The focus of the current proposal is to characterize at the molecular level the Na+/dicarboxylate cotransporters of the renal proximal tubule. These transporters are important to the function of the kidney in their reabsorption of Krebs cycle intermediates, and play a role in acid-base balance and organic anion excretion. The brush border Na+/dicarboxylate cotransporter has been implicated in the development of kidney stones by its regulation of urinary citrate concentrations. The principal investigator has recently cloned and sequenced a rabbit renal Na+/dicarboxylate cotransporter, NaDC-1 and the human homolog, hNaDC-1. NaDC-1 appears to correspond to the low affinity Na+/dicarboxylate cotransporter of the brush border membrane. The first specific aim of this study is to characterize the transport properties and tissue distribution of NaDC-1 and hNaDC-1. The second specific aim will address the hypothesis that acute regulation of transporter function occurs at the protein level, possibly by phosphorylation. The third specific aim is to clone and sequence the high affinity Na+/dicarboxylate cotransporter found on the renal proximal tubule basolateral membrane. The fourth specific aim will test the hypothesis that the secondary structure of NaDC-1 has eight transmembrane domains. The fifth specific aim will test the hypothesis that histidines are involved in substrate binding by NaDC-1, and that chimeras between NaDC-1 and related transporters can provide information on domains important to substrate recognition and binding. These studies should provide fundamental information on the functional properties of this family of sodium-dependent transporters, and on the physiological role of these transporters in the kidney.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Scientist Development Award - Research (K02)
Project #
5K02DK002429-04
Application #
2904948
Study Section
Special Emphasis Panel (SRC)
Program Officer
Rankin, Tracy L
Project Start
1996-08-10
Project End
2001-07-31
Budget Start
1999-08-01
Budget End
2000-07-31
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Neurosciences
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Yao, Xiaozhou; Pajor, Ana M (2002) Arginine-349 and aspartate-373 of the Na(+)/dicarboxylate cotransporter are conformationally sensitive residues. Biochemistry 41:1083-90
Li, H; Pajor, A M (2002) Functional characterization of CitM, the Mg2+-citrate transporter. J Membr Biol 185:9-16
Pajor, A M; Gangula, R; Yao, X (2001) Cloning and functional characterization of a high-affinity Na(+)/dicarboxylate cotransporter from mouse brain. Am J Physiol Cell Physiol 280:C1215-23
Pajor, A M (2001) Conformationally sensitive residues in transmembrane domain 9 of the Na+/dicarboxylate co-transporter. J Biol Chem 276:29961-8
Zhang, F F; Pajor, A M (2001) Topology of the Na(+)/dicarboxylate cotransporter: the N-terminus and hydrophilic loop 4 are located intracellularly. Biochim Biophys Acta 1511:80-9
Pajor, A M; Sun, N N (2000) Molecular cloning, chromosomal organization, and functional characterization of a sodium-dicarboxylate cotransporter from mouse kidney. Am J Physiol Renal Physiol 279:F482-90
Pajor, A M (2000) Molecular properties of sodium/dicarboxylate cotransporters. J Membr Biol 175:8-Jan
Yao, X; Pajor, A M (2000) The transport properties of the human renal Na(+)- dicarboxylate cotransporter under voltage-clamp conditions. Am J Physiol Renal Physiol 279:F54-64
Pajor, A M; Kahn, E S; Gangula, R (2000) Role of cationic amino acids in the Na+/dicarboxylate co-transporter NaDC-1. Biochem J 350 Pt 3:677-83
Griffith, D A; Pajor, A M (1999) Acidic residues involved in cation and substrate interactions in the Na+/dicarboxylate cotransporter, NaDC-1. Biochemistry 38:7524-31

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