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Am J Physiol Heart Circ Physiol 284: H71-H80, 2003. First published August 29, 2002; doi:10.1152/ajpheart.00392.2002
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Vol. 284, Issue 1, H71-H80, January 2003

Regulation of N- and C-type inactivation of Kv1.4 by pHo and K+: evidence for transmembrane communication

Xiaoyan Li1,2, Glenna C. L. Bett1, Xuejun Jiang1, Vladimir E. Bondarenko1, Michael J. Morales1, and Randall L. Rasmusson1

1 Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York 14214-3005; and 2 Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei, China 430060

Kv1.4 encodes a slowly recovering transient outward current (Ito), which inactivates by a fast N-type (intracellular ball and chain) mechanism but has slow recovery due to C-type inactivation. C-type inactivation of the NH2-terminal deletion mutant (fKv1.4Delta N) was inhibited by 98 mM extracellular K+ concentration ([K+]o), whereas N-type was unaffected. In 98 mM [K+]o, removal of intracellular K+ concentration ([K+]i) speeded C-type inactivation but had no effect on N-type inactivation, suggesting that C-type inactivation is sensitive to K+ binding to intracellular sites. C-type inactivation is thought to involve closure of the extracellular pore mouth. However, a valine to alanine mutation on the intracellular side of S6 (V561A) of fKv1.4Delta N alters recovery and results in anomalous speeding of C-type inactivation with increasing [K+]o. Extracellular pH (pHo) modulated both N- and C-type inactivation through an S5-H5 linker histidine (H508) with acidosis speeding both N- and C-type inactivation. Mutation of an extracellular lysine to a tyrosine (K532Y) slowed C-type inactivation and inhibited the pH dependence of both N- and C-type inactivation. These results suggest that mutations, [K+], and pH modulate inactivation through membrane-spanning mechanisms involving S6.

voltage-gated channel; ion; Kv1.1; ataxia


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