Molecular characterization of an aquaporin cDNA from brain: Candidate osmoreceptor and regulator of water balance

Jin Sup Jung, Ratan V. Bhat, Gregory M. Preston, William B. Guggino, Jay M. Baraban, Peter Agre

Research output: Contribution to journalArticlepeer-review


The aquaporins transport water through membranes of numerous tissues, but the molecular mechanisms for sensing changes in extracellular osmolality and regulating water balance in brain are unknown. We have isolated a brain aquaporin by homology cloning. Like aquaporin 1 (AQP1, also known as CHIP, channel-forming integral membrane protein of 28 kDa), the deduced polypeptide has six putative transmembrane domains but lacks cysteines at the known mercury-sensitive sites. Two initiation sites were identified encoding polypeptides of 301 and 323 amino acids; expression of each in Xenopus oocytes conferred a 20-fold increase in osmotic water permeability not blocked by 1 mM HgCl2, even after substitution of cysteine at the predicted mercury-sensitive site. Northern analysis and RNase protection demonstrated the mRNA to be abundant in mature rat brain but only weakly detectable in eye, kidney, intestine, and lung. In situ hybridization of brain localized the mRNA to ependymal cells lining the aqueduct, glial cells forming the edge of the cerebral cortex and brainstem, vasopressin-secretory neurons in supraoptic and paraventricular nuclei of hypothalamus, and Purkinje cells of cerebellum. Its distinctive expression pattern implicates this fourth mammalian member of the aquaporin water channel family (designated gene symbol, AQP4) as the osmoreceptor which regulates body water balance and mediates water flow within the central nervous system.

Original languageEnglish (US)
Pages (from-to)13052-13056
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number26
StatePublished - Dec 20 1994


  • Purkinje cells
  • cerebrospinal fluid
  • ependymal cells
  • vasopressin-secretory neurons
  • water channel

ASJC Scopus subject areas

  • General


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