Reversible connexin 43 dephosphorylation during hypoxia and reoxygenation is linked to cellular ATP levels

Mark S. Turner, Guy A. Haywood, P. Andréka, Lijing You, Patricia E. Martin, W. Howard Evans, Keith A. Webster, Nanette H. Bishopric

Research output: Article

60 Citations (Scopus)

Abstract

Altered gap junction coupling of cardiac myocytes during ischemia may contribute to development of lethal arrhythmias. The phosphoprotein connexin 43 (Cx43) is the major constituent of gap junctions. Dephosphorylation of Cx43 and uncoupling of gap junctions occur during ischemia, but the significance of Cx43 phosphorylation in this setting is unknown. Here we show that Cx43 dephosphorylation in synchronously contracting myocytes during ischemia is reversible, independent of hypoxia, and closely associated with cellular ATP levels. Cx43 became profoundly dephosphorylated during hypoxia only when glucose supplies were limited and was completely rephosphorylated within 30 minutes of reoxygenation. Similarly, direct reduction of ATP by various combinations of metabolic inhibitors and by ouabain was closely paralleled by loss of phosphoCx43 and recovery of phosphoCx43 accompanied restoration of ATP. Dephosphorylation of Cx43 could not be attributed to hypoxia, acid pH or secreted metabolites, or to AMP-activated protein kinase; moreover, the process was selective for Cx43 because levels of phospho-extracellular signal regulated kinase (ERK)1/2 were increased throughout. Rephosphorylation of Cx43 was not dependent on new protein synthesis, or on activation of protein kinases A or G, ERK1/2, p38 mitogen-activated protein kinase, or Jun kinase; however, broad-spectrum protein kinase C inhibitors prevented Cx43 rephosphorylation while also sensitizing myocytes to reoxygenation-mediated cell death. We conclude that Cx43 is reversibly dephosphorylated and rephosphorylated during hypoxia and reoxygenation by a novel mechanism that is sensitive to nonlethal fluctuations in cellular ATP. The role of this regulated phosphorylation in the adaptation to ischemia remains to be determined.

Original languageEnglish
Pages (from-to)726-733
Number of pages8
JournalCirculation Research
Volume95
Issue number7
DOIs
Publication statusPublished - okt. 1 2004

Fingerprint

Connexin 43
Adenosine Triphosphate
Gap Junctions
Ischemia
Muscle Cells
Phosphorylation
Hypoxia
Cyclic GMP-Dependent Protein Kinases
AMP-Activated Protein Kinases
Mitogen-Activated Protein Kinase 3
Protein C Inhibitor
Phosphoproteins
Mitogen-Activated Protein Kinase 1
p38 Mitogen-Activated Protein Kinases
Ouabain
Protein Kinase Inhibitors
Cyclic AMP-Dependent Protein Kinases
Cardiac Myocytes
Protein Kinase C
Cardiac Arrhythmias

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Reversible connexin 43 dephosphorylation during hypoxia and reoxygenation is linked to cellular ATP levels. / Turner, Mark S.; Haywood, Guy A.; Andréka, P.; You, Lijing; Martin, Patricia E.; Evans, W. Howard; Webster, Keith A.; Bishopric, Nanette H.

In: Circulation Research, Vol. 95, No. 7, 01.10.2004, p. 726-733.

Research output: Article

Turner, Mark S. ; Haywood, Guy A. ; Andréka, P. ; You, Lijing ; Martin, Patricia E. ; Evans, W. Howard ; Webster, Keith A. ; Bishopric, Nanette H. / Reversible connexin 43 dephosphorylation during hypoxia and reoxygenation is linked to cellular ATP levels. In: Circulation Research. 2004 ; Vol. 95, No. 7. pp. 726-733.
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T1 - Reversible connexin 43 dephosphorylation during hypoxia and reoxygenation is linked to cellular ATP levels

AU - Turner, Mark S.

AU - Haywood, Guy A.

AU - Andréka, P.

AU - You, Lijing

AU - Martin, Patricia E.

AU - Evans, W. Howard

AU - Webster, Keith A.

AU - Bishopric, Nanette H.

PY - 2004/10/1

Y1 - 2004/10/1

N2 - Altered gap junction coupling of cardiac myocytes during ischemia may contribute to development of lethal arrhythmias. The phosphoprotein connexin 43 (Cx43) is the major constituent of gap junctions. Dephosphorylation of Cx43 and uncoupling of gap junctions occur during ischemia, but the significance of Cx43 phosphorylation in this setting is unknown. Here we show that Cx43 dephosphorylation in synchronously contracting myocytes during ischemia is reversible, independent of hypoxia, and closely associated with cellular ATP levels. Cx43 became profoundly dephosphorylated during hypoxia only when glucose supplies were limited and was completely rephosphorylated within 30 minutes of reoxygenation. Similarly, direct reduction of ATP by various combinations of metabolic inhibitors and by ouabain was closely paralleled by loss of phosphoCx43 and recovery of phosphoCx43 accompanied restoration of ATP. Dephosphorylation of Cx43 could not be attributed to hypoxia, acid pH or secreted metabolites, or to AMP-activated protein kinase; moreover, the process was selective for Cx43 because levels of phospho-extracellular signal regulated kinase (ERK)1/2 were increased throughout. Rephosphorylation of Cx43 was not dependent on new protein synthesis, or on activation of protein kinases A or G, ERK1/2, p38 mitogen-activated protein kinase, or Jun kinase; however, broad-spectrum protein kinase C inhibitors prevented Cx43 rephosphorylation while also sensitizing myocytes to reoxygenation-mediated cell death. We conclude that Cx43 is reversibly dephosphorylated and rephosphorylated during hypoxia and reoxygenation by a novel mechanism that is sensitive to nonlethal fluctuations in cellular ATP. The role of this regulated phosphorylation in the adaptation to ischemia remains to be determined.

AB - Altered gap junction coupling of cardiac myocytes during ischemia may contribute to development of lethal arrhythmias. The phosphoprotein connexin 43 (Cx43) is the major constituent of gap junctions. Dephosphorylation of Cx43 and uncoupling of gap junctions occur during ischemia, but the significance of Cx43 phosphorylation in this setting is unknown. Here we show that Cx43 dephosphorylation in synchronously contracting myocytes during ischemia is reversible, independent of hypoxia, and closely associated with cellular ATP levels. Cx43 became profoundly dephosphorylated during hypoxia only when glucose supplies were limited and was completely rephosphorylated within 30 minutes of reoxygenation. Similarly, direct reduction of ATP by various combinations of metabolic inhibitors and by ouabain was closely paralleled by loss of phosphoCx43 and recovery of phosphoCx43 accompanied restoration of ATP. Dephosphorylation of Cx43 could not be attributed to hypoxia, acid pH or secreted metabolites, or to AMP-activated protein kinase; moreover, the process was selective for Cx43 because levels of phospho-extracellular signal regulated kinase (ERK)1/2 were increased throughout. Rephosphorylation of Cx43 was not dependent on new protein synthesis, or on activation of protein kinases A or G, ERK1/2, p38 mitogen-activated protein kinase, or Jun kinase; however, broad-spectrum protein kinase C inhibitors prevented Cx43 rephosphorylation while also sensitizing myocytes to reoxygenation-mediated cell death. We conclude that Cx43 is reversibly dephosphorylated and rephosphorylated during hypoxia and reoxygenation by a novel mechanism that is sensitive to nonlethal fluctuations in cellular ATP. The role of this regulated phosphorylation in the adaptation to ischemia remains to be determined.

KW - AMP kinase

KW - Connexin43

KW - Gap junctions

KW - Glycolysis

KW - Ischemia

KW - Okadaic acid

KW - Protein phosphatases

KW - Protein phosphorylation

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