Molecular mechanisms of sea urchin egg activation at fertilization.

摘要

The emerging picture in echinoderm fertilization indicates that sperm-mediated egg activation, either through direct contact with cell surface receptors, or by delivery of an activating factor (or both), stimulates the activity of PLCgamma to produce IP3 and DAG. IP3 then serves to release calcium from internal stores leading to egg activation. This thesis project explored the role of Src family tyrosine kinases in sea urchin egg activation, since (i) tyrosine phosphorylation is one of the earliest detectable events in echinoderm eggs (ii) it has been shown for tyrosine kinases to be sufficient for activation of echinoderm eggs (iii) PLCgamma is activated through tyrosine phosphorylation, and finally (iv) a number of tyrosine kinases, specifically Src family of tyrosine kinases, have been identified in echinoderm eggs. Chapter 1 is a general introduction. In Chapter 2 the tyrosine phosphorylation of the sperm receptor is described. In Chapter 1 the identification of several members of the Src family tyrosine kinases which undergo fertilization-mediated dynamics in activity is reported. Chapter 4 presents the partial purification of one of the candidate Src family tyrosine kinases. Chapter 5 explores the necessity of Src family tyrosine kinases in sea urchin egg activation as determined by by injection of dominant negative reagents, and chapter 6 is the summary chapter. Collectively, the data presented in this thesis argue for an essential role for Src family of tyrosine kinases. in egg activation and pave the way for future work in purifying and identifying these tyrosine kinases.