Mechanism of sperm capacitation and the acrosome reaction: role of protein kinases

Abstract

Mammalian sperm must undergo a series of biochemical and physiological modifications, collectively called capacitation, in the female reproductive tract prior to the acrosome reaction (AR). The mechanisms of these modifications are not well characterized though protein kinases were shown to be involved in the regulation of intracellular Ca 21 during both capacitation and the AR. In the present review, we summarize some of the signaling events that are involved in capacitation. During the capacitation process, phosphatidyl-inositol-3-kinase (PI3K) is phosphorylated/activated via a protein kinase A (PKA)-dependent cascade, and downregulated by protein kinase C a (PKCa). PKCa is active at the beginning of capacitation, resulting in PI3K inactivation. During capacitation, PKCa as well as PP1c2 is degraded by a PKA-dependent mechanism, allowing the activation of PI3K. The activation of PKA during capacitation depends mainly on cyclic adenosine monophosphate (cAMP) produced by the bicarbonate-dependent soluble adenylyl cyclase. This activation of PKA leads to an increase in actin polymerization, an essential process for the development of hyperactivated motility, which is necessary for successful fertilization. Actin polymerization is mediated by PIP 2 in two ways: first, PIP 2 acts as a cofactor for phospholipase D (PLD) activation, and second, as a molecule that binds and inhibits actin-severing proteins such as gelsolin. Tyrosine phosphorylation of gelsolin during capacitation by Src family kinase (SFK) is also important for its inactivation. Prior to the AR, gelsolin is released from PIP 2 and undergoes dephosphorylation/activation, resulting in fast F-actin depolymerization, leading to the AR.

Acetylproteomic Analysis Reveals Functional Implications of Lysine Acetylation in Human Spermatozoa (sperm)

“…When enrichment efficiency was compared, the percentage of acetylated peptides over total peptides ranged from ϳ12 to 31%, which was higher than that of polyclonal antibodies (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)see Ref. 32).…”

“…The importance of phosphorylation, an essential PTM in sperm differentiation, maturation, and fertilization, has been well established (16,17). Acetylation as a broad and abundant PTM comparable with phosphorylation (18), however, has not been well analyzed in human sperm.…”

Evaluation of two diluents for the storage of fresh and cryopreserved semen of Harris hawk (Parabuteo unicinctus)

“…This phenomenon occurs because the PVL contains progesterone. When progesterone interacts with its receptor on the sperm membrane, it causes Ca 2+ to enter the cell, leading to an AR (Sasanami et al 2007, Lemoine et al 2009, Ickowicz et al 2012.…”

Sperm RNA as a Mediator of Genomic Plasticity

“…Several reports, the most recent of which focused on sperm capacitation, have provided evidence that sperm RNA can be translated de novo [47,48]. Capacitation is the term used to describe the events that take place following ejaculation that enables the spermatozoon to undergo an eggpenetrating acrosome reaction [49,50]. These newly synthesised proteins may serve to replace older proteins that are degraded or lost during capacitation.…”