Zonisamide can ameliorate the voltage-dependence alteration of the T-type calcium channel CaV3.1 caused by a mutation responsible for spinocerebellar ataxia

• Published in: Molecular brain Vol. 13; no. 1; pp. 1 - 163
• Main Authors: Hara, Naoyuki, Morino, Hiroyuki, Matsuda, Yukiko, Satoh, Kenichi, Hashimoto, Kouichi, Maruyama, Hirofumi, Kawakami, Hideshi
• Format: Journal Article
• Language: English
• Published: London BioMed Central Ltd 26.11.2020; BioMed Central; BMC
• Subjects: Ataxia; CACNA1G; Calcium; Calcium channels; Calcium channels (T-type); Calcium channels (voltage-gated); CaV3.1; Cerebellar ataxia; Cerebellum; Epilepsy; Experiments; Genetic aspects; Medical research; Medicine, Experimental; Movement disorders; Mutants; Mutation; Neurodegenerative diseases; Neurophysiology; Parkinson's disease; Potassium; Reagents; SCA42; Spinocerebellar ataxia; T-type calcium channel; Tremor; Zonisamide; United States > US; Japan; Germany
• ISSN: 1756-6606; 1756-6606
• DOI: 10.1186/s13041-020-00700-7

Abstract Spinocerebellar ataxia (SCA) 42 is caused by a mutation in CACNA1G , which encodes the low voltage-gated calcium channel Ca V 3.1 (T-type). Patients with SCA42 exhibit a pure form of cerebellar ataxia. We encountered a patient with the p.Arg1715His mutation, suffering from intractable resting tremor, particularly head tremor. This symptom improved with the administration of low-dose of zonisamide (ZNS), a T-type calcium channel blocker effective for treating Parkinson’s disease and epilepsy. Previous electrophysiological studies showed that the voltage dependence of this mutant Ca V 3.1 was shifted toward the positive potential. This abnormal shift was considered a factor related to disease onset and symptoms. In this study, we performed whole-cell recordings of GFP-expressing HEK293T cells that expressed wild-type or mutant Ca V 3.1 and investigated the changes in the abnormal shift of voltage dependence of the mutant Ca V 3.1. The results showed that ZNS in an amount equivalent to the patient’s internal dose significantly ameliorated the abnormal shift in the mutant Ca V 3.1, giving values close to those in the wild-type. On the other hand, ZNS did not affect the voltage dependence of wild-type Ca V 3.1. Because Ca V 3.1 is known to be involved in tremogenesis, modulation of the voltage dependence of mutant Ca V 3.1 by ZNS might have contributed to improvement in the intractable tremor of our patient with SCA42. Moreover, efonidipine, another T-type calcium channel blocker, had no effect on tremors in our patient with SCA42 and did not improve the abnormal shift in the voltage dependence of the mutant Ca V 3.1. This indicates that ZNS is distinct from other T-type calcium channel blockers in terms of modulation of the voltage dependence of the mutant Ca V 3.1.