Evidence for the involvement of proline-directed serine/threonine phosphorylation in sperm capacitation.
To become fertilization competent, mammalian sperm undergo changes in the female reproductive tract termed capacitation. Capacitation correlates with an increase in tyrosine phosphorylation; however, less is known about the role of serine/threonine phosphorylation in this process. Proline-directed phosphorylation is one of the major regulatory phosphorylation events in many cellular processes such as cell proliferation and differentiation. Using mitotic phosphoprotein monoclonal-2 (MPM-2) antibody in this study, we observed that several mouse sperm proteins in the range of 70-250 kDa underwent increased serine/threonine-proline phosphorylation during capacitation. In contrast to the time course of tyrosine phosphorylation, proline-directed phosphorylation could be observed at shorter time points of sperm incubation, and it was found to be independent of NaHCO(3) and adenosine 3'5'-cyclic monophosphate (cAMP). Similar to the regulation of the increase in tyrosine phosphorylation, cholesterol acceptors such as bovine serum albumin (BSA) or 2-hydroxypropyl-beta-cyclodextrin (2-OH-propyl-beta-CD) were essential for the regulation of proline-directed phosphorylation in mouse sperm. Furthermore, it was also found to be BSA dependent in human sperm. Among proline-directed kinases, extracellular signal-regulated kinase 1/2 (ERK1/2) is present in mammalian sperm; nevertheless, U0126 and PD098059, two inhibitors of the ERK pathway, did not block this phosphorylation in mouse sperm. In conclusion, capacitation is associated with an increase in proline-directed phosphorylation linked to cholesterol efflux in the sperm.
Jha
K N
KN
Center for Research in Contraceptive and Reproductive Health, Department of Cell Biology, University of Virginia, Charlottesville, VA, USA.
Salicioni
A M
AM
Arcelay
E
E
Chertihin
O
O
Kumari
S
S
Herr
J C
JC
Visconti
P E
PE
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D020816:Amino Acid Motifs; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015153:Blotting, Western; D003994:Bucladesine / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D002417:Cattle; D002784:Cholesterol / Q000378:metabolism*; D000242:Cyclic AMP / Q000819:agonists; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008938:Mitosis; D009570:Nitriles / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011392:Proline / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D017693:Sodium Bicarbonate / Q000494:pharmacology; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D002070:Butadienes; D005419:Flavonoids; D009570:Nitriles; D010750:Phosphoproteins; C113580:U 0126; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D012710:Serum Albumin, Bovine; D003994:Bucladesine; D017693:Sodium Bicarbonate; D002784:Cholesterol; D011392:Proline; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D015056:1-Methyl-3-isobutylxanthine