PKCθ plays an essential role in activation of mature T cells via stimulation of AP-1 and NF-κB, and is known to selectively translocate to the immunological synapse in antigen-stimulated T cells. Recently, we reported that a Vav/Rac pathway which depends on actin cytoskeleton reorganization mediates selective recruitment of PKCθ to the membrane or cytoskeleton and its catalytic activation by anti-CD3/CD28 costimulation. Because this pathway acted selectively on PKCθ, we addressed here the question of whether the translocation and activation of PKCθ in T cells is regulated by a unique pathway distinct from the conventional mechanism for PKC activation, i.e., PLC-mediated production of DAG. Using three independent approaches, i.e., a selective PLC inhibitor, a PLCγ1-deficient T cell line, or a dominant negative PLCγ1 mutant, we demonstrate that CD3/CD28-induced membrane recruitment and COOH-terminal phosphorylation of PKCθ are largely independent of PLC. In contrast, the same inhibitory strategies blocked the membrane translocation of PKCα. Membrane or lipid raft recruitment of PKCθ (but not PKCα) was absent in T cells treated with phosphatidylinositol 3-kinase (PI3-K) inhibitors or in Vav-deficient T cells, and was enhanced by constitutively active PI3-K. 3-phosphoinositide-dependent kinase-1 (PDK1) also upregulated the membrane translocation of PKCθ, but did not associate with it. These results provide evidence that a nonconventional PI3-K– and Vav-dependent pathway mediates the selective membrane recruitment and, possibly, activation of PKCθ in T cells.
Translocation of PKCθ in T cells is mediated by a nonconventional, PI3-K– and Vav-dependent pathway, but does not absolutely require phospholipase C
Abbreviations used in this paper: APC, antigen-presenting cell; cPKC, conventional PKC; DIG, detergent-insoluble glycolipid (fraction); GFP, green fluorescent protein; IS, immunological synapse; NFAT, nuclear factor of activated T cells; nPKC, novel PKC; PDK1, 3-phosphoinositide-dependent kinase-1; PH, pleckstrin-homology; PI3-K, phosphatidylinositol 3-kinase; SMAC, supramolecular activation cluster; TCR, T cell receptor.
Martin Villalba, Kun Bi, Junru Hu, Yoav Altman, Paul Bushway, Eric Reits, Jacques Neefjes, Gottfried Baier, Robert T. Abraham, Amnon Altman; Translocation of PKCθ in T cells is mediated by a nonconventional, PI3-K– and Vav-dependent pathway, but does not absolutely require phospholipase C . J Cell Biol 15 April 2002; 157 (2): 253–263. doi: https://doi.org/10.1083/jcb.200201097
Download citation file:
Sign in
Client Account
Sign in via your Institution
Sign in via your InstitutionEmail alerts
Advertisement
Advertisement