Person:

Bouley, Richard

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‐PK1 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.

Uncontrolled inflammation is one of the leading causes of kidney failure. Pro-inflammatory responses can occur in the absence of infection, a process called sterile inflammation. Here we show that the purinergic receptor P2Y14 (GPR105) is specifically and highly expressed in collecting duct intercalated cells (ICs) and mediates sterile inflammation in the kidney. P2Y14 is activated by UDP-glucose, a damage-associated molecular pattern molecule (DAMP) released by injured cells. We found that UDP-glucose increases pro-inflammatory chemokine expression in ICs as well as MDCK-C11 cells, and UDP-glucose activates the MEK1/2-ERK1/2 pathway in MDCK-C11 cells. These effects were prevented following inhibition of P2Y14 with the small molecule PPTN. Tail vein injection of mice with UDP-glucose induced the recruitment of neutrophils to the renal medulla. This study identifies ICs as novel sensors, mediators and effectors of inflammation in the kidney via P2Y14.