title: AQP2 is necessary for vasopressin- and forskolin-mediated filamentous actin depolymerization in renal epithelial cells.
abstract: Remodeling of the actin cytoskeleton is required for vasopressin (VP)-induced aquaporin 2 (AQP2) trafficking. Here, we asked whether VP and forskolin (FK)-mediated F-actin depolymerization depends on AQP2 expression. Using various MDCK and LLC-PK1 cell lines with different AQP2 expression levels, we performed F-actin quantification and immunofluorescence staining after VP/FK treatment. In MDCK cells, in which AQP2 is delivered apically, VP/FK mediated F-actin depolymerization was significantly correlated with AQP2 expression levels. A decrease of apical membrane associated F-actin was observed upon VP/FK treatment in AQP2 transfected, but not in untransfected cells. There was no change in basolateral actin staining under these conditions. In LLC-PK(1) cells, which deliver AQP2 basolaterally, a significant VP/FK mediated decrease in F-actin was also detected only in AQP2 transfected cells. This depolymerization response to VP/FK was significantly reduced by siRNA knockdown of AQP2. By immunofluorescence, an inverse relationship between plasma membrane AQP2 and membrane-associated F-actin was observed after VP/FK treatment again only in AQP2 transfected cells. This is the first report showing that VP/FK mediated F-actin depolymerization is dependent on AQP2 protein expression in renal epithelial cells, and that this is not dependent on the polarity of AQP2 membrane insertion.
authors.affiliation: Massachusetts General Hospital Center for Systems Biology, Program in Membrane Biology and Nephrology Division, Massachusetts General Hospital and Harvard Medical School ,  Boston, Massachusetts ,  USA.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Yui
authors.forename: Hua Jenny
authors.initials: HJ
authors.lastname: Lu
authors.forename: Richard
authors.initials: R
authors.lastname: Bouley
authors.forename: Dennis
authors.initials: D
authors.lastname: Brown