Protein kinase A and protein kinase Cα/PPP1CC2 play opposing roles in the regulation of phosphatidylinositol 3-kinase activation in bovine sperm

Rotman, Tali; Etkovitz, Nir; Spiegel, Ayala; Rubinstein, Sara; Breitbart, Haim

doi:10.1530/rep-09-0314

Cited by 23 publications

(19 citation statements)

References 49 publications

(82 reference statements)

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“…It has been shown elsewhere that PKA activity in bovine sperm increases during capacitation [38]. Moreover, we showed that PKC and PP1γ2 degradation in bovine sperm capacitation depend on PKA activity [38]. Thus, we hypothesized that PKA mediates AKAP3 degradation.…”

Section: Resultsmentioning

confidence: 86%

“…During sperm capacitation bicarbonate activates sperm sAC to produce cAMP which activates PKA C by releasing it from the AKAP complex [5–7]. Under capacitation conditions AKAP3 is degraded towards the end of the capacitation (Figures 1, 4, 8a) We have previously shown that PKA activity was increased during incubation of bovine sperm in capacitation medium and under these conditions we find PKA-dependent degradation of PKC and PP1 [38]. In this study we showed that activation of PKA increased AKAP3 degradation (Figures 6B, 8b), however to our surprise, we found that inhibition of PKA activity by H89 does not block, but rather accelerates, AKAP3 degradation (Figures 5, 8d).…”

Section: Discussionmentioning

confidence: 93%

“…In order to explain the differential effect of intracellular alkalization versus treatment with Ht31 on RII degradation, we assumed that intracellular alkalization specifically affects AKAP3 degradation, causing a relatively small increase in unbound RII, whereas Ht31 induces the release of RII from all AKAPs, resulting in high levels of unbound RII, which is highly sensitive to degradation. The mechanism of AKAP3 degradation differs from that of PKCα and PP1γ2 degradation described by us elsewhere [38]. In both cases, cAMP enhances degradation, however, the PKA inhibitor H89 enhances AKAP3 degradation but inhibits PKCα or PP1γ2 degradation [38].…”

Section: Discussionmentioning

confidence: 99%

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Dissociation between AKAP3 and PKARII Promotes AKAP3 Degradation in Sperm Capacitation

et al. 2013

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Ejaculated spermatozoa must undergo a series of biochemical modifications called capacitation, prior to fertilization. Protein-kinase A (PKA) mediates sperm capacitation, although its regulation is not fully understood. Sperm contain several A-kinase anchoring proteins (AKAPs), which are scaffold proteins that anchor PKA. In this study, we show that AKAP3 is degraded in bovine sperm incubated under capacitation conditions. The degradation rate is variable in sperm from different bulls and is correlated with the capacitation ability. The degradation of AKAP3 was significantly inhibited by MG-132, a proteasome inhibitor, indicating that AKAP3 degradation occurs via the proteasomal machinery. Treatment with Ca2+-ionophore induced further degradation of AKAP3; however, this effect was found to be enhanced in the absence of Ca2+ in the medium or when intracellular Ca2+ was chelated the degradation rate of AKAP3 was significantly enhanced when intracellular space was alkalized using NH4Cl, or when sperm were treated with Ht31, a peptide that contains the PKA-binding domain of AKAPs. Moreover, inhibition of PKA activity by H89, or its activation using 8Br-cAMP, increased AKAP3 degradation rate. This apparent contradiction could be explained by assuming that binding of PKA to AKAP3 protects AKAP3 from degradation. We conclude that AKAP3 degradation is regulated by intracellular alkalization and PKARII anchoring during sperm capacitation.

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Section: Resultsmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

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Dissociation between AKAP3 and PKARII Promotes AKAP3 Degradation in Sperm Capacitation

et al. 2013

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“…75 Recently, we showed that PKCa undergoes degradation and dephosphorylation during capacitation. 76 This downregulation of PKCa occurs at the same time as the phosphorylation of Tyr467 on phosphatidyl-inositol-3-kinase (PI3K) regulatory subunit p85 is increased.…”

Section: Protein Kinases a And Cmentioning

confidence: 99%

“…At the beginning of the capacitation process, PKCa and PP1c2 are active and present in high levels and inhibit (directly or indirectly) PI3K phosphorylation. 76 With ongoing capacitation, PKA mediates PKCa and PP1c2 degradation, the inhibition of PI3K by PKCa/PP1c2 is relaxed and PI3K phosphorylation/activation by PKA can occur.…”

Section: Pi3kmentioning

confidence: 99%

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

Ickowicz¹,

Finkelstein²,

Breitbart³

2012

Asian J Androl

194

128

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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.

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Distinct segment‐specific functions of calyculin A‐sensitive protein phosphatases in the regulation of cAMP‐triggered events in ejaculated bull spermatozoa

Mizuno

Isono

Kojima

et al. 2015

Molecular Reproduction Devel

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Livestock spermatozoa possess more tenacious suppressors of cAMP-triggered events-including capacitation-associated changes-than laboratory animal spermatozoa, leading to flagellar hyperactivation. In order to identify the suppressors, we examined effects of an inhibitor of serine/threonine protein phosphatases (calyculin A) on cAMP-triggered changes in the protein phosphorylation state, and subsequent occurrence of hyperactivation and acrosome reaction in ejaculated bull spermatozoa. Ejaculated spermatozoa were incubated in cAMP-supplemented medium, then assessed for motility, acrosome morphology, and phosphorylated protein localization. The addition of calyculin A greatly enhanced cAMP-triggered protein phosphorylation at serine/threonine and tyrosine residues in the connecting piece and induction of flagellar hyperactivation. Most hyperactivated spermatozoa exhibited extremely asymmetrical bends at the middle piece, which produced intensive twisting or figure-eight movements. In the sperm head, however, cAMP-triggered dephosphorylation of serine/threonine-phosphorylated proteins and subsequent acrosome reaction were abolished by the addition of calyculin A. Based on these results, we suggest that calyculin A-sensitive protein phosphatases in the connecting piece are suppressors of cAMP-triggered events leading to hyperactivation. By contrast, similar protein phosphatases in the sperm head accelerate cAMP-triggered events leading to the acrosome reaction. These findings are consistent with the indication that calyculin A-sensitive protein phosphatases have distinct functions in the regulation of cAMP-triggered events in different regions of ejaculated bull spermatozoa.

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Protein kinase A and protein kinase Cα/PPP1CC2 play opposing roles in the regulation of phosphatidylinositol 3-kinase activation in bovine sperm

Cited by 23 publications

References 49 publications

Dissociation between AKAP3 and PKARII Promotes AKAP3 Degradation in Sperm Capacitation

Dissociation between AKAP3 and PKARII Promotes AKAP3 Degradation in Sperm Capacitation

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

Distinct segment‐specific functions of calyculin A‐sensitive protein phosphatases in the regulation of cAMP‐triggered events in ejaculated bull spermatozoa

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