Molecular cloning and characterization of an aquaporin cDNA from salivary, lacrimal, and respiratory tissues

S. Raina, G. M. Preston, W. B. Guggino, P. Agre

Research output: Contribution to journalArticlepeer-review

340 Scopus citations


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 (P(f)) 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.

Original languageEnglish (US)
Pages (from-to)1908-1912
Number of pages5
JournalJournal of Biological Chemistry
Issue number4
StatePublished - 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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