Involvement of cyclins and cdc2 serine/threonine protein kinase in human sperm cell function

Abstract

The presence and roles of mitotic cyclins (cyclin A and cyclin B1) and cdc2 and related (having an N-terminal PSTAIRE conserved sequence) serine/threonine protein kinases were investigated by use of specific antibodies. The cyclin A and cyclin B1 antibodies reacted specifically with the acrosomal regions of human sperm cells in the indirect immunofluorescence technique (IFT) and recognized the specific band of p60 (cyclin A) and p62 (cyclin B1) on the Western blot of sodium deoxycholate (DOC)-solubilized noncapacitated human sperm preparation. Both antibodies reacted more strongly with the specific cell region/band of capacitated sperm than with that of noncapacitated sperm. The cdc2 and PSTAIRE antibodies also reacted predominantly with the acrosomal regions of human sperm cells in IFT and recognized the specific band of 34 kDa corresponding to p34 cdc2 protein on the Western blot of DOC-solubilized noncapacitated human sperm preparation. Again, both antibodies reacted more strongly with the specific cell region/band of capacitated sperm than with that of noncapacitated sperm. The cyclin A antibodies (but not the cyclin B1 antibodies) and cdc2 antibodies as well as the PSTAIRE antibodies significantly (p = 0.02 to p < 0.001) increased (rather than decreased) the human sperm penetration rates of zona- free hamster ova; the cyclin A and cdc2 antibodies showed the strongest enhancing effects. These three antibodies significantly increased the acrosome reaction and release of acrosin activity from the sperm cells. There was no significant effect of these antibodies on percentage of motility, though they significantly affected various sperm motility characteristics, especially the velocity, amplitude of lateral head displacement, and beat cross frequency-the motility parameters involved in hyperactivation phenomenon of sperm cells. These results suggest the presence and possible involvement of mitotic cyclins (especially cyclin A) and of cdc2 and related serine/threonine protein kinases in the human sperm cell capacitation and/or acrosome reaction.