IDENTIFICATION OF PHOSPHOPROTEINS COUPLED TO INITIATION OF MOTILITY IN LIVE EPIDIDYMAL MOUSE SPERM

A method for collecting live immotile cauda epididymal mouse sperm tha t initiate motility by dilution into an activation buffer is described . Sperm in collection buffer showed low percent motility (MOT) and pop ulation progression (PRG) that increased 10-fold and 9-fold, respectiv ely, during the first 2 min after dilution into activation buffer. Wes tern phosphoserine (pS), phosphothreonine (pT), and phosphotyrosine (p Y) analysis revealed a 120 kDa protein that markedly increased in pT c ontent during initiation of motility and may be related to FP130, the motility-coupled axonemal protein of sea urchin sperm. A prominent 82 kDa protein that was pS and pT-phosphorylated in immotile and motile s perm is likely the fibrous sheath component AKAP82 that is phosphoryla ted during spermatogenesis. Analysis of live human sperm also identifi ed a prominent 120 kDa pT protein. Thus it appears that phosphorylatio n of FP130 and related 120 kDa proteins in mouse, and perhaps human sp erm, represent common targets during motility initiation in sperm. (C) 1998 Academic Press.