To discuss recent reports on the function and importance of the renal primary cilium, a widely distributed organelle.
Most epithelial cells, including those in the kidney, express a solitary primary cilium. The primary cilium functions as a flow sensor in cultured renal epithelial cells (MDCK and mouse collecting tubule) mediating a large increase in intracellular calcium concentration. Flow sensing is shown to reside in the cilium itself and to involve the proteins polycystin 1 and 2, defects in which are associated with the majority of cases of human polycystic kidney disease. The role of the cilium in flow-dependent potassium secretion by the collecting tubule and in sensing of chemical components of the luminal fluid are also described.
The primary cilium is mechanically sensitive and serves as a flow sensor in cultured renal epithelia. Bending the cilium by mechanical means or flow causes a large, prolonged transient increase in intracellular calcium. The mechanically sensitive protein in the cilium is a polycystin.
aCenter for Salt and Water Research, University of Aarhus, Aarhus, Denmark and bLaboratory of Kidney and Electrolyte Metabolism, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
Correspondence to Dr. Helle A. Praetorius, Center for Water and Salt Research, Institute for Experimental Clinical Research, University of Aarhus, Brendstrupgaardsvej 1, DK-8200 Aarhus C, Denmark Tel: +45 895 230 46; e-mail: firstname.lastname@example.org