A tyrosine-phosphorylated 55-kilodalton motility-associated bovine sperm protein is regulated by cyclic adenosine 3',5'-monophosphates and calcium

Srinivasan Vijayaraghavan, Kevin D. Trautman, Said A. Goueli, Daniel W. Carr

Research output: Contribution to journalArticle

78 Scopus citations


Sperm motility is regulated by protein phosphorylation. We have recently shown that a serine/threonine phosphatase system is involved in motility regulation. Two of the components of the phosphatase system, GSK-3 and PP1γ2, are regulated by tyrosine phosphorylation. During our investigation of sperm tyrosine-phosphorylated proteins we discovered a 55-kDa protein whose tyrosine phosphorylation correlates closely to the motility state of sperm. This protein is tyrosine phosphorylated to a much higher degree in motile caudal than in immotile caput epididymal sperm. Motility inhibition of caudal epididymal sperm by protein kinase A (PKA) anchoring inhibition or by ionomycin-induced calcium overload led to the virtual disappearance of tyrosine phosphorylation of the 55-kDa protein. Conversely, treatment of sperm with motility activators, isobutylmethylxanthine of 8-bromo-cAMP, resulted in increased tyrosine phosphorylation of the protein. The protein was present in the soluble 100 000 x g supernatants of sperm extracts and was heat labile. Chromatography through diethylaminoethyl-cellulose and Western blot analysis showed that this 55-kDa protein is not a regulatory subunit of PKA or α-tubulin. Our results represent the identification of a soluble protein whose tyrosine phosphorylation varies directly with motility and suggest that motility regulation may involve cross talk between PKA, calcium, and tyrosine kinase pathways.

Original languageEnglish (US)
Pages (from-to)1450-1457
Number of pages8
JournalBiology of reproduction
Issue number6
StatePublished - Jun 1 1997


ASJC Scopus subject areas

  • Reproductive Medicine
  • Cell Biology

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