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

Abstract

The mechanism of Ca2+ influx in nonexcitable cells is not known yet. According to the capacitative hypothesis, Ca2+ influx is triggered by IP3-mediated Ca2+ release from the intracellular Ca2+ stores. Conversely, many workers have reported a lack of association between release and influx. In this work, the role of diacylglycerol (DAG) as the mediator of T-cell receptor (TCR)-driven Ca2+ influx in T cells was investigated. Stimulation of mouse splenic T cells with naturally occurring DAG caused Ca2+ entry in a dose- and time-dependent manner. Such stimulation was blocked by Ni2+, a divalent cation known to block Ca2+ channels. Inhibition of protein kinase C (PKC) by calphostin C did not inhibit, but slightly enhanced, the DAG-stimulated Ca2+ entry. However, inhibition of DAG metabolism by DAG kinase and lipase inhibitors enhanced the DAG-stimulated Ca2+ entry. DAG lipase and kinase inhibitors also enhanced the Ca2+ entry in T cells stimulated through TCR/CD3 complex with anti-CD3 antibody. Calphostin C did not affect the anti-CD3-stimulated Ca2+ entry. These results showed that TCR-driven Ca2+ influx in T cells is mediated by DAG through a novel mechanism(s) independent of PKC activation. J. Cell. Biochem. 78:222–230, 2000. © 2000 Wiley-Liss, Inc.