The receptor for urokinase-type plasminogen activator is expressed during mouse spermatogenesis

Urokinase-type plasminogen activator (uPA) binds to a plasma membrane receptor (uPAR) that localizes plasmin generation to the cell environment. Mouse spermatozoa have surface-bound uPA, which appears to be acquired from genital tract secretions at ejaculation. We determined the presence of uPAR mRNA in spermatogenic cells and their uPA-binding activity. Northern blot and in situ hybridization demonstrated the presence of uPAR mRNA in germ cells. Binding of uPA, but not of a mutant enzyme lacking the receptor-binding domain, indicated the presence of uPAR on spermatids and spermatozoa. The uPAR and/or receptor-bound uPA may be involved in spermatogenesis, spermatozoa maturation or fertilization.