NDLI: Constitutive inactivation of the hKv1.5 mutant channel, H463G, in K$^{+}$-free solutions at physiological pH

Content Provider	Springer Nature Link
Author	Zhang, Shetuan Eduljee, Cyrus Kwan, Daniel C. H. Kehl, Steven J. Fedida, David
Copyright Year	2005
Abstract	Extracellular acidification and reduction of extracellular K$^{+}$ are known to decrease the currents of some voltage-gated potassium channels. Although the macroscopic conductance of WT hKv1.5 channels is not very sensitive to [K$^{+}$]$_{o}$ at pH 7.4, it is very sensitive to [K$^{+}$]$_{o}$ at pH 6.4, and in the mutant, H463G, the removal of K$^{+}$ $_{o}$ virtually eliminates the current at pH 7.4. We investigated the mechanism of current regulation by K$^{+}$ $_{o}$ in the Kv1.5 H463G mutant channel at pH 7.4 and the wild-type channel at pH 6.4 by taking advantage of Na$^{+}$ permeation through inactivated channels. Although the H463G currents were abolished in zero [K$^{+}$]$_{o}$, robust Na$^{+}$ tail currents through inactivated channels were observed. The appearnnce of H463G Na$^{+}$ currents with a slow rising phase on repolarization after a very brief depolarization (2 ms) suggests that channels could activate directly from closed-inactivated states. In wild-type channels, when intracellular K$^{+}$ was replaced by NMG$^{+}$ and the inward Na$^{+}$ current was recorded, addition of 1 mM K$^{+}$ prevented inactivation, but changing pH from 7.4 to 6.4 reversed this action. The data support the idea that C-type inactivation mediated at R487 in Kv1.5 channels is influenced by H463 in the outer pore. We conclude that both acidification and reduction of [K$^{+}$]$_{o}$ inhibit Kv1.5 channels through a common mechananism (i.e., by increasing channel inactivation, which occurs in the resting state or develops very rapidly after activation).
Starting Page	221
Ending Page	230
Page Count	10
File Format	PDF
ISSN	10859195
Journal	Cell Biochemistry and Biophysics
Volume Number	43
Issue Number	2
e-ISSN	15590283
Language	English
Publisher	Humana Press
Publisher Date	2005-01-01
Publisher Place	Totowa
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Biochemistry Pharmacology/Toxicology Biotechnology Cell Biology
Content Type	Text
Resource Type	Article
Subject	Cell Biology Medicine Biochemistry Biophysics

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