title: Vav1/Rac-dependent actin cytoskeleton reorganization is required for lipid raft clustering in T cells.
abstract: Formation of the immunological synapse (IS) in T cells involves large scale molecular movements that are mediated, at least in part, by reorganization of the actin cytoskeleton. Various signaling proteins accumulate at the IS and are localized in specialized membrane microdomains, known as lipid rafts. We have shown previously that lipid rafts cluster and localize at the IS in antigen-stimulated T cells. Here, we provide evidence that lipid raft polarization to the IS depends on an intracellular pathway that involves Vav1, Rac, and actin cytoskeleton reorganization. Thus, lipid rafts did not translocate to the IS in Vav1-deficient (Vav1-/-) T cells upon antigen stimulation. Similarly, T cell receptor transgenic Jurkat T cells also failed to translocate lipid rafts to the IS when transfected with dominant negative Vav1 mutants. Raft polarization induced by membrane-bound cholera toxin cross-linking was also abolished in Jurkat T cells expressing dominant negative Vav1 or Rac mutants and in cells treated with inhibitors of actin polymerization. However, Vav overexpression that induced F-actin polymerization failed to induce lipid rafts clustering. Therefore, Vav is necessary, but not sufficient, to regulate lipid rafts clustering and polarization at the IS, suggesting that additional signals are required.
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA.
authors.forename: M
authors.initials: M
authors.lastname: Villalba
authors.forename: K
authors.initials: K
authors.lastname: Bi
authors.forename: F
authors.initials: F
authors.lastname: Rodriguez
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Schoenberger
authors.forename: A
authors.initials: A
authors.lastname: Altman
mesh_terms: D000199:Actins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D003599:Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D019169:Jurkat Cells; D021962:Membrane Microdomains / Q000378:metabolism*; D016296:Mutagenesis; D011493:Protein Kinase C / Q000378:metabolism; D000074121:Protein Kinase C-theta; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051567:Proto-Oncogene Proteins c-vav; D013601:T-Lymphocytes / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D020744:rac GTP-Binding Proteins