BOR - Papers in Press, published online ahead of print
October 14, 2002.
Biol Reprod 2002, 10.1095/biolreprod.102.005082
BIOLOGY OF REPRODUCTION 68, 207213 (2003)
DOI: 10.1095/biolreprod.102.005082
© 2003 by the Society for the Study of Reproduction, Inc.
Porcine Sperm Capacitation and Tyrosine Kinase Activity Are Dependent on Bicarbonate and Calcium but Protein Tyrosine Phosphorylation Is Only Associated with Calcium1
Steve Tardifa,
Charlotte Dubéa, and
Janice L. Bailey2,a
a Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4
Mammalian sperm undergo capacitation in the female reproductive tract or under defined conditions in vitro. Although capacitation is now considered to be mediated by intracellular signaling events, including protein phosphorylation, the regulation of the transduction mechanisms is poorly understood. The objective of the present study was to evaluate the importance of medium components on capacitation of porcine sperm, the appearance of an Mr 32 000 sperm protein (p32), and activity of a tyrosine kinase (TK-32). As determined by the ability of the sperm to undergo the A23187-induced acrosome reaction, pig sperm require bicarbonate and calcium but not BSA for capacitation in vitro. The appearance of p32 was assessed by immunoblotting SDS-extracted and separated sperm proteins using an anti-phosphotyrosine antibody. The appearance of p32 requires calcium, although p32 appears even in the absence of bicarbonate in the incubation medium, demonstrating that the appearance of this tyrosine phosphoprotein is not a final end point of pig sperm capacitation. An in-gel tyrosine kinase renaturation assay showed that TK-32 activity depends on calcium and bicarbonate in the incubation medium. Immunoprecipitation experiments using an anti-phosphotyrosine antibody and inhibitor demonstrated that p32 and TK-32 are different proteins. These data indicate that the signal transduction mechanisms of capacitation in pig sperm are different from those in other mammals, suggesting that certain species specificity may exist with respect to this phenomenon.
1 This research was funded by the Natural Sciences and Engineering Research Council of Canada and the Fonds pour la Formation de Chercheurs et l'Aide à la Recherche.
2 Correspondence: Janice L. Bailey, Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Pavillon Paul-Comtois, Université Laval, Sainte-Foy, QC, Canada G1K 7P4. FAX: 481 656 3766; janice.bailey{at}crbr.ulaval.ca
Copyright © 2003 by the Society for the Study of Reproduction.