Inhibition of TCR/CD3-mediated signaling by a mutant of the hematopoietically expressed G16 GTP-binding protein.
We have investigated the role of the hematopoietically expressed G16 GTP-binding protein on T cell activation. We constructed transfectants of Jurkat T cells that express a function-deficient mutant of G alpha 16 predicted to prevent activation of this G protein. Upon stimulation with anti-CD3 epsilon antibodies, mutant G alpha 16 transfectants display a profound defect in the production of IL-2 and IL-10, as well as in the expression of CD69. In contrast, the phorbol 12-myristate 13-acetate (PMA)-induced IL-10 production and CD69 expression, and the ionomycin plus PMA-induced IL-2 production are not affected. Consistent with the reduction in cytokine production is the inhibition of early signaling events in the mutant G alpha 16-expressing cells. There are significant reductions in anti-epsilon-induced tyrosine phosphorylation of zeta, epsilon, ZAP-70, and phospholipase C gamma 1, as well as in intracellular Ca2+ mobilization. In accordance with the effects on tyrosine phosphorylation is the reduction of TCR/CD3-mediated Fyn and Lck activities in G alpha 16 mutant cells. Even though the mechanism through which the G alpha 16 mutant mediates inhibition of T cell activation is not known, the data suggest a model where G proteins become activated upon TCR/CD3 engagement and regulate the activation of tyrosine kinases and subsequent downstream signaling events that lead to the activation of cytokine genes.
Zhou
J
J
Department of Biology, Molecular Biology Institute, San Diego State University, CA 92182-4614, USA.
Stanners
J
J
Kabouridis
P
P
Han
H
H
Tsoukas
C D
CD
D000409:Alanine / Q000235:genetics; D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D017252:CD3 Complex / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation / Q000235:genetics; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics*; D015870:Gene Expression / Q000276:immunology; D005998:Glycine / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D016753:Interleukin-10 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000201:enzymology / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D019169:Jurkat Cells; D037181:Lectins, C-Type; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000037:antagonists & inhibitors; D016297:Mutagenesis, Site-Directed; D051966:Phospholipase C gamma; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors; D051076:Proto-Oncogene Proteins c-fyn; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D014162:Transfection / Q000276:immunology; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099192:CD69 Antigens
D000409:Alanine; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D002118:Calcium; D019204:GTP-Binding Proteins; D005998:Glycine; D016753:Interleukin-10; D007376:Interleukin-2; D007527:Isoenzymes; D037181:Lectins, C-Type; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051966:Phospholipase C gamma; D011518:Proto-Oncogene Proteins; D051076:Proto-Oncogene Proteins c-fyn; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D010738:Type C Phospholipases; D014443:Tyrosine; D000099192:CD69 Antigens; C494957:FYN protein, human