title: Polycystin-1 and polycystin-2 are both required to amplify inositol-trisphosphate-induced Ca2+ release.
abstract: Autosomal dominant polycystic kidney disease is caused by loss-of-function mutations in the PKD1 or PKD2 genes encoding respectively polycystin-1 and polycystin-2. Polycystin-2 stimulates the inositol trisphosphate (IP(3)) receptor (IP(3)R), a Ca(2+)-release channel in the endoplasmic reticulum (ER). The effect of ER-located polycystin-1 is less clear. Polycystin-1 has been reported both to stimulate and to inhibit the IP(3)R. We now studied the effect of polycystin-1 and of polycystin-2 on the IP(3)R activity under conditions where the cytosolic Ca(2+) concentration was kept constant and the reuptake of released Ca(2+) was prevented. We also studied the interdependence of the interaction of polycystin-1 and polycystin-2 with the IP(3)R. The experiments were done in conditionally immortalized human proximal-tubule epithelial cells in which one or both polycystins were knocked down using lentiviral vectors containing miRNA-based short hairpins. The Ca(2+) release was induced in plasma membrane-permeabilized cells by various IP(3) concentrations at a fixed Ca(2+) concentration under unidirectional (45)Ca(2+)-efflux conditions. We now report that knock down of polycystin-1 or of polycystin-2 inhibited the IP(3)-induced Ca(2+) release. The simultaneous presence of the two polycystins was required to fully amplify the IP(3)-induced Ca(2+) release, since the presence of polycystin-1 alone or of polycystin-2 alone did not result in an increased Ca(2+) release. These novel findings indicate that ER-located polycystin-1 and polycystin-2 operate as a functional complex. They are compatible with the view that loss-of-function mutations in PKD1 and in PKD2 both cause autosomal dominant polycystic kidney disease.
authors.affiliation: Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven Campus Gasthuisberg O&N I, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Mekahli
authors.forename: E
authors.initials: E
authors.lastname: Sammels
authors.forename: T
authors.initials: T
authors.lastname: Luyten
authors.forename: K
authors.initials: K
authors.lastname: Welkenhuyzen
authors.forename: L P
authors.initials: LP
authors.lastname: van den Heuvel
authors.forename: E N
authors.initials: EN
authors.lastname: Levtchenko
authors.forename: R
authors.initials: R
authors.lastname: Gijsbers
authors.forename: G
authors.initials: G
authors.lastname: Bultynck
authors.forename: J B
authors.initials: JB
authors.lastname: Parys
authors.forename: H
authors.initials: H
authors.lastname: De Smedt
authors.forename: L
authors.initials: L
authors.lastname: Missiaen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability; D003600:Cytosol / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D061252:Feeder Cells; D055785:Gene Knockdown Techniques; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D035683:MicroRNAs / Q000235:genetics; D041681:NIH 3T3 Cells; D016891:Polycystic Kidney, Autosomal Dominant / Q000378:metabolism / Q000473:pathology; D061251:Primary Cell Culture; D025941:Protein Interaction Mapping; D050396:TRPP Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D002118:Calcium; D015544:Inositol 1,4,5-Trisphosphate; D053496:Inositol 1,4,5-Trisphosphate Receptors; D035683:MicroRNAs; D050396:TRPP Cation Channels