Antigen receptor-mediated phosphoinositide hydrolysis in murine T Cells is not initiated via G-protein activation

Abstract

Ligation of the antigen receptors on both T and B lymphocytes induces phosphoinositide (P1) hydrolysis, Ca^{2 +} -mobilization and protein kinase C activation. The activation of the phosphoinositide- specific phosphodiesterase(PPI-PDE) following crossllnking of surface lg receptors on B cells is controlled by an uncharacterized guanine nucleotide-regulatory (G) protein. Here we have used permeabilized murine T cells (both resting T cells and a conalbumin specific CD4-positive T cell clone) to investigate a role for G protein(s) in coupling the TCR to the PPI-PDE. We found that anti TCR McAB (or processed antigen) induced PI hydrolysis cannot be uncoupled by permeabillzing T cells, as occurs with classical G protein linked receptors. Furthermore, the TCR mediated release of inositol phosphates in permeabilized T cells was not enhanced by non-hydrolyzable analogs of GTP, nor inhibited by GDP analogs. These findings therefore argue strongly against the concept that TCR-mediated P1 hydrolysis is G-protein controlled.