Identification of ischemia-regulated phosphorylation sites in connexin43: A possible target for the antiarrhythmic peptide analogue rotigaptide (ZP123)

Protein kinase Cε mediates salutary effects on electrical coupling induced by ischemic preconditioning

“…43 It is important to note that the significance of Cx43 phosphorylation at Ser368 in the heart remains controversial as several groups have reported conflicting findings. 26,45,46 Our finding that Cx43 phosphorylation at Ser368 increases after 30 min of global ischemia is consistent with a recent study, also in the mouse, from Ek-Vitorin et al 26 However, Matsushita et al and Axelsen et al report decreased Cx43 phosphorylation at Ser368 in the rat heart subjected to hypoxic perfusion 45 or global ischemia. 46 Of course, changes in electrical coupling during ischemia could involve changes in Cx43 phosphorylation at PKC-independent residues.…”

“…26,45,46 Our finding that Cx43 phosphorylation at Ser368 increases after 30 min of global ischemia is consistent with a recent study, also in the mouse, from Ek-Vitorin et al 26 However, Matsushita et al and Axelsen et al report decreased Cx43 phosphorylation at Ser368 in the rat heart subjected to hypoxic perfusion 45 or global ischemia. 46 Of course, changes in electrical coupling during ischemia could involve changes in Cx43 phosphorylation at PKC-independent residues. To address this possibility, we probed Cx43 phosphorylation state at four other Cterminal residues (Ser262, Ser255, Ser279/282, and Tyr265) and observed no differences in any group of hearts compared to wild-type control.…”

“…To address this possibility, we probed Cx43 phosphorylation state at four other Cterminal residues (Ser262, Ser255, Ser279/282, and Tyr265) and observed no differences in any group of hearts compared to wild-type control. However, Lampe et al 46 have recently reported dephosphorylation of Cx43 at casein kinase 1 sites Ser325/328/330 coinciding with lateralization of Cx43 during ischemia. Interestingly, dephosphorylation of Cx43 during hypoxia has also been linked to decreased availability of ATP.…”

Protein kinase C as a stress sensor

“…Examination of the residues surrounding the S368 of Cx43 would, therefore, predict that this would be a PKCγ phosphorylation site while S262 would be a PKCε site. This has been found to be the case [56][57][58][59].…”

“…In attempts to identify which kinases phosphorylate Cx43, it was shown that both PKCα and PKCε phosphorylate Cx43 at multiple serines (S365, S368, S369, S372, and S373) in the C-terminus of Cx43 [56,57]. The antiarrhythmic peptide, Rotigaptide [97, see Fig.4], postponed dephosphorylation of Ser 297 and Ser 368 [58]. Dephosphorylation of these residues was correlated with an extended time to asystole following 30 minutes of ischemia due to preservation of conductance currents through gap junctions.…”