Heteromerization of Kir2.x potassium channels contributes to the phenotype of Andersen's syndrome

TLDR

Andersen's syndrome, an autosomal dominant disorder caused by mutations in the potassium channel Kir2.1, manifests as cardiac arrhythmias, periodic paralysis, and dysmorphic bone structure. The study aimed to determine whether heteromerization of Kir2.1 with wild‑type Kir2.2 and Kir2.3 channels contributes to the Andersen's syndrome phenotype. Our experiments show that Kir2.x channels form functional heteromers with Kir2.2 and Kir2.3, evidenced by conductance in HEK293 cells, Ba²⁺‑sensitive currents in Xenopus oocytes, altered IC₅₀ values, dominant‑negative effects, co‑immunoprecipitation in guinea pig cardiomyocytes, and intracellular domain interactions, suggesting that mutant Kir2.1 tetramerization with wild‑type subunits drives Andersen's syndrome pleiotropy.

Abstract

Andersen's syndrome, an autosomal dominant disorder related to mutations of the potassium channel Kir2.1, is characterized by cardiac arrhythmias, periodic paralysis, and dysmorphic bone structure. The aim of our study was to find out whether heteromerization of Kir2.1 channels with wild-type Kir2.2 and Kir2.3 channels contributes to the phenotype of Andersen's syndrome. The following results show that Kir2.x channels can form functional heteromers: ( i ) HEK293 cells transfected with Kir2.x–Kir2.y concatemers expressed inwardly rectifying K + channels with a conductance of 28–30 pS. ( ii ) Expression of Kir2.x–Kir2.y concatemers in Xenopus oocytes produced inwardly rectifying, Ba 2+ sensitive currents. ( iii ) When Kir2.1 and Kir2.2 channels were coexpressed in Xenopus oocytes the IC 50 for Ba 2+ block of the inward rectifier current differed substantially from the value expected for independent expression of homomeric channels. ( iv ) Coexpression of nonfunctional Kir2.x constructs, in which the GYG region of the pore region was replaced by AAA, with wild-type Kir2.x channels produced both homomeric and heteromeric dominant-negative effects. ( v ) Kir2.1 and Kir2.3 channels could be coimmunoprecipitated in membrane extracts from isolated guinea pig cardiomyocytes. ( vi ) Yeast two-hybrid analysis showed interaction between the N- and C-terminal intracellular domains of different Kir2.x subunits. Coexpression of Kir2.1 mutants related to Andersen's syndrome with wild-type Kir2.x channels showed a dominant negative effect, the extent of which varied between different mutants. Our results suggest that differential tetramerization of the mutant allele of Kir2.1 with wild-type Kir2.1, Kir2.2, and Kir2.3 channels represents the molecular basis of the extraordinary pleiotropy of Andersen's syndrome.