Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NHE1, NHE2, and NHE3 are well-characterized cloned members of the mammalian Na(+)/H(+) exchanger (NHE) gene family. Given the specialized function and regulation of NHE1, NHE2, and NHE3, we compared basal turnover numbers of NHE1, NHE2, and NHE3 measured in the same cell system: PS120 fibroblasts lacking endogenous NHEs. NHE1, NHE2, and NHE3 were epitope tagged with vesicular stomatitis virus glycoprotein (VSVG). The following characteristics were determined on the same passage of cells transfected with NHE1V, NHE2V, or NHE3V: 1) maximal reaction velocity (V(max)) by (22)Na(+) uptake and fluorometery, 2) total amount of NHE protein by quantitative Western analysis with internal standards of VSVG-tagged maltose-binding protein, and 3) cell surface expression by cell surface biotinylation. Cell surface expression (percentage of total NHE) was 88.8 +/- 3.5, 64.6 +/- 3.3, 20.0 +/- 2.6, and 14.0 +/- 1.3 for NHE1V, 85- and 75-kDa NHE2V, and NHE3V, respectively. Despite these divergent cell surface expression levels, turnover numbers for NHE1, NHE2, and NHE3 were similar (80.3 +/- 9.6, 92.1 +/- 8.6, and 99.2 +/- 9.1 s(-1), when V(max) was determined using (22)Na uptake at 22 degrees C and 742 +/- 47, 459 +/- 16, and 609 +/- 39 s(-1) when V(max) was determined using fluorometry at 37 degrees C). These data indicate that, in the same cell system, intrinsic properties that determine turnover number are conserved among NHE1, NHE2, and NHE3.
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PMID:Na(+)/H(+) exchangers (NHE1-3) have similar turnover numbers but different percentages on the cell surface. 1060 Jul 62

Cell biological approaches were used to examine the location and function of the brush border (BB) Na(+)/H(+) exchanger NHE3 in the opossum kidney (OK) polarized renal proximal tubule cell line. NHE3 epitope tagged with the vesicular stomatitis virus glycoprotein epitope (NHE3V) was stably expressed and called OK-E3V cells. On the basis of cell surface biotinylation studies, these cells had 10-15% of total NHE3 on the BB. Intracellular NHE3V largely colocalized with Rab11 and to a lesser extent with EEA1. The BB location of NHE3V was examined by confocal microscopy relative to the lectins wheat germ aggluttinin (WGA) and phytohemagluttin E (PHA-E), as well as the B subunit of cholera toxin (CTB). The cells were pyramidal, and NHE3 was located in microvilli in the center of the apical surface. In contrast, PHA-E, WGA, and CTB were diffusely distributed on the BB. Detergent extraction showed that total NHE3V was largely soluble in Triton X-100, whereas virtually all surface NHE3V was insoluble. Sucrose density gradient centrifugation demonstrated that total NHE3V migrated at the same size as approximately 400- and approximately 900-kDa standards, whereas surface NHE3V was enriched in the approximately 900-kDa form. Under basal conditions, NHE3 cycled between the cell surface and the recycling pathway through a phosphatidylinositol (PI) 3-kinase-dependent mechanism. Measurements of surface and intracellular pH were obtained by using FITC-WGA. Internalization of FITC-WGA occurred largely into the juxtanuclear compartment that contained Rab11 and NHE3V. pH values on the apical surface and in endosomes in the presence of the NHE3 blocker, S3226, were elevated, showing that NHE3 functioned to acidify both compartments. In conclusion, NHE3V in OK cells exists in distinct domains both in the center of the apical surface and in a juxtanuclear compartment. In the BB fraction, NHE3 is largely in the detergent-insoluble fraction in lipid rafts and/or in large heterogenous complexes ranging from approximately 400 to approximately 900 kDa.
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PMID:Na(+)/H(+) exchanger 3 is in large complexes in the center of the apical surface of proximal tubule-derived OK cells. 1217 49