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 kinase-A)-mediated phosphorylation of a group of largely unidentified flagellar 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 presumably localize the activity of the kinase near specific targets in the sperm flagellum. In this way, pro-hAKAP82 and hAKAP82 may be involved in regulating sperm motility. Similar to its homologues in other species, pro-hAKAP82 is proteolytically processed to hAKAP82. However, the amount of processing of pro-hAKAP82 in human spermatozoa is less than the amount of processing of the precursor in other species. We postulated that this lower extent of processing may be related to lower percentages of human sperm motility. In addition, both pro-hAKAP82 and hAKAP82 are tyrosine phosphorylated in a capacitation-dependent manner. Since capacitation is associated with hyperactivated motility, we postulated that tyrosine phosphorylation of pro-hAKAP82/hAKAP82 is associated with changes in motility. However, using a combination of immunofluorescence and immunoblotting approaches, we found no evidence for an association between either processing or tyrosine phosphorylation of pro-hAKAP82/hAKAP82 and significant differences in motility in spermatozoa from normal men.
Turner
R M
RM
Center for Research on Reproduction and Women's Health, Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, 421 Curie Blvd., Philadelphia, PA 19104, USA.
Eriksson
R L
RL
Gerton
G L
GL
Moss
S B
SB
D054758:A Kinase Anchor Proteins; D000595:Amino Acid Sequence; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*; D012016:Reference Values; D029589:Seminal Plasma Proteins; D013075:Sperm Capacitation; D013081:Sperm Motility / Q000502:physiology*; D013082:Sperm Tail / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D054758:A Kinase Anchor Proteins; C485480:AKAP4 protein, human; D011498:Protein Precursors; D011506:Proteins; D029589:Seminal Plasma Proteins; C116030:pro-AKAP82 protein, mammalian; D014443:Tyrosine