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1 Department of Pediatrics, Yamagata University School of Medicine, Yamagata, Japan
2 Section of Developmental Neurophysiology, Okazaki Institute for Integrative Bioscience, Okazaki, Aichi, Japan; School of Life Science, Graduate University for Advanced Studies, Okazaki, Aichi, Japan
3 Section of Developmental Neurophysiology, Okazaki Institute for Integrative Bioscience, Okazaki, Aichi, Japan
4 Howard Hughes Medical Institute and Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States
5 Section of Developmental Neurophysiology, Okazaki Institute for Integrative Bioscience, Okazaki, Japan; National Institute for Physiological Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan; School of Life Science, Graduate University for Advanced Studies, Okazaki, Aichi, Japan; Neuroscience Research Institute, AIST, Tsukuba, Ibaraki, Japan
6 Pediatrics, Yamagata University School of Medicine, Yamagata, Yamagata, Japan
* To whom correspondence should be addressed. E-mail: yokamura{at}nips.ac.jp.
Ankyrin-G, a modular protein, plays a critical role in clustering voltage-gated sodium channels (Nav channels) in nodes of Ranvier and initial segments of mammalian neurons. However, direct effects of ankyrin-G on electrophysiological properties of Nav channels remain elusive. In this study, we explored whether ankyrin-G has a role in modifying gating properties of the neuronal Nav1.6 channel that is predominantly localized at nodes of Ranvier and initial segments. TsA201 cells transfected with the human Nav1.6 cDNA alone exhibited significant persistent sodium current (Ina-p). On the other hand, Ina-p was barely detected upon co-expression with ankyrin-G. Ankyrin-B, another ankyrin, did not show such an effect. Expression of chimeras between the two isoforms of ankyrin suggests that the membrane-binding domain of ankyrin-G is critical for reducing the Ina-p of Nav1.6. These results suggest that ankyrin-G regulates neuronal excitability not only through clustering Nav channels but also by directly modifying their channel gating.
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