Ceramide triggers intracellular calcium release via the IP3 receptor in Xenopus laevis oocytes

Ceramide, a product of sphingomyelin turnover, is a lipid second messenger that mediates diverse signaling pathways, including those leading to cell c ycle arrest and differentiation. The mechanism(s) by which ceramide signals downstream events have not been fully elucidated. Here we show that, in Xe nopus laevis oocytes, ceramide-induced maturation is associated with the re lease of intracellular calcium stores. Ceramide caused a dose-dependent ele vation in the second messenger inositol 1,4,5-trisphosphate (IP3) via activ ation of G(q/11)alpha and phospholipase C-beta X Elevation of IP3, in turn, activated the IP3 receptor calcium release channel on the endoplasmic reti culum, resulting in a rise in cytoplasmic calcium. Thus our study demonstra tes that cross talk between the ceramide and phosphoinositide signaling pat hways modulates intracellular calcium homeostasis.