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      Kv3.3 channels harbouring a mutation of spinocerebellar ataxia type 13 alter excitability and induce cell death in cultured cerebellar Purkinje cells.

      1 , , ,
      The Journal of physiology
      Wiley

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          Abstract

          The cerebellum plays crucial roles in controlling sensorimotor functions. The neural output from the cerebellar cortex is transmitted solely by Purkinje cells (PCs), whose impairment causes cerebellar ataxia. Spinocerebellar ataxia type 13 (SCA13) is an autosomal dominant disease, and SCA13 patients exhibit cerebellar atrophy and cerebellar symptoms. Recent studies have shown that missense mutations in the voltage-gated K(+) channel Kv3.3 are responsible for SCA13. In the rodent brain, Kv3.3 mRNAs are expressed most strongly in PCs, suggesting that the mutations severely affect PCs in SCA13 patients. Nevertheless, how these mutations affect the function of Kv3.3 in PCs and, consequently, the morphology and neuronal excitability of PCs remains unclear. To address these questions, we used lentiviral vectors to express mutant mouse Kv3.3 (mKv3.3) channels harbouring an R424H missense mutation, which corresponds to the R423H mutation in the Kv3.3 channels of SCA13 patients, in mouse cerebellar cultures. The R424H mutant-expressing PCs showed decreased outward current density, broadened action potentials and elevated basal [Ca(2+)]i compared with PCs expressing wild-type mKv3.3 subunits or those expressing green fluorescent protein alone. Moreover, expression of R424H mutant subunits induced impaired dendrite development and cell death selectively in PCs, both of which were rescued by blocking P/Q-type Ca(2+) channels in the culture conditions. We therefore concluded that expression of R424H mutant subunits in PCs markedly affects the function of endogenous Kv3 channels, neuronal excitability and, eventually, basal [Ca(2+)]i, leading to cell death. These results suggest that PCs in SCA13 patients also exhibit similar defects in PC excitability and induced cell death, which may explain the pathology of SCA13.

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          Author and article information

          Journal
          J Physiol
          The Journal of physiology
          Wiley
          1469-7793
          0022-3751
          Jan 01 2014
          : 592
          : 1
          Affiliations
          [1 ] T. Irie: Division of Pharmacology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan. irie@nihs.go.jp or H. Hirai: Department of Neurophysiology, Gunma University Graduate School of Medicine, 3-39-22 Shouwa-machi, Maebashi-shi, Gunma 371-8511, Japan. Email: hirai@gunma-u.ac.jp.
          Article
          jphysiol.2013.264309
          10.1113/jphysiol.2013.264309
          3903362
          24218544
          b3b24800-82bf-48d0-8fba-0267e4d1ddb4
          History

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