X Zehua Chen

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Vitamin C (L-ascorbic acid) is essential for many enzymatic reactions, in which it serves to maintain prosthetic metal ions in their reduced forms (for example, Fe2+, Cu+), and for scavenging free radicals in order to protect tissues from oxidative damage. The facilitative sugar transporters of the GLUT type can transport the oxidized form of the vitamin,(More)
Calcium is a major component of the mineral phase of bone and serves as a key intracellular second messenger. Postnatally, all bodily calcium must be absorbed from the diet through the intestine. Here we report the properties of a calcium transport protein (CaT1) cloned from rat duodenum using an expression cloning strategy in Xenopus laevis oocytes, which(More)
Polycystic kidney diseases are genetic disorders in which the renal parenchyma is progressively replaced by fluid-filled cysts. Two members of the polycystin family (polycystin-1 and -2) are mutated in autosomal dominant polycystic kidney disease (ADPKD), and polycystin-L is deleted in mice with renal and retinal defects. Polycystins are membrane proteins(More)
Mutations in polycystins-1 and -2 (PC1 and PC2) cause autosomal dominant polycystic kidney disease (ADPKD), which is characterized by progressive development of epithelial renal cysts, ultimately leading to renal failure. The functions of these polycystins remain elusive. Here we show that PC2 is a Ca(2+)-permeable cation channel with properties distinct(More)
Transcellular calcium transport occurs in many epithelial tissues including intestine, kidney, and placenta. We identified the human ortholog (hCaT1) of a recently cloned rat calcium transport protein, CaT1, that mediates intestinal calcium uptake. hCaT1 messenger RNA is present in the gastrointestinal tract, including esophagus, stomach, duodenum, jejunum,(More)
Histidyl residues in peptide transporters PepT1 and PepT2 are believed to participate in proton and substrate binding and to be crucial to the transporters' functional activities. In the present study, we performed mutagenesis of rabbit PepT1. We mutated three histidine residues (H57, H111, and H121) predicted to reside in transmembrane segments, as well as(More)
Kidney proximal tubule cells take up Krebs cycle intermediates for metabolic purposes and for secretion of organic anions through dicarboxylate/organic anion exchange. Alteration in reabsorption of citrate is closely related to renal stone formation. The presence of distinct types of sodium-coupled dicarboxylate transporters has been postulated on either(More)
The metabolism of Krebs cycle intermediates is of fundamental importance for eukaryotic cells. In the kidney, these intermediates are transported actively into epithelial cells. Because citrate is a potent inhibitor for calcium stone formation, excessive uptake results in nephrolithiasis due to hypocitraturia. We report the cloning and characterization of a(More)
Active absorption of calcium from the intestine and reabsorption of calcium from the kidney are major determinants of whole body calcium homeostasis. Two recently cloned proteins, CaT1 and ECaC, have been postulated to mediate apical calcium uptake by rat intestine and rabbit kidney, respectively. By screening a rat kidney cortex library with a CaT1 probe,(More)
Yeast membrane proteins SMF1, SMF2, and SMF3 are homologues of the DCT1 metal ion transporter family. Their functional characteristics and the implications of these characteristics in vivo have not yet been reported. Here we show that SMF1 expressed in Xenopus oocytes mediates H(+)-dependent Fe(2+) transport and uncoupled Na(+) flux. SMF1-mediated Fe(2+)(More)