Uroplakins are a group of urothelial differentiation-related membrane proteins. They are components of the asymmetric unit membrane (AUM), which forms the apical plaques of mammalian urothelium and is believed to play a role in strengthening the urothelial apical surface thus preventing the cells from rupturing during bladder distention . Uroplakin-1a (UPK1A) belongs to the tetraspanin (TM4SF) family. UPK1A plays an important role in normal bladder epithelial physiology, possibly in regulating membrane permeability of superficial umbrella cells or in stabilizing the apical membrane.