Calcium release at fertilization in starfish eggs is mediated by phospholipase Cgamma.
J Cell Biol
; 138(6): 1303-11, 1997 Sep 22.
Article
in En
| MEDLINE
| ID: mdl-9298985
ABSTRACT
Although inositol trisphosphate (IP3) functions in releasing Ca2+ in eggs at fertilization, it is not known how fertilization activates the phospholipase C that produces IP3. To distinguish between a role for PLCgamma, which is activated when its two src homology-2 (SH2) domains bind to an activated tyrosine kinase, and PLCbeta, which is activated by a G protein, we injected starfish eggs with a PLCgamma SH2 domain fusion protein that inhibits activation of PLCgamma. In these eggs, Ca2+ release at fertilization was delayed, or with a high concentration of protein and a low concentration of sperm, completely inhibited. The PLCgammaSH2 protein is a specific inhibitor of PLCgamma in the egg, since it did not inhibit PLCbeta activation of Ca2+ release initiated by the serotonin 2c receptor, or activation of Ca2+ release by IP3 injection. Furthermore, injection of a PLCgamma SH2 domain protein mutated at its phosphotyrosine binding site, or the SH2 domains of another protein (the phosphatase SHP2), did not inhibit Ca2+ release at fertilization. These results indicate that during fertilization of starfish eggs, activation of phospholipase Cgamma by an SH2 domain-mediated process stimulates the production of IP3 that causes intracellular Ca2+ release.
Full text:
1
Database:
MEDLINE
Main subject:
Type C Phospholipases
/
Sperm-Ovum Interactions
/
Starfish
/
Calcium
/
Isoenzymes
Type of study:
Diagnostic_studies
Limits:
Animals
Language:
En
Year:
1997
Type:
Article