title: Testis-specific isoform of angiotensin-converting enzyme (tACE) is involved in the regulation of bovine sperm capacitation.
abstract: We hypothesized that the testis-specific isoform of angiotensin-converting enzyme (tACE) is released during bovine sperm capacitation, and its peptidase activity is required for capacitation. Specific objectives of this study were to (i) develop an anti-tACE antibody; (ii) characterize expression of tACE in bovine testes and sperm; and (iii) determine the role of tACE in capacitation. A 110-kDa protein, consistent with the mass of tACE, was detected in sperm extract by our anti-tACE immunoserum. This immunotarget localized at the acrosomal region and principal piece, but was only expressed in testis of mature bulls. When bull sperm were incubated in Sp-TALP (0 and 4 hr) plus 10 µg/ml heparin (capacitation group) or 10 µg/ml heparin + 10 µM captopril (an ACE inhibitor) for 4 hr, the number of acrosome-reacted (40.1 vs. 24.0%, respectively) and hyperactivated (15.0 vs. 9.7%) sperm increased, and tyrosine phosphoprotein content were higher (p < 0.05) for sperm in heparin alone. tACE activity was also higher (0.04 U/ml; p < 0.01) in incubation medium of sperm exposed to heparin compared to 0- and 4-hr incubation controls or heparin + captopril conditions (0, 0.005, and 0.009 U/ml, respectively). Furthermore, capacitation-associated shedding of a portion of tACE into the medium decreased sperm content of the 110-kDa tACE, but concurrently increased the abundance of a 60-kDa tACE variant. Thus, a portion of the extracellular region of tACE (containing its catalytic site) is released from bovine sperm during capacitation, and tACE activity may be required for sperm capacitation.
authors.affiliation: Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada.
authors.forename: Mina
authors.initials: M
authors.lastname: Ojaghi
authors.affiliation: Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Kastelic
authors.affiliation: Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada.
authors.forename: Jacob
authors.identifier: 0000-0001-7156-8718
authors.initials: J
authors.lastname: Thundathil
mesh_terms: D000177:Acrosome / Q000201:enzymology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D002417:Cattle; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D006493:Heparin / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology*; D013737:Testis / Q000201:enzymology*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D007527:Isoenzymes; D006493:Heparin; D002216:Captopril; D007703:Peptidyl-Dipeptidase A
keywords: bull sperm; capacitation; tACE