Regulation of Purified and Reconstituted Connexin 43 Hemichannels by Protein Kinase C-mediated Phosphorylation of Serine 368

Xiaoyong Bao, Luis Reuss, Guillermo A. Altenberg

Research output: Contribution to journalArticle

111 Scopus citations

Abstract

Indirect evidence suggests that the permeability of connexin 43 (Cx43) gap-junctional channels (connexons) to small organic molecules (Mr < 1,000) is decreased by protein kinase C (PKC)-mediated phosphorylation of Ser-368. However, it is currently unknown whether this effect is produced directly by phosphorylation of this residue or whether cytoplasmic regulatory factors are required for the decrease in Cx43 gap-junctional channel permeability. Here we studied the effects of PKC-mediated phosphorylation on purified recombinant wild-type Cx43 and a PKC-unresponsive mutant (S368A). Our studies show that (a) PKC phosphorylates Ser-368, (b) the phosphorylation by PKC of purified and reconstituted connexons abolishes sucrose and Lucifer Yellow permeability, (c) the regulation of Cx43 by PKC is the direct result of phosphorylation of Ser-368 and does not involve intermediary regulatory factors, and (d) phosphorylation of Ser-368 produces a conformational change in purified Cx43 as demonstrated by changes in intrinsic Trp fluorescence and proteolytic digestion pattern. We conclude that phosphorylation of Ser-368 by PKC induces a conformational change of Cx43 that results in a decrease in connexon permeability.

Original languageEnglish (US)
Pages (from-to)20058-20066
Number of pages9
JournalJournal of Biological Chemistry
Volume279
Issue number19
DOIs
StatePublished - May 7 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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