title: Beta2-chimaerin provides a diacylglycerol-dependent mechanism for regulation of adhesion and chemotaxis of T cells.
abstract: The small GTPase Rac contributes to regulation of cytoskeletal rearrangement during chemokine-induced lymphocyte adhesion and migration in a multi-step process that is very precisely coordinated. Chimaerins are Rac1-specific GTPase-activating proteins of unknown biological function, which have a canonical diacylglycerol C1-binding domain. Here we demonstrate endogenous expression of beta2-chimaerin in T lymphocytes and study the functional role of this protein in phorbol ester and chemokine (CXCL12)-regulated T-cell responses. We used green fluorescent protein-tagged beta2-chimaerin and phorbol ester stimulation to investigate changes in protein localization in living lymphocytes. Our results demonstrate that active Rac cooperates with C1-dependent phorbol ester binding to induce sustained GFP-beta2-chimaerin localization to the membrane. Subcellular distribution of GFP beta2-chimaerin in living cells showed no major changes following CXCL12 stimulation. Nonetheless Rac1-GTP levels were severely inhibited in GFP-beta2-chimaerin-expressing cells, which displayed reduced CXCL12-induced integrin-dependent adhesion and spreading. This effect was dependent on chimaerin GTPase-activating protein function and required diacylglycerol generation. Whereas beta2-chimaerin overexpression decreased static adhesion, it enhanced CXCL12-dependent migration via receptor-dependent diacylglycerol production. These studies demonstrate that beta2-chimaerin provides a novel, diacylglycerol-dependent mechanism for Rac regulation in T cells and suggest a functional role for this protein in Rac-mediated cytoskeletal remodeling.
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología/CSIC, Cantoblanco, E-28049 Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Siliceo
authors.forename: David
authors.initials: D
authors.lastname: García-Bernal
authors.forename: Silvia
authors.initials: S
authors.lastname: Carrasco
authors.forename: Ernesto
authors.initials: E
authors.lastname: Díaz-Flores
authors.forename: Federico
authors.initials: F
authors.lastname: Coluccio Leskow
authors.forename: Federico C
authors.initials: FC
authors.lastname: Leskow
authors.forename: Joaquín
authors.initials: J
authors.lastname: Teixidó
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Kazanietz
authors.forename: Isabel
authors.initials: I
authors.lastname: Mérida
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology*; D004075:Diglycerides / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D019169:Jurkat Cells; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D004075:Diglycerides; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D019010:Vascular Cell Adhesion Molecule-1; C079844:beta-chimaerin; D020830:rac1 GTP-Binding Protein; D013755:Tetradecanoylphorbol Acetate