title: A Single Amino Acid Deletion (ΔF1502) in the S6 Segment of CaV2.1 Domain III Associated with Congenital Ataxia Increases Channel Activity and Promotes Ca2+ Influx.
abstract: Mutations in the CACNA1A gene, encoding the pore-forming CaV2.1 (P/Q-type) channel α1A subunit, result in heterogeneous human neurological disorders, including familial and sporadic hemiplegic migraine along with episodic and progressive forms of ataxia. Hemiplegic Migraine (HM) mutations induce gain-of-channel function, mainly by shifting channel activation to lower voltages, whereas ataxia mutations mostly produce loss-of-channel function. However, some HM-linked gain-of-function mutations are also associated to congenital ataxia and/or cerebellar atrophy, including the deletion of a highly conserved phenylalanine located at the S6 pore region of α1A domain III (ΔF1502). Functional studies of ΔF1502 CaV2.1 channels, expressed in Xenopus oocytes, using the non-physiological Ba2+ as the charge carrier have only revealed discrete alterations in channel function of unclear pathophysiological relevance. Here, we report a second case of congenital ataxia linked to the ΔF1502 α1A mutation, detected by whole-exome sequencing, and analyze its functional consequences on CaV2.1 human channels heterologously expressed in mammalian tsA-201 HEK cells, using the physiological permeant ion Ca2+. ΔF1502 strongly decreases the voltage threshold for channel activation (by ~ 21 mV), allowing significantly higher Ca2+ current densities in a range of depolarized voltages with physiological relevance in neurons, even though maximal Ca2+ current density through ΔF1502 CaV2.1 channels is 60% lower than through wild-type channels. ΔF1502 accelerates activation kinetics and slows deactivation kinetics of CaV2.1 within a wide range of voltage depolarization. ΔF1502 also slowed CaV2.1 inactivation kinetic and shifted the inactivation curve to hyperpolarized potentials (by ~ 28 mV). ΔF1502 effects on CaV2.1 activation and deactivation properties seem to be of high physiological relevance. Thus, ΔF1502 strongly promotes Ca2+ influx in response to either single or trains of action potential-like waveforms of different durations. Our observations support a causative role of gain-of-function CaV2.1 mutations in congenital ataxia, a neurodevelopmental disorder at the severe-most end of CACNA1A-associated phenotypic spectrum.
authors.affiliation: Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Bahamonde
authors.affiliation: Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Selma Angèlica
authors.initials: SA
authors.lastname: Serra
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Oliver
authors.initials: O
authors.lastname: Drechsel
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Rubayte
authors.initials: R
authors.lastname: Rahman
authors.affiliation: Pediatric Neurology Research Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Marcé-Grau
authors.affiliation: Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Prieto
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: Stephan
authors.initials: S
authors.lastname: Ossowski
authors.affiliation: Pediatric Neurology Research Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Alfons
authors.initials: A
authors.lastname: Macaya
authors.affiliation: Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Fernández-Fernández
mesh_terms: D001259:Ataxia / Q000151:congenital / Q000235:genetics* / Q000473:pathology; D001921:Brain / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000235:genetics*; D002648:Child; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D059906:Neuroimaging; D017384:Sequence Deletion / Q000235:genetics* / Q000502:physiology
chemical_list: D002118:Calcium; D020864:Calcium Channels, N-Type