Evidence for the activation of PAR-2 by the sperm protease, acrosin: expression of the receptor on oocytes

Proteinase-activated receptor-2 (PAR-2) is a member of a family of G-protei n-coupled, seven-transmembrane domain receptors that are activated by prote olytic 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 fluorescen t quenched substrate representing the cleavage site of PAR-2, This substrat e was cleaved with kinetics similar to those of the known PAR-2 activators, trypsin and mast cell tryptase, Acrosin was also shown to induce significa nt intracellular calcium responses in Chinese hamster ovary cells stably ex pressing intact human PAR-2, most probably due to activation of the recepto r. Immunohistochemical studies using PAR-2 specific antibodies indicated th at 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, (C) 2000 Federation of European Biochemical.