A tyrosine-phosphorylated 55-kilodalton motility-associated bovine sperm protein is regulated by cyclic adenosine 3',5'-monophosphates and calcium.
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 PP1gamma2, 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 or 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 alpha-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.
Vijayaraghavan
S
S
Oregon Regional Primate Research Center, Beaverton 97006, USA. vijay@teleport.com
Trautman
K D
KD
Goueli
S A
SA
Carr
D W
DW
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry; D013081:Sperm Motility / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
D010455:Peptides; D010750:Phosphoproteins; D014404:Tubulin; C024152:phosphorylated motility protein, bovine sperm; D019000:Phosphotyrosine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium