201
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Abstract
The regulation of many immunological events depends on systems that mediate dynamic actin reorganization in response to signals from the cell membrane. The Wiskott-Aldrich syndrome protein (WASp) is the founding member of a family of proteins that have emerged as crucial effectors of Rho GTPases and activators of the cytoskeletal-organizing complex Arp2/3. Now, WASp has been shown to be intimately involved in many pathways that influence the function of the immune system. Disturbances in these systems result in the complex immunodysregulation of Wiskott-Aldrich syndrome.
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Affiliation(s)
- Adrian J Thrasher
- Molecular Immunology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
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202
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Howard MJ, Isacke CM. The C-type lectin receptor Endo180 displays internalization and recycling properties distinct from other members of the mannose receptor family. J Biol Chem 2002; 277:32320-31. [PMID: 12068012 DOI: 10.1074/jbc.m203631200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Endo180/urokinase plasminogen activator receptor-associated protein together with the mannose receptor, the phospholipase A(2) receptor, and DEC-205/MR6-gp200 comprise the four members of the mannose receptor family. These receptors have a unique structural composition due to the presence of multiple C-type lectin-like domains within a single polypeptide backbone. In addition, they are all constitutively internalized from the plasma membrane via clathrin-mediated endocytosis and recycled back to the cell surface. Endo180 is a multifunctional receptor displaying Ca(2+)-dependent lectin activity, collagen binding, and association with the urokinase plasminogen activator receptor, and it has a proposed role in extracellular matrix degradation and remodeling. Within their short cytoplasmic domains, all four receptors contain both a conserved tyrosine-based and dihydrophobic-based putative endocytosis motif. Unexpectedly, Endo180 was found to be distinct within the family in that the tyrosine-based motif is not required for efficient delivery to and recycling from early endosomes. By contrast, receptor internalization is completely dependent on the dihydrophobic motif and modulated by a conserved upstream acidic residue. Furthermore, unlike the mannose receptor, Endo180 does not function as a phagocytic receptor in vitro. These findings demonstrate that despite an overall structural similarity, members of this receptor family employ distinct trafficking mechanisms that may reflect important differences in their physiological functions.
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Affiliation(s)
- Matthew J Howard
- Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, Mary-Jean Mitchell Green Building, Chester Beatty Laboratories, 237 Fulham Rd., London SW3 6JB, United Kingdom
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203
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Morehead J, Coppens I, Andrews NW. Opsonization modulates Rac-1 activation during cell entry by Leishmania amazonensis. Infect Immun 2002; 70:4571-80. [PMID: 12117970 PMCID: PMC128177 DOI: 10.1128/iai.70.8.4571-4580.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Lesions caused by Leishmania amazonensis normally heal, but relapses occur due to parasite persistence in host tissues. It has been proposed that infection of fibroblasts plays an important role in this process by providing the parasites with a safe haven in which to replicate. However, most previous studies have focused on the entry of Leishmania into macrophages, a process mediated by serum opsonins. To gain insight into a possible role of nonopsonic entry in the intracellular persistence of amastigotes, we examined the invasion of Chinese hamster ovary (CHO) cells. Amastigotes entered CHO cells by a cytochalasin D, genistein, wortmannin, and 2,3-butanedione monoxime-sensitive pathway and replicated within phagolysosomes. However, unlike most phagocytic processes described to date, amastigote internalization in CHO cells involved activation of the GTPases Rho and Cdc42 but not Rac-1. When uptake was mediated by fibronectin or when amastigotes were opsonized with immunoglobulin G and internalized by Fc receptor-expressing CHO cells, Rac-1 activation was restored and found to be required for parasite internalization. Given the essential role of Rac in assembly of the respiratory burst oxidase, invasion through this nonopsonic, Rac-1-independent pathway may play a central role in the intracellular survival of Leishmania in immune hosts.
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Affiliation(s)
- J Morehead
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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204
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Kawasaki Y, Nakagawa A, Nagaosa K, Shiratsuchi A, Nakanishi Y. Phosphatidylserine binding of class B scavenger receptor type I, a phagocytosis receptor of testicular sertoli cells. J Biol Chem 2002; 277:27559-66. [PMID: 12016218 DOI: 10.1074/jbc.m202879200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Testicular Sertoli cells phagocytose apoptotic spermatogenic cells in a manner depending on the membrane phospholipid phosphatidylserine (PS) expressed at the surface of the latter cell type. Our previous studies have indicated that class B scavenger receptor type I (SR-BI) is responsible for the PS-mediated phagocytosis by Sertoli cells. We examined here whether SR-BI binds directly to PS. A cell line acquired the ability to bind to PS-exposing apoptotic cells and to incorporate PS-containing liposomes when it was forced to express SR-BI. Furthermore, the extracellular domain of rat SR-BI fused with human Fc (SRBIecd-Fc) bound to PS with a dissociation equilibrium constant of 2.4 x 10(-7) m in a cell-free solid-phase assay, whereas other phospholipids including phosphatidylethanolamine, phosphatidylinositol, and phosphatidylcholine were poor binding targets. The binding activity was enhanced when CaCl(2) was included in the assay or when SRBIecd-Fc was pre-treated with N-glycanase. A portion of the extracellular domain spanning amino acid positions 33 and 191 (numbered with respect to the amino terminus) fused with Fc (SRBI33-191-Fc) showed activity and phospholipid specificity equivalent to those of SRBIecd-Fc. Finally, SRBI33-191-Fc bound to the surface of apoptotic cells with externalized PS, and the injection of SRBI33-191-Fc into the seminiferous tubules of live mice increased the number of apoptotic spermatogenic cells. These results allowed us to conclude that SR-BI is a phagocytosis-inducing PS receptor of Sertoli cells.
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Affiliation(s)
- Yuki Kawasaki
- Graduate School of Natural Science and Technology, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-0934, Japan
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205
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Schmidt A, Hall A. Guanine nucleotide exchange factors for Rho GTPases: turning on the switch. Genes Dev 2002; 16:1587-609. [PMID: 12101119 DOI: 10.1101/gad.1003302] [Citation(s) in RCA: 923] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Anja Schmidt
- MRC Laboratory for Molecular Cell Biology, Cancer Research UK Oncogene and Signal Transduction Group, University College London, London WC1E 6BT, UK.
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206
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Abstract
Whether the endocytic uptake of a given molecule is mediated through clathrin-coated pits or not is a classical criterion used to characterize its endocytic pathway(s). Hence, clathrin-dependent endocytosis has been associated with highly selective and efficient uptake, whereas clathrin-independent endocytosis appeared to be confined to bulk uptake of fluid-phase markers. This scholastic view has recently been challenged using newly developed molecular tools that allow for the first time a functional and mechanistic analysis of these less well-characterized clathrin-independent pathways, including caveolar uptake and macropinocytosis. Furthermore, several studies point to a critical role of lateral lipid asymmetry--lipid rafts/microdomains--in membrane sorting. We will discuss the potential role of these structures in endocytosis and the possibility that differential sorting at the plasma membrane predisposes the ensuing intracellular fate of a given molecule as well as its physiological function.
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Affiliation(s)
- Ludger Johannes
- Institut Curie, UMR144 CNRS, Traffic and Signaling Laboratory, 26 rue d'Ulm, 75005 Paris Cedex 05, France.
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207
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Barreiro O, Yanez-Mo M, Serrador JM, Montoya MC, Vicente-Manzanares M, Tejedor R, Furthmayr H, Sanchez-Madrid F. Dynamic interaction of VCAM-1 and ICAM-1 with moesin and ezrin in a novel endothelial docking structure for adherent leukocytes. J Cell Biol 2002; 157:1233-45. [PMID: 12082081 PMCID: PMC2173557 DOI: 10.1083/jcb.200112126] [Citation(s) in RCA: 452] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Ezrin, radixin, and moesin (ERM) regulate cortical morphogenesis and cell adhesion by connecting membrane adhesion receptors to the actin-based cytoskeleton. We have studied the interaction of moesin and ezrin with the vascular cell adhesion molecule (VCAM)-1 during leukocyte adhesion and transendothelial migration (TEM). VCAM-1 interacted directly with moesin and ezrin in vitro, and all of these molecules colocalized at the apical surface of endothelium. Dynamic assessment of this interaction in living cells showed that both VCAM-1 and moesin were involved in lymphoblast adhesion and spreading on the endothelium, whereas only moesin participated in TEM, following the same distribution pattern as ICAM-1. During leukocyte adhesion in static or under flow conditions, VCAM-1, ICAM-1, and activated moesin and ezrin clustered in an endothelial actin-rich docking structure that anchored and partially embraced the leukocyte containing other cytoskeletal components such as alpha-actinin, vinculin, and VASP. Phosphoinositides and the Rho/p160 ROCK pathway, which participate in the activation of ERM proteins, were involved in the generation and maintenance of the anchoring structure. These results provide the first characterization of an endothelial docking structure that plays a key role in the firm adhesion of leukocytes to the endothelium during inflammation.
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Affiliation(s)
- Olga Barreiro
- Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain
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208
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Carréno S, Caron E, Cougoule C, Emorine LJ, Maridonneau-Parini I. p59Hck isoform induces F-actin reorganization to form protrusions of the plasma membrane in a Cdc42- and Rac-dependent manner. J Biol Chem 2002; 277:21007-16. [PMID: 11904303 DOI: 10.1074/jbc.m201212200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Hck is a protein kinase of the Src family specifically expressed in phagocytes as two isoforms, p59Hck and p61Hck, localized at the plasma membrane and lysosomes, respectively. Their individual involvement in functions ascribed to Hck, phagocytosis, cell migration, and lysosome mobilization, is still unclarified. To investigate the specific role of p59Hck, a constitutively active variant in fusion with green fluorescent protein (p59Hck(ca)) was expressed in HeLa cells. p59Hck(ca) was found at focal adhesion sites and triggered reorganization of the actin cytoskeleton, leading to plasma membrane protrusions where it co-localized with F-actin. Similarly, microinjection of p59Hck(ca) cDNA in J774.A1 macrophages induced membrane protrusions. Whereas kinase activity and membrane association of p59Hck were dispensable for location at focal adhesions, p59Hck-induced membrane protrusions were dependent on kinase activity, plasma membrane association, and Src homology 2 but not Src homology 3 domain and were inhibited by dominant-negative forms of Cdc42 or Rac but not by blocking Rho activity. A dominant negative form of p59Hck inhibited the Cdc42- and Rac-dependent FcgammaRIIa-mediated phagocytosis. Expression of the Cdc42/Rac-interacting domain of p21-activated kinase in macrophages abolished the p59Hck(ca)-induced morphological changes. Therefore, p59Hck-triggered remodeling of the actin cytoskeleton depends upon the activity of Cdc42 and Rac to promote formation of membrane protrusions necessary for phagocytosis and cell migration.
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Affiliation(s)
- Sébastien Carréno
- Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique UMR 5089, 205 route de Narbonne, Toulouse cedex 31077, France
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209
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Abstract
The phagocytic response of innate immune cells such as macrophages is defined by the activation of complex signaling networks that are stimulated by microbial contact. Many individual proteins have been demonstrated to participate in phagocytosis, and the application of high-throughput tools has indicated that many more remain to be described. In this review, we examine this complexity and describe how during recognition, multiple receptors are simultaneously engaged to mediate internalization, activate microbial killing, and induce the production of inflammatory cytokines and chemokines. Many signaling molecules perform multiple functions during phagocytosis, and these molecules are likely to be key regulators of the process. Indeed, pathogenic microorganisms target many of these molecules in their attempts to evade destruction.
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Affiliation(s)
- David M Underhill
- Institute for Systems Biology, 1441 North 34 Street, Seattle, Washington 98103, USA.
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210
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Shao F, Merritt PM, Bao Z, Innes RW, Dixon JE. A Yersinia effector and a Pseudomonas avirulence protein define a family of cysteine proteases functioning in bacterial pathogenesis. Cell 2002; 109:575-88. [PMID: 12062101 DOI: 10.1016/s0092-8674(02)00766-3] [Citation(s) in RCA: 333] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A Yersinia effector known as YopT and a Pseudomonas avirulence protein known as AvrPphB define a family of 19 proteins involved in bacterial pathogenesis. We show that both YopT and AvrPphB are cysteine proteases, and their proteolytic activities are dependent upon the invariant C/H/D residues conserved in the entire YopT family. YopT cleaves the posttranslationally modified Rho GTPases near their carboxyl termini, releasing them from the membrane. This leads to the disruption of actin cytoskeleton in host cells. The proteolytic activity of AvrPphB is essential for autoproteolytic cleavage of an AvrPphB precursor as well as for eliciting the hypersensitive response in plants. These findings provide new insights into mechanisms of animal and plant pathogenesis.
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Affiliation(s)
- Feng Shao
- Department of Biological Chemistry, Medical School and Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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211
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Coleman ML, Olson MF. Rho GTPase signalling pathways in the morphological changes associated with apoptosis. Cell Death Differ 2002; 9:493-504. [PMID: 11973608 DOI: 10.1038/sj.cdd.4400987] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2001] [Revised: 10/26/2001] [Accepted: 11/05/2001] [Indexed: 01/06/2023] Open
Abstract
The killing and removal of superfluous cells is an important step during embryonic development, tissue homeostasis, wound repair and the resolution of inflammation. A specific sequence of biochemical events leads to a form of cell death termed apoptosis, and ultimately to the disassembly of the dead cell for phagocytosis. Dynamic rearrangements of the actin cytoskeleton are central to the morphological changes observed both in apoptosis and phagocytosis. Recent research has highlighted the importance of Rho GTPase signalling pathways to these changes in cellular architecture. In this review, we will discuss how these signal transduction pathways affect the structure of the actin cytoskeleton and allow for the efficient clearance of apoptotic cells.
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Affiliation(s)
- M L Coleman
- Cancer Research Campaign Centre for Cell and Molecular Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK
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212
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Abstract
Animals have an immune system to fight off challenges from both viruses and bacteria. The first line of defence is innate immunity, which is composed of cells that engulf pathogens as well as cells that release potent signalling molecules to activate an inflammatory response and the adaptive immune system. Pathogenic bacteria have evolved a set of weapons, or effectors, to ensure survival in the host. Yersinia spp. use a type III secretion system to translocate these effector proteins, called Yops, into the host. This report outlines how Yops thwart the signalling machinery of the host immune system.
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Affiliation(s)
- Stephen J Juris
- University of Michigan, 1301 East Catherine, 4433 Medical Science I, Ann Arbor, MI 48109-0606, USA
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213
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Patel JC, Hall A, Caron E. Vav regulates activation of Rac but not Cdc42 during FcgammaR-mediated phagocytosis. Mol Biol Cell 2002; 13:1215-26. [PMID: 11950933 PMCID: PMC102263 DOI: 10.1091/mbc.02-01-0002] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Phagocytosis is the process whereby cells direct the spatially localized, receptor-driven engulfment of particulate materials. It proceeds via remodeling of the actin cytoskeleton and shares many of the core cytoskeletal components involved in adhesion and migration. Small GTPases of the Rho family have been widely implicated in coordinating actin dynamics in response to extracellular signals and during diverse cellular processes, including phagocytosis, yet the mechanisms controlling their recruitment and activation are not known. We show herein that in response to ligation of Fc receptors for IgG (FcgammaR), the guanine nucleotide exchange factor Vav translocates to nascent phagosomes and catalyzes GTP loading on Rac, but not Cdc42. The Vav-induced Rac activation proceeds independently of Cdc42 function, suggesting distinct roles for each GTPase during engulfment. Moreover, inhibition of Vav exchange activity or of Cdc42 activity does not prevent Rac recruitment to sites of particle attachment. We conclude that Rac is recruited to Fcgamma membrane receptors in its inactive, GDP-bound state and that Vav regulates phagocytosis through subsequent catalysis of GDP/GTP exchange on Rac.
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Affiliation(s)
- Jayesh C Patel
- Medical Research Council Laboratory for Molecular Cell Biology, Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, United Kingdom
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214
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Higgs HN, Pollard TD. Regulation of actin filament network formation through ARP2/3 complex: activation by a diverse array of proteins. Annu Rev Biochem 2002; 70:649-76. [PMID: 11395419 DOI: 10.1146/annurev.biochem.70.1.649] [Citation(s) in RCA: 545] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Actin filament assembly and turnover drive many forms of cellular motility, particularly extension of the leading edge of locomoting cells and rocketing of pathogenic microorganisms through host cell cytoplasm. De novo nucleation of actin filaments appears to be required for these movements. A complex of seven proteins called Arp2/3 complex is the best characterized cellular initiator of actin filament nucleation. Arp2/3 complex is intrinsically inactive, relying on nucleation promoting factors for activation. WASp/Scar family proteins are prominent cellular nucleation promoting factors. They bring together an actin monomer and Arp2/3 complex in solution or on the side of an existing actin filament to initiate a new filament that grows in the barbed end direction. WASp and N-WASP are intrinsically autoinhibited, and their activity is regulated by Rho-family GTPases such as Cdc42, membrane polyphosphoinositides, WIP/verprolin, and SH3 domain proteins. These interactions provide a final common pathway for many signaling inputs to regulate actin polymerization. Microorganisms either activate Arp2/3 complex directly or usurp N-WASP to initiate actin polymerization.
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Affiliation(s)
- H N Higgs
- Structural Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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215
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Rossman KL, Worthylake DK, Snyder JT, Siderovski DP, Campbell SL, Sondek J. A crystallographic view of interactions between Dbs and Cdc42: PH domain-assisted guanine nucleotide exchange. EMBO J 2002; 21:1315-26. [PMID: 11889037 PMCID: PMC125919 DOI: 10.1093/emboj/21.6.1315] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2001] [Revised: 01/21/2002] [Accepted: 01/21/2002] [Indexed: 12/24/2022] Open
Abstract
Dbl-related oncoproteins are guanine nucleotide exchange factors (GEFs) specific for Rho guanosine triphosphatases (GTPases) and invariably possess tandem Dbl (DH) and pleckstrin homology (PH) domains. While it is known that the DH domain is the principal catalytic subunit, recent biochemical data indicate that for some Dbl-family proteins, such as Dbs and Trio, PH domains may cooperate with their associated DH domains in promoting guanine nucleotide exchange of Rho GTPases. In order to gain an understanding of the involvement of these PH domains in guanine nucleotide exchange, we have determined the crystal structure of a DH/PH fragment from Dbs in complex with Cdc42. The complex features the PH domain in a unique conformation distinct from the PH domains in the related structures of Sos1 and Tiam1.Rac1. Consequently, the Dbs PH domain participates with the DH domain in binding Cdc42, primarily through a set of interactions involving switch 2 of the GTPase. Comparative sequence analysis suggests that a subset of Dbl-family proteins will utilize their PH domains similarly to Dbs.
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Affiliation(s)
- Kent L. Rossman
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
| | - David K. Worthylake
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
| | - Jason T. Snyder
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
| | - David P. Siderovski
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
| | - Sharon L. Campbell
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
| | - John Sondek
- Department of Biochemistry and Biophysics, Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA Corresponding author e-mail:
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216
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Bayless KJ, Davis GE. The Cdc42 and Rac1 GTPases are required for capillary lumen formation in three-dimensional extracellular matrices. J Cell Sci 2002; 115:1123-36. [PMID: 11884513 DOI: 10.1242/jcs.115.6.1123] [Citation(s) in RCA: 170] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Here we show a requirement for the Cdc42 and Rac1 GTPases in endothelial cell (EC) morphogenesis in three-dimensional extracellular matrices. Cdc42 and Rac1 specifically regulate EC intracellular vacuole and lumen formation in both collagen and fibrin matrices. Clostridium difficile toxin B(which blocks all three Rho GTPases) completely inhibited the ability of ECs to form both vacuoles and lumens, whereas C3 transferase, a selective inhibitor of Rho, did not. Expression of either dominant-negative (N17) or constitutively active (V12) Cdc42 using recombinant adenoviruses dramatically inhibited EC vacuole and lumen formation in both collagen and fibrin matrices. Both vacuole and lumen formation initiated in ECs expressing dominant-negative(N17) Rac1 but later collapsed, indicating a role for Rac1 during later stages of vessel development. Analysis of cultures using confocal microscopy revealed green fluorescent protein-V12Rac1, -Rac1 wild-type and -Cdc42 wild-type chimeric proteins targeted to intracellular vacuole membranes during the lumen formation process. Also, expression of the verprolin-cofilin-acidic domain of N-WASP, a downstream Cdc42 effector, in ECs completely interfered with vacuole and lumen formation. These results collectively reveal a novel role for Cdc42 and Rac1 in the process of EC vacuole and lumen formation in three-dimensional extracellular matrices.
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Affiliation(s)
- Kayla J Bayless
- Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas 77843-1114, USA
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217
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Luna A, Matas OB, Martínez-Menárguez JA, Mato E, Durán JM, Ballesta J, Way M, Egea G. Regulation of protein transport from the Golgi complex to the endoplasmic reticulum by CDC42 and N-WASP. Mol Biol Cell 2002; 13:866-79. [PMID: 11907268 PMCID: PMC99605 DOI: 10.1091/mbc.01-12-0579] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Actin is involved in the organization of the Golgi complex and Golgi-to-ER protein transport in mammalian cells. Little, however, is known about the regulation of the Golgi-associated actin cytoskeleton. We provide evidence that Cdc42, a small GTPase that regulates actin dynamics, controls Golgi-to-ER protein transport. We located GFP-Cdc42 in the lateral portions of Golgi cisternae and in COPI-coated and non-coated Golgi-associated transport intermediates. Overexpression of Cdc42 and its activated form Cdc42V12 inhibited the retrograde transport of Shiga toxin from the Golgi complex to the ER, the redistribution of the KDEL receptor, and the ER accumulation of Golgi-resident proteins induced by the active GTP-bound mutant of Sar1 (Sar1[H79G]). Coexpression of wild-type or activated Cdc42 and N-WASP also inhibited Golgi-to-ER transport, but this was not the case in cells expressing Cdc42V12 and N-WASP(Delta WA), a mutant form of N-WASP that lacks Arp2/3 binding. Furthermore, Cdc42V12 recruited GFP-N-WASP to the Golgi complex. We therefore conclude that Cdc42 regulates Golgi-to-ER protein transport in an N-WASP-dependent manner.
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Affiliation(s)
- Ana Luna
- Departament de Biologia Cel.lular i Anatomia Patològica, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, E-08036 Barcelona, Spain
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218
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Beningo KA, Wang YL. Fc-receptor-mediated phagocytosis is regulated by mechanical properties of the target. J Cell Sci 2002; 115:849-56. [PMID: 11865040 DOI: 10.1242/jcs.115.4.849] [Citation(s) in RCA: 235] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Phagocytosis is an actin-based process used by macrophages to clear particles greater than 0.5 μm in diameter. In addition to its role in immunological responses, phagocytosis is also necessary for tissue remodeling and repair. To prevent catastrophic autoimmune reactions, phagocytosis must be tightly regulated. It is commonly assumed that the recognition/selection of phagocytic targets is based solely upon receptor-ligand binding. Here we report an important new criterion, that mechanical parameters of the target can dramatically affect the efficiency of phagocytosis. When presented with particles of identical chemical properties but different rigidity, macrophages showed a strong preference to engulf rigid objects. Furthermore, phagocytosis of soft particles can be stimulated with the microinjection of constitutively active Rac1 but not RhoA, and with lysophosphatidic acid, an agent known to activate the small GTP-binding proteins of the Rho family. These data suggest a Rac1-dependent mechanosensory mechanism for phagocytosis, which probably plays an important role in a number of physiological and pathological processes from embryonic development to autoimmune diseases.
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Affiliation(s)
- Karen A Beningo
- University of Massachusetts Medical School, Department of Physiology, 377 Plantation, Room 327, Worcester, MA 01605, USA
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219
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Ushinsky SC, Harcus D, Ash J, Dignard D, Marcil A, Morchhauser J, Thomas DY, Whiteway M, Leberer E. CDC42 is required for polarized growth in human pathogen Candida albicans. EUKARYOTIC CELL 2002; 1:95-104. [PMID: 12455975 PMCID: PMC118047 DOI: 10.1128/ec.1.1.95-104.2002] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cdc42p is a member of the RAS superfamily of GTPases and plays an essential role in polarized growth in many eukaryotic cells. We cloned the Candida albicans CaCDC42 by functional complementation in Saccharomyces cerevisiae and analyzed its function in C. albicans. A double deletion of CaCDC42 was made in a C. albicans strain containing CaCDC42 under the control of the PCK1 promoter. When expression of the heterologous copy of CaCDC42 was repressed in this strain, the cells ceased proliferation. These arrested cells were large, round, and unbudded and contained predominantly two nuclei. The PCK1-mediated overexpression of wild-type CaCdc42p had no effect on cells. However, in cells overexpressing CaCdc42p containing the dominant-negative D118A substitution, proliferation was blocked and the arrested cells were large, round, unbudded, and multinucleated, similar to the phenotype of the cdc42 double-deletion strain. Cells overexpressing CaCdc42p containing the hyperactive G12V substitution also ceased proliferation in yeast growth medium; in this case the arrested cells were multinucleated and multibudded. An intact CAAX box is essential for the phenotypes associated with either CaCdc42p(G12V) or CaCdc42p(D118A) ectopic expression, suggesting that membrane attachment is involved in CaCdc42p function. In addition, the lethality caused by ectopic expression of CaCdc42p(G12V) was suppressed by deletion of CST20 but not by deletion of CaCLA4. CaCdc42p function was also examined under hypha-inducing conditions. Cdc42p depletion prior to hyphal induction trapped cells in a round, unbudded state, while depletion triggered at the same time as hyphal induction permitted the initiation of germ tubes that failed to be extended. Ectopic expression of either the G12V or D118A substitution protein modified hyphal formation in a CAAX box-dependent manner. Thus, CaCdc42p function appears important for polarized growth of both the yeast and hyphal forms of C. albicans.
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Affiliation(s)
- Sophia C Ushinsky
- Eukaryotic Genetics, National Research Council Biotechnology Research Institute, Montreal, Quebec, Canada
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220
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Abstract
Enteropathogenic species of the genus Yersinia penetrate the intestinal epithelium and then spread to the lymphatic system, where they proliferate extracellularly. At this location, most other bacteria are effectively ingested and destroyed by the resident phagocytes. Yersinia, on the other hand binds to receptors on the external surface of phagocytes, and from this location it blocks the capacity of these cells to exert their phagocytic function via different receptors. The mechanism behind the resistance to phagocytosis involves the essential virulence factor YopH, a protein tyrosine phosphatase that is translocated into interacting target cells via a type III secretion machinery. YopH disrupts peripheral focal complexes of host cells, seen as a rounding up of infected cells. The focal complex proteins that are dephosphorylated by YopH are focal adhesion kinase and Crk-associated substrate, the latter of which is a common substrate in both professional and non-professional phagocytes. In macrophages additional substrates have been found, the Fyn-binding/SLP-76-associated protein and SKAP-HOM. Phagocytosis is a rapid process that is activated when the bacterium interacts with the phagocyte. Consequently, the effect exerted by a microbe to block this process has to be rapid and precise. This review deals with the mechanisms involved in impeding uptake as well as with the role of the YopH substrates and focal complex structures in normal cell function.
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Affiliation(s)
- Maria Fällman
- Department of Molecular Biology, Umeå University, Sweden.
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221
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Diakonova M, Bokoch G, Swanson JA. Dynamics of cytoskeletal proteins during Fcgamma receptor-mediated phagocytosis in macrophages. Mol Biol Cell 2002; 13:402-11. [PMID: 11854399 PMCID: PMC65636 DOI: 10.1091/mbc.01-05-0273] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Particle ingestion by phagocytosis results from sequential rearrangements of the actin cytoskeleton and overlying membrane. To assemble a chronology of molecular events during phagosome formation and to examine the contributions of phosphoinositide 3-kinase (PI 3-kinase) to these dynamics, a method was developed for synchronizing Fcgamma receptor-mediated phagocytosis by murine macrophages. Erythrocytes opsonized with complement component C3bi were bound to macrophages at 37degrees C, a condition that does not favor particle phagocytosis. Addition of soluble anti-erythrocyte IgG resulted in rapid opsonization of the bound erythrocytes, followed by their immediate internalization via phagocytosis. Cellular content of F-actin, as measured by binding of rhodamine-phalloidin, increased transiently during phagocytosis, and this increase was not diminished by inhibitors of PI 3-kinase. Immunofluorescence localization of myosins in macrophages fixed at various times during phagocytosis indicated that myosins II and IXb were concentrated in early phagosomes, myosin IC increased later, and myosin V appeared after phagosome closure. Other cytoskeletal proteins showed similar variations in the timing of their appearance in phagosomes. The PI 3-kinase inhibitor wortmannin did not change the dynamics of PI 3-kinase or ezrin localization but prevented the loss of PAK1 from phagosomes. These results suggest that PI 3-kinase deactivates PAK1, and that this may be needed for phagosome closure.
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Affiliation(s)
- Maria Diakonova
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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222
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Zha X, Genest J, McPherson R. Endocytosis is enhanced in Tangier fibroblasts: possible role of ATP-binding cassette protein A1 in endosomal vesicular transport. J Biol Chem 2001; 276:39476-83. [PMID: 11504722 DOI: 10.1074/jbc.m105067200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A human genetic disorder, Tangier disease, has been linked recently to mutations in ATP-binding cassette protein A1 (ABCA1). In addition to its function in apoprotein A-I-mediated lipid removal, ABCA1 was also shown to be a phosphatidylserine (PS) translocase that facilitates PS exofacial flipping. This PS translocation is crucial for the plasma membrane to produce protrusions enabling the engulfment of apoptotic cells. In this report, we show that ABCA1 also plays a role in endocytosis. Receptor-mediated endocytosis, probed by both transferrin and low density lipoprotein, is up-regulated by more than 50% in homozygous Tangier fibroblasts in comparison with controls. Fluid-phase uptake is increased similarly. We also demonstrate that bulk membrane flow, including lipid endocytosis and exocytosis, is accelerated greatly in Tangier cells. Moreover, endocytosis is similarly enhanced in normal fibroblasts when ABCA1 function is inhibited by glyburide, whereas glyburide has no effect on endocytosis in Tangier cells. In addition, we demonstrate a decreased annexin V binding in Tangier fibroblasts as compared with controls, supporting the notion that PS transmembrane distribution is indeed defective in the presence of ABCA1 mutations. Furthermore, adding a PS analog to the exofacial leaflet of the plasma membrane normalizes endocytosis in Tangier cells. Taken together, these data demonstrate that ABCA1 plays an important role in endocytosis. We speculate that this is related to the PS translocase function of ABCA1. A loss of functional ABCA1, as in the case of Tangier cells, enhances membrane inward bending and facilitates endocytosis.
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Affiliation(s)
- X Zha
- Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada
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223
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Castellano F, Le Clainche C, Patin D, Carlier MF, Chavrier P. A WASp-VASP complex regulates actin polymerization at the plasma membrane. EMBO J 2001; 20:5603-14. [PMID: 11598004 PMCID: PMC125672 DOI: 10.1093/emboj/20.20.5603] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Proteins of the Wiskott-Aldrich syndrome and Ena/VASP families both play essential functions in the regulation of actin dynamics at the cell leading edge. However, possibilities of functional interplay between members of these two families have not been addressed. Here we show that, in hemopoietic cells, recruitment of the C-terminal VCA (Verprolin homology, Cofilin homology, Acidic) domain of WASp at the plasma membrane by a ligand technique using rapamycin as an intermediate is not sufficient to elicit efficient Arp2/3 complex-mediated actin polymerization. Other domains of WASp, in particular the proline-rich domain, are required for the formation of actin-rich structures. An in vitro analysis demonstrates that the proline-rich domain of WASp binds VASP with an affinity of approximately 10(6) M(-1). In addition, WASp and VASP both accumulate in actin-rich phagocytic cups. Finally, in a reconstituted motility medium, VASP enhances actin-based propulsion of WASp-coated beads in a fashion reminiscent of its effect on Listeria movement. We propose that VASP and WASp cooperation is essential in stimulating actin assembly and membrane protrusion at the leading edge.
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Affiliation(s)
| | - Christophe Le Clainche
- Laboratoire de la Dynamique de la Membrane et du Cytosquelette, Centre National de la Recherche Scientifique UMR 144, Institut Curie, 26 rue d’Ulm, 75241 Paris Cedex 5 and
Laboratoire d’Enzymologie et Biochimie Structurale, CNRS, 91198 Gif-sur-Yvette, France Corresponding author e-mail:
| | | | - Marie-France Carlier
- Laboratoire de la Dynamique de la Membrane et du Cytosquelette, Centre National de la Recherche Scientifique UMR 144, Institut Curie, 26 rue d’Ulm, 75241 Paris Cedex 5 and
Laboratoire d’Enzymologie et Biochimie Structurale, CNRS, 91198 Gif-sur-Yvette, France Corresponding author e-mail:
| | - Philippe Chavrier
- Laboratoire de la Dynamique de la Membrane et du Cytosquelette, Centre National de la Recherche Scientifique UMR 144, Institut Curie, 26 rue d’Ulm, 75241 Paris Cedex 5 and
Laboratoire d’Enzymologie et Biochimie Structurale, CNRS, 91198 Gif-sur-Yvette, France Corresponding author e-mail:
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224
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Gumienny TL, Brugnera E, Tosello-Trampont AC, Kinchen JM, Haney LB, Nishiwaki K, Walk SF, Nemergut ME, Macara IG, Francis R, Schedl T, Qin Y, Van Aelst L, Hengartner MO, Ravichandran KS. CED-12/ELMO, a novel member of the CrkII/Dock180/Rac pathway, is required for phagocytosis and cell migration. Cell 2001; 107:27-41. [PMID: 11595183 DOI: 10.1016/s0092-8674(01)00520-7] [Citation(s) in RCA: 445] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The C. elegans genes ced-2, ced-5, and ced-10, and their mammalian homologs crkII, dock180, and rac1, mediate cytoskeletal rearrangements during phagocytosis of apoptotic cells and cell motility. Here, we describe an additional member of this signaling pathway, ced-12, and its mammalian homologs, elmo1 and elmo2. In C. elegans, CED-12 is required for engulfment of dying cells and for cell migrations. In mammalian cells, ELMO1 functionally cooperates with CrkII and Dock180 to promote phagocytosis and cell shape changes. CED-12/ELMO-1 binds directly to CED-5/Dock180; this evolutionarily conserved complex stimulates a Rac-GEF, leading to Rac1 activation and cytoskeletal rearrangements. These studies identify CED-12/ELMO as an upstream regulator of Rac1 that affects engulfment and cell migration from C. elegans to mammals.
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Affiliation(s)
- T L Gumienny
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11743, USA
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225
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Wu YC, Tsai MC, Cheng LC, Chou CJ, Weng NY. C. elegans CED-12 acts in the conserved crkII/DOCK180/Rac pathway to control cell migration and cell corpse engulfment. Dev Cell 2001; 1:491-502. [PMID: 11703940 DOI: 10.1016/s1534-5807(01)00056-9] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have identified and characterized a novel C. elegans gene, ced-12, that functions in the conserved GTPase signaling pathway mediated by CED-2/Crkll, CED-5/DOCK180, and CED-10/Rac to control cell migration and phagocytosis of apoptotic cells. We provide evidence that ced-12 likely acts upstream of ced-10 during cell migration and phagocytosis and that CED-12 physically interacts with CED-5 and forms a ternary complex with CED-2 in vitro. We propose that the formation and localization of a CED-2-CED-5-CED-12 ternary complex to the plasma membrane activates CED-10, leading to the cytoskeletal reorganization that occurs in the polarized extension of cell surfaces in engulfing cells and migrating cells. We suggest that CED-12 counterparts in higher organisms regulate cytoskeleton dynamics, as CED-12 does in C. elegans.
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Affiliation(s)
- Y C Wu
- Department of Zoology, National Taiwan University, Taipei.
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226
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Abstract
Exposure of cells to a variety of external signals causes rapid changes in plasma membrane morphology. Plasma membrane dynamics, including membrane ruffle and microspike formation, fusion or fission of intracellular vesicles, and the spatial organization of transmembrane proteins, is directly controlled by the dynamic reorganization of the underlying actin cytoskeleton. Two members of the Rho family of small GTPases, Cdc42 and Rac, have been well established as mediators of extracellular signaling events that impact cortical actin organization. Actin-based signaling through Cdc42 and Rac ultimately results in activation of the actin-related protein (Arp) 2/3 complex, which promotes the formation of branched actin networks. In addition, the activity of both receptor and non-receptor protein tyrosine kinases along with numerous actin binding proteins works in concert with Arp2/3-mediated actin polymerization in regulating the formation of dynamic cortical actin-associated structures. In this review we discuss the structure and role of the cortical actin binding protein cortactin in Rho GTPase and tyrosine kinase signaling events, with the emphasis on the roles cortactin plays in tyrosine phosphorylation-based signal transduction, regulating cortical actin assembly, transmembrane receptor organization and membrane dynamics. We also consider how aberrant regulation of cortactin levels contributes to tumor cell invasion and metastasis.
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Affiliation(s)
- S A Weed
- Department of Craniofacial Biology, University of Colorado Health Sciences Center, Denver, Colorado, CO 80262, USA.
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227
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Werner E, Kheradmand F, Isberg RR, Werb Z. Phagocytosis mediated by Yersinia invasin induces collagenase-1 expression in rabbit synovial fibroblasts through a proinflammatory cascade. J Cell Sci 2001; 114:3333-43. [PMID: 11591821 PMCID: PMC2788993 DOI: 10.1242/jcs.114.18.3333] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We show that the interaction of the Yersinia surface protein, invasin, with rabbit synovial fibroblasts mediates bead phagocytosis and induces expression of interleukin 1α (IL-1α), tumor necrosis factor-α (TNF-α) and MMP-1/collagenase-1 (CL-1). Presentation of invasin as a ligand on the surface of 4.5 μm beads induced phagocytosis and increased CL-1 expression 20-fold after 24 hours. By contrast, presentation of invasin as a spreading substrate did not induce CL-1 expression. CL-1 induction following phagocytosis of invasin-coated beads was mediated by a mechanism dependent on high-affinity binding to β1 integrins and the function of the small GTPase RhoA. Expression of a function-perturbing mutant, RhoAN19, abrogated bead-induced CL-1 expression. RhoA activation coupled bead phagocytosis with signal transduction because expression of constitutively active mutant RhoV14 was sufficient to trigger CL-1 expression. The signal-transduction cascade elicited by bead phagocytosis triggered NFκB activation, stimulating a proinflammatory cellular response with transient increases in TNF-α production that peaked at 2 hours and induction of IL-1α that was sustained for at least 10 hours. Inhibition of IL-1α function by blocking antibodies or IL-1 receptor antagonist showed that IL-1α is the autocrine intermediary for subsequent CL-1 induction.
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Affiliation(s)
- Erica Werner
- Department of Anatomy, University of California, San Francisco, CA 94143-0452, USA
| | - Farrah Kheradmand
- Department of Anatomy, University of California, San Francisco, CA 94143-0452, USA
| | - Ralph R. Isberg
- Department of Microbiology and Molecular Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Zena Werb
- Department of Anatomy, University of California, San Francisco, CA 94143-0452, USA
- Author for correspondence ()
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228
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Al-Haddad A, Shonn MA, Redlich B, Blocker A, Burkhardt JK, Yu H, Hammer JA, Weiss DG, Steffen W, Griffiths G, Kuznetsov SA. Myosin Va bound to phagosomes binds to F-actin and delays microtubule-dependent motility. Mol Biol Cell 2001; 12:2742-55. [PMID: 11553713 PMCID: PMC59709 DOI: 10.1091/mbc.12.9.2742] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We established a light microscopy-based assay that reconstitutes the binding of phagosomes purified from mouse macrophages to preassembled F-actin in vitro. Both endogenous myosin Va from mouse macrophages and exogenous myosin Va from chicken brain stimulated the phagosome-F-actin interaction. Myosin Va association with phagosomes correlated with their ability to bind F-actin in an ATP-regulated manner and antibodies to myosin Va specifically blocked the ATP-sensitive phagosome binding to F-actin. The uptake and retrograde transport of phagosomes from the periphery to the center of cells in bone marrow macrophages was observed in both normal mice and mice homozygous for the dilute-lethal spontaneous mutation (myosin Va null). However, in dilute-lethal macrophages the accumulation of phagosomes in the perinuclear region occurred twofold faster than in normal macrophages. Motion analysis revealed saltatory phagosome movement with temporarily reversed direction in normal macrophages, whereas almost no reversals in direction were observed in dilute-lethal macrophages. These observations demonstrate that myosin Va mediates phagosome binding to F-actin, resulting in a delay in microtubule-dependent retrograde phagosome movement toward the cell center. We propose an "antagonistic/cooperative mechanism" to explain the saltatory phagosome movement toward the cell center in normal macrophages.
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Affiliation(s)
- A Al-Haddad
- Institut für Zellbiologie und Biosystemtechnik, FB Biowissenschaften, Universität Rostock, D-18051 Rostock, Germany
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229
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Santamarina-Fojo S, Remaley AT, Neufeld EB, Brewer HB. Regulation and intracellular trafficking of the ABCA1 transporter. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)30266-2] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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230
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Kuwae A, Yoshida S, Tamano K, Mimuro H, Suzuki T, Sasakawa C. Shigella invasion of macrophage requires the insertion of IpaC into the host plasma membrane. Functional analysis of IpaC. J Biol Chem 2001; 276:32230-9. [PMID: 11413141 DOI: 10.1074/jbc.m103831200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Shigella infects residential macrophages via the M cell entry, after which the pathogen induces macrophage cell death. The bacterial strategy of macrophage infection, however, remains largely speculative. Wild type Shigella flexneri (YSH6000) invaded macrophages more efficiently than the noninvasive mutants, where YSH6000 induced large scale lamellipodial extension including ruffle formation around the bacteria. When macrophages were infected with the noninvasive ipaC mutant, the invasiveness and induction of membrane extension were dramatically reduced as compared with that of YSH6000. J774 macrophages infected with YSH6000 showed tyrosine phosphorylation of several proteins including paxillin and c-Cbl, and this pattern was distinctive from those stimulated by Salmonella typhimurium or phorbol ester. Upon addition of IpaC into the external medium of macrophages, membrane extensions were rapidly induced, and this promoted uptake of Escherichia coli. The exogenously added IpaC was found to be integrated into the host cell membrane as detected by immunostaining. The IpaC domain required for the induction of membrane extension from J774 was narrowed down within the region of residues 117-169, which contains a putative membrane-spanning sequence. Our data indicate that Shigella directs its own entry into macrophages, and the IpaC domain which is required for the association with its host membrane is crucial.
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Affiliation(s)
- A Kuwae
- Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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231
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Longenecker KL, Lewis ME, Chikumi H, Gutkind JS, Derewenda ZS. Structure of the RGS-like domain from PDZ-RhoGEF: linking heterotrimeric g protein-coupled signaling to Rho GTPases. Structure 2001; 9:559-69. [PMID: 11470431 DOI: 10.1016/s0969-2126(01)00620-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND The multidomain PDZ-RhoGEF is one of many known guanine nucleotide exchange factors that upregulate Rho GTPases. PDZ-RhoGEF and related family members play a critical role in a molecular signaling pathway from heterotrimeric G protein-coupled receptors to Rho proteins. A approximately 200 residue RGS-like (RGSL) domain in PDZ-RhoGEF and its homologs is responsible for the direct association with Galpha12/13 proteins. To better understand structure-function relationships, we initiated crystallographic studies of the RGSL domain from human PDZ-RhoGEF. RESULTS A recombinant construct of the RGSL domain was expressed in Escherichia coli and purified, but it did not crystallize. Alternative constructs were designed based on a novel strategy of targeting lysine and glutamic acid residues for mutagenesis to alanine. A triple-point mutant functionally identical to the wild-type protein was crystallized, and its structure was determined by the MAD method using Se-methionine (Se-Met) incorporation. A molecular model of the RGSL domain was refined at 2.2 A resolution, revealing an all-helical tertiary fold with the mutations located at intermolecular lattice contacts. CONCLUSIONS The first nine helices adopt a fold similar to that observed for RGS proteins, although the sequence identity with other such known structures is below 20%. The last three helices are an integral extension of the RGS fold, packing tightly against helices 3 and 4 with multiple hydrophobic interactions. Comparison with RGS proteins suggests features that are likely relevant for interaction with G proteins. Finally, we conclude that the strategy used to produce crystals was beneficial and might be applicable to other proteins resistant to crystallization.
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Affiliation(s)
- K L Longenecker
- Department of Molecular Physiology and Biological Physics, University of Virginia, P.O. Box 800736, Charlottesville, VA 22908, USA
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233
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Asano S, Mishima M, Nishida E. Coronin forms a stable dimer through its C-terminal coiled coil region: an implicated role in its localization to cell periphery. Genes Cells 2001; 6:225-35. [PMID: 11260266 DOI: 10.1046/j.1365-2443.2001.00416.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND Coronin is an actin-binding protein, which contains WD (Trp-Asp) repeats and a coiled-coil motif, and plays a role in regulating organization of the actin cytoskeletal network. Coronin localizes to the cell periphery, is involved in lamellipodium extension, and has an implicated role in cytokinesis, cell motility and phagocytosis. RESULTS Our experiments with two different tagged forms of Xenopus coronin (Xcoronin) have shown that Xcoronin forms an oligomer. This oligomer complex is stable, resistant to 2.4 M NaCl, 0.6 M KI or 2 M urea. Physiochemical analysis of endogenous Xcoronin and the protein expressed in COS7 cells or in bacteria has revealed that the oligomer complex is an Xcoronin dimer. A C-terminal coiled-coil motif of Xcoronin is necessary and sufficient for the dimerization. Mutations in the coiled-coil motif generated dimerization deficient mutants of Xcoronin. Moreover, these mutant forms of Xcoronin failed to localize to the cell periphery, suggesting that dimerization is important for the proper subcellular localization of Xcoronin. CONCLUSION Xcoronin forms a stable dimer via its C-terminal coiled-coil region. We propose that coronin dimerization is necessary for its proper subcellular localization and function.
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Affiliation(s)
- S Asano
- Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Japan
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234
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Utech M, Höbbel G, Rust S, Reinecke H, Assmann G, Walter M. Accumulation of RhoA, RhoB, RhoG, and Rac1 in fibroblasts from Tangier disease subjects suggests a regulatory role of Rho family proteins in cholesterol efflux. Biochem Biophys Res Commun 2001; 280:229-36. [PMID: 11162504 DOI: 10.1006/bbrc.2000.4061] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Tangier disease (TD) is an inherited disorder of lipid metabolism characterized by very low high density lipoprotein (HDL) plasma levels, cellular cholesteryl ester accumulation and reduced cholesterol excretion in response to HDL apolipoproteins. Molecular defects in the ATP binding cassette transporter 1 (ABCA1) have recently been identified as the cause of TD. ABCA1 plays a key role in the translocation of cholesterol across the plasma membrane, and defective ABCA1 causes cholesterol storage in TD cells. However, the exact relationship of many of the biochemical and morphological abnormalities in TD to ABCA1 is unknown. Since small GTP-binding proteins are important regulators of many cellular functions, we characterized these proteins in normal and TD fibroblasts using the [alpha-32P]GTP overlay technique and Western blotting of SDS and isoelectric focusing gels. Our results indicate that GTP-binding proteins of the Rho family (RhoA, RhoB, RhoG, Rac-1) are enriched in fibroblasts from TD patients. The accumulation of small G proteins may have potential implications for the TD phenotype and the regulation of cholesterol excretion in TD cells.
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Affiliation(s)
- M Utech
- Institut für Klinische Chemie und Laboratoriumsmedizin, Universität Munster, Albert-Schweitzer-Str. 33, 48149 Münster, Germany
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