Effects of nonselective cation channels and PI3K on endothelin-1-induced PYK2 tyrosine phosphorylation in C6 glioma cells.

We recently demonstrated that endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) in C6 glioma cells. In the present study, we investigated the effects of NSCCs on the ET-1-induced proline-rich tyrosine kinase 2 (PYK2) phosphorylation in C6 glioma cells. In addition, we examined the effects of phosphoinositide 3-kinase (PI3K) on the ET-1-induced NSCCs activation and PYK2 phosphorylation. The PI3K inhibitors wortmannin and LY-294002 inhibited ET-1-induced Ca2+ influx through NSCC-2 but not NSCC-1. On the other hand, addition of these inhibitors after stimulation with ET-1 failed to suppress Ca2+ influx through NSCC-2. PYK2 phosphorylation was abolished by blocking Ca2+ influx through NSCCs. The PI3K inhibitors blocked the NSCC-2-dependent part of ET-1-induced PYK2 phosphorylation. These results indicate that 1) NSCC-2 is stimulated by ET-1 via a PI3K-dependent cascade, whereas NSCC-1 is stimulated via a PI3K-independent cascade; 2) PI3K seems to be required for the activation of the Ca2+ entry, but not for its maintenance; 3) Ca2+ influx through NSCC-1 and NSCC-2 plays an essential role in ET-1-induced PYK2 phosphorylation; and 4) PI3K is involved in the ET-1-induced PYK2 phosphorylation that depends on the Ca2+ influx through NSCC-2.