Desensitization of IP_3-induced Ca~(2+) release by overexression of a constitutively active Gq#alpha# protein converts ventral to dorsal fate in Xenopus early embryos

摘要

The constitutively active Gq#alpha# mutant construct (Gq#alpha#Q-L) in Xenopus early embryos was overexpressed and the effects on dorsoventral patterning examined. It was found that prolonged stimulation of inositol 1,4,5-trisphosphate (IP_3)-Ca~(2+) signaling by overexpression of Gq#alpha#Q-L led to desensitization of IP_3-induced Ca~(2+) release (IICR). Desensitization of IICR on the ventral side specifically induced an ectopic dorsal axis due to the conversion of ventral marginal mesoderm to adopt a dorsal fate. This effect of desensitization resembles that of inhibitory antibodies against the IP_3 receptor, as reported previously. These results strengthen the earlier finding that active IP_3-Ca~(2+) signaling functions in ventral signaling during the early embryonic development of Xenopus. Furthermore, the nature of downregulation of the Xenopus IP_3 receptor through continuous stimulation of IP_3-Ca~(2+) signaling might play a role in regulating endogenous IP_3-Ca~(2+) signaling in Xenopus early development.