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Miletic AV, Graham DB, Sakata-Sogawa K, Hiroshima M, Hamann MJ, Cemerski S, Kloeppel T, Billadeau DD, Kanagawa O, Tokunaga M, Swat W. Vav links the T cell antigen receptor to the actin cytoskeleton and T cell activation independently of intrinsic Guanine nucleotide exchange activity. PLoS One 2009; 4:e6599. [PMID: 19672294 PMCID: PMC2719804 DOI: 10.1371/journal.pone.0006599] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 07/09/2009] [Indexed: 12/19/2022] Open
Abstract
Background T cell receptor (TCR) engagement leads to formation of signaling microclusters and induction of rapid and dynamic changes in the actin cytoskeleton, although the exact mechanism by which the TCR initiates actin polymerization is incompletely understood. The Vav family of guanine nucleotide exchange factors (GEF) has been implicated in generation of TCR signals and immune synapse formation, however, it is currently not known if Vav's GEF activity is required in T cell activation by the TCR in general, and in actin polymerization downstream of the TCR in particular. Methodology/Principal Findings Here, we report that Vav1 assembles into signaling microclusters at TCR contact sites and is critical for TCR-initiated actin polymerization. Surprisingly, Vav1 functions in TCR signaling and Ca++ mobilization via a mechanism that does not appear to strictly depend on the intrinsic GEF activity. Conclusions/Significance We propose here a model in which Vav functions primarily as a tyrosine phosphorylated linker-protein for TCR activation of T cells. Our results indicate that, contrary to expectations based on previously published studies including from our own laboratory, pharmacological inhibition of Vav1's intrinsic GEF activity may not be an effective strategy for T cell-directed immunosuppressive therapy.
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Affiliation(s)
- Ana V. Miletic
- Department of Pathology and Immunology, Washington University School of Medicine and Siteman Cancer Center, St. Louis, Missouri, United States of America
| | - Daniel B. Graham
- Department of Pathology and Immunology, Washington University School of Medicine and Siteman Cancer Center, St. Louis, Missouri, United States of America
| | - Kumiko Sakata-Sogawa
- Research Unit for Single Molecule Immunoimaging, RIKEN Center for Allergy and Immunology, Yokohama, Kanagawa, Japan
| | - Michio Hiroshima
- Research Unit for Single Molecule Immunoimaging, RIKEN Center for Allergy and Immunology, Yokohama, Kanagawa, Japan
| | - Michael J. Hamann
- Department of Immunology and Division of Oncology Research, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America
| | - Saso Cemerski
- Department of Pathology and Immunology, Washington University School of Medicine and Siteman Cancer Center, St. Louis, Missouri, United States of America
| | - Tracie Kloeppel
- Department of Pathology and Immunology, Washington University School of Medicine and Siteman Cancer Center, St. Louis, Missouri, United States of America
| | - Daniel D. Billadeau
- Department of Immunology and Division of Oncology Research, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America
| | - Osami Kanagawa
- Laboratory for Autoimmune Regulation, RIKEN Center for Allergy and Immunology, Yokohama, Kanagawa, Japan
| | - Makio Tokunaga
- Research Unit for Single Molecule Immunoimaging, RIKEN Center for Allergy and Immunology, Yokohama, Kanagawa, Japan
- Structural Biology Center, National Institute of Genetics, The Graduate University for Advanced Studies, Mishima, Shizuoka, Japan
- Department of Genetics, The Graduate University for Advanced Studies, Mishima, Shizuoka, Japan
| | - Wojciech Swat
- Department of Pathology and Immunology, Washington University School of Medicine and Siteman Cancer Center, St. Louis, Missouri, United States of America
- * E-mail:
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Park ER, Eblen ST, Catling AD. MEK1 activation by PAK: a novel mechanism. Cell Signal 2007; 19:1488-96. [PMID: 17314031 PMCID: PMC2233889 DOI: 10.1016/j.cellsig.2007.01.018] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2006] [Revised: 01/12/2007] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
Extracellular signal-Regulated Kinase (ERK) controls a variety of cellular processes, including cell proliferation and cell motility. While oncogenic mutations in Ras and B-Raf result in deregulated ERK activity and proliferation and migration in some tumor cells, other tumors exhibit elevated ERK signaling in the absence of these mutations. Here we provide evidence that PAK can directly activate MEK1 by a mechanism distinct from conventional Ras/Raf mediated activation. We find that PAK phosphorylation of MEK1 serine 298 stimulates MEK1 autophosphorylation on the activation loop, and activation of MEK1 activity towards ERK in in vitro reconstitution experiments. Serines 218 and/or 222 in the MEK1 activation loop are required for PAK-stimulated MEK1 activity towards ERK. MEK2, which is a poor target for PAK phosphorylation in cells, is not activated in this manner. Tissue culture experiments verify that this mechanism is used in suspended fibroblasts expressing mutationally activated PAK1. We speculate that aberrant signaling through PAK may directly induce anchorage-independent MEK1 activation in tumor cells lacking oncogenic Ras or Raf mutations, and that this mechanism may contribute to localized MEK signaling in focal contacts and adhesions during cell adhesion or migration.
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Affiliation(s)
- Electa R. Park
- Department of Biochemistry, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
| | - Scott T. Eblen
- Department of Pharmacology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Andrew D. Catling
- Department of Pharmacology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
- Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
- *Corresponding author. Department of Pharmacology, Medical Education Building, 1901 Perdido Street, New Orleans, LA 70112, United States. Tel.: +1 504 568 4740; fax: +1 504 568 2361. E-mail address: (A.D. Catling)
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Baust T, Czupalla C, Krause E, Bourel-Bonnet L, Hoflack B. Proteomic analysis of adaptor protein 1A coats selectively assembled on liposomes. Proc Natl Acad Sci U S A 2006; 103:3159-64. [PMID: 16492770 PMCID: PMC1413908 DOI: 10.1073/pnas.0511062103] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Coat components localize to specific membrane domains, where they sort selected transmembrane proteins. To study how clathrin coats are stabilized on such domains and to identify the protein networks involved, we combined proteomic screens and in vitro liposome-based assays that recapitulate the fidelity of protein sorting in vivo. Our study identifying approximately 40 proteins on AP-1A-coated liposomes revealed that AP-1A coat assembly triggers the concomitant recruitment of Rac1, its effectors, and the Wave/Scar complex as well as that of Rab11 and Rab14. The coordinated recruitment of these different machineries requires a mosaic of membrane components comprising the GTPase ADP-ribosylation factor 1, sorting signals in selected transmembrane proteins, and phosphatidylinositol 4-phosphate. These results demonstrate that the combinatorial use of low-affinity binding sites present on the same membrane domain accounts not only for a selective coat assembly but also for the coordinated assembly of selected machineries required for actin polymerization and subsequent membrane fusion.
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Affiliation(s)
- Thorsten Baust
- *Biotechnological Center, Dresden University of Technology, Tatzberg 47-51, 01307 Dresden,Germany
| | - Cornelia Czupalla
- *Biotechnological Center, Dresden University of Technology, Tatzberg 47-51, 01307 Dresden,Germany
| | - Eberhard Krause
- Institute of Molecular Pharmacology, Robert-Rössle-Strasse 10, 13125 Berlin,Germany; and
| | - Line Bourel-Bonnet
- Faculté de Pharmacie de Lille, Laboratoire de Chimie Organique, 3, Rue du Pr. Laguesse, BP 83, 59006 Lille Cedex,France
| | - Bernard Hoflack
- *Biotechnological Center, Dresden University of Technology, Tatzberg 47-51, 01307 Dresden,Germany
- To whom correspondence should be addressed. E-mail:
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Leisner TM, Liu M, Jaffer ZM, Chernoff J, Parise LV. Essential role of CIB1 in regulating PAK1 activation and cell migration. ACTA ACUST UNITED AC 2005; 170:465-76. [PMID: 16061695 PMCID: PMC2171473 DOI: 10.1083/jcb.200502090] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
p21-activated kinases (PAKs) regulate many cellular processes, including cytoskeletal rearrangement and cell migration. In this study, we report a direct and specific interaction of PAK1 with a 22-kD Ca2+-binding protein, CIB1, which results in PAK1 activation both in vitro and in vivo. CIB1 binds to PAK1 within discrete regions surrounding the inhibitory switch domain in a calcium-dependent manner, providing a potential mechanism of CIB1-induced PAK1 activation. CIB1 overexpression significantly decreases cell migration on fibronectin as a result of a PAK1-and LIM kinase–dependent increase in cofilin phosphorylation. Conversely, the RNA interference–mediated depletion of CIB1 increases cell migration and reduces normal adhesion-induced PAK1 activation and cofilin phosphorylation. Together, these results demonstrate that endogenous CIB1 is required for regulated adhesion-induced PAK1 activation and preferentially induces a PAK1-dependent pathway that can negatively regulate cell migration. These results point to CIB1 as a key regulator of PAK1 activation and signaling.
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Affiliation(s)
- Tina M Leisner
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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