Relationship between sperm motility and the processing and tyrosine phosphorylation of two human sperm fibrous sheath proteins, pro-hAKAP82 and hAKAP82
Rmo. Turner et al., Relationship between sperm motility and the processing and tyrosine phosphorylation of two human sperm fibrous sheath proteins, pro-hAKAP82 and hAKAP82, MOL HUM REP, 5(9), 1999, pp. 816-824
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.