Smad ubiquitination regulatory factor-2 controls gap junction intercellular communication by modulating endocytosis and degradation of connexin43

J Cell Sci. 2012 Sep 1;125(Pt 17):3966-76. doi: 10.1242/jcs.093500. Epub 2012 May 23.

Abstract

Gap junctions consist of arrays of intercellular channels that enable adjacent cells to communicate both electrically and metabolically. Gap junction channels are made of a family of integral membrane proteins called connexins, of which the best-studied member is connexin43. Gap junctions are dynamic plasma membrane domains, and connexin43 has a high turnover rate in most tissue types. However, the mechanisms involved in the regulation of connexin43 endocytosis and transport to lysosomes are still poorly understood. Here, we demonstrate by live-cell imaging analysis that treatment of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) induces endocytosis of subdomains of connexin43 gap junctions. The internalized, connexin43-enriched vesicles were found to fuse with early endosomes, which was followed by transport of connexin43 to the lumen of early endosomes. The HECT E3 ubiquitin ligase smad ubiquitination regulatory factor-2 (Smurf2) was found to be recruited to connexin43 gap junctions in response to TPA treatment. Depletion of Smurf2 by small interfering RNA resulted in enhanced levels of connexin43 gap junctions between adjacent cells and increased gap junction intercellular communication. Smurf2 depletion also counteracted the TPA-induced endocytosis and degradation of connexin43. Collectively, these data identify Smurf2 as a novel regulator of connexin43 gap junctions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Communication* / drug effects
  • Cell Line
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Connexin 43
  • Cycloheximide / pharmacology
  • Endocytosis* / drug effects
  • Endosomes / drug effects
  • Endosomes / metabolism
  • Epithelial Cells / cytology*
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Gap Junctions / drug effects
  • Gap Junctions / metabolism*
  • Protein Binding / drug effects
  • Protein Transport / drug effects
  • Proteolysis* / drug effects
  • Rats
  • Tetradecanoylphorbol Acetate / pharmacology
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination / drug effects

Substances

  • Connexin 43
  • Cycloheximide
  • Smurf2 protein, rat
  • Ubiquitin-Protein Ligases
  • Tetradecanoylphorbol Acetate