Loss of primary cilia results in deregulated and unabated apical calcium entry in ARPKD collecting duct cells

Am J Physiol Renal Physiol. 2006 Jun;290(6):F1320-8. doi: 10.1152/ajprenal.00463.2005. Epub 2006 Jan 5.


Recent genetic analysis has identified a pivotal role of primary cilia in the pathogenesis of polycystic kidney disease (PKD). However, little is known regarding how cilia loss/dysfunction contributes to cyst development. In epithelial cells, changes in apical fluid flow induce cilia-mediated Ca2+ entry via polycystin-2 (PC2), a cation channel. The Oak Ridge Polycystic Kidney (orpk) mouse contains a mutated Tg737 gene that disrupts expression of polaris, a protein required for ciliogenesis. These studies examine the effect of cilia malformation on Ca2+ entry in orpk cilia(-) collecting duct principal cells, and in orpk cells in which wild-type Tg737 was reintroduced, orpk cilia(+). [Ca2+]i was monitored in confluent cell monolayers using fluorescence microscopy. Intrinsic apical Ca2+ entry was measured by Mn2+ quenching and Ca2+ depletion/readdition under flow conditions below the threshold for stimulation. We found that unstimulated apical Ca2+ entry was markedly increased in cilia(-) cells and was sensitive to Gd3+, an inhibitor of PC2. Electrophysiological measurements demonstrate increased abundance of an apical channel, consistent with PC2, in cilia(-) cells. Immunofluorescence studies revealed that PC2, normally expressed on and at the base of cilia in orpk cilia(+) cells, was observed throughout the apical membrane in cilia(-) cells. Furthermore, cilia(-) cells displayed elevated subapical Ca2+ levels measured with the near-membrane Ca2+ indicator FFP-18. We propose that cilia exert a tonic regulatory influence on apical Ca2+ entry, and absence of cilia results in loss of spatial organization of PC2, causing unregulated Ca2+ entry and elevations in subapical [Ca2+], a factor which may contribute to cyst formation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Cell Membrane Permeability
  • Cells, Cultured
  • Cilia / pathology*
  • Cilia / physiology
  • Fluorescent Antibody Technique
  • Fluorescent Dyes
  • Fura-2 / analogs & derivatives
  • Gadolinium / pharmacology
  • Kidney Tubules, Collecting / metabolism
  • Kidney Tubules, Collecting / ultrastructure*
  • Manganese / metabolism
  • Mice
  • Polycystic Kidney, Autosomal Dominant / genetics
  • Polycystic Kidney, Autosomal Dominant / pathology*
  • TRPP Cation Channels / antagonists & inhibitors
  • TRPP Cation Channels / metabolism
  • Tumor Suppressor Proteins / genetics


  • Fluorescent Dyes
  • TRPP Cation Channels
  • Tg737Rpw protein, mouse
  • Tumor Suppressor Proteins
  • fura-FFP18
  • polycystic kidney disease 2 protein
  • Manganese
  • Gadolinium
  • Calcium
  • Fura-2