Evidence that fertilization activates starfish eggs by sequential activation of a Src-like kinase and phospholipase cgamma.
Recent evidence has indicated a requirement for a Src family kinase in initiating Ca(2+) release at fertilization in starfish eggs (Giusti, A. F., Carroll, D. J., Abassi, Y. A., Terasaki, M., Foltz, K. R., and Jaffe, L. A. (1999) J. Biol. Chem. 274, 29318-29322). We now show that injection of Src protein into starfish eggs initiates Ca(2+) release and DNA synthesis, as occur at fertilization. These responses depend on the phosphorylation state of the Src protein; only the kinase active form is effective. Like Ca(2+) release at fertilization, the Ca(2+) release in response to Src protein injection is inhibited by prior injection of the SH2 domains of phospholipase Cgamma. These findings support the conclusion that in starfish, sperm-egg interaction causes egg activation by sequential activation of a Src-like kinase and phospholipase Cgamma. Injection of the SH2 domain of Src, which inhibits Ca(2+) release at fertilization, does not inhibit Ca(2+) release caused by Src protein injection. This indicates that the requirement for a Src SH2 domain interaction is upstream of Src activation in the pathway leading to Ca(2+) release at fertilization.
Giusti
A F
AF
Marine Biological Laboratory, Woods Hole, Massachusetts 02543, the Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
Xu
W
W
Hinkle
B
B
Terasaki
M
M
Jaffe
L A
LA
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004261:DNA Replication; D004789:Enzyme Activation; D005260:Female; D005306:Fertilization / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D009865:Oocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D051966:Phospholipase C gamma; D013215:Starfish; D010738:Type C Phospholipases / Q000378:metabolism*; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
D007527:Isoenzymes; D019061:src-Family Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium