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)

Two kidney water channels have been identified: CHIP28 in proximal tubule and thin descending limb, and WCH-CD in collecting duct apical membrane. An homologous cDNA (WCH3) was obtained from rat kidney and found to encode a 276 amino acid, 29 kDa protein with 39% amino acid identity to rat CHIP28, 50% to WCH-CD and 49% to MIP26. The WCH3 transcript of 2.5 kb was expressed exclusively in kidney and was upregulated in dehydrated rats. Cell-free translation produced an approximately 28 kDa protein. Analysis of the predicted amino acid sequence indicated a hydrophobic protein with 4-6 membrane-spanning domains, with one N-linked glycosylation site, two conserved NPA boxes common to MIP26 family proteins, and conserved residue C189 common to water channels. WCH3 is a new member of the MIP26 family of channel-forming proteins in mammalian kidney.
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PMID:Cloning of a novel rat kidney cDNA homologous to CHIP28 and WCH-CD water channels. 750 72

Two mercurial-inhibitable water-transporting proteins have been identified: CHIP28, an erythrocyte water channel also expressed in kidney tubules and selected extrarenal epithelia, and WCH-CD, a kidney collecting duct water channel. In searching for a protein responsible for the high transcellular water permeability in lung alveolus, we cloned a 32-kDa water channel (mercurial-insensitive water channel (MIWC)) from a rat lung cDNA library with several novel features. Water permeability was strongly increased in Xenopus oocytes expressing MIWC in a mercurial-insensitive manner, in contrast to known water channels. By in situ hybridization, MIWC showed an unique distribution in cells that do not express CHIP28, including kidney papillary vasa recta, cells lining the subarachnoid space and ventricles in brain, the inner nuclear layer in retina, and the conjunctival epithelium. An alternatively spliced form of MIWC with a 165-base pair deletion in the coding sequence was also identified; relative expression of the spliced mRNA was tissue-specific. The MIWC water channel may participate in the urinary concentrating mechanism, the absorption of cerebrospinal fluid, and other physiological processes.
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PMID:Molecular cloning of a mercurial-insensitive water channel expressed in selected water-transporting tissues. 750 89

We recently cloned a cDNA of the collecting duct apical membrane water channel of rat kidney, which is important for the formation of concentrated urine (Fushima, K., S. Uchida, Y. Hara, Y. Hirata, F. Marumo, and S. Sasaki. 1993. Nature [Lond.]. 361:549-552). Since urine concentrating ability varies among mammalian species, we examined whether an homologous protein is present in human kidney. By screening a human kidney cDNA library, we isolated a cDNA clone, designated human aquaporin of collecting duct (hAQP-CD), that encodes a 271-amino acid protein with 91% identity to rat AQP-CD. mRNA expression of hAQP-CD was predominant in the kidney medulla compared with the cortex, immunohistochemical staining of hAQP-CD was observed only in the collecting duct cells, and the staining was dominant in the apical domain. Functional expression study in Xenopus oocytes confirmed that hAQP-CD worked as a water channel. Western blot analysis of human kidney medulla indicated that the molecular mass of hAQP-CD is 29 kD, which is the same mass expected from the amino acid sequence. Chromosomal mapping of the hAQP-CD gene assigned its location to chromosome 12q13. These results could be important for future studies of the pathophysiology of human urinary concentration mechanisms in normal and abnormal states.
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PMID:Cloning, characterization, and chromosomal mapping of human aquaporin of collecting duct. 751 Jul 18

A new member of the family of water channel proteins (aquaporin-CHIP) related to the major intrinsic protein (MIP) family is described. The cDNA coding for this amphibian CHIP was cloned from frog (Rana esculenta) urinary bladder, a model for the kidney collecting duct, using a RT-PCR cloning strategy. The encoded protein, designated FA-CHIP (frog aquaporin-CHIP), shows 77.4%, 42.4% and 35.6% identity with the three proteins now referred to as the aquaporins of the MIP family, i.e., human CHIP28, WCH-CD and gamma-TIP, respectively. Xenopus leavis injected with FA-CHIP cRNA exhibited a marked increase of the osmotic water permeability.
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PMID:Sequence and functional expression of an amphibian water channel, FA-CHIP: a new member of the MIP family. 751 88

Two recently cloned water channels, CHIP28 and WCH-CD, are homologous to MIP26, an integral membrane channel-forming protein found in lens fiber plasma membranes. CHIP28 is found in basolateral and apical plasma membranes of kidney proximal tubules and thin descending limbs of Henle, whereas WCH-CD is apically located in collecting duct principal cells. So far, the putative water channel that may be responsible for the high constitutive permeability of principal cell basolateral membranes has not been identified. Interestingly, freeze-fracture electron microscopy has shown that characteristic orthogonal arrays of intramembrane particles (OAPs) are found on the basolateral plasma membranes of collecting duct principal cells, and that morphologically identical OAPs present in lens fiber cell plasma membranes contain the protein MIP26. Similar OAPs have also been detected on plasma membranes of other cell types including gastric parietal cells, astroglial cells and skeletal muscle fibers. By indirect immunofluorescence, western blotting and northern blotting, MIP26 was found only in lens fibers. In addition, functional studies on reconstituted and oocyte-expressed MIP26 excluded the possibility that MIP26 might be a basolateral water channel in the kidney. However, a polyclonal antibody raised against skeletal muscle sarcolemmal vesicles, which are enriched in OAPs, produced an intense staining of principal cell basolateral plasma membranes in kidney collecting duct and immunoprecipitated a 28 kDa protein from kidney papilla. The immunoprecipitated protein from papilla was not recognized by anti-CHIP28 or anti-MIP26 antibodies, indicating that principal cell basolateral membranes contain a novel member of the CHIP/MIP family. Because this antibody also stained brain astrocyte end feet, which are enriched in OAPs, it is possible that the 28 kDa protein is related to these structures. We conclude that OAPs probably contain related but distinct proteins that may have different membrane channel functions in different cell types.
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PMID:A 28 kDa sarcolemmal antigen in kidney principal cell basolateral membranes: relationship to orthogonal arrays and MIP26. 752 41

AQP-CD is a vasopressin-regulated water channel expressed exclusively in the renal collecting duct. We have previously shown that AQP-CD is present in the apical plasma membrane and subapical vesicles of collecting duct cells, consistent with membrane-shuttling mechanisms that have been proposed to explain the short-term action of [Arg8] vasopressin (AVP) to regulate apical water permeability. We propose here that AVP may also have long-term actions on the collecting duct to regulate the expression of the AQP-CD water channel. We used immunoblotting, immunohistochemistry, and in vitro perfusion of renal tubules to investigate water channel regulation in collecting ducts of diabetes insipidus (Brattleboro) rats treated with a 5-day infusion of AVP or vehicle. Immunoblotting and immunohistochemistry demonstrated that collecting ducts of vehicle-infused Brattleboro rats had markedly reduced expression of AQP-CD relative to normal rats. In response to AVP infusion there was a nearly 3-fold increase in AQP-CD expression as detected by immunoblotting. Immunocytochemistry demonstrated that the increased expression was predominantly in the apical plasma membrane and subapical vesicles of collecting duct cells. Inner medullary collecting ducts of AVP-infused Brattleboro rats displayed a 3-fold increase in osmotic water permeability relative to vehicle-infused controls, in parallel with the change in AQP-CD expression. Based on these findings, we conclude that (i) long-term infusion of AVP, acting either directly or indirectly, regulates expression of the AQP-CD water channel and (ii) AQP-CD is the predominant AVP-regulated water channel.
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PMID:Regulation of collecting duct water channel expression by vasopressin in Brattleboro rat. 752 27

Mutations in the X-chromosomal V2 receptor gene are known to cause nephrogenic diabetes insipidus (NDI). Besides the X-linked form, an autosomal mode of inheritance has been described. Recently, mutations in the autosomal gene coding for water-channel aquaporin 2 (AQP2) of the renal collecting duct were reported in an NDI patient. In the present study, missense mutations and a single nucleotide deletion in the aquaporin 2 gene of three NDI patients from consanguineous matings are described. Expression studies in Xenopus oocytes showed that the missense AQP2 proteins are nonfunctional. These results prove that mutations in the AQP2 gene cause autosomal recessive NDI.
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PMID:Patients with autosomal nephrogenic diabetes insipidus homozygous for mutations in the aquaporin 2 water-channel gene. 752 15

The water channel CHIP28 accounts for the high water permeability of proximal tubules and thin descending limbs of Henle; a homologous water channel, WCH-CD, in the apical membrane of collecting duct principal cells, may be the vasopressin-sensitive water channel. We show here that one antiserum, raised against CHIP28, immunostains the basolateral membrane of collecting duct principal cells, in addition to staining CHIP28 in other cells. This serum was named anti-basolateral integral protein (anti-BLIP) to distinguish it from other anti-CHIP28 antisera. By Western blotting, BLIP serum recognized both CHIP28 and MIP26, and it stained lens fibers, which contain MIP26 but not CHIP28. BLIP antiserum immunoprecipitated a 28-kDa band, a broad 35- to 50-kDa band, and an approximately 16-kDa band from kidney papilla. It also stained the basolateral membrane of gastric parietal cells, which were not stained with anti-CHIP28 or anti-MIP26 antibodies. BLIP antiserum immunoprecipitated a 28-kDa protein band from stomach; this protein was not precipitated by anti-CHIP28 antibodies. These results suggest that basolateral membranes of principal cells and parietal cells contain a protein(s) that shares common epitopes with CHIP28 and MIP26. Finally, BLIP but not CHIP28 antiserum stained mesothelial (but not epithelial) cells of toad urinary bladder, a further indication that the BLIP antiserum recognizes a protein distinct from CHIP28.
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PMID:A basolateral CHIP28/MIP26-related protein (BLIP) in kidney principal cells and gastric parietal cells. 752 36

Vasopressin-regulated water permeability of the kidney collecting duct is a key component of the urine concentration machinery. Recently, a cDNA for AQP-CD, the vasopressin-regulated water channel, initially reported as WCH-CD, has been isolated (K. Fushimi, S. Uchida, Y. Hara, Y. Hirata, F. Marumo, and S. Sasaki. Nature Lond. 361: 549-552, 1993). AQP-CD was expressed in oocyte membrane using a Xenopus expression vector, and functional characteristics of AQP-CD were examined. Osmotic water permeability (Pf) of oocytes expressing AQP-CD was 138 +/- 19 microns/s (mean +/- SE), 12 times greater than the control (11 +/- 3 microns/s), 90% inhibited by 0.3 mM HgCl2, and weakly temperature dependent (energy of activation for Pf was 4.0 kcal/mol). Urea influx measured from 15-min [14C]urea uptake by oocytes injected with AQP-CD/expression vector 1 cRNA was 86 +/- 17% of the control. Two-electrode voltage-clamp experiments revealed insignificant ion conductance of AQP-CD. Immunoblots of membranes from rat kidney medulla and oocytes expressing AQP-CD using anti-AQP-CD COOH-terminal antibody showed a 29-kDa protein and 35- to 50-kDa high-molecular-mass forms. Immunohistochemistry showed apical and subapical localization of AQP-CD in the collecting duct principal cells. Our results indicated that AQP-CD is a 29-kDa protein, a selective water channel, distinct from a urea channel, and localized to the membranes of vasopressin-sensitive components in kidney collecting duct principal cells.
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PMID:Functional characterization and cell immunolocalization of AQP-CD water channel in kidney collecting duct. 752 58

The human AQP2 (collecting duct water channel, aquaporin 2) gene encodes a 271 amino acid protein and is a member of the MIP (major intrinsic protein of lens fiber) gene family. Using two-color fluorescence in situ hybridization on high-resolution R-banded chromosomes and human genomic DNA clones for AQP2 and MIP as probes, we found that both genes mapped closely within the human chromosome region 12q13.
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PMID:Human AQP2 and MIP genes, two members of the MIP family, map within chromosome band 12q13 on the basis of two-color FISH. 752 61


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