title: Formins regulate the actin-related protein 2/3 complex-independent polarization of the centrosome to the immunological synapse.
abstract: T cell receptor (TCR)-mediated cytoskeletal reorganization is considered to be actin-related protein (Arp) 2/3 complex dependent. We therefore examined the requirement for Arp2/3- and formin-dependent F-actin nucleation during T cell activation. We demonstrated that without Arp2/3-mediated actin nucleation, stimulated T cells could not form an F-actin-rich lamellipod, but instead produced polarized filopodia-like structures. Moreover, the microtubule-organizing center (MTOC, or centrosome), which rapidly reorients to the immunological synapse through an unknown mechanism, polarized in the absence of Arp2/3. Conversely, the actin-nucleating formins, Diaphanous-1 (DIA1) and Formin-like-1 (FMNL1), did not affect TCR-stimulated F-actin-rich structures, but instead displayed unique patterns of centrosome colocalization and controlled TCR-mediated centrosome polarization. Depletion of FMNL1 or DIA1 in cytotoxic lymphocytes abrogated cell-mediated killing. Altogether, our results have identified Arp2/3 complex-independent cytoskeletal reorganization events in T lymphocytes and indicate that formins are essential cytoskeletal regulators of centrosome polarity in T cells.
authors.affiliation: Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Gomez
authors.forename: Karan
authors.initials: K
authors.lastname: Kumar
authors.forename: Ricardo B
authors.initials: RB
authors.lastname: Medeiros
authors.forename: Yoji
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Leibson
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Billadeau
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000276:immunology / Q000378:metabolism*; D000199:Actins / Q000276:immunology / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism; D016764:Cell Polarity / Q000276:immunology*; D018385:Centrosome / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000276:immunology / Q000378:metabolism*; D003599:Cytoskeleton / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D000080865:Formins; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D008855:Microscopy, Electron, Scanning; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C108962:DIAPH1 protein, human; C476204:FMNL1 protein, human; D000080865:Formins