title: A multifunctional aqueous channel formed by CFTR.
abstract: The cystic fibrosis gene product (CFTR) is a complex protein that functions as an adenosine 3,5-monophosphate (cAMP)-stimulated ion channel and possibly as a regulator of intracellular processes. In order to determine whether the CFTR molecule contains a functional aqueous pathway, anion, water, and urea transport were measured in Xenopus oocytes expressing CFTR. Cyclic AMP agonists induced a Cl- conductance of 94 microsiemens and an increase in water permeability of 4 x 10(-4) centimeter per second that was inhibited by a Cl- channel blocker and was dependent on anion composition. CFTR has a calculated single channel water conductance of 9 x 10(-13) cubic centimeter per second, suggesting a pore-like aqueous pathway. Oocytes expressing CFTR also showed cAMP-stimulated transport of urea but not the larger solute sucrose. Thus CFTR contains a cAMP-stimulated aqueous pore that can transport anions, water, and small solutes. The results also provide functional evidence for water movement through an ion channel.
mesh_terms: D000818:Animals; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes; D014508:Urea / Q000378:metabolism; D014867:Water / Q000378:metabolism; D014981:Xenopus
chemical_list: C505032:CFTR protein, human; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D014867:Water; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D014508:Urea; D000242:Cyclic AMP