title: Two-pore channels provide insight into the evolution of voltage-gated Ca2+ and Na+ channels.
abstract: Four-domain voltage-gated Ca(2+) and Na(+) channels (CaV, NaV) underpin nervous system function and likely emerged upon intragenic duplication of a primordial two-domain precursor. To investigate if two-pore channels (TPCs) may represent an intermediate in this evolutionary transition, we performed molecular docking simulations with a homology model of TPC1, which suggested that the pore region could bind antagonists of CaV or NaV. CaV or NaV antagonists blocked NAADP (nicotinic acid adenine dinucleotide phosphate)-evoked Ca(2+) signals in sea urchin egg preparations and in intact cells that overexpressed TPC1. By sequence analysis and inspection of the model, we predicted a noncanonical selectivity filter in animal TPCs in which the carbonyl groups of conserved asparagine residues are positioned to coordinate cations. In contrast, a distinct clade of TPCs [TPCR (for TPC-related)] in several unicellular species had ion selectivity filters with acidic residues more akin to CaV. TPCRs were predicted to interact strongly with CaV antagonists. Our data suggest that acquisition of a "blueprint" pharmacological profile and changes in ion selectivity within four-domain voltage-gated ion channels may have predated intragenic duplication of an ancient two-domain ancestor.
authors.affiliation: Department of Pharmacology, Cambridge University, Cambridge CB2 1PD, UK. mtur2@cam.ac.uk patel.s@ucl.ac.uk.
authors.forename: Taufiq
authors.initials: T
authors.lastname: Rahman
authors.affiliation: Department of Cell Developmental Biology, University College London, London WC1E 6BT, UK.
authors.forename: Xinjiang
authors.initials: X
authors.lastname: Cai
authors.affiliation: Department of Pharmaceutical Sciences, Thomas Jefferson University School of Pharmacy, Philadelphia, PA 19107, USA.
authors.forename: G Cristina
authors.initials: GC
authors.lastname: Brailoiu
authors.affiliation: Department of Anatomy and Cell Biology and Center for Substance Abuse Research, Temple University, Philadelphia, PA 19140, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Abood
authors.affiliation: Department of Pharmacology and Center for Substance Abuse Research, Temple University, Philadelphia, PA 19140, USA.
authors.forename: Eugen
authors.initials: E
authors.lastname: Brailoiu
authors.affiliation: Department of Cell Developmental Biology, University College London, London WC1E 6BT, UK. mtur2@cam.ac.uk patel.s@ucl.ac.uk.
authors.forename: Sandip
authors.initials: S
authors.lastname: Patel
mesh_terms: D000818:Animals; D001216:Asparagine / Q000378:metabolism; D001483:Base Sequence; D015220:Calcium Channels / Q000235:genetics*; D020864:Calcium Channels, N-Type / Q000235:genetics*; D002412:Cations / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication / Q000235:genetics*; D016013:Likelihood Functions; D008957:Models, Genetic; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D009249:NADP / Q000031:analogs & derivatives / Q000378:metabolism; D010802:Phylogeny; D012617:Sea Urchins; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D061566:Voltage-Gated Sodium Channels / Q000235:genetics*; D000097903:Two-Pore Channels
chemical_list: D001216:Asparagine; D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D002412:Cations; D009249:NADP; D061566:Voltage-Gated Sodium Channels; C407357:TPCN1 protein, human; D000097903:Two-Pore Channels; C024376:NAADP