Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation

BMC Physiol. 2003 Oct 15;3:12. doi: 10.1186/1472-6793-3-12.

Abstract

Background: Aquaporin-1 (AQP1) functions as an osmotic water channel and a gated cation channel. Activation of the AQP1 ion conductance by intracellular cGMP was hypothesized to involve the carboxyl (C-) terminus, based on amino acid sequence alignments with cyclic-nucleotide-gated channels and cGMP-selective phosphodiesterases.

Results: Voltage clamp analyses of human AQP1 channels expressed in Xenopus oocytes demonstrated that the nitric oxide donor, sodium nitroprusside (SNP; 3-14 mM) activated the ionic conductance response in a dose-dependent manner. Block of soluble guanylate cyclase prevented the response. Enzyme immunoassays confirmed a linear dose-dependent relationship between SNP and the resulting intracellular cGMP levels (up to 1700 fmol cGMP /oocyte at 14 mM SNP). Results here are the first to show that the efficacy of ion channel activation is decreased by mutations of AQP1 at conserved residues in the C-terminal domain (aspartate D237 and lysine K243).

Conclusions: These data support the idea that the limited amino acid sequence similarities found between three diverse classes of cGMP-binding proteins are significant to the function of AQP1 as a cGMP-gated ion channel, and provide direct evidence for the involvement of the AQP1 C-terminal domain in cGMP-mediated ion channel activation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence / physiology
  • Amino Acids / genetics
  • Amino Acids / metabolism*
  • Animals
  • Aquaporin 1
  • Aquaporins / biosynthesis
  • Aquaporins / chemistry*
  • Aquaporins / genetics
  • Aquaporins / physiology*
  • Blood Group Antigens
  • Conserved Sequence / physiology
  • Cyclic GMP / biosynthesis
  • Cyclic GMP / physiology*
  • Cyclic Nucleotide-Gated Cation Channels
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Ion Channels / chemistry
  • Ion Channels / drug effects
  • Ion Channels / metabolism
  • Ion Channels / physiology
  • Membrane Potentials / drug effects
  • Membrane Potentials / genetics
  • Membrane Potentials / physiology
  • Mutagenesis, Site-Directed / genetics
  • Mutagenesis, Site-Directed / physiology
  • Nitric Oxide Donors / pharmacology
  • Nitroprusside / pharmacology
  • Oocytes / chemistry
  • Oocytes / cytology
  • Oocytes / metabolism
  • Osmotic Pressure
  • Patch-Clamp Techniques / methods
  • Peptides / physiology*
  • Protein Structure, Tertiary / physiology
  • Xenopus laevis / embryology
  • Xenopus laevis / genetics
  • Xenopus laevis / metabolism

Substances

  • AQP1 protein, human
  • Amino Acids
  • Aquaporins
  • Blood Group Antigens
  • Cyclic Nucleotide-Gated Cation Channels
  • Ion Channels
  • Nitric Oxide Donors
  • Peptides
  • Aquaporin 1
  • Nitroprusside
  • Cyclic GMP