Model for the participation of PP1, PP2A, and PP2B during human sperm capacitation.

<p>(1) The first event of capacitation is the efflux of cholesterol mediated by albumin (BSA), (2) causing an increase in membrane fluidity that allows the entry of Ca2+ and HCO3-. These ions activate the soluble adenylyl cyclase (SACY) which increases the level of cAMP (3) and allow PKA activation. (4) PKA increases the phosphorylation of proteins in Ser/Thr residues. (5) This activates tyrosine kinases (PTK), (6) which produce an increase in protein Tyr phosphorylation. (7) Finally, the sperm cells capacitate. (8) Our results indicate that the Ser/Thr phosphatases, PP1, PP2A and PP2B, inactivate during capacitation and this allow sperm to capacitate. (9) Battistone et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081286#pone.0081286-Battistone1" target="_blank">[24]</a> propose that down-regulation of PP1 and PP2A is mediate by SFK and is a parallel pathways to the PKA/cAMP pathway.