title: Two heterozygous Cav3.2 channel mutations in a pediatric chronic pain patient: recording condition-dependent biophysical effects.
abstract: We report expression system-dependent effects of heterozygous mutations (P769L and A1059S) in the Cav3.2 CACNA1H gene identified in a pediatric patient with chronic pain and absence seizures. The mutations were introduced individually into recombinant channels and then analyzed by means of electrophysiology. When both mutants were co-expressed in tsA-201 cells, we observed a loss of channel function, with significantly smaller current densities across a wide range of voltages (-40 to +20 mV). In addition, when both mutant channels were co-expressed, the channels opened at a more depolarizing potential with a ~5-mV right shift in the half-activation potential, with no changes in half-inactivation potential and the rate of recovery from inactivation. Interestingly, when both mutants were co-expressed in the neuronal-derived CAD cells in a different extracellular milieu, the effect was remarkably different. Although not statistically significant (p < 0.07), current densities appeared augmented compared to wild-type channels and the difference in the half-activation potential was lost. This could be attributed to the replacement of extracellular sodium and potassium with tetraethylammonium chloride. Our results show that experimental conditions can be a confounding factor in the biophysical effects of T-type calcium channel mutations found in certain neurological disorders.
authors.affiliation: Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada.
authors.forename: Ivana A
authors.initials: IA
authors.lastname: Souza
authors.affiliation: Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Gandini
authors.affiliation: Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada.
authors.forename: Miranda M
authors.initials: MM
authors.lastname: Wan
authors.affiliation: Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada. zamponi@ucalgary.ca.
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000200:Action Potentials; D000293:Adolescent; D020747:Calcium Channels, T-Type / Q000235:genetics* / Q000378:metabolism; D059350:Chronic Pain / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D004832:Epilepsy, Absence / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D020125:Mutation, Missense
chemical_list: C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type
keywords: Calcium channel; Epilepsy; HEK cells; Mutation; Pain; T-type