Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous functional studies of toad bladder endosomes have been complicated by the presence of multiple endosome subpopulations each possessing different permeability characteristics. To identify and characterize both water channel-containing vesicles (WCV) and other endosome subpopulations, we combined flow cytometry, electron microscopy, stop-flow fluorometry, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Flow cytometry of endosomes identified distinct populations of fluorescein-labeled endosomes in bladders after removal of antidiuretic hormone (ADH) stimulation (ADH withdrawal). Centrifugation separated the larger fluorescein-labeled vesicles, sedimenting at lower speed (intermediate pellet, IP), from the smaller fluorescein-labeled vesicles, sedimenting at high speed (high-speed pellet, HSP). Permeability and structural studies of these subpopulations revealed the following. 1) IP endosomes labeled 10 min after ADH withdrawal (ADH IP) represented a highly purified population of WCV with high water permeability (Pf) that exhibited a low-activation energy and sensitivity to organic mercurials. 2) IP endosomes from unstimulated bladders did not contain functional water channels. 3) HSP from either ADH withdrawal or unstimulated bladders exhibited low Pf and acidified after addition of extravesicular ATP; moreover, protein compositions of purified HSP were distinct from those of purified IP. These results suggest that HSPs represent constitutive and not ADH-sensitive endosomes. 4) High permeability to protons (PH+) was seen in ADH IP endosomes but not the other fractions, providing strong evidence that the ADH water channel conducts protons. 5) Multivesicular bodies (MVB) exhibited low Pf and PH+, indicating that they do not possess functional water channels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Functional and structural characterization of endosomes from toad bladder epithelial cells. 163 45

The extreme hyperosmotic conditions that exist in the renal inner medulla enable the urinary concentrating mechanism to function. In this study, we evaluated whether stress-related molecular chaperones are induced in response to hyperosmotic stress in mouse inner medullary collecting duct (mIMCD3) cells. Exposure of cells to medium supplemented with 100 mM NaCl for 4 or 24 h resulted in an increase in heat shock protein-72 (HSP-72) (inducible form) by Western blot. Immunocytochemistry confirmed the increase of HSP-72 and showed that hyperosmotic stress resulted in a localization of HSP-72 predominantly to the nucleoplasm that surrounds the nucleoli and to the cytoplasm, a subcellular distribution pattern different from that seen with heat shock. Using a denatured protein (casein)-affinity column with ATP elution, we identified a number of putative molecular chaperones (46, 60, 78, and 200 kDa) that are upregulated in response to 4 h of hyperosmotic NaCl treatment. Microsequencing identified one of these proteins to be the mitochondrial chaperone mtHSP-70, a member of HSP-70 family, and another to be similar to beta-actin. We also found high levels of HSP-72 in cells chronically adapted to hypertonicity, indicating that chaperones are still required to maintain certain cellular functions even after nonperturbing organic osmolytes are known to accumulate. These results suggest an important role for molecular chaperones in the adaptation of renal medullary epithelial cells to the hyperosmotic conditions that exist in the inner medulla in vivo.
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PMID:Induction of molecular chaperones by hyperosmotic stress in mouse inner medullary collecting duct cells. 924 87

The epithelial Na+ channel (ENaC) provides for Na+ absorption in various types of epithelia including the kidney, lung, and colon where ENaC is localized to the apical membrane to enable Na+ entry into the cell. The degree of Na+ entry via ENaC largely depends on the number of active channels localized to the cell membrane, and is tightly controlled by interactions with ubiquitin ligases, kinases, and G-proteins. While regulation of ENaC endocytosis has been well-studied, relatively little is understood of the proteins that govern ENaC exocytosis. We hypothesized that the annexin II light chain, p11, could participate in the transport of ENaC along the exocytic pathway. Our results demonstrate that all three ENaC channel subunits interacted with p11 in an in vitro binding assay. Furthermore, p11 was able to immunoprecipitate ENaC in epithelial cells. Quantitative mass spectrometry of affinity-purified ENaC-p11 complexes recovered several other trafficking proteins including HSP-90 and annexin A6. We also report that p11 exhibits a robust protein expression in cortical collecting duct epithelial cells. However, the expression of p11 in these cells was not influenced by either short-term or long-term exposure to aldosterone. To determine whether the p11 interaction affected ENaC function, we measured amiloride sensitive Na+ currents in Xenopus oocytes or mammalian epithelia co-expressing ENaC and p11 or a siRNA to p11. Results from these experiments showed that p11 significantly augmented ENaC current, whereas knockdown of p11 decreased current. Further, knockdown of p11 reduced ENaC cell surface population suggesting p11 promotes membrane insertion of ENaC. Overall, our findings reveal a novel protein interaction that controls the number of ENaC channels inserted at the membrane via the exocytic pathway.
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PMID:Annexin II Light Chain p11 Interacts With ENaC to Increase Functional Activity at the Membrane. 3080 70