Compromised sperm protein phosphorylation after capacitation, swim-up, and zona pellucida exposure in teratospermic domestic cats.

Tyrosine phosphorylated proteins recently have been found in mouse and human spermatozoa. Our objectives were to (1) determine if domestic cat spermatozoa also express tyrosine phosphorylated proteins, and (2) examine the changes in protein phosphorylation between normospermic and teratospermic domestic cats following sperm capacitation, swim-up separation and exposure to zona pellucida (ZP). Membranes from cat spermatozoa contained two phosphorylated proteins of molecular weights 160 kDa and 95 kDa (designated as p160 and p95) that immunoreacted with monoclonal antibodies to tyrosine phosphate. The p95 protein was distinct from sperm-specific hexokinase. Following capacitation, the extent of phosphorylation of p95 was increased (P < 0.05) 3-fold in normospermic cats compared to only 1.75-fold in teratospermic cats. Similarly, phosphorylation of p160 also increased (P < 0.05) 2.4-fold in normospermic compared to 1.84-fold in teratospermic cats. Although swim-up separation increased the percentage of normal spermatozoa in teratospermic ejaculates, phosphorylation of p95 in swim-up, aliquots was increased (P < 0.05) only 1.95-fold in teratospermic cats compared to 2.9-fold in normospermic counterparts. Likewise, phosphorylation of p160 was lower (P < 0.05) in teratospermic (1.5-fold) compared to normospermic cats (2.0-fold) cats. Phosphorylation also was influenced by exposure to cat ZP proteins (P < 0.05). Solubilized cat ZP bound to the sperm proteins of apparent molecular mass 120, 95, 50, 42, 30, 27, 23 and 20 kDa, suggesting a direct binding interaction between p95 and the ZP. Overall, these findings (1) indicate the presence of tyrosine phosphorylated proteins in the domestic cat spermatozoon that directly interact with homologous ZP glycoproteins; (2) demonstrate that cat sperm hexokinase is not phosphorylated on tyrosine residues; and (3) suggest that the diminished phosphorylation efficiency of sperm from teratospermic cats may result in a compromise in capacitation and the acrosome reaction.