Two Distinct Signals Determine the Basolateral Targeting of AQP4 in the Renal Epithelial Cell Line MDCK

Abstract

To fulfill their physiological role in water handling by the kidney, aquaporins are differentially targeted to the apical and the basolateral membranes of epithelial kidney cells. For example, whereas AQP1 exhibits an un-polarized distribution in the proximal tubule cells (Sabolic et al., 1992,Nielsen et al., 1993), AQP2 is specifically targeted to the apical membranes of the principal cells in the collecting duct (Fushimi et al., 1993,Nielsen et al., 1993). On the other hand, AQP3 and AQP4 are exclusively localized in the basolateral membranes of these cells (Ecelbarger et al., 1995,Frigeri et al., 1995). Although a great deal of information about the cellular distribution of aquaporins in the body has emerged from previous studies, the mechanisms underlying their targeting in polarized epithelial cells remain poorly understood.