Renal sodium homeostasis, a major determinant of blood pressure, is regulated by a variety of endocrine, autocrine, and neural factors. The molecular mechanism by which these factors act is not well understood but involves regulation of the rate of tubular sodium reabsorption. Several lines of evidence indicate that regulation of Na+,K+-ATPase activity is, at least in part, responsible for the reduced sodium reabsorption induced by dopamine in renal proximal tubules. At the cellular level, dopamine triggers a specific signaling cascade that ultimately leads to endocytosis of membrane Na+,K+-ATPase, a process that we have demonstrated is responsible for the decreased Na+,K+-ATPase activity.
The aims of this proposal are: 1) To determine how the signal originated by phosphorylation of Na+,K+-ATPase alpha-subunit Ser-18 is transmitted to other domains of the a-subunit, such as the polyproline site (81-TPPPTTP-87) and the """"""""endocytic sequence"""""""" (537-YLEL). 2) To test the hypothesis that PI3K binds to the Na+,K+-ATPase alpha-subunit polyproline site (81-TPPPTTP-87) and forms a scaffold for recruitment of other proteins that participate in the endocytosis of Na+,K+-ATPase molecules. 3) To identify the location and size of the intracellular pool that exchanges Na+,K+-ATPase molecules with the plasma membrane during dopamine induced Na+,K+-ATPase endocytosis. 4) To identify the stage(s) within the dopamine signaling cascade that is/are sensitive to changes of intracellular sodium concentration. 5) To test the in vivo regulatory role of dopamine by producing transgenic mice that express Na+,K+-ATPase molecules that are resistant to regulation by dopamine. These studies will provide insight into the molecular mechanism by which dopamine promotes renal sodium excretion in proximal tubules. Alterations in the regulation of kidney sodium reabsorption are often found on patients with congestive heart failure, cirrhosis, renal failure, and hypertension. Better knowledge of the mechanism of regulation of proteins involved in renal sodium transport will facilitate the development of new approaches in the treatment of patients with these disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK062195-04
Application #
7116313
Study Section
General Medicine B Study Section (GMB)
Program Officer
Ketchum, Christian J
Project Start
2003-09-01
Project End
2008-08-31
Budget Start
2006-09-01
Budget End
2008-08-31
Support Year
4
Fiscal Year
2006
Total Cost
$232,863
Indirect Cost
Name
University of Houston
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
036837920
City
Houston
State
TX
Country
United States
Zip Code
77204
Efendiev, Riad; Budu, Claudia E; Bertorello, Alejandro M et al. (2008) G-protein-coupled receptor-mediated traffic of Na,K-ATPase to the plasma membrane requires the binding of adaptor protein 1 to a Tyr-255-based sequence in the alpha-subunit. J Biol Chem 283:17561-7
Cinelli, Angel R; Efendiev, Riad; Pedemonte, Carlos H (2008) Trafficking of Na-K-ATPase and dopamine receptor molecules induced by changes in intracellular sodium concentration of renal epithelial cells. Am J Physiol Renal Physiol 295:F1117-25
Efendiev, R; Das-Panja, K; Cinelli, A R et al. (2007) Localization of intracellular compartments that exchange Na,K-ATPase molecules with the plasma membrane in a hormone-dependent manner. Br J Pharmacol 151:1006-13
Efendiev, Riad; Cinelli, Angel R; Leibiger, Ingo B et al. (2006) FRET analysis reveals a critical conformational change within the Na,K-ATPase alpha1 subunit N-terminus during GPCR-dependent endocytosis. FEBS Lett 580:5067-70
Chen, Zongpei; Krmar, Rafael T; Dada, Laura et al. (2006) Phosphorylation of adaptor protein-2 mu2 is essential for Na+,K+-ATPase endocytosis in response to either G protein-coupled receptor or reactive oxygen species. Am J Respir Cell Mol Biol 35:127-32
Efendiev, Riad; Pedemonte, Carlos H (2006) Contrary to rat-type, human-type Na,K-ATPase is phosphorylated at the same amino acid by hormones that produce opposite effects on enzyme activity. J Am Soc Nephrol 17:31-8
Pedemonte, Carlos H; Efendiev, Riad; Bertorello, Alejandro M (2005) Inhibition of Na,K-ATPase by dopamine in proximal tubule epithelial cells. Semin Nephrol 25:322-7
Efendiev, Riad; Chen, Zongpei; Krmar, Rafael T et al. (2005) The 14-3-3 protein translates the NA+,K+-ATPase {alpha}1-subunit phosphorylation signal into binding and activation of phosphoinositide 3-kinase during endocytosis. J Biol Chem 280:16272-7
Efendiev, Riad; Krmar, Rafael T; Ogimoto, Goichi et al. (2004) Hypertension-linked mutation in the adducin alpha-subunit leads to higher AP2-mu2 phosphorylation and impaired Na+,K+-ATPase trafficking in response to GPCR signals and intracellular sodium. Circ Res 95:1100-8