title: Roles of heterotrimeric and monomeric G proteins in sperm-induced activation of mouse eggs.
abstract: Results of several lines of experimentation suggest that sperm-induced egg activation has several features in common with G protein-coupled receptor signal transduction mechanisms. We report that microinjection of GDP beta S into metaphase II-arrested mouse eggs blocks sperm-induced egg activation. Since GDP beta S inactivates both heterotrimeric and monomeric classes of G proteins, the involvement of members of each of these families in sperm-induced egg activation was evaluated. Neither pertussis toxin treatment of eggs nor microinjection of eggs with inhibitory antibodies toward G alpha q blocked sperm-induced egg activation. Nevertheless, microinjection of phosducin, a protein that binds tightly to free G protein beta gamma subunits, specifically inhibited second polar body emission, the fertilization evoked decrease of H1 kinase activity and pronucleus formation. Microinjection of phosducin, however, did not inhibit the fertilization-induced modifications of the zona pellucida and microinjection of beta gamma t did not result in egg activation in the absence of sperm. Inactivation of the monomeric Rho family of G proteins with C3 transferase from Clostridium botulinum inhibited emission of the second polar body and cleavage to the 2-cell stage, but did not affect the modifications of the zona pellucida or pronucleus formation. Microinjection of Rasval12, which is a constitutively active form of Ras, did not result in egg activation in the absence of sperm. Moreover, microinjection of either an anti-Ras neutralizing antibody (Y13-259) or a dominant negative form of Ras (RasT) did not affect events of sperm-induced egg activation. In contrast, microinjection of RasT inhibited embryo cleavage to the 2-cell stage. These results suggest that both heterotrimeric and monomeric G proteins are involved in various aspects of sperm-induced egg activation.
authors.affiliation: Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia 19104.
authors.forename: G D
authors.initials: GD
authors.lastname: Moore
authors.forename: T
authors.initials: T
authors.lastname: Ayabe
authors.forename: P E
authors.initials: PE
authors.lastname: Visconti
authors.forename: R M
authors.initials: RM
authors.lastname: Schultz
authors.forename: G S
authors.initials: GS
authors.lastname: Kopf
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins; D002970:Cleavage Stage, Ovum / Q000187:drug effects; D005136:Eye Proteins / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D020555:GTP-Binding Protein Regulators; D019204:GTP-Binding Proteins; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008845:Microinjections; D010750:Phosphoproteins / Q000494:pharmacology; D011108:Polymers / Q000494:pharmacology; D006656:Protamine Kinase / Q000378:metabolism; D011494:Protein Kinases / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013084:Sperm-Ovum Interactions / Q000187:drug effects*; D015044:Zona Pellucida / Q000187:drug effects / Q000201:enzymology; D018631:ras Proteins / Q000494:pharmacology
chemical_list: D005136:Eye Proteins; D020555:GTP-Binding Protein Regulators; D010750:Phosphoproteins; D011108:Polymers; C065631:phosducin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011494:Protein Kinases; D006656:Protamine Kinase; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D018631:ras Proteins