Hopkins Marine Station Student Paper

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Title: Is tyrosine kinase activity necessary for fertilization-induced glucose-6-phosphate dehydrogenase release in Strongylocentrotus purpuratus eggs?
Student Author(s): Agrawala, Geetika
Faculty Advisor(s): Epel, David
Pages: 23
Location: Final Papers Biology 175H
Date: June 1995
Abstract: The activity of the pentose phosphate shunt increases soon after fertilization of Strongylocentrotus purpuratus eggs, and this increase is correlated with a change in the intracellular distribution of glucose-6-phosphate dehydrogenase (G6PD), the first and rate-limiting enzyme in the pentose shunt. This enzyme is found in a bound, inactive state in unfertilized eggs and in a soluble, active state in newly fertilized zygotes. The signaling pathway that links fertilization to the release of G6PD from the bound state is not known. In this study, I have investigated whether tyrosine kinase activity is involved in fertilization-induced G6PD release in sea urchin eggs.
I determined that G6PD release does not occur in unfertilized eggs treated with bindin or antibody against the sperm receptor. These two treatments activate the specific tyrosine kinase that phosphorylates the sperm receptor. I also found that inhibition of general tyrosine kinase activity using the tyrosine kinase inhibitors genistein and tyrphostin 51 does not block G6PD release in sea urchin zygotes. As deduced by immunoprecipitation of phosphotyrosines, genistein is inhibiting tyrosine kinase activity while tyrphostin 51 is not. These preliminary data show that those tyrosine kinases which are inhibited by genistein are not involved with G6PD release after fertilization. I also discuss the possible reasons why tyrphostin 51, bindin, and anti-receptor antibody treatment may have given inconclusive data.
Notes: Published in The Stanford Biologist, 1996 1:19-26