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First published online December 15, 2003

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Sperm capacity decreased

Prior to fertilization, spermatozoa must undergo capacitation - a maturation process in which they react to signals in the female reproductive tract and acquire the ability to undergo tyrosine phosphorylation in response to cyclic AMP. Ca²⁺ is a potential regulator of the process; however, its effects on capacitation and tyrosine phosphorylation are disputed. John Aitken and co-workers now clear up the controversy by demonstrating that Ca²⁺ negatively regulates this signalling pathway (see p. 211). They confirm the importance of tyrosine phosphorylation for capacitation and show that extracellular Ca²⁺ reduces its extent in human and mouse spermatozoa. Interestingly, they find that this is associated with reduced ATP levels and can be mimicked by glucose deprivation. Suspecting that Ca²⁺-dependent ATPases such as the SERCA Ca²⁺ pump might be involved, the authors go on to demonstrate, using radiolabelled probes, that spermatozoa have many such ATPases. They then show that the SERCA inhibitor thapsigargin also suppresses tyrosine phosphorylation. Their findings thus not only indicate that Ca²⁺ inhibits tyrosine phosphorylation during capacitation but reveal the importance of ATP-dependent pumps - which could be significant in the context of male infertility, given the known correlation between sperm function and ATP levels.

Related articles in JCS:

Analysis of the mechanism by which calcium negatively regulates the tyrosine phosphorylation cascade associated with sperm capacitation

Mark A. Baker, Louise Hetherington, Heath Ecroyd, Shaun D. Roman, and R. John Aitken
JCS 2004 117: 211-222. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content