title: Down-regulation of Kir2.6 channel by c-termini mutation D252N and its association with the susceptibility to Thyrotoxic Periodic Paralysis.
abstract: Inward rectifying potassium - Kir - channels drive the resting potential to potassium reversal potential and, when disrupted, might be related to muscular diseases. Recently, Thyrotoxic Periodic Paralysis (TPP) has emerged as a channelopathy related to mutations in KCNJ18 gene, which encodes Kir2.6 channel. TPP is a neuromuscular disorder characterized by a triad of muscle weakness, hypokalemia, and thyrotoxicosis, the latter being essential for the crisis. Direct sequencing revealed two heterozygous mutations - D252N and R386C - in two TPP patients. KCNJ18 cDNAs were cloned into mammalian expression plasmids and transiently expressed in HEK 293T cells to investigate the functional effects of Kir2.6 mutations. Patch-clamp and confocal laser scanning microscopy experiments were carried out, comparing the WT channel to its mutants. D252N mutation down-regulates the Kir2.6 activity, decreasing the K+current density (∼34%) when compared to the WT channel; whereas the mutation R386C shows no significant changes from WT. The mutant D252N Kir2.6 channel also showed a substantial reduction of ∼51% in membrane abundance relative to WT channel. Our study describes the functional consequences of a single amino acid change in Kir2.6 channel. Further analysis regarding hormonal conditions and Kir channel expression are required to provide new clues about the TPP pathophysiology.
authors.affiliation: Laboratório de Neurobiologia Estrutural e Funcional, Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil; Laboratório de Endocrinologia Molecular e Translacional, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Rolf Matias
authors.initials: RM
authors.lastname: Paninka
authors.affiliation: Laboratório de Neurobiologia Estrutural e Funcional, Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Estevão
authors.initials: E
authors.lastname: Carlos-Lima
authors.affiliation: Laboratório de Endocrinologia Molecular e Translacional, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Lindsey
authors.affiliation: Laboratório de Endocrinologia Molecular e Translacional, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Ilda S
authors.initials: IS
authors.lastname: Kunii
authors.affiliation: Laboratório de Endocrinologia Molecular e Translacional, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil. Electronic address: mrdsilva@unifesp.br.
authors.forename: Magnus R
authors.initials: MR
authors.lastname: Dias-da-Silva
authors.affiliation: Laboratório de Neurobiologia Estrutural e Funcional, Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil. Electronic address: arcisio.miranda@unifesp.br.
authors.forename: Manoel
authors.initials: M
authors.lastname: Arcisio-Miranda
mesh_terms: D000328:Adult; D002462:Cell Membrane / Q000378:metabolism; D053447:Channelopathies / Q000150:complications / Q000235:genetics*; D015536:Down-Regulation; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D006801:Humans; D007008:Hypokalemia / Q000235:genetics; D008297:Male; D018908:Muscle Weakness / Q000235:genetics; D009154:Mutation; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000502:physiology; D013971:Thyrotoxicosis / Q000235:genetics
chemical_list: C546860:KCNJ18 protein, human; D024661:Potassium Channels, Inwardly Rectifying
keywords: Kir channel; Kir2.6; Thyrotoxic Periodic Paralysis; potassium channel