Diacylglycerol mediates the T-cell receptor-driven Ca2+ influx in T cells by a novel mechanism independent of protein kinase C activation

The mechanism of Ca2+ influx in nonexcitable cells is not known yet. Accord ing to the capacitative hypothesis, Ca2+ influx is triggered by IP3-mediate d Ca2+ release from the intracellular Ca2+ stores. Conversely, many workers have reported a lack of association between release and influx. In this wo rk, the role of diacylglycerol (DAG) as the mediator or T-cell influx in T cells was investigated. Stimulation of mouse splenic T cells with occurring DAG caused Ca2+ entry in a dose- and time-dependent manner. Such stimulati on was blocked by Ni2+, a divalent cation known to block Ca2+ channels. Inh ibition of protein kinase C (PKC) by calphostin C did not inhibit, but slig htly enhanced, the DAG-stimulated Ca2+ entry. However, inhibition of DAC me tabolism by DAC kinase and lipase inhibitors enhanced the DAG-stimulated Ca 2+ entry. DAC lipase and kinase inhibitors also enhanced the Ca2+ entry in T cells stimulated through TCR/CD3 complex with anti-CD3 antibody. Calphost in C did not affect the anti-CD3-stimulated Ca2+ entry. These results shelv ed that TCR-driven Ca2+ influx in T cells is mediated by DAC through a nove l mechanism(s) independent or PKC activation. (C) 2000 Wiley-Liss, Inc.