title: The human CFTR protein expressed in CHO cells activates aquaporin-3 in a cAMP-dependent pathway: study by digital holographic microscopy.
abstract: The transmembrane water movements during cellular processes and their relationship to ionic channel activity remain largely unknown. As an example, in epithelial cells it was proposed that the movement of water could be directly linked to cystic fibrosis transmembrane conductance regulator (CFTR) protein activity through a cAMP-stimulated aqueous pore, or be dependent on aquaporin. Here, we used digital holographic microscopy (DHM) an interferometric technique to quantify in situ the transmembrane water fluxes during the activity of the epithelial chloride channel, CFTR, measured by patch-clamp and iodide efflux techniques. We showed that the water transport measured by DHM is fully inhibited by the selective CFTR blocker CFTRinh172 and is absent in cells lacking CFTR. Of note, in cells expressing the mutated version of CFTR (F508del-CFTR), which mimics the most common genetic alteration encountered in cystic fibrosis, we also show that the water movement is profoundly altered but restored by pharmacological manipulation of F508del-CFTR-defective trafficking. Importantly, whereas activation of this endogenous water channel required a cAMP-dependent stimulation of CFTR, activation of CFTR or F508del-CFTR by two cAMP-independent CFTR activators, genistein and MPB91, failed to trigger water movements. Finally, using a specific small-interfering RNA against the endogenous aquaporin AQP3, the water transport accompanying CFTR activity decreased. We conclude that water fluxes accompanying CFTR activity are linked to AQP3 but not to a cAMP-stimulated aqueous pore in the CFTR protein.
authors: Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
authors: Pascal
authors: P
authors: Jourdain
authors: Frédéric
authors: F
authors: Becq
authors: Sylvain
authors: S
authors: Lengacher
authors: Clément
authors: C
authors: Boinot
authors: Pierre J
authors: PJ
authors: Magistretti
authors: Pierre
authors: P
authors: Marquet
mesh_terms: D000818:Animals; D051400:Aquaporin 3 / Q000096:biosynthesis* / Q000378:metabolism; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000096:biosynthesis* / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation; D006696:Holography; D006801:Humans; D008853:Microscopy; D009154:Mutation; D014867:Water / Q000378:metabolism
chemical_list: C496027:AQP3 protein, human; C505032:CFTR protein, human; D014867:Water; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D051400:Aquaporin 3; D000242:Cyclic AMP
keywords: Aquaporin AQP3; CFTR protein; Digital holographic microscopy; F508del-CFTR; Water transport; cAMP pathway