scholarly journals Characterization of the Mitogen-activated Protein Kinase Phosphorylation Sites on the Connexin-43 Gap Junction Protein

1996 ◽  
Vol 271 (7) ◽  
pp. 3779-3786 ◽  
Author(s):  
Bonnie J. Warn-Cramer ◽  
Paul D. Lampe ◽  
Wendy E. Kurata ◽  
Martha Y. Kanemitsu ◽  
Lenora W. M. Loo ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Gap Junction ◽  
Connexin 43 ◽  
Mitogen Activated Protein Kinase ◽  
Phosphorylation Sites ◽  
Junction Protein ◽  
Mitogen Activated Protein ◽  
Gap Junction Protein ◽  
Kinase Phosphorylation

Mechanism of regulation of the gap junction protein connexin 43 by protein kinase C-mediated phosphorylation

2004 ◽  
Vol 286 (3) ◽  
pp. C647-C654 ◽  
Author(s):  
Xiaoyong Bao ◽  
Guillermo A. Altenberg ◽  
Luis Reuss
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Gap Junction ◽  
Connexin 43 ◽  
Molecular Mechanisms ◽  
Xenopus Laevis Oocytes ◽  
Solute Permeability ◽  
Kinase C ◽  
Junction Protein ◽  
Gap Junction Protein

Phosphorylation of the gap junction protein connexin 43 (Cx43) by protein kinase C (PKC) decreases dye coupling in many cell types. We report an investigation of the regulation by PKC of Cx43 gap junctional hemichannels (GJH) expressed in Xenopus laevis oocytes. The activity of GJH was assessed from the uptake of hydrophilic fluorescent probes. PKC inhibitors increased probe uptake in isolated oocytes expressing recombinant Cx43, indicating that the regulatory effect occurs at the hemichannel level. We identified by mutational analysis the carboxy-terminal (CT) domain sequences involved in this response. We found that 1) Ser368 is responsible for the regulation of Cx43 GJH solute permeability by PKC-mediated phosphorylation, 2) CT domain residues 253-270 and 288-359 are not necessary for the effect of PKC, and 3) the prolinerich CT region is not involved in the effect of phosphorylation by PKC. Our results demonstrate that Ser368 (but not Ser372) is involved in the regulation of Cx43 solute permeability by PKC-mediated phosphorylation, and we conclude that different molecular mechanisms underlie the regulation of Cx43 by intracellular pH and PKC-mediated phosphorylation.

scholarly journals Ezrin-anchored PKA phosphorylates serine 369 and 373 on connexin 43 to enhance gap junction assembly, communication, and cell fusion

2018 ◽  
Vol 475 (2) ◽  
pp. 455-476 ◽  
Author(s):  
Aleksandra R. Dukic ◽  
Pascale Gerbaud ◽  
Jean Guibourdenche ◽  
Bernd Thiede ◽  
Kjetil Taskén ◽  
...  
Keyword(s):  
Gap Junction ◽  
Cell Fusion ◽  
Connexin 43 ◽  
Phosphorylation Sites ◽  
Peptide Arrays ◽  
Signaling Complex ◽  
Gap Junction Communication ◽  
Junction Protein ◽  
Gap Junction Protein

A limited number of human cells can fuse to form multinucleated syncytia. In the differentiation of human placenta, mononuclear cytotrophoblasts fuse to form an endocrinologically active, non-proliferative, multinucleated syncytium. This syncytium covers the placenta and manages the exchange of nutrients and gases between maternal and fetal circulation. We recently reported protein kinase A (PKA) to be part of a macromolecular signaling complex with ezrin and gap junction protein connexin 43 (Cx43) that provides cAMP-mediated control of gap junction communication. Here, we examined the associated phosphorylation events. Inhibition of PKA activity resulted in decreased Cx43 phosphorylation, which was associated with reduced trophoblast fusion and differentiation. In vitro studies using peptide arrays, together with mass spectrometry, pointed to serine 369 and 373 of Cx43 as the major PKA phosphorylation sites that increases gap junction assembly at the plasmalemma. A combination of knockdown and reconstitution experiments and gap-fluorescence loss in photobleaching assays with mutant Cx43 containing single or double phosphoserine-mimicking amino acid substitutions in putative PKA phosphorylation sites demonstrated that phosphorylation of S369 and S373 mediated gap junction communication, trophoblast differentiation, and cell fusion.

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