title: Calcium-induced conformational changes in C-terminal tail of polycystin-2 are necessary for channel gating.
abstract: Polycystin-2 (PC2) is a Ca(2+)-permeable transient receptor potential channel activated and regulated by changes in cytoplasmic Ca(2+). PC2 mutations are responsible for ∼15% of autosomal dominant polycystic kidney disease. Although the C-terminal cytoplasmic tail of PC2 has been shown to contain a Ca(2+)-binding EF-hand domain, the molecular basis of PC2 channel gating by Ca(2+) remains unknown. We propose that the PC2 EF-hand is a Ca(2+) sensor required for channel gating. Consistent with this, Ca(2+) binding causes a dramatic decrease in the radius of gyration (R(g)) of the PC2 EF-hand by small angle x-ray scattering and significant conformational changes by NMR. Furthermore, increasing Ca(2+) concentrations cause the C-terminal cytoplasmic tail to transition from a mixture of extended oligomers to a single compact dimer by analytical ultracentrifugation, coupled with a >30 Å decrease in maximum interatomic distance (D(max)) by small angle x-ray scattering. Mutant PC2 channels unable to bind Ca(2+) via the EF-hand are inactive in single-channel planar lipid bilayers and inhibit Ca(2+) release from ER stores upon overexpression in cells, suggesting dominant negative properties. Our results support a model where PC2 channels are gated by discrete conformational changes in the C-terminal cytoplasmic tail in response to changes in cytoplasmic Ca(2+) levels. These properties of PC2 are lost in autosomal dominant polycystic kidney disease, emphasizing the importance of PC2 to kidney cell function. We speculate that PC2 and the Ca(2+)-dependent transient receptor potential channels in general are regulated by similar conformational changes in their cytoplasmic domains that are propagated to the channel pore.
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Andjelka S
authors.initials: AS
authors.lastname: Ćelić
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Edward T
authors.initials: ET
authors.lastname: Petri
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Benbow
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Hodsdon
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520; Departments of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Ehrlich
authors.affiliation: Departments of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520. Electronic address: titus.boggon@yale.edu.
authors.forename: Titus J
authors.initials: TJ
authors.lastname: Boggon
mesh_terms: D002118:Calcium / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D018360:Crystallography, X-Ray; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008954:Models, Biological; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D050396:TRPP Cation Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D002118:Calcium; D050396:TRPP Cation Channels