Immunochemical identification of the glycine receptor/Cl-channel in porcine sperm.

Cl- flux is essential for the mammalian sperm acrosome reaction (AR), a required fertilization event involving fusion of sperm head membranes. Our previous inhibitor studies suggested the involvement of a glycine receptor/Cl- channel (GlyR) in the zona pellucida-initiated mammalian sperm AR. Here, using a monoclonal antibody specific for the alpha (48-kDa) and beta (58-kDa) subunits of the rat spinal cord GlyR (mAb GlyR4a), we provide the first direct evidence for GlyR in mammalian sperm. Immunofluorescence studies with mAb GlyR4a detected immunoreactivity on the porcine sperm periacrosomal plasma membrane, a site supporting GlyR involvement in the AR. In Western immunoblotting studies, mAb GlyR4a bound specifically to porcine sperm proteins of 49.2 +/- 2.2 kDa and 58.0 +/- 2.7 kDa. This is the first direct demonstration of both alpha and beta subunits of GlyR in a nonnervous system cell.