen carbohydrate epitope on their apical surfaces. Colocalization experiments demonstrated that fluoresceinated cationized ferritin did not bind to these stratified cells, indicating that rose bengal is excluded from cells that lack negative charges. Increasing the amounts of divalent cations in the media reduced the cellular area protected against rose bengal uptake. CONCLUSIONS These results indicate that stratification and differentiation of corneal epithelial cells, as measured by the capacity to produce the membrane-associated mucin MUC16 and the mucin-associated T-antigen carbohydrate on their apical surfaces provide protection against rose bengal penetrance in vitro and suggest a role for membrane-associated mucins and their oligosaccharides in the protection of ocular surface epithelia.
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Affiliation(s)
- Pablo Argüeso
- Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
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112
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Mruk DD, Lau ASN, Conway AM. Crosstalk between Rab GTPases and cell junctions. Contraception 2006; 72:280-90. [PMID: 16181972 DOI: 10.1016/j.contraception.2005.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 02/28/2005] [Accepted: 03/26/2005] [Indexed: 11/26/2022]
Abstract
For the past several years, studies from other laboratories, as well as ours, have begun to unravel the mechanism of germ cell movement in the testis by using several in vitro and in vivo models of tight and adherens junction assembly and disassembly, two cellular phenomena that confer cell movement. However, for cell movement to be fully appreciated, the importance of "intracellular" cell movements, such as those involving actin and microtubule filaments, must be better understood. Recent research on Rab GTPases has shown that members of this superfamily function in the trafficking of vesicles containing cargo to distinct subcellular sites such as the plasma membrane while utilizing actin and microtubule filaments as tracks. In this mini-review, we provide an overview of Rab GTPase structure, function, and regulation, while placing added emphasis on the role of Rabs in cell junction dynamics in the testis.
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Affiliation(s)
- Dolores D Mruk
- Population Council, Center for Biomedical Research 1230 York Ave., New York, NY 10021, USA.
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113
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Sun X, Whittaker GR. Entry of influenza virus. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 790:72-82. [PMID: 23884586 DOI: 10.1007/978-1-4614-7651-1_4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
As a major pathogen of human and certain animal species, influenza virus causes wide spread and potentially devastating disease. To initiate infection, the virus first binds to cellular receptors comprising either -(2,3 ) or -(2,6) linked sialic acid. Recent advances in our understanding of the influenza virus receptor and viral host species involved have shed light on the molecular mechanism of how influenza virus transmits across species and adapts to a new host. Following receptor binding, influenza viruses are internalized through multiple endocytic pathways, including both clathrin- and non-clathrin-dependent routes, which have recently been visualized at single viral particle level. The viral envelope then fuses with the endosomal membrane in a low pH-dependent manner and the viral genome is released into the cytosol, followed by further transport to the nucleus where genome replication occurs.
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Affiliation(s)
- Xiangjie Sun
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
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114
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Abstract
Clathrin-mediated endocytosis is the main path for receptor internalization in metazoans and is essential for controlling cell integrity and signaling. It is driven by a large array of protein and lipid interactions that have been deciphered mainly by biochemical and genetic means. To place these interactions into context, and ultimately build a fully operative model of endocytosis at the molecular level, it is necessary to know the kinetic details of the role of each protein in this process. In this review, we describe the recent efforts made, by using live cell imaging, to define clear steps in the formation of endocytic vesicles and to observe the recruitment of key proteins during membrane invagination, the scission of a newly formed vesicle, and its movement away from the plasma membrane.
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Affiliation(s)
- David Perrais
- Laboratoire de Physiologie Cellulaire de la Synapse, CNRS UMR 5091, Université Bordeaux 2, Institut François Magendie, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
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115
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Abstract
In this review I describe the several stages of my research career, all of which were driven by a desire to understand the basic mechanisms responsible for the complex and beautiful organization of the eukaryotic cell. I was originally trained as an electron microscopist in Argentina, and my first major contribution was the introduction of glutaraldehyde as a fixative that preserved the fine structure of cells, which opened the way for cytochemical studies at the EM level. My subsequent work on membrane-bound ribosomes illuminated the process of cotranslational translocation of polypeptides across the ER membrane and led to the formulation, with Gunter Blobel, of the signal hypothesis. My later studies with many talented colleagues contributed to an understanding of ER structure and function and aspects of the mechanisms that generate and maintain the polarity of epithelial cells. For this work my laboratory introduced the now widely adopted Madin-Darby canine kidney (MDCK) cell line, and demonstrated the polarized budding of envelope viruses from those cells, providing a powerful new system that further advanced the field of protein traffic.
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Affiliation(s)
- David D Sabatini
- New York University School of Medicine, New York, NY 10016-6497, USA.
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116
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Lehmann MJ, Sherer NM, Marks CB, Pypaert M, Mothes W. Actin- and myosin-driven movement of viruses along filopodia precedes their entry into cells. ACTA ACUST UNITED AC 2005; 170:317-25. [PMID: 16027225 PMCID: PMC2171413 DOI: 10.1083/jcb.200503059] [Citation(s) in RCA: 305] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Viruses have often been observed in association with the dense microvilli of polarized epithelia as well as the filopodia of nonpolarized cells, yet whether interactions with these structures contribute to infection has remained unknown. Here we show that virus binding to filopodia induces a rapid and highly ordered lateral movement, “surfing” toward the cell body before cell entry. Virus cell surfing along filopodia is mediated by the underlying actin cytoskeleton and depends on functional myosin II. Any disruption of virus cell surfing significantly reduces viral infection. Our results reveal another example of viruses hijacking host machineries for efficient infection by using the inherent ability of filopodia to transport ligands to the cell body.
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Affiliation(s)
- Maik J Lehmann
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
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117
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Hyman T, Shmuel M, Altschuler Y. Actin is required for endocytosis at the apical surface of Madin-Darby canine kidney cells where ARF6 and clathrin regulate the actin cytoskeleton. Mol Biol Cell 2005; 17:427-37. [PMID: 16251360 PMCID: PMC1345679 DOI: 10.1091/mbc.e05-05-0420] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In epithelial cell lines, apical but not basolateral clathrin-mediated endocytosis has been shown to be affected by actin-disrupting drugs. Using electron and fluorescence microscopy, as well as biochemical assays, we show that the amount of actin dedicated to endocytosis is limiting at the apical surface of epithelia. In part, this contributes to the low basal rate of clathrin-dependent endocytosis observed at this epithelial surface. ARF6 in its GTP-bound state triggers the recruitment of actin from the cell cortex to the clathrin-coated pit to enable dynamin-dependent endocytosis. In addition, we show that perturbation of the apical endocytic system by expression of a clathrin heavy-chain mutant results in the collapse of microvilli. This phenotype was completely reversed by the expression of an ARF6-GTP-locked mutant. These observations indicate that concomitant to actin recruitment, the apical clathrin endocytic system is deeply involved in the morphology of the apical plasma membrane.
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Affiliation(s)
- Tehila Hyman
- Department of Pharmacology School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem-Ein Kerem Campus, Jerusalem 91120, Israel
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118
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Abstract
Synapses are highly specialized intercellular junctions that mediate the transmission of information between axons and target cells. A fundamental property of synapses is their ability to modify the efficacy of synaptic communication through various forms of synaptic plasticity. Recent developments in imaging techniques have revealed that synapses exhibit a high degree of morphological plasticity under basal conditions and also in response to neuronal activity that induces alterations in synaptic strength. The underlying molecular basis for this morphological plasticity has attracted much attention, yet its functional significance to the mechanisms of synaptic transmission and synaptic plasticity remains elusive. These morphological changes ultimately require the dynamic actin cytoskeleton, which is the major structural component of synapses. Delineating the physiological roles of the actin cytoskeleton in supporting synaptic transmission and synaptic plasticity, therefore, paves the way for gaining molecular insights into when and how synaptic machineries couple synapse form and function.
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Affiliation(s)
- Christian Dillon
- MRC Cell Biology Unit and Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.
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119
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Naga Prasad SV, Jayatilleke A, Madamanchi A, Rockman HA. Protein kinase activity of phosphoinositide 3-kinase regulates beta-adrenergic receptor endocytosis. Nat Cell Biol 2005; 7:785-96. [PMID: 16094730 DOI: 10.1038/ncb1278] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phosphoinositide 3-kinase (PI(3)K) is a unique enzyme characterized by both lipid and protein kinase activities. Here, we demonstrate a requirement for the protein kinase activity of PI(3)K in agonist-dependent beta-adrenergic receptor (betaAR) internalization. Using PI(3)K mutants with either protein or lipid phosphorylation activity, we identify the cytoskeletal protein non-muscle tropomyosin as a substrate of PI(3)K, which is phosphorylated in a wortmannin-sensitive manner on residue Ser 61. A constitutively dephosphorylated (S61A) tropomyosin mutant blocks agonist-dependent betaAR internalization, whereas a tropomyosin mutant that mimics constitutive phosphorylation (S61D) complements the PI(3)K mutant, with only lipid phosphorylation activity reversing the defective betaAR internalization. Notably, knocking down endogenous tropomyosin expression using siRNAs that target different regions if tropomyosin resulted in complete inhibition of betaAR endocytosis, showing that non-muscle tropomyosin is essential for agonist-mediated receptor internalization. These studies demonstrate a previously unknown role for the protein phosphorylation activity of PI(3)K in betaAR internalization and identify non-muscle tropomyosin as a cellular substrate for protein kinase activity of PI(3)K.
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MESH Headings
- Actins/metabolism
- Adaptor Protein Complex 2/metabolism
- Androstadienes/pharmacology
- Arrestins/metabolism
- Cell Line
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Endocytosis/physiology
- Histones/metabolism
- Humans
- Models, Biological
- Mutation/physiology
- Phosphatidylinositol 3-Kinases/genetics
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphatidylinositol Phosphates/metabolism
- Phosphorylation/drug effects
- Protein Kinase Inhibitors/pharmacology
- Protein Kinases/genetics
- Protein Kinases/metabolism
- RNA, Small Interfering/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Serine/metabolism
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Transfection
- Transferrin/metabolism
- Tropomyosin/genetics
- Tropomyosin/metabolism
- Wortmannin
- beta-Adrenergic Receptor Kinases
- beta-Arrestins
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120
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de Paula Le Sueur L, Collares-Buzato CB, Kalapothakis E, da Cruz-Höfling MA. In vitro effect of the Phoneutria nigriventer spider venom on cell viability, paracellular barrier function and transcellular transport in cultured cell lines. Toxicon 2005; 46:130-41. [PMID: 15949833 DOI: 10.1016/j.toxicon.2005.03.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Accepted: 03/04/2005] [Indexed: 11/24/2022]
Abstract
Phoneutria nigriventer spider venom (PNV) induces, in rats, local edema as result of an increased vascular permeability, as well as causes blood-brain barrier (BBB) breakdown by altering transendothelial transport routes in hippocampal microvessels. In this work we investigated the in vitro effects of PNV on cell viability and cellular transport routes using three cell lines, the ECV304 endothelial-, the C6 glioma- and the MDCK epithelial cells. We showed that PNV (14.6 and 292 microg crude venom/ml culture medium) had no direct cytotoxic effect on both the ECV304 and the MDCK cell lines but slightly reduced the viability of C6 glioma cells (P<0.05) at the highest concentration, as revealed by the cellular neutral red uptake assay. The PNV effects on cell transport were evaluated in MDCK cell line. PNV seems do not cause any disturbance in the paracellular barrier function of the cultured MDCK cells, as shown by the lack of a significant change in the distribution and expression of the junctional proteins, ZO-1, occludin, E-cadherin and the cytoskeletal F-actin. In contrast, PNV-treated MDCK monolayers showed an enhancement in the transepithelial electrical resistance and a tendency towards an increased occludin expression. In addition, the PNV significantly increased the apical endocytosis of HRP, which was not followed by an equivalent exocytosis at the basal side, as revealed by biochemical and ultrastructural methods. We conclude that the venom of P. nigriventer displays a relatively low cytotoxicity in vitro as well as activates directly the endocytic transport pathway in MDCK cells without disrupting the paracellular route.
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Affiliation(s)
- Luciana de Paula Le Sueur
- Departamento de Histologia e Embriologia, Instituto de Biologia, Caixa Postal 6109, Universidade Estadual de Campinas (UNICAMP), CEP 13083-970 Campinas, SP, Brazil
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121
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Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B. Biochem Pharmacol 2005; 69:1773-84. [PMID: 15869745 DOI: 10.1016/j.bcp.2005.03.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2004] [Accepted: 03/09/2005] [Indexed: 11/24/2022]
Abstract
Although risedronate, a nitrogen containing bisphosphonate (BPs), strongly inhibits bone resorption by enhanced apoptosis of osteoclasts, its mechanism remained unclear. In this study, we investigated the molecular mechanism of risedronate-induced apoptosis of U937 cells, with a focus on extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt) pathways, mitochondria-mediated apoptosis, and the effect of disruption of the actin cytoskeleton. Risedronate facilitated the relocation of Ras from membrane to cytosol through inhibited isoprenylation. Accordingly, risedronate suppressed the phosphorylation of ERK 1/2, a downstream survival signaling kinase of Ras, affected the intracellular distribution of Bcl-xL, and induced the mitochondrial membrane depolarization, cytochrome c release, activated caspase cascade and DNA fragmentation. The risedronate-induced apoptosis was effectively suppressed with cyclosporine A plus trifluoperazine, potent inhibitors of mitochondrial membrane permeability transition (MPT). The risedronate-induced apoptosis was independent of Akt, another cAMP-dependent survival signaling kinase. Risedronate facilitated dephosphorylation of Bad at Ser112, an ERK phosphorylation site, but not at Ser136, an Akt phosphorylation site. All of these apoptosis-related changes induced by risedronate were strongly suppressed by cytochalasin B, an inhibitor of actin filament polymerization. These results indicate that risedronate-induced apoptosis in U937 cells involves Ras/ERK, but not Akt signaling pathway, and is dependent on MPT, and that disruption of the actin cytoskeleton inhibits the risedronate-induced apoptosis at its early step.
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122
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Papanikolaou A, Papafotika A, Murphy C, Papamarcaki T, Tsolas O, Drab M, Kurzchalia TV, Kasper M, Christoforidis S. Cholesterol-dependent Lipid Assemblies Regulate the Activity of the Ecto-nucleotidase CD39. J Biol Chem 2005; 280:26406-14. [PMID: 15890655 DOI: 10.1074/jbc.m413927200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CD39 (ecto-nucleoside triphosphate diphosphohydrolase-1; E-NTPDase1) is a plasma membrane ecto-enzyme that regulates purinergic receptor signaling by controlling the levels of extracellular nucleotides. In blood vessels this enzyme exhibits a thromboregulatory role through the control of platelet aggregation. CD39 is localized in caveolae, which are plasma membrane invaginations with distinct lipid composition, similar to dynamic lipid microdomains, called rafts. Cholesterol is enriched together with sphingolipids in both rafts and caveolae, as well as in other specialized domains of the membrane, and plays a key role in their function. Here, we examine the potential role of cholesterol-enriched domains in CD39 function. Using polarized Madin-Darby canine kidney (MDCK) cells and caveolin-1 gene-disrupted mice, we show that caveolae are not essential either for the enzymatic activity of CD39 or for its targeting to plasma membrane. On the other hand, flotation experiments using detergent-free or detergent-based approaches indicate that CD39 associates, at least in part, with distinct lipid assemblies. In the apical membrane of MDCK cells, which lacks caveolae, CD39 is localized in microvilli, which are also cholesterol and raft-dependent membrane domains. Interfering with cholesterol levels using drugs that either deplete or sequester membrane cholesterol results in a strong inhibition of the enzymatic and anti-platelet activity of CD39. The effects of cholesterol depletion are completely reversed by replenishment of membranes with pure cholesterol, but not by cholestenone. These data suggest a functional link between the localization of CD39 in cholesterol-rich domains of the membrane and its role in thromboregulation.
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MESH Headings
- Actins/chemistry
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/chemistry
- Antigens, CD/metabolism
- Apyrase/biosynthesis
- Apyrase/chemistry
- Apyrase/metabolism
- Caveolin 1
- Caveolins/genetics
- Cell Line
- Cell Membrane/metabolism
- Cholesterol/chemistry
- Cholesterol/metabolism
- Cricetinae
- Detergents/pharmacology
- Dogs
- Dose-Response Relationship, Drug
- Endothelium, Vascular/metabolism
- Filipin/pharmacology
- Fluorescent Antibody Technique, Indirect
- Humans
- Immunohistochemistry
- Lipids/chemistry
- Lung/metabolism
- Membrane Microdomains/metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Microscopy, Confocal
- Nystatin/pharmacology
- Placenta/metabolism
- Plasmids/metabolism
- Platelet Aggregation
- Protein Binding
- Protein Structure, Tertiary
- Spleen/metabolism
- Sucrose/pharmacology
- Time Factors
- Transfection
- Umbilical Veins/cytology
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Affiliation(s)
- Agathi Papanikolaou
- Laboratory of Biological Chemistry, Medical School, University of Ioannina, 45110 Ioannina, Greece
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123
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Snoeck V, Goddeeris B, Cox E. The role of enterocytes in the intestinal barrier function and antigen uptake. Microbes Infect 2005; 7:997-1004. [PMID: 15925533 DOI: 10.1016/j.micinf.2005.04.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 01/17/2005] [Accepted: 03/07/2005] [Indexed: 11/28/2022]
Abstract
The intestinal epithelium is a critical interface between the organism and its environment. The cell polarity and structural properties of the enterocytes, limiting the amount of antigen reaching the epithelial surface, form the basis of the integrity of the epithelium. However, apart from their participation in digestive processes, the enterocytes perform more than just a passive barrier function. The resistance of the tight junctions regulates the paracellular transport of antigens. Furthermore, the enterocytes take up and process antigens, involving two functional pathways. In the major pathway, enzymes in the lysosomes degrade the antigens. In the minor direct transcytotic pathway, the antigens are not degraded and are released into the interstitial space. Moreover, the enterocytes can present processed antigens directly to T cells and are often directly involved in immune processes. In inflammatory conditions, the properties of the epithelial barrier and the outcome of the immune response to luminal antigens can be changed.
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Affiliation(s)
- Veerle Snoeck
- Laboratory of Veterinary Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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124
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Magie CR, Parkhurst SM. Rho1 regulates signaling events required for proper Drosophila embryonic development. Dev Biol 2005; 278:144-54. [PMID: 15649467 PMCID: PMC3125077 DOI: 10.1016/j.ydbio.2004.10.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2004] [Revised: 10/19/2004] [Accepted: 10/28/2004] [Indexed: 12/15/2022]
Abstract
The Rho small GTPase has been implicated in many cellular processes, including actin cytoskeletal regulation and transcriptional activation. The molecular mechanisms underlying Rho function in many of these processes are not yet clear. Here we report that in Drosophila, reduction of maternal Rho1 compromises signaling pathways consistent with defects in membrane trafficking events. These mutants fail to maintain expression of the segment polarity genes engrailed (en), wingless (wg), and hedgehog (hh), contributing to a segmentation phenotype. Formation of the Wg protein gradient involves the internalization of Wg into vesicles. The number of these Wg-containing vesicles is reduced in maternal Rho1 mutants, suggesting a defect in endocytosis. Consistent with this, stripes of cytoplasmic beta-catenin that accumulate in response to Wg signaling are narrower in these mutants relative to wild type. Additionally, the amount of extracellular Wg protein is reduced in maternal Rho1 mutants, indicating a defect in secretion. Signaling pathways downregulated by endocytosis, such as the epidermal growth factor receptor (EGFR) and Torso pathways, are hyperactivated in maternal Rho1 mutants, consistent with a general role for Rho1 in regulating signaling events governing proper patterning during Drosophila development.
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Affiliation(s)
- Craig R Magie
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, A1-162, PO Box 19024, Seattle, WA 98109-1024, USA
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125
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Abstract
Myosin motor proteins use the energy derived from ATP hydrolysis to move cargo along actin tracks. Myosin VI, unlike almost all other myosins, moves toward the minus end of actin filaments and functions in a variety of intracellular processes such as vesicular membrane traffic, cell migration, and mitosis. These diverse roles of myosin VI are mediated by interaction with a number of different binding partners present in multi-protein complexes. Myosin VI can work in vitro as a processive dimeric motor and as a nonprocessive monomeric motor, each with a large working stroke. The possibility that both monomeric and dimeric forms of myosin VI operate in the cell may represent an important regulatory mechanism for controlling the multiple steps in transport pathways where nonprocessive and processive motors are required.
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Affiliation(s)
- Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 2XY, United Kingdom.
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126
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Hryciw DH, Pollock CA, Poronnik P. PKC-alpha-mediated remodeling of the actin cytoskeleton is involved in constitutive albumin uptake by proximal tubule cells. Am J Physiol Renal Physiol 2005; 288:F1227-35. [PMID: 15657300 DOI: 10.1152/ajprenal.00428.2003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
One key role of the renal proximal tubule is the reabsorption of proteins from the glomerular filtrate by constitutive receptor-mediated endocytosis. In the opossum kidney (OK) renal proximal tubule cell line, inhibition of protein kinase C (PKC) reduces albumin uptake, although the isoforms involved and mechanisms by which this occurs have not been identified. We used pharmacological and molecular approaches to investigate the role of PKC-alpha in albumin endocytosis. We found that albumin uptake in OK cells was inhibited by the pan-PKC blocker bisindolylmaleimide-1 and the isoform-specific PKC blockers Go-6976 and 2',3,3',4,4'-hexahydroxy-1,1'-biphenyl-6,6'-dimethanol dimethyl ether, indicating a role for PKC-alpha. Overexpression of a kinase deficient PKC-alpha(K368R) but not wild-type PKC-alpha significantly reduced albumin endocytosis. Western blot analysis of fractionated cells showed an increased association of PKC-alpha-green fluorescent protein with the membrane fraction within 10-20 min of exposure to albumin. We used phalloidin to demonstrate that albumin induces the formation of clusters of actin at the apical surface of OK cells and that these clusters correspond to the location of albumin uptake. These clusters were not present in cells grown in the absence of albumin. In cells treated either with PKC inhibitors or overexpressing kinase-deficient PKC-alpha(K368R) this actin cluster formation was significantly reduced. This study identifies a role for PKC-alpha in constitutive albumin uptake in OK cells by mediating assembly of actin microfilaments at the apical membrane.
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Affiliation(s)
- Deanne H Hryciw
- School of Biomedical Sciences, Univ. of Queensland, St Lucia, 4072, Queensland, Australia
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127
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Montagnac G, Yu LCH, Bevilacqua C, Heyman M, Conrad DH, Perdue MH, Benmerah A. Differential Role for CD23 Splice Forms in Apical to Basolateral Transcytosis of IgE/Allergen Complexes. Traffic 2005; 6:230-42. [PMID: 15702991 DOI: 10.1111/j.1600-0854.2005.00262.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The low affinity receptor for IgE (CD23) was recently implicated in the trans-epithelial transport of IgE-allergen complexes from the luminal side of enterocytes in animal models for intestinal allergy. Here, the respective functions of CD23 splice forms, b and bDelta5, in this apical to basolateral transport event have been investigated. First, the new bDelta5 splice form was further characterized, providing evidence that it binds IgE with high affinity, that its expression is induced by sensitization, and that bDelta5, unlike the classical b, undergoes constitutive internalization through clathrin-coated pits. These results suggested that the two CD23 splice forms were likely involved in different transcytotic events. MDCK cell lines expressing either b or bDelta5 were generated to directly test this hypothesis. In both cell lines, CD23 splice forms were localized at the apical membrane as in enterocytes from sensitized mice. Using mouse monoclonal IgE, we obtained evidence showing that bDelta5 mediates the apical to basolateral transport of free IgE, whereas classical b is much more efficient in mediating the transcytosis of IgE/allergen complexes. The present results shed new light on the role of CD23 species in IgE/allergen transepithelial transport and provide a new powerful physiological tool to study apical to basolateral transcytosis, a process which remains poorly characterized.
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Affiliation(s)
- Guillaume Montagnac
- Department of Infectious Diseases, Cochin Institute, INSERM U567- CNRS UMR 8104-Universitè Paris 5, Paris, France
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128
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Beaulieu V, Da Silva N, Pastor-Soler N, Brown CR, Smith PJS, Brown D, Breton S. Modulation of the actin cytoskeleton via gelsolin regulates vacuolar H+-ATPase recycling. J Biol Chem 2004; 280:8452-63. [PMID: 15591047 DOI: 10.1074/jbc.m412750200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The role of the actin cytoskeleton in regulating membrane protein trafficking is complex and depends on the cell type and protein being examined. Using the epididymis as a model system in which luminal acidification is crucial for sperm maturation and storage, we now report that modulation of the actin cytoskeleton by the calcium-activated actin-capping and -severing protein gelsolin plays a key role in regulating vacuolar H(+)-ATPase (V-ATPase) recycling. Epididymal clear cells contain abundant V-ATPase in their apical pole, and an increase in their cell-surface V-ATPase expression correlates with an increase in luminal proton secretion. We have shown that apical membrane accumulation of V-ATPase is triggered by an elevation in cAMP following activation of bicarbonate-regulated soluble adenylyl cyclase in response to alkaline luminal pH (Pastor-Soler, N., Beaulieu, V., Litvin, T. N., Da Silva, N., Chen, Y., Brown, D., Buck, J., Levin, L. R., and Breton, S. (2003) J. Biol. Chem. 278, 49523-49529). Here, we show that clear cells express high levels of gelsolin, indicating a potential role in the functional activity of these cells. When jasplakinolide was used to overcome the severing action of gelsolin by polymerizing actin, complete inhibition of the alkaline pH- and cAMP-induced apical membrane accumulation of V-ATPase was observed. Conversely, when gelsolin-mediated actin filament elongation was inhibited using a 10-residue peptide (PBP10) derived from the phosphatidylinositol 4,5-bisphosphate-binding region (phosphoinositide-binding domain 2) of gelsolin, significant V-ATPase apical membrane mobilization was induced, even at acidic luminal pH. In contrast, the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) and the phospholipase C inhibitor U-73122 inhibited the alkaline pH-induced V-ATPase apical accumulation. Thus, maintenance of the actin cytoskeleton in a depolymerized state by gelsolin facilitates calcium-dependent apical accumulation of V-ATPase in response to luminal pH alkalinization. Gelsolin is present in other cell types that express the V-ATPase in their plasma membrane and recycling vesicles, including kidney intercalated cells and osteoclasts. Therefore, modulation of the actin cortex by this severing and capping protein may represent a common mechanism by which these cells regulate their rate of proton secretion.
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Affiliation(s)
- Valérie Beaulieu
- Program in Membrane Biology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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129
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Niiro H, Allam A, Stoddart A, Brodsky FM, Marshall AJ, Clark EA. The B lymphocyte adaptor molecule of 32 kilodaltons (Bam32) regulates B cell antigen receptor internalization. THE JOURNAL OF IMMUNOLOGY 2004; 173:5601-9. [PMID: 15494510 DOI: 10.4049/jimmunol.173.9.5601] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The B lymphocyte adaptor molecule of 32 kDa (Bam32) is an adaptor that plays an indispensable role in BCR signaling. In this study, we found that upon BCR ligation, Bam32 is recruited to the plasma membrane where it associates with BCR complexes and redistributes and internalizes with BCRs. BCR ligation induced colocalization of Bam32 with lipid rafts, clathrin, and actin filaments. An inhibitor of Src family protein tyrosine kinases (PTKs) blocked both BCR-induced tyrosine phosphorylation of Bam32 and BCR internalization. Moreover, BCR internalization is impaired in Bam32-/- and Lyn-/- cells, and expression of Bam32 with a mutation of its tyrosine phosphorylation site (Y139F) inhibited BCR internalization. These data suggest that Bam32 functions downstream of Src family PTKs to regulate BCR internalization. Bam32 deficiency does not affect tyrosine phosphorylation of clathrin or the association of clathrin with lipid rafts upon BCR cross-linking. However, BCR-induced actin polymerization is impaired in Bam32-/- cells. Collectively, these findings indicate a novel role of Bam32 in connecting Src family PTKs to BCR internalization by an actin-dependent mechanism.
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Affiliation(s)
- Hiroaki Niiro
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
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130
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Campo C, Mason A, Maouyo D, Olsen O, Yoo D, Welling PA. Molecular mechanisms of membrane polarity in renal epithelial cells. Rev Physiol Biochem Pharmacol 2004; 153:47-99. [PMID: 15674648 DOI: 10.1007/s10254-004-0037-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Exciting discoveries in the last decade have cast light onto the fundamental mechanisms that underlie polarized trafficking in epithelial cells. It is now clear that epithelial cell membrane asymmetry is achieved by a combination of intracellular sorting operations, vectorial delivery mechanisms and plasmalemma-specific fusion and retention processes. Several well-defined signals that specify polarized segregation, sorting, or retention processes have, now, been described in a number of proteins. The intracellular machineries that decode and act on these signals are beginning to be described. In addition, the nature of the molecules that associate with intracellular trafficking vesicles to coordinate polarized delivery, tethering, docking, and fusion are also becoming understood. Combined with direct visualization of polarized sorting processes with new technologies in live-cell fluorescent microscopy, new and surprising insights into these once-elusive trafficking processes are emerging. Here we provide a review of these recent advances within an historically relevant context.
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Affiliation(s)
- C Campo
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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131
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Schlecht G, Loucka J, Najar H, Sebo P, Leclerc C. Antigen Targeting to CD11b Allows Efficient Presentation of CD4+ and CD8+ T Cell Epitopes and In Vivo Th1-Polarized T Cell Priming. THE JOURNAL OF IMMUNOLOGY 2004; 173:6089-97. [PMID: 15528345 DOI: 10.4049/jimmunol.173.10.6089] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bordetella pertussis adenylate cyclase (CyaA) is an invasive bacterial toxin that delivers its N-terminal catalytic domain into the cytosol of eukaryotic cells bearing the alpha(M)beta(2) integrin (CD11b/CD18), such as myeloid dendritic cells. This allows use of engineered CyaA for targeted delivery of CD8(+) T cell epitopes into the MHC class I pathway of APC and induction of robust and protective cytotoxic responses. In this study, we demonstrate that CyaA can efficiently codeliver both a CD8(+) T cell epitope (OVA(257-264)) and a CD4(+) T cell epitope (MalE(100-114)) into, respectively, the conventional cytosolic or endocytic routes of processing of murine bone marrow-derived dendritic cells. Upon CyaA delivery, a strong potentiation of the MalE(100-114) CD4(+) T cell epitope presentation is observed as compared with the MalE protein, which depends on CyaA interaction with its CD11b receptor and its subsequent clathrin-mediated endocytosis. In vivo, CyaA induces strong and specific Th1 CD4(+) and CD8(+) T cell responses against, respectively, the MalE(100-114) and OVA(257-264) epitopes. These results underscore the potency of CyaA for design of new vaccines.
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MESH Headings
- ATP-Binding Cassette Transporters/metabolism
- Actins/metabolism
- Adenylate Cyclase Toxin/administration & dosage
- Adenylate Cyclase Toxin/genetics
- Adenylate Cyclase Toxin/immunology
- Adenylate Cyclase Toxin/metabolism
- Amino Acid Sequence
- Animals
- Antigen Presentation/genetics
- Bone Marrow Cells/enzymology
- Bone Marrow Cells/immunology
- Bone Marrow Cells/metabolism
- CD11b Antigen/metabolism
- CD4-Positive T-Lymphocytes/enzymology
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/metabolism
- CD8-Positive T-Lymphocytes/enzymology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- Clathrin-Coated Vesicles/physiology
- Cytotoxicity, Immunologic/genetics
- Dendritic Cells/enzymology
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Drug Delivery Systems/methods
- Endosomes/enzymology
- Endosomes/immunology
- Endosomes/metabolism
- Epitopes, T-Lymphocyte/genetics
- Epitopes, T-Lymphocyte/immunology
- Epitopes, T-Lymphocyte/metabolism
- Escherichia coli Proteins/administration & dosage
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/immunology
- Female
- Genes, Reporter
- Histocompatibility Antigens Class I/metabolism
- Histocompatibility Antigens Class II/metabolism
- Hybridomas
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Molecular Sequence Data
- Ovalbumin/administration & dosage
- Ovalbumin/genetics
- Ovalbumin/immunology
- Peptide Fragments/administration & dosage
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/metabolism
- Peptide Hydrolases/physiology
- Periplasmic Binding Proteins/administration & dosage
- Periplasmic Binding Proteins/genetics
- Periplasmic Binding Proteins/immunology
- Proteasome Endopeptidase Complex/metabolism
- Th1 Cells/enzymology
- Th1 Cells/immunology
- Th1 Cells/metabolism
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/immunology
- Vaccines, Synthetic/metabolism
- Vacuoles/metabolism
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Affiliation(s)
- Géraldine Schlecht
- Unité de Biologie des Régulations Immunitaires, Institut National de la Santé et de la Recherche Médicale E 352, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris cedex 15, Paris, France
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132
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Glatz R, Roberts HLS, Li D, Sarjan M, Theopold UH, Asgari S, Schmidt O. Lectin-induced haemocyte inactivation in insects. JOURNAL OF INSECT PHYSIOLOGY 2004; 50:955-963. [PMID: 15518663 DOI: 10.1016/j.jinsphys.2004.07.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Revised: 06/30/2004] [Accepted: 07/06/2004] [Indexed: 05/24/2023]
Abstract
Most multimeric lectins are adhesion molecules, promoting attachment and spreading on surface glycodeterminants. In addition, some lectins have counter-adhesion properties, detaching already spread cells which then acquire round or spindle-formed cell shapes. Since lectin-mediated adhesion and detachment is observed in haemocyte-like Drosophila cells, which have haemomucin as the major lectin-binding glycoprotein, the two opposite cell behaviours may be the result of lectin-mediated receptor rearrangements on the cell surface. To investigate oligomeric lectins as a possible extracellular driving force affecting cell shape changes, we examined lectin-mediated reactions in lepidopteran haemocytes after cytochalasin D-treatment and observed that while cell-spreading was dependent on F-actin, lectin-uptake was less dependent on F-actin. We propose a model of cell shape changes involving a dynamic balance between adhesion and uptake reactions.
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Affiliation(s)
- Richard Glatz
- Insect Molecular Biology, School of Agriculture, University of Adelaide, Glen Osmond, SA 5064, Australia
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133
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Styers ML, Salazar G, Love R, Peden AA, Kowalczyk AP, Faundez V. The endo-lysosomal sorting machinery interacts with the intermediate filament cytoskeleton. Mol Biol Cell 2004; 15:5369-82. [PMID: 15456899 PMCID: PMC532017 DOI: 10.1091/mbc.e04-03-0272] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cytoskeletal networks control organelle subcellular distribution and function. Herein, we describe a previously unsuspected association between intermediate filament proteins and the adaptor complex AP-3. AP-3 and intermediate filament proteins cosedimented and coimmunoprecipitated as a complex free of microtubule and actin binding proteins. Genetic perturbation of the intermediate filament cytoskeleton triggered changes in the subcellular distribution of the adaptor AP-3 and late endocytic/lysosome compartments. Concomitant with these architectural changes, and similarly to AP-3-null mocha cells, fibroblasts lacking vimentin were compromised in their vesicular zinc uptake, their organellar pH, and their total and surface content of AP-3 cargoes. However, the total content and surface levels, as well as the distribution of the transferrin receptor, a membrane protein whose sorting is AP-3 independent, remained unaltered in both AP-3- and vimentin-null cells. Based on the phenotypic convergence between AP-3 and vimentin deficiencies, we predicted and documented a reduced autophagosome content in mocha cells, a phenotype previously reported in cells with disrupted intermediate filament cytoskeletons. Our results reveal a novel role of the intermediate filament cytoskeleton in organelle/adaptor positioning and in regulation of the adaptor complex AP-3.
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Affiliation(s)
- Melanie L Styers
- Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322, USA
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134
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Schnatwinkel C, Christoforidis S, Lindsay MR, Uttenweiler-Joseph S, Wilm M, Parton RG, Zerial M. The Rab5 effector Rabankyrin-5 regulates and coordinates different endocytic mechanisms. PLoS Biol 2004; 2:E261. [PMID: 15328530 PMCID: PMC514490 DOI: 10.1371/journal.pbio.0020261] [Citation(s) in RCA: 220] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Accepted: 06/11/2004] [Indexed: 01/07/2023] Open
Abstract
The small GTPase Rab5 is a key regulator of clathrin-mediated endocytosis. On early endosomes, within a spatially restricted domain enriched in phosphatydilinositol-3-phosphate [PI(3)P], Rab5 coordinates a complex network of effectors that functionally cooperate in membrane tethering, fusion, and organelle motility. Here we discovered a novel PI(3)P-binding Rab5 effector, Rabankyrin-5, which localises to early endosomes and stimulates their fusion activity. In addition to early endosomes, however, Rabankyrin-5 localises to large vacuolar structures that correspond to macropinosomes in epithelial cells and fibroblasts. Overexpression of Rabankyrin-5 increases the number of macropinosomes and stimulates fluid-phase uptake, whereas its downregulation inhibits these processes. In polarised epithelial cells, this function is primarily restricted to the apical membrane. Rabankyrin-5 localises to large pinocytic structures underneath the apical surface of kidney proximal tubule cells, and its overexpression in polarised Madin-Darby canine kidney cells stimulates apical but not basolateral, non-clathrin-mediated pinocytosis. In demonstrating a regulatory role in endosome fusion and (macro)pinocytosis, our studies suggest that Rab5 regulates and coordinates different endocytic mechanisms through its effector Rabankyrin-5. Furthermore, its active role in apical pinocytosis in epithelial cells suggests an important function of Rabankyrin-5 in the physiology of polarised cells.
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Affiliation(s)
| | - Savvas Christoforidis
- 2Laboratory of Biological Chemistry, Medical SchoolUniversity of Ioannina, IoanninaGreece
| | - Margaret R Lindsay
- 3Institute for Molecular Bioscience, Centre for Microscopy and MicroanalysisSchool of Biomedical Sciences, University of Queensland, Brisbane, QueenslandAustralia
| | | | - Matthias Wilm
- 4European Molecular Biology LaboratoryHeidelbergGermany
| | - Robert G Parton
- 3Institute for Molecular Bioscience, Centre for Microscopy and MicroanalysisSchool of Biomedical Sciences, University of Queensland, Brisbane, QueenslandAustralia
| | - Marino Zerial
- 1Max-Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
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135
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Seddas P, Boissinot S, Strub JM, Van Dorsselaer A, Van Regenmortel MHV, Pattus F. Rack-1, GAPDH3, and actin: proteins of Myzus persicae potentially involved in the transcytosis of beet western yellows virus particles in the aphid. Virology 2004; 325:399-412. [PMID: 15246278 DOI: 10.1016/j.virol.2004.05.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 04/09/2004] [Accepted: 05/11/2004] [Indexed: 10/26/2022]
Abstract
Beet western yellows virus (BWYV) is a Polerovirus that relies on the aphid Myzus persicae for its transmission, in a persistent-circulative mode. To be transmitted, the virus must cross the midgut and the accessory salivary glands (ASG) epithelial barriers in a transcytosis mechanism where vector receptors interact with virions. In this paper, we report in vitro interaction experiments between BWYV and aphid components. Using the M. persicae clone from Colmar, we showed that a set of aphid polypeptides, separated by SDS-PAGE or 2D electrophoresis (2DE), can bind in vitro to purified wild type or mutant particles. Using subcellular fractionation, we showed that the 65-kDa polypeptide identified as symbionin is a soluble protein whereas the other polypeptides seem to be associated more or less strongly to the membrane. We hypothesize that three polypeptides, identified by mass spectrometry as Rack-1, GAPDH3, and actin, may be involved in the epithelial transcytosis of virus particles in the aphid vector.
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Affiliation(s)
- Pascale Seddas
- Unité de Recherche Biologie des Interactions Virus/vecteurs, Institut National de la Recherche Agronomique, 68021 Colmar cedex, France.
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136
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Thomas DDH, Weng N, Groblewski GE. Secretagogue-induced translocation of CRHSP-28 within an early apical endosomal compartment in acinar cells. Am J Physiol Gastrointest Liver Physiol 2004; 287:G253-63. [PMID: 14977633 DOI: 10.1152/ajpgi.00033.2004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ca(2+)-regulated heat-stable protein (CRHSP-28) is a member of the TPD52 protein family that has been shown to regulate Ca(2+)-dependent secretory activity in pancreatic acinar cells. Immunofluorescence microscopy of isolated lobules demonstrated that CRHSP-28 is localized to a supranuclear apical compartment in acini and accumulates immediately below the apical membrane within 2 min of CCK octapeptide (CCK-8) stimulation. Dual-immunofluorescence microscopy demonstrated an endosomal localization of CRHSP-28 that strongly overlapped with early endosomal antigen-1 (EEA-1) on vesicular structures throughout the apical cytoplasm but showed only minimal overlap with the transferrin receptor, which is present in basolaterally derived endosomes. Significant overlapping of CRHSP-28 with the trans-Golgi network marker-38 was also noted in supranuclear regions of acini. Interestingly, treatment of lobules with brefeldin A reversibly disrupted the vesicular localization of CRHSP-28 and EEA-1 within the apical cytoplasm. The CCK-8-induced accumulation of CRHSP-28 in subapical regions of acini was not altered by inhibition of apical endocytosis with the actin filament-disrupting agent latrunculin B. Immunoelectron microscopy confirmed that CRHSP-28 is associated with the limiting membrane of irregularly shaped vesicular structures of low electron density in the apical cytoplasm that are positive for EEA-1 staining. Sparse, but significant, CRHSP-28 immunoreactivity was also observed along the limiting membrane of zymogen granules. Consistent with immunofluorescence data, CRHSP-28 was found to accumulate in clusters on endosomes and positioned between zymogen granules below the cell apex on CCK-8 stimulation. These data indicate that CRHSP-28 is present within endocytic and exocytic compartments of acinar cells and is acutely regulated by secretagogue stimulation.
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Affiliation(s)
- Diana D H Thomas
- Department of Nutritional Sciences, University of Wisconsin, 1415 Linden Drive, Madison, WI 53706, USA
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137
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Wakabayashi Y, Lippincott-Schwartz J, Arias IM. Intracellular trafficking of bile salt export pump (ABCB11) in polarized hepatic cells: constitutive cycling between the canalicular membrane and rab11-positive endosomes. Mol Biol Cell 2004; 15:3485-96. [PMID: 15121884 PMCID: PMC452599 DOI: 10.1091/mbc.e03-10-0737] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The bile salt export pump (BSEP, ABCB11) couples ATP hydrolysis with transport of bile acids into the bile canaliculus of hepatocytes. Its localization in the apical canalicular membrane is physiologically regulated by the demand to secrete biliary components. To gain insight into how such localization is regulated, we studied the intracellular trafficking of BSEP tagged with yellow fluorescent protein (YFP) in polarized WIF-B9 cells. Confocal imaging revealed that BSEP-YFP was localized at the canalicular membrane and in tubulo-vesicular structures either adjacent to the microtubule-organizing center or widely distributed in the cytoplasm. In the latter two locations, BSEP-YFP colocalized with rab11, an endosomal marker. Selective photobleaching experiments revealed that single BSEP-YFP molecules resided in canalicular membranes only transiently before exchanging with intracellular BSEP-YFP pools. Such exchange was inhibited by microtubule and actin inhibitors and was unaffected by brefeldin A, dibutyryl cyclic AMP, taurocholate, or PI 3-kinase inhibitors. Intracellular carriers enriched in BSEP-YFP elongated and dissociated as tubular elements from a globular structure adjacent to the microtubule-organizing center. They displayed oscillatory movement toward either canalicular or basolateral membranes, but only fused with the canalicular membrane. The pathway between canalicular and intracellular membranes that BSEP constitutively cycles within could serve to regulate apical pools of BSEP as well as other apical membrane transporters.
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Affiliation(s)
- Yoshiyuki Wakabayashi
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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138
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Rico-Bautista E, Negrín-Martínez C, Novoa-Mogollón J, Fernández-Perez L, Flores-Morales A. Downregulation of the growth hormone-induced Janus kinase 2/signal transducer and activator of transcription 5 signaling pathway requires an intact actin cytoskeleton. Exp Cell Res 2004; 294:269-80. [PMID: 14980520 DOI: 10.1016/j.yexcr.2003.11.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2003] [Revised: 11/12/2003] [Indexed: 10/26/2022]
Abstract
Transient activation of the signal transducers and activators of transcription (STAT) proteins in response to growth hormone (GH) and other type II cytokines plays a pivotal role on specific gene transcription. The negative regulation of STATs seems to be exerted at the GH receptor (GHR)/Janus Kinase (JAK) complex and involves two main mechanisms: (1) the GH-induced ubiquitination/internalization of GHR and (2) the action of SOCS proteins. Since GH regulates cellular cytoskeleton with potential implications in GH signaling, we investigated the effects of actin cytoskeleton disruption on the kinetics of GH-activated GHR/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 5 (STAT5) signaling pathway. Disruption of the actin-based cytoskeleton with cytochalasin D (CytoD) did not affect the rapid GH induction of JAK2 and STAT5 activities. However, pretreatment of BRL-4 cells with CytoD prolonged both, JAK2/STAT5 tyrosine phosphorylation and STAT5 DNA binding activity, for at least 2 h. Our results demonstrated that the synthesis of the several SOCS proteins (SOCS-1, -2, and -3) was not affected by treatment of the cells with CytoD. On the other hand, the inhibitory actions of SOCS1, 2, and -3 on GH-induced STAT5 reporter activity were partially blocked by disruption of the cytoskeleton. Disassembly of the actin filaments by CytoD is accompanied by accumulation of ubiquitinated forms of GHR but it does not affect GHR internalization. We conclude that the integrity of the actin cytoskeleton network plays an essential role in the negative regulation of GHR/JAK2/STAT5 signaling pathway by facilitating the GHR ubiquitination/degradation through mechanisms acting downstream SOCS.
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139
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Guilherme A, Soriano NA, Bose S, Holik J, Bose A, Pomerleau DP, Furcinitti P, Leszyk J, Corvera S, Czech MP. EHD2 and the Novel EH Domain Binding Protein EHBP1 Couple Endocytosis to the Actin Cytoskeleton. J Biol Chem 2004; 279:10593-605. [PMID: 14676205 DOI: 10.1074/jbc.m307702200] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we identified two novel proteins denoted EH domain protein 2 (EHD2) and EHD2-binding protein 1 (EHBP1) that link clathrin-mediated endocytosis to the actin cytoskeleton. EHD2 contains an N-terminal P-loop and a C-terminal EH domain that interacts with NPF repeats in EHBP1. Disruption of EHD2 or EHBP1 function by small interfering RNA-mediated gene silencing inhibits endocytosis of transferrin into EEA1-positive endosomes as well as GLUT4 endocytosis into cultured adipocytes. EHD2 localizes with cortical actin filaments, whereas EHBP1 contains a putative actin-binding calponin homology domain. High expression of EHD2 or EHBP1 in intact cells mediates extensive actin reorganization. Thus EHD2 appears to connect endocytosis to the actin cytoskeleton through interactions of its N-terminal domain with membranes and its C-terminal EH domain with the novel EHBP1 protein.
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Affiliation(s)
- Adilson Guilherme
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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140
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Abstract
Internalization of receptors, lipids, pathogens, and other cargo at the plasma membrane involves several different pathways and requires coordinated interactions between a variety of protein and lipid molecules. The actin cytoskeleton is an integral part of the cell cortex, and there is growing evidence that F-actin plays a direct role in these endocytic events. Genetic studies in yeast have firmly established a functional connection between actin and endocytosis. Identification of several proteins that may function at the interface between actin and the endocytic machinery has provided further evidence for this association in both yeast and mammalian cells. Several of these proteins are directly involved in regulating actin assembly and could thus harness forces produced during actin polymerization to facilitate specific steps in the endocytic process. Recent microscopy studies in mammalian cells provide powerful evidence that localized recruitment and polymerization of actin occurs at endocytic sites. In this review, we focus on progress made in elucidating the functions of the actin cytoskeleton in endocytosis.
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Affiliation(s)
- Asa E Y Engqvist-Goldstein
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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141
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Abstract
Internalization of membrane, fluid and receptor-bound ligands into cells occurs by at least two endocytic mechanisms. One is dependent on clathrin and responsible for concentrative uptake of growth factors and other ligands, whereas the other operates without clathrin. Clathrin-independent endocytosis, which might involve more than one mechanism, can contribute significantly to the total uptake of membrane and fluid in a cell. The properties and possible roles of clathrin-independent endocytosis are discussed in this article.
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Affiliation(s)
- K Sandvig
- Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
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142
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Mousavi SA, Malerød L, Berg T, Kjeken R. Clathrin-dependent endocytosis. Biochem J 2004; 377:1-16. [PMID: 14505490 PMCID: PMC1223844 DOI: 10.1042/bj20031000] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2003] [Revised: 09/11/2003] [Accepted: 09/23/2003] [Indexed: 11/17/2022]
Abstract
The process by which clathrin-coated vesicles are produced involves interactions of multifunctional adaptor proteins with the plasma membrane, as well as with clathrin and several accessory proteins and phosphoinositides. Here we review recent findings highlighting new insights into mechanisms underlying clathrin-dependent endocytosis.
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Affiliation(s)
- Seyed Ali Mousavi
- Department of Biology, University of Oslo, P.O. Box 1050, Blindern, N-0316 Oslo, Norway
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143
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Basner-Tschakarjan E, Mirmohammadsadegh A, Baer A, Hengge UR. Uptake and trafficking of DNA in keratinocytes: evidence for DNA-binding proteins. Gene Ther 2004; 11:765-74. [PMID: 14724668 DOI: 10.1038/sj.gt.3302221] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The skin is an interesting organ for human gene therapy due to accessibility, immunologic potential and synthesis capabilities. In this study, we attempted to visualize and measure the uptake of naked FITC-labeled plasmid by FACS analysis detecting up to 15% internalization in a dose- and time-dependent manner. Cycloheximide treatment inhibited the uptake by >90%, suggesting a protein-mediated uptake. The inhibition of different internalization pathways demonstrated that blocking macropinocytosis (by amiloride and N,N-dimethylamylorid) reduced DNA uptake by >85%, while the inhibition of clathrin-coated pits (by chlorpromazine) and caveolae (by nystatin/filipin III) did not limit the uptake. Colocalization studies using confocal laser microscopy revealed a time-dependent accumulation of plasmid DNA in endosomes and lysosomes. When a green fluorescent protein (GFP) expression vector was used, specific GFP-RNA became detectable by reverse transcriptase-PCR, whereas measurable amounts of protein could not be identified in FACS experiments. To detect the potential DNA receptors on the keratinocyte surface, membrane proteins were extracted and subjected to South-Western blotting using digoxigenin-labeled calf thymus and lambda-phage DNA. Two DNA-binding proteins, ezrin and moesin, known as plasma membrane-actin linkers, were identified by one- and two-dimensional-South-Western blots and matrix-assisted laser desorption and ionization-mass spectrometry. Ezrin and moesin are functionally associated with a number of transmembrane receptors such as the EGF, CD44 or ICAM-1 receptor. Taken together, naked plasmid DNA seems to enter human keratinocytes through different pathways, mainly by macropinocytosis. Two DNA-binding proteins were identified that seemed to be involved in binding/trafficking of internalized DNA.
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Affiliation(s)
- E Basner-Tschakarjan
- Department of Dermatology, Heinrich Heine-University Düsseldorf, Düsseldorf, Germany
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144
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McTaggart SJ, Eitle E, Harris PJ, Jones CL. Role of Isoprenoids in Cytoskeleton Integrity and Albumin Endocytosis by Opossum Kidney Cells. ACTA ACUST UNITED AC 2004; 97:e77-85. [PMID: 15292678 DOI: 10.1159/000078641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2002] [Accepted: 01/08/2004] [Indexed: 11/19/2022]
Abstract
BACKGROUND The actin cytoskeleton has been increasingly implicated in endocytic events that are involved in the reabsorption of filtered protein by the proximal tubule. Isoprenylated small G proteins have emerged as key regulators of the actin cytoskeleton. This study examines the role of isoprenoid intermediates in organization of the cytoskeleton, and the effect of modification of the cytoskeleton on albumin endocytosis. METHODS The effect of lovastatin on cytoskeleton morphology of opossum kidney cells (OK cells) was determined by staining with fluorescent isothiocyanate (FITC)-phalloidin followed by examination using confocal microscopy. Quantitative effects on albumin binding and uptake were determined using a well-established method. RESULTS Inhibition of isoprenoid synthesis by lovastatin led to morphological disruption of the cytoskeleton with a concentration-dependent decrease in albumin uptake into OK cells. Addition of mevalonate, but not cholesterol, ameliorated the effects of lovastatin on the cytoskeleton and albumin uptake. Selective inhibition of isoprenoid intermediates with a farnesyltransferase inhibitor suggests that geranylgeranylated proteins mediate cytoskeleton organization. CONCLUSION These results confirm the importance of cytoskeleton integrity in albumin endocytosis in renal proximal tubules. While the present data suggest that synthesis of isoprenoids via the mevalonate pathway is a critical step in maintenance of the cytoskeleton, the role of individual small G proteins in control of the cytoskeleton and other endocytic events is yet to be defined.
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Affiliation(s)
- Steven J McTaggart
- Victorian Paediatric Renal Service, Royal Children's Hospital, University of Melbourne, Parkville, Vic., Australia.
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145
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146
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da Costa SR, Okamoto CT, Hamm-Alvarez SF. Actin microfilaments et al.--the many components, effectors and regulators of epithelial cell endocytosis. Adv Drug Deliv Rev 2003; 55:1359-83. [PMID: 14597136 DOI: 10.1016/j.addr.2003.07.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aim of this review is to introduce the advances made over the past several years regarding the participation of actin and actin-associated proteins in clathrin-mediated endocytosis in simple cell models, and then to consider the evidence for the involvement of these effectors in apical clathrin-mediated endocytosis in epithelial cells. Basic mechanisms of clathrin-mediated endocytosis are initially addressed, followed by a detailed description of the actin cytoskeleton: its organization, function and, most importantly, the essential role played by proteins and signaling pathways responsible for the regulation of actin filament dynamics. Our focus then shifts to the GTPase, dynamin and its pivotal role as a bridge between various components of the clathrin endocytic machinery and the actin cytoskeleton. Mechanisms and effectors of dynamin-dependent endocytosis are then described, with a particular emphasis on novel proteins, which link dynamin to actin filaments. We consider additional effectors proposed to interact with actin to facilitate clathrin-mediated endocytosis in a dynamin-independent manner. The multiple roles which actin filaments are thought to play in endocytosis are addressed followed by a more detailed characterization of actin filament participation specifically in apical endocytosis. We conclude by discussing how these concepts may be integrated to improve drug internalization at the apical plasma membrane of epithelial cells.
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Affiliation(s)
- Silvia R da Costa
- Department of Pharmaceutical Sciences, USC School of Pharmacy, 1985 Zonal Avenue, Los Angeles, CA 90033, USA
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147
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Nir S, Nieva JL. Uptake of liposomes by cells: experimental procedures and modeling. Methods Enzymol 2003; 372:235-48. [PMID: 14610816 DOI: 10.1016/s0076-6879(03)72013-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Affiliation(s)
- Shlomo Nir
- Seagram Center for Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot 76100, Israel
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148
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Fomina AF, Deerinck TJ, Ellisman MH, Cahalan MD. Regulation of membrane trafficking and subcellular organization of endocytic compartments revealed with FM1-43 in resting and activated human T cells. Exp Cell Res 2003; 291:150-66. [PMID: 14597416 PMCID: PMC2749753 DOI: 10.1016/s0014-4827(03)00372-0] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
FM1-43, a fluorescent styryl dye that penetrates into and stains membranes, was used to investigate kinetics of constitutive endocytosis and to visualize the fate of endocytic organelles in resting and activated human T lymphocytes. The rate of dye accumulation was strongly temperature dependent and approximately 10-fold higher in activated than in resting T cells. Elevation of cytosolic free Ca2+ concentration with thapsigargin or ionomycin further accelerated the rate of FM1-43 accumulation associated with cytosolic actin polymerization. Direct modulation of actin polymerization affected membrane trafficking. Actin condensation beneath the plasma membrane with calyculin A abolished FM1-43 internalization, whereas actin depolymerization with cytochalasin D had no effect. Photoconversion of DAB by FM1-43 revealed altered endocytic compartment targeting associated with T cell activation. Internalized cargo was carried to lysosome-like compartments in resting T cells and to multivesicular bodies (MVB) in activated T cells. Externalization of exosomes from MVB occurred commonly in activated but not in resting T cells. T cell exosomes contained raft-associated CD3 proteins, GM1 glycosphingolipids, and phosphatidylserine at the outer membrane leaflet. The present study demonstrates the utility of FM1-43 as a marker of membrane trafficking in T cells and reveals possible mechanisms of its modulation during T cell activation.
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Affiliation(s)
- Alla F. Fomina
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Thomas J. Deerinck
- National Center for Microscopy and Imaging Research, Center for Research in Biological Structure and the Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, Center for Research in Biological Structure and the Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Michael D. Cahalan
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
- Corresponding author. Fax: +1-949-824-3143. (M.D. Cahalan)
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149
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Dalby-Payne JR, O'Loughlin EV, Gunning P. Polarization of specific tropomyosin isoforms in gastrointestinal epithelial cells and their impact on CFTR at the apical surface. Mol Biol Cell 2003; 14:4365-75. [PMID: 12960432 PMCID: PMC266757 DOI: 10.1091/mbc.e03-03-0169] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Microfilaments have been reported to be polarized in a number of cell types based both on function and isoform composition. There is evidence that microfilaments are involved in the movement of vesicles and the polarized delivery of proteins to specialized membrane domains. We have investigated the composition of actin microfilaments in gastrointestinal epithelial cells and their role in the delivery of the cystic fibrosis transmembrane conductance regulator (CFTR) into the apical membrane using cultured T84 cells as a model. We identified a specific population of microfilaments containing the tropomyosin (Tm) isoforms Tm5a and/or Tm5b, which are polarized in T84 cell monolayers. Polarization of this microfilament population occurs very rapidly in response to cell-cell and cell-substratum contact and is not inhibited by jasplakinolide, suggesting this involves the movement of intact filaments. Colocalization of Tm5a and/or Tm5b and CFTR was observed in long-term cultures. A reduction in Tm5a and Tm5b expression, induced using antisense oligonucleotides, resulted in an increase in both CFTR surface expression and chloride efflux in response to cAMP stimulation. We conclude that Tm isoforms Tm5a and/or Tm5b mark an apical population of microfilaments that can regulate the insertion and/or retention of CFTR into the plasma membrane.
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Fortuna VA, Martucci RB, Trugo LC, Borojevic R. Hepatic stellate cells uptake of retinol associated with retinol-binding protein or with bovine serum albumin. J Cell Biochem 2003; 90:792-805. [PMID: 14587034 DOI: 10.1002/jcb.10703] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Retinol is stored in liver, and the dynamic balance between its accumulation and mobilization is regulated by hepatic stellate cells (HSC). Representing less than 1% total liver protein, HSC can reach a very high intracellular retinoid (vitamin-A and its metabolites) concentration, which elicits their conversion from the myofibroblast to the fat-storing lipocyte phenotype. Circulating retinol is associated with plasma retinol-binding protein (RBP) or bovine serum albumin (BSA). Here we have used the in vitro model of GRX cells to compare incorporation and metabolism of BSA versus RBP associated [(3)H]retinol in HSC. We have found that lipocytes, but not myofibroblasts, expressed a high-affinity membrane receptor for RBP-retinol complex (KD = 4.93 nM), and both cell types expressed a low-affinity one (KD = 234 nM). The RBP-retinol complex, but not the BSA-delivered retinol, could be dislodged from membranes by treatments that specifically disturb protein-protein interactions (high RBP concentrations). Under both conditions, treatments that disturb the membrane lipid layer (detergent, cyclodextrin) released the membrane-bound retinol. RBP-delivered retinol was found in cytosol, microsomal fraction and, as retinyl esters, in lipid droplets, while albumin-delivered retinol was mainly associated with membranes. Disturbing the clathrin-mediated endocytosis did not interfere with retinol uptake. Retinol derived from the holo-RBP complex was differentially incorporated in lipocytes and preferentially reached esterification sites close to lipid droplets through a specific intracellular traffic route. This direct influx pathway facilitates the retinol uptake into HSC against the concentration gradients, and possibly protects cell membranes from undesirable and potentially noxious high retinol concentrations.
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Affiliation(s)
- Vitor A Fortuna
- Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, 21941-970 Cidade Universitária, Rio de Janeiro, Brazil
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