Akt Phosphorylates Connexin43 on Ser373, a “Mode-1” Binding Site for 14-3-3

Natural Products & Cancer Biology Program, Cancer Research Center, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA.
Cell Communication & Adhesion (Impact Factor: 1.52). 09/2007; 14(5):211-26. DOI: 10.1080/15419060701755958
Source: PubMed


Connexin43 (Cx43) is a membrane-spanning protein that forms channels that bridge the gap between adjacent cells and this allows for the intercellular exchange of information. Cx43 is regulated by phosphorylation and by interacting proteins. "Mode-1" interaction with 14-3-3 requires phosphorylation of Ser373 on Cx43 (Park et al. 2006). Akt phosphorylates and targets a number of proteins to interactions with 14-3-3. Here we demonstrate that Akt phosphorylates Cx43 on Ser373 and Ser369; antibodies recognizing Akt-phosphorylated sites or phospho-Ser "mode-1" 14-3-3-binding sites recognize a protein from EGF-treated cells that migrates as Cx43, and GST-14-3-3 binds to Cx43 phosphorylated endogenously in EGF-treated cells. Confocal microscopy supports the co-localization of Cx43 with Akt and with 14-3-3 at the outer edges of gap junctional plaques. These data suggest that Akt could target Cx43 to an interaction with 14-3-3 that may play a role in the forward trafficking of Cx43 multimers and/or their incorporation into existing gap junctional plaques.

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Available from: Alan F Lau, Oct 07, 2015
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    • "In addition, a recent study found that Akt activation is crucial to disrupt dye transfer in v-Src transformed cells, but inhibition of Akt only recovered the metabolic coupling to 60% (Ito et al., 2010). Since Akt may cause phosphorylation of Ser369 and Ser373 in Cx43 (Park et al., 2007; for details see section on Ser364, Ser365, Ser368, Ser369, Ser372, and Ser373), this indicates that Src kinases controls several intracellular signaling pathways, and thereby affects the phosphorylation of both serine and tyrosine residues in the C-terminal tail of Cx43 with different effects on electrical and metabolic coupling. Together, these studies outlines that the control of gap junction coupling by Src kinases is extremely complex; It depends of a combination of direct phosphorylation of both Tyr247 and Tyr265, as well as interplay with several intracellular signaling pathways controlling Cx43 serine phosphorylation. "
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    ABSTRACT: Gap junctions are comprised of connexins that form cell-to-cell channels which couple neighboring cells to accommodate the exchange of information. The need for communication does, however, change over time and therefore must be tightly controlled. Although the regulation of connexin protein expression by transcription and translation is of great importance, the trafficking, channel activity and degradation are also under tight control. The function of connexins can be regulated by several post translational modifications, which affect numerous parameters; including number of channels, open probability, single channel conductance or selectivity. The most extensively investigated post translational modifications are phosphorylations, which have been documented in all mammalian connexins. Besides phosphorylations, some connexins are known to be ubiquitinated, SUMOylated, nitrosylated, hydroxylated, acetylated, methylated, and γ-carboxyglutamated. The aim of the present review is to summarize our current knowledge of post translational regulation of the connexin family of proteins.
    Frontiers in Pharmacology 10/2013; 4:130. DOI:10.3389/fphar.2013.00130 · 3.80 Impact Factor
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    • "src, via SH2 and 3 domains (Warn- Cramer et al. 1996)], adapter [e.g. ZO-1via PDZ 1(Giepmans and Moolenaar 1998; Toyofuku et al. 1998); 14-3-3 protein (Park et al., 2007)], and cytoskeletal elements [e.g. tubulin (Giepmans et al. 2001)] may also be relevant to longer term regulation of coupling by growth factors. "
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    ABSTRACT: Attenuation in gap junctional coupling has consistently been associated with induction of rapid or synchronous cell division in normal and pathological conditions. In the case of the v-src oncogene, gating of Cx43 gap junction channels has been linked to both direct phosphorylation of tyrosines (Y247 and 265) and phosphorylation of the serine targets of Erk1/2 (S255, 279 and 282) on the cytoplasmic C-terminal domain of Cx43. However, only the latter has been associated with acute, rather than chronic, gating of the channels immediately after v-src expression, a process that is mediated through a "ball-and-chain" mechanism. In this study we show that, while ERK1/2 is necessary for acute closure of gap junction channels, it is not sufficient. Rather, multiple pathways converge to regulate Cx43 coupling in response to expression of v-src, including parallel signaling through PKC and MEK1/2, with additional positive and negative regulatory effects mediated by PI3 kinase, distinguished by the involvement of Akt.
    Journal of Membrane Biology 09/2012; 245(8):495-506. DOI:10.1007/s00232-012-9500-0 · 2.46 Impact Factor
    • "Cx43 phosphorylation at the serine 255 and serine 262 residues by the MAP kinase ERK can occur in response to epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol 13-acetate (TPA) exposure, which is followed by internalization of Cx43 from the plasma membrane and subsequent lysosomal degradation (Leithe et al. 2006; Leithe and Rivedal 2004b; Sirnes et al. 2008, 2009). Akt had also previously been demonstrated to phosphorylate Cx43 (Park et al. 2007), and inhibition of Akt activity using Akt VIII treatment or expression of the dominant negative Akt- K179A mutant reduced the amount of Cx43 at the cell surface (Dunn et al. 2012). Furthermore, closer examination of Akt revealed an increase in ubiquitinated Akt and, in general, Akt kinase activity in response to MG132 treatment, blocking proteasomal degradation (Dunn et al. 2012), which has been demonstrated to increase Akt translocation to the plasma membrane and increased activity due to a phosphorylation event (Feng et al. 2004; Sarbassov et al. 2005). "
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    ABSTRACT: Connexins comprise gap junction channels, which create a direct conduit between the cytoplasms of adjacent cells and provide for intercellular communication. Therefore, the level of total cellular connexin protein can have a direct influence on the level of intercellular communication. Control of connexin protein levels can occur through different mechanisms during the connexin life cycle, such as by regulation of connexin gene expression and turnover of existing protein. The degradation of connexins has been extensively studied, revealing proteasomal, endolysosomal and more recently autophagosomal degradation mechanisms that modulate connexin turnover and, subsequently, affect intercellular communication. Here, we review the current knowledge of connexin degradation pathways.
    Journal of Membrane Biology 07/2012; 245(7):389-400. DOI:10.1007/s00232-012-9461-3 · 2.46 Impact Factor
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