Antigen receptor-mediated phosphoinositide hydrolysis in murine T cells is not initiated via G-protein activation.
Ligation of the antigen receptors on both T and B lymphocytes induces phosphoinositide (PI) hydrolysis, Ca(2+)-mobilization and protein kinase C activation. The activation of the phosphoinositide-specific phosphodiesterase (PPI-PDE) following crosslinking of surface Ig 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 permeabilizing 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 PI hydrolysis is G-protein controlled.
Phillips
R J
RJ
Division of Immunology, National Institute for Medical Research, Mill Hill, London, UK.
Harnett
M M
MM
Klaus
G G
GG
D000818:Animals; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006868:Hydrolysis; D051379:Mice; D010716:Phosphatidylinositols / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
D010716:Phosphatidylinositols; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; D019204:GTP-Binding Proteins