During the past decade, we and others have made tremendous progress in understanding the long-term regulation of urea transport proteins. The overall goals of the next funding period are to investigate whether vasopressin increases the apical plasma membrane accumulation of UT-A1, to determine the vasopressin- stimulated signaling pathway(s) that increase UT-A1 accumulation, and to study the retrieval, turnover, and degradation of UT-A1. Urea and water permeabilities often change together, but there are situations when they are regulated independently of one another in the IMCD. Our proposed studies will provide insights into an intriguing biological question: how does vasopressin, acting through a single receptor, the V2- receptor, regulate urea permeability independently of water permeability in a single nephron segment, the terminal IMCD and, indeed, probably independently within the same cells? HYPOTHESIS I. Vasopressin rapidly increases UT-A1 accumulation in the apical plasma membrane.
Specific Aim 1. Determine whether vasopressin increases UT-A1 accumulation in the apical plasma membrane through the V2-vasopressin receptor. Rationale: our preliminary data show that acute vasopressin administration increases the amount of UT-A1 in the plasma membrane.
Specific Aim 2. Determine which cyclic AMP pathway regulates UT-A1 accumulation in the plasma membrane. Rationale: our Preliminary Data show that activation of Epac, a novel cAMP-dependent but PKA-independent pathway, increases UT-A1 accumulation in the IMCD plasma membrane, but does not change AQP2. These data suggest that vasopressin's ability to independently regulate urea and water results, at least in part, from activation of different cAMP-dependent signaling pathways in IMCD cells. HYPOTHESIS II. Vasopressin regulates UT-A1 retrieval and/or degradation.
Specific Aim 3. Determine the functional half-life of UT-A1 in the apical plasma membrane and the cellular systems responsible for UT-A1 retrieval and/or degradation. Rationale: our Preliminary Data in UT-A1- MDCK cells show that: 1) UT-A1 is a ubiquitinated protein in rat inner medulla and in UT-A1-MDCK cells; and 2) pre-treatment with a proteasome inhibitor produces a marked increase in urea flux (function), UT-A1 protein abundance, and the sizes of biotinylated UT-A1. These data suggest that ubiquitination may regulate retrieval of UT-A1 from the plasma membrane and target it for degradation in the proteasome.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK041707-18
Application #
8018071
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Ketchum, Christian J
Project Start
1989-08-01
Project End
2012-12-31
Budget Start
2011-01-01
Budget End
2012-12-31
Support Year
18
Fiscal Year
2011
Total Cost
$301,260
Indirect Cost
Name
Emory University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Klein, Janet D; Sands, Jeff M (2016) Urea transport and clinical potential of urearetics. Curr Opin Nephrol Hypertens 25:444-51
Sands, Jeff M (2016) Water, Water Everywhere: A New Cause and a New Treatment for Nephrogenic Diabetes Insipidus. J Am Soc Nephrol 27:1872-4
Chen, Ling; LaRocque, Lauren M; Efe, Orhan et al. (2016) Effect of Dapagliflozin Treatment on Fluid and Electrolyte Balance in Diabetic Rats. Am J Med Sci 352:517-523
Ren, Huiwen; Yang, Baoxue; Ruiz, Joseph A et al. (2016) Phosphatase inhibition increases AQP2 accumulation in the rat IMCD apical plasma membrane. Am J Physiol Renal Physiol 311:F1189-F1197
Wang, Juan; Wang, Xiaonan H; Wang, Haidong et al. (2016) Urea Transporter B and MicroRNA-200c Differ in Kidney Outer Versus Inner Medulla Following Dehydration. Am J Med Sci 352:296-301
Reed, Galen D; von Morze, Cornelius; Verkman, Alan S et al. (2016) Imaging Renal Urea Handling in Rats at Millimeter Resolution using Hyperpolarized Magnetic Resonance Relaxometry. Tomography 2:125-135
Keller, Raymond W; Bailey, James L; Wang, Yanhua et al. (2016) Urea transporters and sweat response to uremia. Physiol Rep 4:
Klein, Janet D; Wang, Yanhua; Blount, Mitsi A et al. (2016) Metformin, an AMPK activator, stimulates the phosphorylation of aquaporin 2 and urea transporter A1 in inner medullary collecting ducts. Am J Physiol Renal Physiol 310:F1008-12
Sands, Jeff M; Klein, Janet D (2016) Physiological insights into novel therapies for nephrogenic diabetes insipidus. Am J Physiol Renal Physiol 311:F1149-F1152
Efe, Orhan; Klein, Janet D; LaRocque, Lauren M et al. (2016) Metformin improves urine concentration in rodents with nephrogenic diabetes insipidus. JCI Insight 1:

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