La. Conroy et al., REGULATION OF T-CELL-RECEPTOR-STIMULATED BIVALENT-CATION ENTRY IN JURKAT E6 CELLS - ROLE OF PROTEIN-KINASE-C, Biochemical journal, 303, 1994, pp. 671-677
Stimulation of Jurkat E6 cells with anti-CD3 antibody results in a cha
racteristic rise in [Ca2+](i) which is due to both the release of Ca2 from intracellular stores and the entry of external Ca2+. Individual
components of the [Ca2+](i) increase were investigated by measuring in
tracellular Ca2+ release in the absence of external Ca2+ and determini
ng influx of bivalent cations by following the entry of Mn2+. The incr
ease in [Ca2+](i) induced by anti-CD3 antibody in the presence or abse
nce of extracellular Ca2+ could be inhibited by the non-selective kina
se inhibitor staurosporine, which also inhibits anti-CD3-stimulated ph
ospholipase C activity. Stauosporine also inhibits the influx of bival
ent cations induced by anti-CD3 antibody, but not that induced by depl
etion of intracellular Ca2+ stores using thapsigargin. The effect of s
taurosporine was compared with that of Ro 31-8425, a potent and select
ive inhibitor of protein kinase C (PKC). Ro 31-8425, at concentrations
up to 10 mu M, has no inhibitory effect on the anti-CD3 antibody-indu
ced [Ca2+](i) increase or phospholipase C activity. These studies are
consistent with the concept that augmentation of [Ca2+](i) by stimulat
ed T-cell receptors requires activation of a kinase, probably a tyrosi
ne kinase such as p56(lck), ZAP-70 or p59(fyn), and is independent of
PKC. Phorbol esters inhibit the anti-CD3-stimulated [Ca2+](i) increase
and phospholipase C activity, showing that this can be negatively reg
ulated by PKC. A small potentiation of the anti-CD3 antibody-induced [
Ca2+](i) rise in the presence of extracellular Ca2+ was detected in th
e presence of Ro 31-8425; this suggests that T-cell-receptor ligation
can also limit the increase in [Ca2+](i) via PKC activation.