Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation
Affiliation
Program in Neuroscience, University of Arizona, Tucson, Arizona, 85724-5051, USADept. of Physiology, University of Arizona College of Medicine, Tucson, Arizona, USA
Dept. of Pharmacology, University of Arizona College of Medicine, Tucson, Arizona, USA
Issue Date
2003Metadata
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BioMed CentralCitation
BMC Physiology 2003, 3:12 http://www.biomedcentral.com/1472-6793/3/12Journal
BMC PhysiologyRights
© 2003 Boassa and Yool; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.Collection Information
This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at repository@u.library.arizona.edu.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 (SNP3-14 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.