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Evidence for the involvement of the Rho GTP‐binding protein in egg activation of the ascidian Halocynthia roretzi
Author(s) -
Toratani Satoshi,
Yokosawa Hideyoshi
Publication year - 1995
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1046/j.1440-169x.1995.00004.x
Subject(s) - gtp' , chemistry , inositol , calcium , microinjection , egta , receptor , biology , biochemistry , microbiology and biotechnology , organic chemistry , enzyme
Eggs of the ascidian Halocynthia roretzi are activated by insemination and by treatment with calcium ionophore, leading to elevation of the vitelline coat. Here we describe the effects on egg activation of microinjection of guanosine 5′‐(γ thio) triphosphate (GTPγS, a non‐hydrolyzable GTP analog), heparin (an antagonist of the inositol 1,4,5‐trisphosphate receptor) and a monoclonal antibody to the Rho GTP‐binding protein. Microinjected GTPγS induced elevation of the vitelline coat, but not when it was co‐injected with EGTA or heparin. Pre‐injected heparin or the anti‐Rho monoclonal antibody blocked subsequent sperm‐induced elevation of the vitelline coat, but not calcium ionophore‐induced elevation. We also demonstrated that the amount of cytosolic inositol 1,4,5‐trisphosphate was increased by insemination. These results strongly suggest that the Rho GTP‐binding protein functions prior to the heparin‐blocked inositol 1,4,5‐trisphosphate receptor‐mediated Ca 2+ release in the sperm induced activation process of H. roretzi eggs.