A selectivity filter mutation provides insights into gating regulation of a K+ channel

Abstract

G-protein coupled inwardly rectifying potassium (GIRK) channels are key players in inhibitory neurotransmission in heart and brain. We conducted molecular dynamics simulations to investigate the effect of a selectivity filter (SF) mutation, G154S, on GIRK2 structure and function. We observe mutation-induced loss of selectivity, changes in ion occupancy and altered filter geometry. Unexpectedly, we reveal aberrant SF dynamics in the mutant to be correlated with motions in the binding site of the channel activator Gβγ. This coupling is corroborated by electrophysiological experiments, revealing that GIRK2_wt activation by Gβγ reduces the affinity of Ba²⁺ block. We further present a functional characterization of the human GIRK2_G154S mutant validating our computational findings. This study identifies an allosteric connection between the SF and a crucial activator binding site. This allosteric gating mechanism may also apply to other potassium channels that are modulated by accessory proteins.

Gly selectivity filter (TIGYGYR) mutant of the GIRK2 channel causes rare but severe neurological disorder called the Keppen-Lubinsky syndrome. Here, the authors explore the molecular mechanism of action of this glycine to serine mutant causing disease and identify an allosteric connection between the selectivity filter and a crucial activator binding site.