J Biol Chem, Vol. 275, Issue 2, 1344-1350, January 14, 2000
Regulation of T Cell Receptor- and CD28-induced Tyrosine
Phosphorylation of the Focal Adhesion Tyrosine Kinases Pyk2 and Fak by
Protein Kinase C
A ROLE FOR PROTEIN TYROSINE PHOSPHATASES*
Masahiro
Tsuchida,
Eric R.
Manthei,
Tausif
Alam,
Stuart J.
Knechtle, and
Majed M.
Hamawy
From the Department of Surgery, University of Wisconsin,
Madison, Wisconsin 53792
The T cell receptor (TCR)-CD3 complex and the
costimulatory molecule CD28 are critical for T cell function. Both
receptors utilize protein tyrosine kinases (PTKs) for the
phosphorylation of various signaling molecules, a process that is
critical for the function of both receptors. The PTKs of the focal
adhesion family, Pyk2 and Fak, have been implicated in the signaling of TCR and CD28. We show here evidence for the regulation of TCR- and
CD28-induced tyrosine phosphorylation of the focal adhesion PTKs by
protein kinase C (PKC). Thus, treating Jurkat T cells with the PKC
activator phorbol 12-myristate 13-acetate (PMA) rapidly and strongly
reversed receptor-induced tyrosine phosphorylation of the focal
adhesion PTKs. In contrast, PMA did not affect TCR-induced tyrosine
phosphorylation of CD3
or the PTKs Fyn and Zap-70. However, PMA
induced a strong and rapid dephosphorylation of the linker molecule for
activation of T cells. PMA failed to induce the dephosphorylation of
proteins in PKC-depleted cells or in cells pretreated with the PKC
inhibitor Ro-31-8220, confirming the role of PKC in mediating the PMA
effect on receptor-induced protein tyrosine phosphorylation. The
involvement of protein tyrosine phosphatases (PTPases) in mediating the
dephosphorylation of the focal adhesion PTKs was confirmed by the
failure of PMA to dephosphorylate Pyk2 in cells pretreated with the
PTPase inhibitor orthovanadate. These results implicate PKC in the
regulation of receptor-induced tyrosine phosphorylation of the focal
adhesion PTKs in T cells. The data also suggest a role for PTPases in
the PKC action.
*
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