Identification and spatial distribution of glycine receptor subunits in human sperm

The human sperm surface glycine receptor (GLR) plays a role in an important fertilization event, the sperm acrosome reaction. Here, by western blot analysis, we report the presence of GLRA1, GLRA2, GLRA3, and GLRB subunits in human sperm. Immunolocalization studies showed that the GLRA1 and GLRA2 subunits are present in the equatorial region, the GLRA3 subunit in the flagellar principal piece, and the GLRB subunit in the acrosomal region of sperm. This first demonstration of isoforms of the sperm GLRA subunit and of a differential spatial distribution of the alpha and beta subunits on the surface of mammalian sperm suggests the possibility that human sperm GLRs have more than one function.