Nonspecific Cation Current Associated with Native Polycystin-2 in HEK-293 Cells

Mutations in either PKD1 or PKD2 gene are associated with autosomal dominant polycystic kidney disease, the most common inherited kidney disorder. Polycystin-2 (PC2), the PKD2 gene product, and the related protein polycystin-L, function as Ca(2+)-permeable, nonselective cation channels in different expression systems. This work describes a nonspecific cation current (I(CC)) that is present in native HEK-293 cells and highly associated with a PC2-channel activity. The current is voltage dependent, activating for potentials that are positive to -50 mV and inactivating in a few milliseconds. It is sensitive to Cd(2+), Gd(3+), La(3+), SKF96365, and amiloride. After silencing of PC2 by RNA interfering, cells show a reduced current that is restored by transfection with normal but not truncated PC2. Consistently, I(CC) is abolished by perfusion with an anti-PC2 antibody. Furthermore, heterologous expression of the PC1 cytoplasmic tail significantly increases I(CC) peak amplitude compared with native cells. This is the first characterization of such a current in HEK-293 cells, a widely used expression system for ion channels. These cells, therefore, could be regarded as a suitable and readily accessible tool to study interactions between native PC2/PC1 complex and other membrane proteins, thus contributing to the understanding of autosomal dominant polycystic kidney disease pathogenesis.