Phosphorylation of connexin43 on serine368 by protein kinase C regulates gap junctional communication

Paul D. Lampe, Erica M. TenBroek, Janis M Burt, Wendy E. Kurata, Ross G. Johnson, Alan F. Lau

Research output: Contribution to journalArticle

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Abstract

Phorbol esters (e.g., TPA) activate protein kinase C (PKC), increase connexin43 (Cx43) phosphorylation, and decrease cell-cell communication via gap junctions in many cell types. We asked whether PKC directly phosphorylates and regulates Cx43. Rat epithelial T51B cells metabolically labeled with 32P(i) yielded two-dimensional phosphotryptic maps of Cx43 with several phosphopeptides that increased in intensity upon TPA treatment. One of these peptides comigrated with the major phosphopeptide observed after PKC phosphorylation of immunoaffinity-purified Cx43. Purification of this comigrating peptide and subsequent sequencing indicated that the phosphorylated serine was residue 368. To pursue the functional importance of phosphorylation at this site, fibroblasts from Cx43(-/-) mice were transfected with either wild-type (Cx43wt) or mutant Cx43 (Cx43-S368A). Intercellular dye transfer studies revealed different responses to TPA and were followed by single channel analyses. TPA stimulation of T51B cells or Cx43wt-transfected fibroblasts caused a large increase in the relative frequency of ≃50-pS channel events and a concomitant loss of ≃100-pS channel events. This change to ≃50-pS events was absent when cells transfected with Cx43-S368A were treated with TPA. These data strongly suggest that PKC directly phosphorylates Cx43 on S368 in vivo, which results in a change in single channel behavior that contributes to a decrease in intercellular communication.

Original languageEnglish (US)
Pages (from-to)1503-1512
Number of pages10
JournalJournal of Cell Biology
Volume149
Issue number7
DOIs
StatePublished - Jun 26 2000

Fingerprint

Connexin 43
Protein Kinase C
Communication
Phosphorylation
Phosphopeptides
Fibroblasts
Peptides
Gap Junctions
Phorbol Esters
Cell Communication
Serine
Coloring Agents
Epithelial Cells

Keywords

  • Carcinogenesis
  • Connexins
  • Gap junctions
  • Phosphorylation
  • Tumor promoter

ASJC Scopus subject areas

  • Cell Biology

Cite this

Phosphorylation of connexin43 on serine368 by protein kinase C regulates gap junctional communication. / Lampe, Paul D.; TenBroek, Erica M.; Burt, Janis M; Kurata, Wendy E.; Johnson, Ross G.; Lau, Alan F.

In: Journal of Cell Biology, Vol. 149, No. 7, 26.06.2000, p. 1503-1512.

Research output: Contribution to journalArticle

Lampe, Paul D. ; TenBroek, Erica M. ; Burt, Janis M ; Kurata, Wendy E. ; Johnson, Ross G. ; Lau, Alan F. / Phosphorylation of connexin43 on serine368 by protein kinase C regulates gap junctional communication. In: Journal of Cell Biology. 2000 ; Vol. 149, No. 7. pp. 1503-1512.
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abstract = "Phorbol esters (e.g., TPA) activate protein kinase C (PKC), increase connexin43 (Cx43) phosphorylation, and decrease cell-cell communication via gap junctions in many cell types. We asked whether PKC directly phosphorylates and regulates Cx43. Rat epithelial T51B cells metabolically labeled with 32P(i) yielded two-dimensional phosphotryptic maps of Cx43 with several phosphopeptides that increased in intensity upon TPA treatment. One of these peptides comigrated with the major phosphopeptide observed after PKC phosphorylation of immunoaffinity-purified Cx43. Purification of this comigrating peptide and subsequent sequencing indicated that the phosphorylated serine was residue 368. To pursue the functional importance of phosphorylation at this site, fibroblasts from Cx43(-/-) mice were transfected with either wild-type (Cx43wt) or mutant Cx43 (Cx43-S368A). Intercellular dye transfer studies revealed different responses to TPA and were followed by single channel analyses. TPA stimulation of T51B cells or Cx43wt-transfected fibroblasts caused a large increase in the relative frequency of ≃50-pS channel events and a concomitant loss of ≃100-pS channel events. This change to ≃50-pS events was absent when cells transfected with Cx43-S368A were treated with TPA. These data strongly suggest that PKC directly phosphorylates Cx43 on S368 in vivo, which results in a change in single channel behavior that contributes to a decrease in intercellular communication.",
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AB - Phorbol esters (e.g., TPA) activate protein kinase C (PKC), increase connexin43 (Cx43) phosphorylation, and decrease cell-cell communication via gap junctions in many cell types. We asked whether PKC directly phosphorylates and regulates Cx43. Rat epithelial T51B cells metabolically labeled with 32P(i) yielded two-dimensional phosphotryptic maps of Cx43 with several phosphopeptides that increased in intensity upon TPA treatment. One of these peptides comigrated with the major phosphopeptide observed after PKC phosphorylation of immunoaffinity-purified Cx43. Purification of this comigrating peptide and subsequent sequencing indicated that the phosphorylated serine was residue 368. To pursue the functional importance of phosphorylation at this site, fibroblasts from Cx43(-/-) mice were transfected with either wild-type (Cx43wt) or mutant Cx43 (Cx43-S368A). Intercellular dye transfer studies revealed different responses to TPA and were followed by single channel analyses. TPA stimulation of T51B cells or Cx43wt-transfected fibroblasts caused a large increase in the relative frequency of ≃50-pS channel events and a concomitant loss of ≃100-pS channel events. This change to ≃50-pS events was absent when cells transfected with Cx43-S368A were treated with TPA. These data strongly suggest that PKC directly phosphorylates Cx43 on S368 in vivo, which results in a change in single channel behavior that contributes to a decrease in intercellular communication.

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