Vasopressin regulates urea transport by activating two cyclic AMP (cAMP) dependent signaling pathways: protein kinase A and exchange protein activated by cAMP. This results in increases of both the phosphorylation and apical plasma membrane accumulation of the UT-A1 urea transporter. The hypertonicity present in the inner medulla can act independently of vasopressin as a powerful stimulus of urea transport. Hypertonicity stimulates urea transport by increasing both UT-A1 phosphorylation and plasma membrane accumulation. However, the signaling pathway by which this occurs is unknown. We have new preliminary data showing that hypertonicity stimulates urea permeability via protein kinase C (PKC). We also have preliminary data suggesting that PKC1 is the specific PKC isozyme involved since: 1) hypertonicity activates PKC1 in rat inner medullary collecting ducts (IMCDs);and 2) PKC1 knock-out mice have a urine concentrating defect and a reduction in UT-A1 protein abundance. Thus, maximal stimulation of urea transport and UT-A1 activity in the terminal IMCD requires stimulation by both cAMP and PKC1. Our overall goal is to investigate the regulation of UT-A1 by PKC. We will test the hypothesis that PKC1 stimulates UT-A1 function through changes in UT-A1 phosphorylation.
Aim 1 will determine the mechanism by which PKC regulates UT-A1 phosphorylation.
Aim 2 will determine the site(s) in UT-A1 and the cellular location of phosphorylation by PKC.
Aim 3 will determine the interdependence of PKC and PKA in the regulation of UT-A1 membrane accumulation, activity, phosphorylation, and phosphatase-mediated dephosphorylation.
Aim 4 will determine the mechanism for the urine concentrating defect in PKC"""""""" knock-out mice. Our proposed studies are highly significant as they are likely to yield new information on mechanisms underlying dysregulation of water homeostasis. Elucidation of non-cAMP mechanisms for increasing urea transport, which in turn would increase urine concentrating ability, could form the basis for future translational studies of novel therapeutic approaches to congenital nephrogenic diabetes insipidus.

Public Health Relevance

Urea plays a critical role in the urinary concentrating mechanism, and therefore, in the regulation of water balance. Our studies into the regulation of urea transport will advance our understanding of the urinary concentrating mechanism. This could yield new therapies for nephrogenic diabetes insipidus and will become increasingly important with the development of protein kinase C inhibitors for the treatment of diabetes mellitus.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Cellular and Molecular Biology of the Kidney Study Section (CMBK)
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Ketchum, Christian J
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Emory University
Internal Medicine/Medicine
Schools of Medicine
United States
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Kitada, Kento; Daub, Steffen; Zhang, Yahua et al. (2017) High salt intake reprioritizes osmolyte and energy metabolism for body fluid conservation. J Clin Invest 127:1944-1959
Hou, Ruida; Alemozaffar, Mehrdad; Yang, Baoxue et al. (2017) Identification of a Novel UT-B Urea Transporter in Human Urothelial Cancer. Front Physiol 8:245
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
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
Qian, Xiaoqian; Sands, Jeff M; Song, Xiang et al. (2016) Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation. Pflugers Arch 468:1161-70
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
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
Klein, Janet D; Wang, Yanhua; Mistry, Abinash et al. (2016) Transgenic Restoration of Urea Transporter A1 Confers Maximal Urinary Concentration in the Absence of Urea Transporter A3. J Am Soc Nephrol 27:1448-55
Weiner, I David; Mitch, William E; Sands, Jeff M (2015) Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion. Clin J Am Soc Nephrol 10:1444-58

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