Dissection of thymocyte signaling pathways by in vivo expression of pertussis toxin ADP-ribosyltransferase.
Stimulation of the T lymphocyte antigen receptor-CD3 complex (TCR-CD3) causes T cell activation by a process associated with increased phosphatidylinositol-specific phospholipase C (PI-PLC) activity. Evidence exists suggesting that GTP-binding (G) proteins, particularly the pertussis toxin (PT)-sensitive Gi proteins, participate in this signal transduction pathway. To clarify the role of Gi proteins in TCR-CD3 signaling, and to investigate other possible functions of Gi molecules in T cells, we expressed the S1 subunit of PT in the thymocytes of transgenic mice using the lymphocyte-specific lck promoter. Transgenic thymocytes contained S1 activity and exhibited profound depletion of Gi protein PT substrates in a manner suggesting their inactivation by S1 in vivo. Nevertheless, treatment of transgenic thymocytes with mitogenic stimuli provoked normal increases in intracellular free Ca2+ concentrations and IL-2 secretion, indicating that Gi proteins are not required for T cell activation. These normal signaling responses notwithstanding, mature thymocytes accumulated in lck-PT mice and did not appear in secondary lymphoid organs or in the circulation. Viewed in the context of the known features of Bordetella pertussis infection, our results suggest that a PT-sensitive signaling process, probably involving Gi proteins, regulates thymocyte emigration.
Chaffin
K E
KE
Howard Hughes Medical Institute, University of Washington, Seattle 98195.
Beals
C R
CR
Wilkie
T M
TM
Forbush
K A
KA
Simon
M I
MI
Perlmutter
R M
RM
D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D015345:Oligonucleotide Probes; D037342:Pertussis Toxin; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D010566:Virulence Factors, Bordetella / Q000235:genetics / Q000378:metabolism
D007376:Interleukin-2; D015345:Oligonucleotide Probes; D010566:Virulence Factors, Bordetella; D009243:NAD; D011065:Poly(ADP-ribose) Polymerases; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium