Pertussis toxin-sensitive G-proteins are not involved in activation of T-lymphocytes.
Multiple effects of pertussis toxin (PT) on Jurkat T-cells can be distinguished on the basis of their dose-response and their kinetics. High concentrations of PT deliver to cells an activating signal resulting in a rapid rise in [Ca2+]i followed by IL-2 synthesis. This activation is accompanied (within 2 h) by a down-regulation of the CD3/TCR complex from the cell surface. Cells then become refractory towards stimulation by CD3 mAb or PHA. All these effects, referred to as 'mitogenic effects', present the same dose-response curves with an EC50 of 0.5 micrograms/ml. Short term effects (PT-induced Ca2+ movements, down-regulation of CD3/TCR complex and inhibition of PHA and CD3-induced Ca2+ signal) are observed under conditions where no PT-induced ADP-ribosylation can be detected. In contrast, ADP-ribosylation of the 40,000 alpha-subunit of G-proteins requires a sustained (18 h) incubation of intact cells in the presence of low concentration (EC50 = 0.3 ng/ml) of PT. Dose-response curves for PT-dependent ADP-ribosylation and mitogenic effects are separated by three orders of magnitude. Covalent modification of G-protein has no effect on CD3-induced increase in [Ca2+]i and IL-2 synthesis induced by a combination of phorbol ester and either CD3 mAb, PHA or calcium ionophore. These data indicate that transduction of the mitogenic signal does not involve a PT-sensitive G-protein. Furthermore, inhibition of mitogenic signals following PT treatment results from a PT-induced activation leading to a down-regulation of the CD3/T cell receptor complex.
Modesto
J
J
INSERM U210, Faculté de Médecine Pasteur, Nice, France.
Breittmayer
J P
JP
Grenier-Brossette
N
N
Fehlmann
M
M
Cousin
J L
JL
D000244:Adenosine Diphosphate / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism; D015536:Down-Regulation; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D007376:Interleukin-2 / Q000096:biosynthesis; D007700:Kinetics; D008213:Lymphocyte Activation / Q000502:physiology*; D037342:Pertussis Toxin; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D012266:Ribose / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D010566:Virulence Factors, Bordetella; D000244:Adenosine Diphosphate; D012266:Ribose; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium