PKCα reduces the lipid kinase activity of the p110α/p85α PI3K through the phosphorylation of the catalytic subunit

Sipeki, Szabolcs; Bander, Erzsébet; Parker, Peter J.; Farago, Anna F.

doi:10.1016/j.bbrc.2005.10.194

Cited by 17 publications

(20 citation statements)

References 24 publications

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“…This effect was transient, with maximal inhibition observed at 30 min of PKC stimulation and recovery to near basal levels by 2 h. The ability of member(s) of the PKC family to negatively regulate PI3K and/or Akt activity has been noted in other systems, including adipocytes (77), phaeochromocytoma cells (78), vascular smooth muscle cells (79,80), kidney epithelial cells (81,82), human airway epithelial cells (82), prostate cancer cells (83), and keratinocytes (84), pointing to a widespread role of PKC signaling in control of this pathway. Interestingly, PKC␣ (but not PKC⑀) was recently reported to inhibit the lipid kinase activity of PI3K in vitro through direct phosphorylation of its p110␣ catalytic subunit (85). PKCs have also been shown to phosphorylate various upstream modulators of PI3K activity, including receptors and docking proteins, and thus attenuate downstream PI3K signaling (86 -88).…”

Section: Discussionmentioning

confidence: 99%

Protein Kinase C-mediated Down-regulation of Cyclin D1 Involves Activation of the Translational Repressor 4E-BP1 via a Phosphoinositide 3-Kinase/Akt-independent, Protein Phosphatase 2A-dependent Mechanism in Intestinal Epithelial Cells

Guan

Song

Pysz

et al. 2007

Journal of Biological Chemistry

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We reported previously that protein kinase C␣ (PKC␣), a negative regulator of cell growth in the intestinal epithelium, inhibits cyclin D1 translation by inducing hypophosphorylation/activation of the translational repressor 4E-BP1. The current study explores the molecular mechanisms underlying PKC/PKC␣-induced activation of 4E-BP1 in IEC-18 nontransformed rat ileal crypt cells. PKC signaling is shown to promote dephosphorylation of Thr 45 and Ser 64 on 4E-BP1, residues directly involved in its association with eIF4E. Consistent with the known role of the phosphoinositide 3-kinase (PI3K)/Akt/mTOR pathway in regulation of 4E-BP1, PKC signaling transiently inhibited PI3K activity and Akt phosphorylation in IEC-18 cells. However, PKC/PKC␣-induced activation of 4E-BP1 was not prevented by constitutively active mutants of PI3K or Akt, indicating that blockade of PI3K/Akt signaling is not the primary effector of 4E-BP1 activation. This idea is supported by the fact that PKC activation did not alter S6 kinase activity in these cells. Further analysis indicated that PKC-mediated 4E-BP1 hypophosphorylation is dependent on the activity of protein phosphatase 2A (PP2A). PKC signaling induced an ϳ2-fold increase in PP2A activity, and phosphatase inhibition blocked the effects of PKC agonists on 4E-BP1 phosphorylation and cyclin D1 expression. H 2 O 2 and ceramide, two naturally occurring PKC␣ agonists that promote growth arrest in intestinal cells, activate 4E-BP1 in PKC/PKC␣-dependent manner, supporting the physiological significance of the findings. Together, our studies indicate that activation of PP2A is an important mechanism underlying PKC/ PKC␣-induced inhibition of cap-dependent translation and growth suppression in intestinal epithelial cells. Members of the protein kinase C (PKC)3 family of signal transduction molecules have been implicated in regulation of fundamental cellular processes, including cell growth and cell cycle progression, differentiation, survival/apoptosis, protein translation, membrane trafficking, receptor desensitization, and migration (1-10). Increasing evidence supports a key role for PKC signaling in the maintenance of intestinal homeostasis (1,11,12), and aberrations in PKC expression and function occur early during intestinal tumorigenesis (13). Previous studies from this laboratory have demonstrated that PKC/PKC␣ signaling triggers a program of cell cycle withdrawal in intestinal epithelial cells characterized by rapid down-regulation of cyclin D1, increased expression of Cip/Kip cyclin-dependent kinase inhibitors, and activation of the growth suppressor function of members of the pocket protein family (14, 15). Downregulation of cyclin D1 precedes various hallmark events of cell cycle exit, pointing to the importance of regulation of this cyclin in PKC-mediated growth arrest in intestinal epithelial cells.Analysis of the mechanisms underlying PKC/PKC␣-mediated down-regulation of cyclin D1 identified PKC␣ as a negative regulator of cyclin D1 translation (7). PKC/PKC␣ signaling activates t...

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Section: Discussionmentioning

confidence: 99%

Protein Kinase C-mediated Down-regulation of Cyclin D1 Involves Activation of the Translational Repressor 4E-BP1 via a Phosphoinositide 3-Kinase/Akt-independent, Protein Phosphatase 2A-dependent Mechanism in Intestinal Epithelial Cells

Guan

Song

Pysz

et al. 2007

Journal of Biological Chemistry

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“…The PI3K catalytic and regulatory subunits are present in sperm (Jungnickel et al 2007), and the PI3K catalytic subunit inhibitor wortmannin (10 nM) inhibits PI3K and PIP 3 production in bovine sperm (Etkovitz et al 2007). In other cell types, it has been shown that PKCa can inhibit PI3K activity directly (Sipeki et al 2006) or indirectly (Guan et al 2007). In bovine sperm, activation of PKC leads to PI3K inhibition (Etkovitz et al 2007).…”

Section: Cmentioning

confidence: 99%

PKA and CaMKII mediate PI3K activation in bovine sperm by inhibition of the PKC/PP1 cascade

Rotfeld¹,

Hillman²,

Ickowicz³

et al. 2014

Reproduction

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To enable fertilization, spermatozoa must undergo several biochemical processes in the female reproductive tract, collectively called capacitation. These processes involve protein kinase A (PKA)-dependent protein tyrosine phosphorylation including phosphatidylinositol-3-kinase (PI3K). It is not known how PKA, a serine/threonine (S/T) kinase, mediates tyrosine phosphorylation of proteins. We recently showed that inhibition of S/T phosphatase 1 (PP1) causes a significant increase in phospho-PI3K. In this study, we propose a mechanism by which PKA and PP1 mediate an increase in PI3K tyrosine phosphorylation and implicate calmodulin-dependent kinase II (CaMKII) in this process. Inhibition of sperm PP1 or PKC, stimulated CaMKII phosphorylation/activation, and inhibition of PKC enhanced PP1 phosphorylation/inactivation. Inhibition of CaMKII, using KN-93, caused significant reduction in phospho-PP1, indicating its activation. Moreover, KN-93 prevented the dephosphorylation/inactivation of PKC. We therefore suggest that CaMKII inhibits PKC, leading to PP1 inhibition and the reciprocal auto-activation of CaMKII. Thus, CaMKII can regulate its own activation by inhibiting the PKC/PP1 cascade. Inhibition of Src family kinases (SFK) caused significant inhibition of CaMKII and PP1 phosphorylation, suggesting that SFK activity results in PP1 inhibition and CaMKII activation. Activation of sperm PKA by 8Br-cAMP revealed an increase in phosphoCaMKII, which was inhibited by PKA inhibitor. Tyrosine phosphorylation of PI3K was stimulated by 8Br-cAMP and by PKC or PP1 inhibition and was abrogated by CaMKII inhibition. Furthermore, phosphorylation/activation of the tyrosine kinase Pyk2 was enhanced by PP1 inhibition, and this activation is blocked by CaMKII inhibition. Thus, PKA activates Src, which inhibits PP1, leading to CaMKII and Pyk2 activation, resulting in PI3K tyrosine phosphorylation/activation.

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“…In other cell types, it was shown that PRKCA can inhibit PI3K directly or indirectly (Sipeki et al 2006, Guan et al 2007). We showed here that upon PRKC inhibition (by inhibitors or by long-time PMA treatment), PI3K phosphorylation was enhanced (Figs 3 and 5).…”

Section: Regulation Of Pi3k In Spermmentioning

confidence: 99%

“…3C). Two possible mechanisms for PI3K inhibition by PRKCA were proposed: 1) PRKCA directly phosphorylates PI3K catalytic subunit, as was found in other cell type (Sipeki et al 2006), leading to autophosphorylation on Ser608 in the regulatory subunit, resulting in PI3K inhibition (Foukas et al 2004). 2) PRKCA activates protein phosphatases which remove the phosphate from Ser83 in the p85 subunit of PI3K (activation site; Cosentino et al 2007), leading to PI3K inhibition.…”

Section: Regulation Of Pi3k In Spermmentioning

confidence: 99%

“…It was also shown that the PI3K catalytic and regulatory subunits are present in sperm (Jungnickel et al 2007), and the PI3K catalytic subunit inhibitor wortmannin (WT) inhibited PI3K and PIP 3 production in bovine sperm (Etkovitz et al 2007). In other cell types, it has been shown that PRKCA can inhibit PI3K activity directly (Sipeki et al 2006) or indirectly (Guan et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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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

Rotman¹,

Etkovitz²,

Spiegel³

et al. 2010

Reproduction

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In order to acquire fertilization competence, spermatozoa have to undergo biochemical changes in the female reproductive tract, known as capacitation. Signaling pathways that take place during the capacitation process are much investigated issue. However, the role and regulation of phosphatidylinositol 3-kinase (PI3K) in this process are still not clear. Previously, we reported that short-time activation of protein kinase A (PRKA, PKA) leads to PI3K activation and protein kinase Ca (PRKCA, PKCa) inhibition. In the present study, we found that during the capacitation PI3K phosphorylation/activation increases. PI3K activation was PRKA dependent, and down-regulated by PRKCA. PRKCA is found to be highly active at the beginning of the capacitation, conditions in which PI3K is not active. Moreover, inhibition of PRKCA causes significant activation of PI3K. Similar activation of PI3K is seen when the phosphatase PPP1 is blocked suggesting that PPP1 regulates PI3K activity. We found that during the capacitation PRKCA and PPP1CC2 (PP1g2) form a complex, and the two enzymes were degraded during the capacitation, suggesting that this degradation enables the activation of PI3K. This degradation is mediated by PRKA, indicating that in addition to the direct activation of PI3K by PRKA, this kinase can enhance PI3K phosphorylation indirectly by enhancing the degradation and inactivation of PRKCA and PPP1CC2.

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PKCα reduces the lipid kinase activity of the p110α/p85α PI3K through the phosphorylation of the catalytic subunit

Cited by 17 publications

References 24 publications

Protein Kinase C-mediated Down-regulation of Cyclin D1 Involves Activation of the Translational Repressor 4E-BP1 via a Phosphoinositide 3-Kinase/Akt-independent, Protein Phosphatase 2A-dependent Mechanism in Intestinal Epithelial Cells

Protein Kinase C-mediated Down-regulation of Cyclin D1 Involves Activation of the Translational Repressor 4E-BP1 via a Phosphoinositide 3-Kinase/Akt-independent, Protein Phosphatase 2A-dependent Mechanism in Intestinal Epithelial Cells

PKA and CaMKII mediate PI3K activation in bovine sperm by inhibition of the PKC/PP1 cascade

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

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