Functional Studies Of Human Sperm Protein Erp57

Human infertility is a growing concem and while many assisted reproductive technologies exist their success rates are low. Thus, developing tests, possibly by assessing proteins involved in fertilization that could predict the outcome of these technologies is of great significance. To identify candidate proteins, we used two-dimensional PAGE and MALDI-TOF techniques and detected the ERp57 protein from human testis protein profile. Immunohistochemistry showed that ERp57 was mostly located on spermatogenic cell cytoplasm from spermatocyte to the spermatozoa phases and Leydig cells of human testes; it was present in low levels in Sertoli cells. Moreover, ERp57 was evident in human spermatozoa, primarily in the acrosome and tail, and might undergo modification during human capacitation. Blocking ERp57 with antibodies significantly inhibited human sperm from penetrating zona-free hamster eggs in a dose-dependent manner. Finally, expression levels of ERp57 were associated with fertility; they were decreased dramatically in IVF patients with low fertilization rate compared to those with a high rate or fertile sperm donors. Taken together, these results show that ERp57 is a component of human sperm acrosome proteins that play a critical role in gamete fusion. Furthermore, ERp57 could be a novel phenotype marker for male infertility and has the potential to be used to assess sperm selections for IVF.