Inhibition of mouse acrosome reaction and sperm-zona pellucida binding by anti-human sperm membrane protein 1 antibody

AIM: To investigate the possible functions of human sperm membrane protein (hSMP-1) in the process of fertilization. METHODS: A 576-bp cDNA fragment of HSD-1 gene coding for the extracellular domain of hSMP-1 was cloned and expressed. The localization of this protein on human and mouse sperm was determined by indirect immunofluorescent staining by using anti-recombinant hSMP-1 (anti-rhSMP-1) antibodies. Sperm acrosome reaction and sperm-zona pellucida (ZP) binding assay were carried out in 10-week-old BALB/c mice. RESULTS: Recombinant hSMP-1 was successfully cloned and expressed. The expression of the native protein was limited on the acrosome of human and mouse sperm. Treatment of anti-rhSMP-1 antibodies significantly decreased the average number of sperms bound to each egg. Meanwhile, the percentage of acrosome reaction was decreased in comparison to pre-immune control after treatment with anti-rhSMP-1 (P < 0.05). CONCLUSION: The results suggest that anti-rhSMP-1 antibody inhibited mouse acrosome reaction and sperm-ZP binding.