Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several membranes of the kidney are highly water permeable, thereby enabling this organ to retain large quantities of water. Recently, the molecular identification of water channels responsible for this high water permeability has finally been accomplished. At present, four distinct renal water channels have been identified, all members of the family of major intrinsic proteins. Aquaporin 1 (AQP1), aquaporin 2 (AQP2) and the mercury-insensitive water channel (MIWC) are water-selective channel proteins, whereas the fourth, referred to as aquaporin 3 (AQP3), permits transport of urea and glycerol as well. Furthermore, a putative renal water channel (WCH3) has been found. AQP1 is expressed in apical and basolateral membranes of proximal tubules and descending limbs of Henle, AQP2 predominantly in apical membranes of principal and inner medullary collecting duct cells and AQP3 in basolateral membranes of kidney collecting duct cells. MIWC is expressed in the inner medulla of the kidney and has been suggested to be localised in the vasa recta. The human genes encoding AQP1 and AQP2 have been cloned, permitting deduction of their amino acid sequence, prediction of their two-dimensional structure by hydropathy analysis, speculations on their way of functioning and DNA analysis in patients with diseases possibly caused by mutant aquaporins. Mutations in the AQP1 gene were recently detected in clinically normal individuals, a finding which contradicts the presumed vital importance of this protein. Mutations in the AQP2 gene were shown to cause autosomal recessive nephrogenic diabetes insipidus. The renal unresponsiveness to arginine vasopressin, which characterises this disease, is in accordance with the assumption that AQP2 is the effector protein of the renal vasopressin pathway.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Discovery of aquaporins: a breakthrough in research on renal water transport. 754 Aug 50

Like mammalian kidney collecting duct, the water permeability of frog urinary bladder epithelial cells is antidiuretic hormone (ADH)-sensitive. In kidney, this permeability is mediated by water channels named aquaporins. We recently reported the cloning of the frog aquaporin CHIP (FA-CHIP), a water channel from frog urinary bladder. FA-CHIP has 79% identity with rat Aquaporin 1 (AQP1) and only 42% identity with the kidney collecting duct Aquaporin 2 (AQP2). The purpose of this study was to examine the localization of FA-CHIP in frog urinary bladder. We raised antibodies against peptides of 15 to 17 residues, encompassing the N-ter and C-ter regions of FA-CHIP. Anti-FA-CHIP antibodies were used for Western blotting, indirect immunofluorescence microscopy and gold labeling electron microscopy in urinary bladder and other frog tissues. By Western blotting of frog urinary bladder total homogenate, the antibodies recognized a band of 29 kDa and glycosylated forms of the protein between 40 and 70 kDa. No signal was found on membrane preparations from epithelial cell homogenate. FA-CHIP was also found in frog skin, brain, gall bladder, and lung. In immunofluorescence microscopy on urinary bladder sections, FA-CHIP was localized to endothelial cells of blood capillaries and on mesothelial cells of the serosal face. Red blood cells, epithelial and basal cells were unstained. The localization of FA-CHIP in cell plasma membranes was confirmed by gold labeling electron microscopy. In other positive tissues, FA-CHIP was also localized to capillaries. In brain, plasma membranes of epithelial cells were also stained. In conclusion, like its mammalian homologue AQP1, FA-CHIP appears to be localized to constitutively water permeable cells of frog. Therefore, it belongs to the AQP1 family of proteins although unlike AQP1, FA-CHIP is absent from red blood cells and kidney. In frog urinary bladder and skin, FA-CHIP probably plays an important role in water transport across the barriers in series with the ADH-sensitive epithelial cells.
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PMID:Localization of the FA-CHIP water channel in frog urinary bladder. 924 82

Mammalian aquaporins constitute a family of so far 10 related water channel proteins which mediate osmotically driven water fluxes across the plasma membrane. Because regulation of the ionic composition and osmolality of inner ear fluids is of great functional significance, we investigated the expression patterns of aquaporins in five defined areas of the rat inner ear by RT-PCR. The tissues used were stria vascularis, endolymphatic sac, Reissner's membrane, vestibulum and organ of Corti. Aquaporin 1 transcripts were detected in all tissues and are probably constitutive. Aquaporin 5 was only expressed in the organ of Corti and in Reissner's membrane. We show that aquaporin 2, so far considered to be specific to the principal cells of the renal collecting duct, is expressed in the endolymphatic sac. Aquaporin 2 expression was not detected in any other inner ear region. The postnatal appearance of aquaporin 2 transcripts in the endolymphatic sac resembled that in the kidney, i.e. it increased postnatally until day 4. The full-length DNA for aquaporin 2 was cloned from cDNA of the endolymphatic sac. It had an irrelevant Ile54Thr mutation because it could be functionally expressed in Xenopus oocytes. Also exclusively in the endolymphatic sac of the inner ear, we detected transcripts for aquaporin isoforms 3 and 4 which are known to be expressed in the renal principal cells. In the kidney, aquaporin 2 regulation involves vasopressin-stimulated, cAMP-dependent phosphorylation of Ser256 of aquaporin 2 which is stored in cytosolic vesicles. These storage vesicles also contain a serpentine calcium/polycation-sensing receptor. Vesicle shuffling to the plasma membrane involves proteins such as vesicle-associated membrane protein VAMP2, syntaxin-4 and the small GTPase Rab3a. Using RT-PCR we were able to demonstrate the expression of all of these components. By analogy the data suggest that in the endolymphatic sac of the inner ear a system for cellular water permeability is in place which may share many similarities with that characterized in the principal cells of the renal collecting duct. These findings may have a number of interesting pharmacological implications which need to be addressed in future studies.
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PMID:Expression pattern of aquaporin water channels in the inner ear of the rat. The molecular basis for a water regulation system in the endolymphatic sac. 1039 50

Within the past decade an entire family of membrane proteins--aquaporins--which function as transmembrane water channels has been identified; they occur throughout the plant, animal, and bacterial kingdoms. Several family members permit glycerol and urea permeability. Most aquaporins are inhibited by mercury. Constitutively expressed aquaporin 1 is the major permeability channel of the proximal tubule, descending thin limb of the loop of Henle, and it is also found in vasa recta. Aquaporin 2 is expressed in the principal cells of the collecting duct where it shuttles between intracellular vesicles and the apical membrane in response to vasopressin. Aquaporin 2 mutations cause nephrogenic diabetes insipidus; increased aquaporin 2 activity is implicated in the pathophysiology of heart failure, cirrhosis, and nephrotic syndrome. Aquaporins 3 and 4 provide basolateral membrane water channels in the collecting duct. These 4 channels and 6 others are also found elsewhere throughout the body. The physiological importance of several of the channels remains unknown. Aquaporin 1 inhibitors might induce useful diuresis, but humans who lack aquaporin 1 have no significant clinical disease. Inhibition of aquaporin 2 activity by vasopressin receptor antagonists may be useful in heart failure, cirrhosis, nephrotic syndrome, and the syndrome of inappropriate antidiuretic hormone (ADH) release.
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PMID:Aquaporin mediated water flux as a target for diuretic development. 1059 41

Aquaporin (AQP) water channels are important in the function of the kidney. Constitutively expressed AQP1 in the proximal tubule and descending limb is important in normal fluid absorption and in the counter-current multiplication system. The vasopressin-regulated shuttling of AQP2 is essential in antidiuresis and the regulation of water balance. Genetic damage to AQPs, or pathological changes in expression or function, impair renal water handling. The most striking examples of this involve disruption of AQP2 function, which can result in profound nephrogenic diabetes insipidus. Aquaporin 1 is present in capillaries and venules and appears to be important in peritoneal dialysis, where it appears to represent the "ultrasmall pores" of the three-pore model. Decreased expression or function of AQP1 may be responsible for some cases of ultrafiltration failure, but further evidence will be required to establish whether this is the case.
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PMID:Aquaporins: roles in renal function and peritoneal dialysis. 1133 May 71