Proteinase-activated receptor-2 (PAR-2) is a member of a family of G-protein-coupled, seven-transmembrane domain receptors that are activated by proteolytic cleavage. The receptor is expressed in a number of different tissues and potential physiological activators identified thus far include trypsin and mast cell tryptase. Acrosin, a trypsin-like serine proteinase found in spermatozoa of all mammals, was found to cleave a model peptide fluorescent quenched substrate representing the cleavage site of PAR-2. This substrate was cleaved with kinetics similar to those of the known PAR-2 activators, trypsin and mast cell tryptase. Acrosin was also shown to induce significant intracellular calcium responses in Chinese hamster ovary cells stably expressing intact human PAR-2, most probably due to activation of the receptor. Immunohistochemical studies using PAR-2 specific antibodies indicated that the receptor is expressed by mouse oocytes, which suggests that acrosin may play additional role(s) in the fertilization process via the activation of PAR-2 on oocytes.

1 AbstractAbstractAbstractAbstract Proteins secreted in the male reproductive tract play a key role in post-testicular development of sperm and in further steps needed for fertilization. Sperm maturation represents a key step in the reproduction process. Sperm, during the passage through the epididymis undergoes significant changes due to proteolytic and glycolytic activities in the epididymal fluid. Inhibitor of acrosin protects spermatozoa and reproductive epithelium against proteolytic degradation and also protects binding sites for ZP on sperm plasma membrane. In boar reproductive system acrosin inhibitor (AI) was found in seminal plasma and on sperm plasma membrane. Polyclonal antibody recognized AI in extracts of the cauda epididymidis, seminal vesicles, prostate, and Cowper's glands. Using immunofluorescence method has revealed the AI in the epithelium and lumen of these organs but also on the surface of epididymal and ejaculated spermatozoa. We registered the increasing signal of AI from caput to cauda epididymis. Gene expression of AI mRNA was detected in the epididymis, seminal vesicles, prostate, and Cowper's glands and increased gradually throughout the epididymal duct. In present study, we also monitored AI in boar epididymal fluid and spermatozoa along the organ. In the epididymis, AI may...