Characterization of Single Channel Currents from Primary Cilia of Renal Epithelial Cells

MALAY K. RAYCHOWDHURY,MARGARET MCLAUGHLIN, ARNOLT J. RAMOS, NICOLAS MONTALBETTI, RICHARD BOULEY,DENNIS A. AUSIELLO, AND HORACIO F. CANTIELLO

JOURNAL OF BIOLOGICAL CHEMISTRY

Año: 2005 vol. 280 p. 34718 - 34722

0021-9258

The primary cilium is a ubiquitous, non-motile microtubular organelle lacking the central pair of microtubules found in motile cilia. Primary cilia are surrounded by a membrane, which has a unique complement of membrane proteins, and may thus be functionally different from the plasma membrane. The function of the primary cilium remains largely unknown. However, primary cilia have important sensory transducer properties, including the response of renal epithelial cells to fluid flow or mechanical stimulation. Recently, renal cystic diseases have been associated with dysfunctional ciliary proteins. Although the sensory properties of renal epithelial primary cilia may be associated with functional channel activity in the organelle, information in this regard is still lacking. This may be related to the inherent difficulties in assessing electrical activity in this rather small and narrow organelle. In the present study, we provide the first direct electrophysiological evidence for the presence of single channel currents from isolated primary cilia of LLC-PK1 renal epithelial cells. Several channel phenotypes wereobserved, and addition of vasopressin increased cation channel activity, which suggests the regulation, by the cAMP pathway of ciliary conductance. Ion channel reconstitution of ciliary versus plasma membranes indicated a much higher channel density in cilia. At least three channel proteins, polycystin-2, TRPC1, and  interestingly, the -epithelial sodium channel, were immunodetected in this organelle. Ion channel activity in the primary cilium of renal cells may be an important component of its role as a sensory transducer.versus plasma membranes indicated a much higher channel density in cilia. At least three channel proteins, polycystin-2, TRPC1, and  interestingly, the -epithelial sodium channel, were immunodetected in this organelle. Ion channel activity in the primary cilium of renal cells may be an important component of its role as a sensory transducer.