TCR, LFA-1, and CD28 play unique and complementary roles in signaling T cell cytoskeletal reorganization.
T cells interacting with APCs undergo rearrangement of surface receptors and cytoskeletal elements to face the zone of contact with the APC. This polarization process is thought to affect T cell signaling by organizing a specialized domain on the T cell surface and to direct T cell effector function toward the appropriate APC. We have investigated the contribution of TCR, CD28, and LFA-1 signaling to T cell cytoskeletal polarization by assaying the response of an Ag-specific Th1 clone toward a panel of transfected APCs expressing MHC class II alone or in combination with ICAM-1 or B7-1. We show that polarization of talin, an actin-binding protein, occurs in response to integrin engagement. In contrast, reorientation of the T cell microtubule-organizing center (MTOC) is dependent on and directed toward the site of TCR signaling, regardless of whether integrins or costimulatory molecules are engaged. MTOC reorientation in response to peptide-MHC complexes is sensitive to the phosphatidylinositol 3-kinase inhibitor wortmannin. CD28 coengagement overcomes this sensitivity, as does activation via Ab cross-linking of the TCR or via covalent peptide-MHC complexes, suggesting that phosphatidylinositol 3-kinase is not required per se but rather plays a role in signal amplification. Engagement of TCR in trans with LFA-1 results in separation of MTOC reorientation and cortical cytoskeletal polarization events, indicating that the two processes are not directly mechanistically linked. These studies show that T cells mobilize individual cytoskeletal components in response to distinct and specific cell surface interactions.
Sedwick
C E
CE
Department of Pharmacology and Physiology, University of Chicago, Chicago, IL 60637, USA.
Morgan
M M
MM
Jusino
L
L
Cannon
J L
JL
Miller
J
J
Burkhardt
J K
JK
D000199:Actins / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000938:Antigen-Presenting Cells / Q000276:immunology; D018122:B7-1 Antigen / Q000235:genetics / Q000378:metabolism; D018106:CD28 Antigens / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D016764:Cell Polarity; D003599:Cytoskeleton / Q000276:immunology* / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D016608:Talin / Q000378:metabolism; D018417:Th1 Cells / Q000276:immunology / Q000648:ultrastructure; D014162:Transfection; D000077191:Wortmannin