title: Phospholipase C-dependent Ca2+ release by worm and mammal sperm factors.
abstract: Egg activation in all animals evidently requires the synthesis of inositol 1,4,5-trisphosphate (InsP(3)) from phosphatidylinositol 4,5-bisphosphate (PIP(2)) by phospholipase C (PLC). Depending on the organism, InsP(3) elicits either calcium oscillations or a single wave, which in turn initiates development. A soluble component in boar sperm that activates mammalian eggs has been suggested to be a PLC isoform. We tested this hypothesis in vitro using egg microsomes of Chaetopterus. Boar sperm factor elicited Ca(2+) release from the microsomes by an InsP(3)-dependent mechanism. The PLC inhibitor U-73122, but not its inactive analog U-73343, blocked the response to sperm factor but not to InsP(3). U-73122 also inhibited the activation of fertilized and parthenogenetic eggs. Chaetopterus sperm also contained a similar activity. These results strongly support the hypothesis that sperm PLCs are ubiquitous mediators of egg activation at fertilization.
authors.affiliation: Department of Biology, Howard University, 415 College Street, NW, Washington, DC 20059-0001, USA.
authors.forename: Kethurah P
authors.initials: KP
authors.lastname: Howell
authors.forename: Aurelia
authors.initials: A
authors.lastname: Skipwith
authors.forename: Antony
authors.initials: A
authors.lastname: Galione
authors.forename: William R
authors.initials: WR
authors.lastname: Eckberg
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004963:Estrenes / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009865:Oocytes / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000378:metabolism; D011077:Polychaeta / Q000502:physiology*; D011760:Pyrrolidinones / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology*; D013094:Spermatozoa / Q000737:chemistry* / Q000378:metabolism; D013552:Swine; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004963:Estrenes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D010738:Type C Phospholipases; D002118:Calcium