title: Evidence that fertilization activates starfish eggs by sequential activation of a Src-like kinase and phospholipase cgamma.
abstract: 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.
authors.affiliation: Marine Biological Laboratory, Woods Hole, Massachusetts 02543, the Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Giusti
authors.forename: W
authors.initials: W
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Hinkle
authors.forename: M
authors.initials: M
authors.lastname: Terasaki
authors.forename: L A
authors.initials: LA
authors.lastname: Jaffe
mesh_terms: 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*
chemical_list: D007527:Isoenzymes; D019061:src-Family Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium