Phospholipase C-beta 3 mediates the thrombin-induced Ca2+ response in glial cells

Abstract

Phospholipase C-P (PLC-beta) hydrolyses phosphatidylinositol 4,5-bisphosphate and generates inositol 1,4,5-trisphosphate in response to activation of various G protein-coupled receptors (GPCRs). Using glial cells from knock-out mice lacking either PLC-beta 1 [PLC-PI (-/-) or PLC-beta 3 PLC-beta 3 we examined which isotype of PLC-P participated in the cellular signaling events triggered by thrombin. Generation of inositol phosphates (IPs) was enhanced by thrombin in PLC-beta 1 (-/-) cells, but was negligible in PLC-beta 3 (-/-) cells. Expression of PLC-beta 3 in PLC-beta 3 (-/-) cells resulted in an increase in pertussis toxin (PTx)-sensitive H's in response to thrombin as well as to PARI-specific peptide, while expression of PLC-beta 1 in PLC-beta 1 (-/-) cells did not have any effect on IP generation. The thrombin-induced [Ca2+](i) increase was delayed and attenuated in PLC-beta 3 (-/-) cells, but normal in PLC-beta 1 (-/-) cells. Pertussis toxin evoked a delayed [Ca2+](i) increase in PLC-beta 3 (-/-) cells as well as in PLC-PI (-/-) cells. These results suggest that activation of PLC-beta 3 by pertussis toxin-sensitive G proteins is responsible for the transient [Ca2+](i) increase in response to thrombin, whereas the delayed [Ca2+](i) increase may be due to activation of some other PLC, such as PLC-beta 4, acting via PTx-insensitive G proteins.