Permeability to both water and cations through Aquaporin-1 (AQP1) channels suggests an impressive multifunctional capacity. These channels are essential for osmotic water movement, and potentially important for cGMP-dependent signaling in brain choroid plexus and other tissues. Sequence similarity between (AQP1) and cyclic-nucleotide-gated (CNG) channels implicates the carboxy (C-) terminus as the binding domain. Our central hypothesis is that cGMP binds to the C-terminus and gates cationic current through a central pore in AQP1, and that ion channel activity is further governed by protein-kinase interactions. We use patch clamp, voltage clamp, site-directed mutagenesis, proteomic and protein biochemistry methods to address fundamental properties of AQPI in an oocyte expression system, and in choroid plexus, which abundantly expresses AQP1. Solved crystal structure data for AQP1 allow the informed selection of regions for mutagenesis and further analysis.
The first aim i s to evaluate the role of conserved residues in the C-terminal domain of cloned human AQP1 in the response to cGMP. In collaboration with Dr. J. Karpen, an expert in CNG channels, we will test for alterations in binding and channel activity in wild type and mutant AQP1 channels using a photoactivated covalent ligand.
The second aim i s to locate the ion pore, suggested by preliminary data to be in the center of the tetramer at the four-fold axis of symmetry.
The third aim i s to assess the roles of receptor tyrosine kinase-mediated phosphorylation and protein-protein interaction with the ephrin receptor EphB2 in governing activity of AQP1 ion channels.
The fourth aim i s to determine potential physiological relevance by discovering whether an AQP1 ionic conductance is present in rat choroid plexus (primary cultures), a tissue in which native AQP1 is abundantly expressed. Our work was the first to show that AQP1 is a gated ion channel. This property of cGMP-dependent ion channel activity may be significant to signaling in the brain, peripheral nervous system, vascular system and heart, and may in part enable pathophysiological growth in cancer, since these are tissues in which AQP1 is expressed. Discovery of the fundamental properties of AQP1 channels may open opportunities for therapeutic intervention in human diseases involving fluid and salt imbalance in the brain and other organs.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM059986-06
Application #
6931183
Study Section
Molecular, Cellular and Developmental Neurosciences 2 (MDCN)
Program Officer
Shapiro, Bert I
Project Start
2000-04-01
Project End
2007-11-30
Budget Start
2005-12-01
Budget End
2006-11-30
Support Year
6
Fiscal Year
2006
Total Cost
$281,086
Indirect Cost
Name
University of Arizona
Department
Physiology
Type
Schools of Medicine
DUNS #
806345617
City
Tucson
State
AZ
Country
United States
Zip Code
85721
Kourghi, Mohamad; Pei, Jinxin V; De Ieso, Michael L et al. (2016) Bumetanide Derivatives AqB007 and AqB011 Selectively Block the Aquaporin-1 Ion Channel Conductance and Slow Cancer Cell Migration. Mol Pharmacol 89:133-40
Baetz, Nicholas W; Stamer, W Daniel; Yool, Andrea J (2012) Stimulation of aquaporin-mediated fluid transport by cyclic GMP in human retinal pigment epithelium in vitro. Invest Ophthalmol Vis Sci 53:2127-32
Yool, Andrea J; Campbell, Ewan M (2012) Structure, function and translational relevance of aquaporin dual water and ion channels. Mol Aspects Med 33:553-61
Migliati, Elton; Meurice, Nathalie; DuBois, Pascale et al. (2009) Inhibition of aquaporin-1 and aquaporin-4 water permeability by a derivative of the loop diuretic bumetanide acting at an internal pore-occluding binding site. Mol Pharmacol 76:105-12
Baetz, N W; Hoffman, E A; Yool, A J et al. (2009) Role of aquaporin-1 in trabecular meshwork cell homeostasis during mechanical strain. Exp Eye Res 89:95-100
Stamer, W Daniel; Chan, Darren W H; Conley, Shannon M et al. (2008) Aquaporin-1 expression and conventional aqueous outflow in human eyes. Exp Eye Res 87:349-55
Yool, Andrea J (2007) Functional domains of aquaporin-1: keys to physiology, and targets for drug discovery. Curr Pharm Des 13:3212-21
Yool, Andrea J (2007) Aquaporins: multiple roles in the central nervous system. Neuroscientist 13:470-85
Yool, Andrea J (2007) Dominant-negative suppression of big brain ion channel activity by mutation of a conserved glutamate in the first transmembrane domain. Gene Expr 13:329-37
Yu, Jin; Yool, Andrea J; Schulten, Klaus et al. (2006) Mechanism of gating and ion conductivity of a possible tetrameric pore in aquaporin-1. Structure 14:1411-23

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