D. Vassilopoulos et al., EFFECTS OF AN AMINOSTEROID INHIBITOR OF PHOSPHOLIPASE C-DEPENDENT PROCESSES ON THE TCR-MEDIATED SIGNAL-TRANSDUCTION PATHWAY IN HUMAN T-CELLS, Clinical immunology and immunopathology, 77(1), 1995, pp. 59-68
Phospholipase C (PLC) is a key enzyme in the T cell antigen receptor (
TCR)-mediated signal transduction pathway in human T cells. Agonist-in
duced PLC activation leads to a cascade of intracellular events that u
ltimately regulate gene transcription and T cell activation. We studie
d the effects of U-73122, a putative inhibitor of PLC-dependent events
, on TCR/CD3 complex-mediated early and late events in human T cells.
Both anti-CD3 monoclonal antibody-induced 1,4,5-inositol trisphosphate
(IF,) and free intracytoplasmic calcium [Ca2+](i) increases were inhi
bited by U-73122 (0.05-0.1 mu M), but not by the related inactive anal
og, U-73343. U-73122 did not affect thapsigargin-evoked [Ca2+](i) incr
ease in T cells, indicating a specific mode of inhibition of CD3 signa
ling. Late events in T cell activation like CD3-mediated T cell prolif
eration and mitogen-induced interleukin 2 receptor (IL2-R) expression
were also inhibited by this agent. T cell proliferation induced by a c
ombination of a phorbol ester and ionomycin was not affected by U-7312
2, Although an agonist effect on basal IF, and [Ca2+](i) levels was ob
served with high concentrations of U-73122, the inhibitor alone did no
t induce any proliferative effect or IL2-R expression in T cells. Our
results demonstrate for the first time that U-73122 is a specific inhi
bitor of PLC-dependent processes in human T cells and could serve as a
valuable tool for studying T cell signal transduction pathways. (C) 1
995 Academic Press, Inc.