title: Ca(2+)-independent induction of acrosome reaction by protein kinase C in human sperm.
abstract: We report that activated protein kinase C (PKC) can induce acrosome reaction independently of elevated Ca2+. Addition of 12-O-tetradecanoyl phorbol-13-acetate or the membrane-permeable diacylglycerol analog 1-oleoyl-2-acetylglycerol to ejaculated human sperm resulted in stimulation of acrosomal reaction (2- to 3-fold), provided the sperm underwent capacitation. Induction of acrosome reaction by 12-O-tetradecanoyl phorbol-13-acetate was blocked by the PKC inhibitor staurosporine or by down-regulation of endogenous PKC, but not by removal of extracellular Ca2+. Acrosome reaction was also enhanced by the Ca2+ ionophore ionomycin in a Ca(2+)-dependent, PKC-independent fashion. Immunohistochemical analysis with type-specific PKC antibodies revealed the presence of PKC alpha and PKC beta II in the equatorial segment, whereas PKC beta I and PKC epsilon staining was found in the principal piece of the tail. Acrosome reaction, thus far believed to be induced only by elevated Ca2+, can therefore be triggered by activated PKC in a Ca(2+)-independent fashion. The PKC subtypes potentially involved in acrosome reaction are most likely alpha and beta II, whereas the beta I- and epsilon-subspecies might be involved in regulation of flagellar motility of human sperm.
authors.affiliation: Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Rotem
authors.forename: G F
authors.initials: GF
authors.lastname: Paz
authors.forename: Z T
authors.initials: ZT
authors.lastname: Homonnai
authors.forename: M
authors.initials: M
authors.lastname: Kalina
authors.forename: J
authors.initials: J
authors.lastname: Lax
authors.forename: H
authors.initials: H
authors.lastname: Breitbart
authors.forename: Z
authors.initials: Z
authors.lastname: Naor
mesh_terms: D000177:Acrosome / Q000502:physiology* / Q000648:ultrastructure; D000328:Adult; D000470:Alkaloids / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000502:physiology; D004075:Diglycerides; D015536:Down-Regulation / Q000187:drug effects; D005089:Exocytosis / Q000502:physiology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013075:Sperm Capacitation / Q000502:physiology; D013081:Sperm Motility / Q000187:drug effects; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013094:Spermatozoa / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D004075:Diglycerides; D015759:Ionomycin; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium