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.
Subject(s)
Aquaporin 3/biosynthesis , Cyclic AMP/metabolism , Cystic Fibrosis Transmembrane Conductance Regulator/biosynthesis , Epithelial Cells/metabolism , Animals , Aquaporin 3/metabolism , CHO Cells , Cell Line , Cricetinae , Cricetulus , Cystic Fibrosis Transmembrane Conductance Regulator/metabolism , Gene Expression Regulation , Holography , Humans , Microscopy , Mutation , Water/metabolismABSTRACT
Objective To study the effect of controlled ovarian Hyperstimulation(COH)on expression of AQP3 mRNA in mouse oocytes at metaphase Ⅱ. Methods Twenty female mice(6-7 weeks) were randomly allocated into 2 groups, mice in COH group were superovulated by intraperitoneal injection of 7.5 IU pregnant mare's serum gonadotropin(PMSG) followed by 5 IU human chorionic gonadotropin(HCG) after 46-48?h. Nothing was given to mice in control group and the estrus cycle was observed at 9?am everyday. 12-16?h following hCG injection (COH group) or at 8?am next day after the estrus (control group), mice were killed by cervical dislocation. The oviducts were excised.Cumulus masses were recovered from the dilated ampullae under a dissecting microscope,digested granulosa cells using hyaluronidase. Semi-quantitative real-time PCR of AQP3 mRNA in mouse MⅡoocytes was investigated with ?-actin as the internal control. Results Oocytes swelling assay showed that AQP3 mRNA expressed in mouse MⅡ oocytes. Using semi-quantitative real-time PCR, the expression of AQP3 mRNA was significantly decreased(P
