Evidence for an erbstatin-sensitive tyrosine kinase functioning in ascidian egg activation.
It has been proposed that protein tyrosine phosphorylation plays an important role in sperm-induced egg activation. To obtain evidence for the involvement of tyrosine kinases at an early stage in the egg activation process, we analyzed the effects of tyrosine kinase inhibitors on surface contraction of fertilized eggs of the ascidian Ciona savignyi and analyzed their effects on cleavage. We found that only erbstatin analog inhibited surface contraction, which was observed 5 min after insemination. With respect to the cleavage that occurs around 50 min after insemination, tyrophostin A1 and genistein, together with erbstatin analog, showed inhibitory effects. In addition, transient tyrosine phosphorylation of at least five proteins was observed 2-5 min after insemination, followed by tyrosine phosphorylation of one protein 30-40 min after insemination. Among proteins tyrosine-phosphorylated at the former stage, tyrosine phosphorylation of a 75 kD protein was inhibited by erbstatin analog. Thus, an erbstatin-sensitive tyrosine kinase functions at an early stage in the ascidian egg activation process.
Ueki
K
K
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Yokosawa
H
H
D000818:Animals; D015153:Blotting, Western; D005260:Female; D006873:Hydroquinones / Q000494:pharmacology*; D008297:Male; D010063:Ovum / Q000187:drug effects* / Q000201:enzymology* / Q000502:physiology; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism* / Q000502:physiology; D013084:Sperm-Ovum Interactions / Q000187:drug effects; D014561:Urochordata
D006873:Hydroquinones; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; C048212:erbstatin