Relationship between sperm motility and the processing and tyrosine phosphorylation of two human sperm fibrous sheath proteins, pro-hAKAP82 and hAKAP82

Sperm motility is regulated by the cAMP-dependent protein kinase (protein k inase-A)-mediated phosphorylation of a group of largely unidentified flagel lar proteins. Human AKAP82 (hAKAP82) and its precursor protein, pro-hAKAP82 , are members of the A-kinase anchor protein (AKAP) family. These proteins tether protein kinase-A to the fibrous sheath of human spermatozoa and pres umably localize the activity of the kinase near specific targets in the spe rm flagellum. In this way, pro-hAKAP82 and hAKAP82 may be involved in regul ating sperm motility. Similar to its homologues in other species, pro-hAKAP 82 is proteolytically processed to hAKAP82. However, the amount of processi ng of pro-hAKAP82 in human spermatozoa is less than the amount of processin g of the precursor in other species. We postulated that this lower extent o f processing may be related to lower percentages of human sperm motility. I n addition, both pro-hAKAP82 and hAKAP82 are tyrosine phosphorylated in a c apacitation-dependent manner. Since capacitation is associated with hyperac tivated motility, we postulated that tyrosine phosphorylation of pro-hAKAP8 2/hAKAP82 is associated with changes in motility. However, using a combinat ion of immunofluorescence and immunoblotting approaches, we found no eviden ce for an association between either processing or tyrosine phosphorylation of pro-hAKAP82/hAKAP82 and significant differences in motility in spermato zoa from normal men.