Evidence for the involvement of proline-directed serine/threonine phosphorylation in sperm capacitation.

TitleEvidence for the involvement of proline-directed serine/threonine phosphorylation in sperm capacitation.
Publication TypeJournal Article
Year of Publication2006
AuthorsJha KN, Salicioni AM, Arcelay E, Chertihin O, Kumari S, Herr JC, Visconti PE
JournalMolecular human reproduction
Date Published2006 Dec
Keywords1-Methyl-3-isobutylxanthine, Amino Acid Motifs, Animals, Antibodies, Monoclonal, beta-Cyclodextrins, Blotting, Western, Bucladesine, Butadienes, Cattle, Cholesterol, Cyclic AMP, Flavonoids, Humans, Male, Mice, Mitogen-Activated Protein Kinase 1, Mitogen-Activated Protein Kinase 3, Mitosis, Nitriles, Phosphoproteins, Phosphorylation, Proline, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, Serum Albumin, Bovine, Sodium Bicarbonate, Sperm Capacitation, Spermatozoa
AbstractTo 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.
Alternate JournalMol. Hum. Reprod.
PubMed ID17050774