title: T cell receptor-dependent tyrosine phosphorylation of beta2-chimaerin modulates its Rac-GAP function in T cells.
abstract: The actin cytoskeleton has an important role in the organization and function of the immune synapse during antigen recognition. Dynamic rearrangement of the actin cytoskeleton in response to T cell receptor (TCR) triggering requires the coordinated activation of Rho family GTPases that cycle between active and inactive conformations. This is controlled by GTPase-activating proteins (GAP), which regulate inactivation of Rho GTPases, and guanine exchange factors, which mediate their activation. Whereas much attention has centered on guanine exchange factors for Rho GTPases in T cell activation, the identity and functional roles of the GAP in this process are largely unknown. We previously reported beta2-chimaerin as a diacylglycerol-regulated Rac-GAP that is expressed in T cells. We now demonstrate Lck-dependent phosphorylation of beta2-chimaerin in response to TCR triggering. We identify Tyr-153 as the Lck-dependent phosphorylation residue and show that its phosphorylation negatively regulates membrane stabilization of beta2-chimaerin, decreasing its GAP activity to Rac. This study establishes the existence of TCR-dependent regulation of beta2-chimaerin and identifies a novel mechanism for its inactivation.
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas, E-28049 Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Siliceo
authors.forename: Isabel
authors.initials: I
authors.lastname: Mérida
mesh_terms: D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D007376:Interleukin-2; D009363:Neoplasm Proteins; D011948:Receptors, Antigen, T-Cell; C079844:beta-chimaerin; D014443:Tyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D020744:rac GTP-Binding Proteins