Solution Structure and Function of the “Tandem Inactivation Domain” of the Neuronal A-type Potassium Channel Kv1.4

Abstract

Cumulative inactivation of voltage-gated (Kv) K؉ channels shapes the presynaptic action potential and determines timing and strength of synaptic transmission. Kv1.4 channels exhibit rapid "ball-and-chain"-type inactivation gating. Different from all other Kv␣ subunits, Kv1.4 harbors two inactivation domains at its N terminus. Here we report the solution structure and function of this "tandem inactivation domain" using NMR spectroscopy and patch clamp recordings. Inactivation domain 1 (ID1, residues 1-38) consists of a flexible N terminus anchored at a 5-turn helix, whereas ID2 (residues 40 -50) is a 2.5-turn helix made up of small hydrophobic amino acids. Functional analysis suggests that only ID1 may work as a pore-occluding ball domain, whereas ID2 most likely acts as a "docking domain" that attaches ID1 to the cytoplasmic face of the channel. Deletion of ID2 slows inactivation considerably and largely impairs cumulative inactivation. Together, the concerted action of ID1 and ID2 may promote rapid inactivation of Kv1.4 that is crucial for the channel function in short term plasticity.

Heme impairs the ball-and-chain inactivation of potassium channels

“…The initial chemical shift index-based structure (Fig. S3, Upper) comparison indicated potential differences to a structure of an elongated construct reported earlier [1KN7 (22)]. We therefore decided to obtain an independent 3D starting structure by in silico structure predictions with CS-Rosetta and CHESHIRE to be used for the docking experiments with the heme moiety.…”

KW-7158 [(2S)-(+)-3,3,3-Trifluoro-2-hydroxy-2-methyl-N-(5,5,10-trioxo-4,10-dihydrothieno[3,2-c][1]benzothiepin-9-yl)propanamide] Enhances A-Type K+ Currents in Neurons of the Dorsal Root Ganglion of the Adult Rat

“…3). Among the inactivating K ϩ currents known to be expressed in DRG neurons, only Kv1 subtypes are sensitive to TEA blockade (Wissmann et al, 2003), thus the most likely target for the KW-7158 facilitatory effect is a Kv4 K ϩ channel subtype (Pongs, 1992;Tkatch et al, 2000).…”

The Effects of Ginsenoside Rg3 on Human Kv1.4 Channel Currents without the N-Terminal Rapid Inactivation Domain

“…2D). 5) Treatment of Rg 3 to hKv1.4D2-61 channels produced larger inhibitions of non-inactivating plateau than peak outward K ϩ currents in a concentration-dependent manner. Mutation of K531 hKv1.4D2-61 to K531Y hKv1.4D2-61 and raising extracellular [K ϩ ] o abolished Rg 3 -mediated inhibitions of non-inactivating plateau outward K ϩ currents (Figs.…”

“…2D, Con). 5,9) In the absence of Rg 3 , both hKv1.4 and hKv1.4D2-61 channel currents were elicited by voltage pulses more positive than Ϫ40 mV, and current amplitude increased linearly with further depolarization (Figs. 2E, F; * pϽ0.05 * * pϽ0.01 at ϩ60 mV, nϭ7-8).…”

“…Thus, N-terminal deletions remove inactivation and induce non-inactivating persistent outward K ϩ currents and C-type inactivation. [3][4][5] Recently, we reported that ginsenoside Rg 3 (20-S-protopanaxadiol-3-[O-b-D-glucopyranosyl (1→2)-b-glucopyranoside]) (Rg 3 ) inhibits voltage-dependent transient human Kv1.4 (hKv1.4) channel currents by forming hydrogen bonds between Rg 3 and amino acids, including K531 residue of the channels, using the site-directed mutagenesis method. 6) In this report, we present evidence that Rg 3 inhibits preferentially non-inactivating persistent rather than peak outward currents in N-terminal (D2-61) deleted hKv1.4 (hKv1.4D2-61) channels.…”