Phosphatidylinositol-3-kinase regulates PKCtheta activity in cytotoxic T cells.
Protein kinase C (PKC) theta plays a crucial role in T cell activation. We, therefore, examined the regulation of PKCtheta activity in cytotoxic T lymphocytes (CTL). We demonstrated that PMA did not stimulate PKCtheta activation and phospholipase C inhibition did not block anti-CD3-stimulated PKCtheta activation in a CTL clone. This suggests that diacylglycerol is neither sufficient nor required for PKCtheta activation. Furthermore, PKCtheta was only activated in a CTL clone stimulated with plate-bound anti-CD3 but not soluble anti-CD3. However, PMA or cross-linked anti-CD3 stimulated phosphorylation of PKCtheta as measured by a migratory shift, suggesting that phosphorylation was not sufficient for activity. Phosphatidylinositol 3-kinase activity was required for anti-CD3, but not PMA, stimulated phosphorylation and for immobilized anti-CD3-triggered PKCtheta activity. A substantial fraction of PKCtheta was constitutively membrane associated and PMA or CD3 stimulation did not significantly increase membrane association. Our data indicate that phosphorylation of PKCtheta is not a suitable surrogate measurement for PKCtheta activity and that additional, yet to be defined steps, are required for the regulation of PKCtheta enzymatic activity in CTL.
Puente
Lawrence G
LG
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alta., Canada T6G2S2.
Mireau
Laura R
LR
Lysechko
Tara L
TL
Ostergaard
Hanne L
HL
D000818:Animals; D017252:CD3 Complex / Q000502:physiology; D002999:Clone Cells; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000276:immunology; D007939:Leukemia L1210 / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism* / Q000494:pharmacology; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology*
D017252:CD3 Complex; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C