Structure of the voltage-gated potassium channel K _V 1.3: Insights into the inactivated conformation and binding to therapeutic leads

Abstract

The voltage-gated potassium channel K V 1.3 is an important therapeutic target for the treatment of autoimmune and neuroinflammatory diseases. The recent structures of K V 1.3, Shaker-IR (wild-type and inactivating W434F mutant) and an inactivating mutant of rat K V 1.2-K V 2.1 paddle chimera (K V Chim-W362F+S367T+V377T) reveal that the transition of voltage-gated potassium channels from the open-conducting conformation into the non-conducting inactivated conformation involves the rupture of a key intra-subunit hydrogen bond that tethers the selectivity filter to the pore helix. Breakage of this bond allows the side chains of residues at the external end of the selectivity filter (Tyr447 and Asp449 in K V 1.3) to rotate outwards, dilating the outer pore and disrupting ion permeation. Binding of the peptide dalazatide (ShK-186) and an antibody-ShK fusion to the external vestibule of K V 1.3 narrows and stabilizes the selectivity filter in the open-conducting conformation, although K + efflux is blocked by the peptide occluding the pore through the interaction of ShK-Lys22 with the backbone carbonyl of K V 1.3-Tyr447 in the selectivity filter. Electrophysiological studies on ShK and the closely-related peptide HmK show that ShK blocks K V 1.3 with significantly higher potency, even though molecular dynamics simulations show that ShK is more flexible than HmK. Binding of the anti-K V 1.3 nanobody A0194009G09 to the turret and residues in the external loops of the voltage-sensing domain enhances the dilation of the outer selectivity filter in an exaggerated inactivated conformation. These studies lay the foundation to further define the mechanism of slow inactivation in K V channels and can help guide the development of future K V 1.3-targeted immuno-therapeutics.

Selective block of human Kv1.1 channels and an epilepsy‐associated gain‐of‐function mutation by AETX‐K peptide

“…Of course, the binding interface of the Kv1.1 channel, which exhibits a net −5 charge across the extracellular loops that form the outer vestibule, also contributes to the structure of the complex. Of note, our finding that SAK1 blocks Kv1.3 by an Arg‐dependent non‐classical mechanism like Hui1, 12 suggests that the model of ShK with Kv1.3 that assumed Lys 22 to be in the pore may need to be revisited 38 …”

Venomics Reveals the Venom Complexity of Sea Anemone Heteractis magnifica

“…These peptide toxins have therapeutic potential for autoimmune diseases involving effective memory T cells activated by Kv1.3 potassium channels [25]. Eventually, ShK-186 was developed, which was 100 times more selective for Kv1.3 than for Kv1.1, Kv1.4 and Kv1.6 [61][62][63]. These ShK-like peptides have not been reported in the venom proteomes of other sea anemone species.…”

Harnessing AlphaFold to reveal state secrets: Prediction of hERG closed and inactivated states

“…Consequently, they suggested this backbone rearrangement as a fundamental molecular mechanism underlying C-type inactivation in K + channels (31). In other studies on Shaker and Kv1.3 channels, dilation in the upper SF has been proposed to be a potential C-type inactivation mechanism but without notable constriction at the SF glycine (32)(33)(34)(35). The inactivation processes across various K+ channels may exhibit similarities to some degree, but possess distinct differences that could account for the observed variability in inactivation rates among different K+ channels(1).…”