Translocation of PKC[theta] in T cells is mediated by a nonconventional, PI3-K- and Vav-dependent pathway, but does not absolutely require phospholipase C.
PKCtheta plays an essential role in activation of mature T cells via stimulation of AP-1 and NF-kappaB, 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 PKCtheta to the membrane or cytoskeleton and its catalytic activation by anti-CD3/CD28 costimulation. Because this pathway acted selectively on PKCtheta, we addressed here the question of whether the translocation and activation of PKCtheta 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 PLCgamma1-deficient T cell line, or a dominant negative PLCgamma1 mutant, we demonstrate that CD3/CD28-induced membrane recruitment and COOH-terminal phosphorylation of PKCtheta are largely independent of PLC. In contrast, the same inhibitory strategies blocked the membrane translocation of PKCalpha. Membrane or lipid raft recruitment of PKCtheta (but not PKCalpha) 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 PKCtheta;, 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 PKCtheta in T cells.
Villalba
Martin
M
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA.
Bi
Kun
K
Hu
Junru
J
Altman
Yoav
Y
Bushway
Paul
P
Reits
Eric
E
Neefjes
Jacques
J
Baier
Gottfried
G
Abraham
Robert T
RT
Altman
Amnon
A
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017353:Gene Deletion; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019169:Jurkat Cells; D051379:Mice; D018613:Microscopy, Confocal; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D051567:Proto-Oncogene Proteins c-vav; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D064413:3-Phosphoinositide-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D015513:Oncogene Proteins; D019869:Phosphatidylinositol 3-Kinases; D051966:Phospholipase C gamma; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D017346:Protein Serine-Threonine Kinases; D051567:Proto-Oncogene Proteins c-vav; D010738:Type C Phospholipases; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse; C076233:PRKCQ protein, human; C489593:Prkcq protein, mouse