Glycogen synthase kinase-3β promotes cyst expansion in polycystic kidney disease

Polycystic kidney diseases (PKDs) are inherited disorders characterized by the formation of fluid filled renal cysts. Elevated cAMP levels in PKDs stimulate progressive cyst enlargement involving cell proliferation and transepithelial fluid secretion often leading to end-stage renal disease. The glycogen synthase kinase-3 (GSK3) family of protein kinases consists of GSK3 alpha and GSK3 beta isoforms and has a crucial role in multiple cellular signaling pathways. We previously found that GSK3 beta, a regulator of cell proliferation, is also crucial for cAMP generation and vasopressin-mediated urine concentration by the kidneys. However, the role of GSK3 beta in the pathogenesis of PKDs is not known. Here we found that GSK3 beta expression and activity were markedly upregulated and associated with cyst-lining epithelia in the kidneys of mice and humans with PKD. Renal collecting duct-specific gene knockout of GSK3 beta or pharmacological inhibition of GSK3 effectively slowed down the progression of PKD in mouse models of autosomal recessive or autosomal dominant PKD. GSK3 inactivation inhibited cAMP generation and cell proliferation resulting in reduced cyst expansion, improved renal function, and extended life span. GSK3 beta inhibition also reduced pERK, c-Myc, and cyclin-D1, known mitogens in proliferation of cystic epithelial cells. Thus, GSK3 beta has a novel functional role in PKD pathophysiology, and its inhibition may be therapeutically useful to slow down cyst expansion and progression of PKD.