Exploring the Inwardly Rectifying Potassium Channel Kir2.1 and Andersen’s Syndrome in the Skeletal Muscle

Abstract

Andersen's Syndrome (AS) is a rare autosomal disorder that has been defined with periodic paralysis, cardiac arrhythmia, and development anomalies. AS has been linked to the KCNJ2 gene which encodes for the strong inward rectifier K+ channel Kir2.1. Kir2.1 channel function and involvement in AS periodic paralysis in skeletal muscle is poorly understood, although it has been suggested that these channels help set the resting membrane potential and control the action potential duration in heart. Over 30 (AS associated) mutations have been identified on the KCNJ2 gene, and when expressed in mammalian cell lines, several AS mutants are properly trafficked to the cell membrane but produce silent channels while others may disrupt channel trafficking. Skeletal muscles have complex structures (such as neuromuscular junctions, sarcoplasmic membranes, and transverse tubules) working in concert to provide the appropriate responses to nerve impulse and metabolic processes. The excitation-contraction process is well controlled within these compartments; hence precise localization of the Kir2.1 channel in this tissue may well define its function.Here we used an adenovirus infection strategy to express wild type and AS associated mutant Kir2.1 channels in mouse skeletal muscle and extracted these muscles for immunohistochemical staining and functional analysis. Antibodies against subcellular muscle markers (such as ryanodine receptor, dihydropyridine receptor and dystrophin) were used to localize the Kir2.1 and AS associated mutants in skeletal muscle tissue. The distribution of these channels in the transverse tubules may imply that not only do these channels help set the resting membrane potential in the skeletal muscle but they may play another role in the excitation-contraction coupling process. Further functional experiments were performed on these adenovirus-Kir2.1 infected skeletal muscles to determine the effect of the mutations on muscle force frequency and fatigue.