Differential inhibition of T cell receptor signal transduction and early activation events by a selective inhibitor of protein-tyrosine kinase.
Engagement of the TCR (CD3-Ti) by Ag/MHC, CD3 mAb, or lectin mitogen stimulates the very early tyrosine phosphorylation of several cellular substrates including TCR-zeta. The T cell specific protein-tyrosine kinase (PTK), p56lck, has been implicated in the tyrosine phosphorylation of TCR-zeta. However, the significance of this event with regard to CD3-Ti signal transduction remains unclear. Herein, we have investigated the effect of the selective PTK inhibitor genistein (4',5,7-trihydroxyisoflavone) on cellular events associated with activation via CD3-Ti triggering. Genistein inhibited the T cell PTK, p56lck, in a dose-dependent fashion with an ID50 = 40 microM. Genistein also inhibited CD3 mAb or PHA-induced TCR-zeta chain phosphorylation in intact peripheral blood T cells. Genistein blocked the expression of IL-2 and IL-2R (CD25) in T cells stimulated with PHA/PMA or CD3 mAb/PMA, but did not inhibit the de novo expression of the CD69 early activation Ag, which is induced primarily by a PKC-dependent pathway. IL-2 and CD25 expression induced by calcium ionophore A23187 and PMA was largely refractory to inhibition by genistein, suggesting an effect of the drug on calcium-dependent pathways stimulated via CD3-Ti triggering. In this last regard, genistein partially inhibited the CD3 mAb-induced rise in [Ca2+]i but did not inhibit PHA- or CD3 mAb-induced phosphatidylinositol hydrolysis. Consequently, protein-tyrosine phosphorylation does not appear to be a prerequisite for CD3-Ti-mediated activation of phosphatidylinositol-specific phospholipase C activity and PIP2 hydrolysis. An alternative role for PTK in CD3-Ti signal transduction is suggested.
Trevillyan
J M
JM
Veterans Affairs Medical Center, Texas Tech University Health Sciences Center, Amarillo 79106.
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Atluru
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Phillips
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Bjorndahl
J M
JM
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000502:physiology; D017252:CD3 Complex; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D019833:Genistein; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics / Q000378:metabolism; D007529:Isoflavones / Q000494:pharmacology*; D037181:Lectins, C-Type; D008213:Lymphocyte Activation; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D000001:Calcimycin; D002118:Calcium; D019833:Genistein; D007376:Interleukin-2; D007529:Isoflavones; D037181:Lectins, C-Type; D010716:Phosphatidylinositols; D011505:Protein-Tyrosine Kinases; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D013755:Tetradecanoylphorbol Acetate; D000099192:CD69 Antigens