Tyrosine Phosphorylation Pattern in Sperm Proteins Isolated from Normospermic and Teratospermic Men

Introduction: In mammalian system, spermatozoa are not able to fertilize the oocyteimmediately upon ejaculation, thus they undergo a series of biochemical and molecularchanges which is termed capacitation. During sperm capacitation, signal transductionpathways are activated which lead to protein tyrosine phosphorylation. Tyrosinephosphorylated proteins have an important role in sperm capacitation such as hyperactivemotility, interaction with zona pellucida and acrosome reaction. Evaluation of tyrosinephosphorylation pattern is important for further understanding of molecular mechanisms offertilization and the etiology of sperm dysfunctions and abnormalities such as teratospermia.The goal of this study is to characterize tyrosine phosphorylation pattern in sperm proteinsisolated from normospermic and teratospermic infertile men attending Avicenna InfertilityClinic in Tehran.Materials and Methods: Semen samples were collected and the spermatozoa were isolatedusing Percoll gradient centrifugation. Then the spermatozoa were incubated up to 6h at 37°Cwith 5% CO2 in 3% Bovine Serum Albumin-supplemented Ham’s F-10 for capacitation totake place. The total proteins from spermatozoa were extracted and were subjected to SDSPAGEbefore and after capacitation. To evaluate protein tyrosine phosphorylation pattern,western blotting with specific antibody against phosphorylated tyrosines was performed.Results: The results upon western blotting showed: 1) at least six protein bands were detectedbefore capacitation in the spermatozoa from normospermic samples. However, comparablelevels of tyrosine phosphorylation was not observed in the spermatozoa from teratospermicsamples. 2) The intensity of protein tyrosine phosphorylation appears to have been increasedduring capacitation in the normospermic relative to the teratospermic group.Conclusion: For the first time, these findings demonstrate and suggest that the differences inthe types of proteins and diminished tyrosine phosphorylation efficiency in sperm fromteratospermic men may be responsible for their compromised capacitation and lowfertilization success rates.