title: Molecular cloning of a mercurial-insensitive water channel expressed in selected water-transporting tissues.
abstract: 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.
authors.affiliation: Department of Medicine and Physiology, University of California, San Francisco 94143-0532.
authors.forename: H
authors.initials: H
authors.lastname: Hasegawa
authors.forename: T
authors.initials: T
authors.lastname: Ma
authors.forename: W
authors.initials: W
authors.lastname: Skach
authors.forename: M A
authors.initials: MA
authors.lastname: Matthay
authors.forename: A S
authors.initials: AS
authors.lastname: Verkman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051398:Aquaporin 1; D020346:Aquaporins; D001483:Base Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D018076:DNA, Complementary; D007473:Ion Channels / Q000235:genetics*; D008168:Lung / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism*; D014981:Xenopus
chemical_list: C496022:Aqp1 protein, rat; D020346:Aquaporins; D018076:DNA, Complementary; D007473:Ion Channels; D008565:Membrane Proteins; D012333:RNA, Messenger; D014867:Water; D051398:Aquaporin 1; C094483:mercurial-insensitive water channel