Molecular Cloning and Characterization of an Aquaporin cDNA from Salivary, Lacrimal, and Respiratory Tissues

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Title: Molecular Cloning and Characterization of an Aquaporin cDNA from Salivary, Lacrimal, and Respiratory Tissues
Author: Preston, G M; Raina, S; Agre, P; Guggino, W B
Abstract: The Aquaporin family of water channels plays a fundamental role in transmembrane water movements in numerous plant and animal tissues. Since the molecular pathway by which water is secreted by salivary glands is unknown, a cDNA was isolated from rat submandibular gland by homology cloning. Similar to other Aquaporins, the salivary cDNA encodes a 265-residue polypeptide with six putative transmembrane domains separated by five connecting loops (A-E); the NH2- and COOH-terminal halves of the polypeptide are sequence-related, and each contains the motif Asn-Pro-Ala. A mercurial-inhibition site is present in extracellular loop E, and cytoplasmic loop D contains a cAMP-protein kinase phosphorylation consensus. In vitro translation yielded a 27-kDa polypeptide, and expression of the cRNA in Xenopus oocytes conferred a 20-fold increase in osmotic water permeability (Pf) which was reversibly inhibited by 1 mM HgCl2. Northern analysis demonstrated a 1.6-kilobase mRNA in submandibular, parotid, and sublingual salivary glands, lacrimal gland, eye, trachea, and lung. In situ hybridization revealed a strong hybridization over the corneal epithelium in eye and over the secretory lobules in salivary glands. These studies have identified a new mammalian member of the Aquaporin water channel family (gene symbol AQP5) which is implicated in the generation of saliva, tears, and pulmonary secretions.
URI: http://jhir.library.jhu.edu/handle/1774.2/33896
Date: 1995-01-27
Citation: J Biol Chem. 1995 Jan 27;270(4):1908-12. doi: 10.1074/jbc.270.4.1908
Subject: Lacrimal Apparatus/metabolism
Trachea/metabolism
Lung/metabolism
Submandibular Gland/metabolism
Ion Channels/biosynthesis
Aquaporins

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