Rat Aquaporin-5 Is pH-Gated Induced by Phosphorylation and Is Implicated in Oxidative Stress

Int J Mol Sci. 2016 Dec 13;17(12):2090. doi: 10.3390/ijms17122090.

Abstract

Aquaporin-5 (AQP5) is a membrane water channel widely distributed in human tissues that was found up-regulated in different tumors and considered implicated in carcinogenesis in different organs and systems. Despite its wide distribution pattern and physiological importance, AQP5 short-term regulation was not reported and mechanisms underlying its involvement in cancer are not well defined. In this work, we expressed rat AQP5 in yeast and investigated mechanisms of gating, as well as AQP5's ability to facilitate H₂O₂ plasma membrane diffusion. We found that AQP5 can be gated by extracellular pH in a phosphorylation-dependent manner, with higher activity at physiological pH 7.4. Moreover, similar to other mammalian AQPs, AQP5 is able to increase extracellular H₂O₂ influx and to affect oxidative cell response with dual effects: whereas in acute oxidative stress conditions AQP5 induces an initial higher sensitivity, in chronic stress AQP5 expressing cells show improved cell survival and resistance. Our findings support the involvement of AQP5 in oxidative stress and suggest AQP5 modulation by phosphorylation as a novel tool for therapeutics.

Keywords: aquaporin; hydrogen peroxide; oxidative stress; pH gating; permeability; phosphorylation; reactive oxygen species; yeast.

MeSH terms

  • Animals
  • Aquaporin 5 / chemistry
  • Aquaporin 5 / metabolism*
  • Cell Membrane Permeability / drug effects
  • Glucose / pharmacology
  • Humans
  • Hydrogen Peroxide / metabolism
  • Hydrogen Peroxide / toxicity
  • Hydrogen-Ion Concentration
  • Oxidation-Reduction / drug effects
  • Oxidative Stress* / drug effects
  • Phosphorylation / drug effects
  • Protein Transport / drug effects
  • Rats
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / metabolism
  • Subcellular Fractions / metabolism
  • Water / metabolism

Substances

  • Aquaporin 5
  • Water
  • Hydrogen Peroxide
  • Glucose