K(ATP) channel Kir62 subunit distribution differs between muscles and between fiber types in skeletal muscle

Abstract

The activity of the ATP-sensitive potassium (KATP) channel, whose sensitivity to ATP and ability to permit K+ flux together allow the channel to couple the metabolic state of a cell to its membrane excitability, is important in several tissues for the maintenance of glucose homeostasis and cytoprotection. In skeletal muscle specifically, the channel has been shown to be involved in cell volume regulation, modulation of glucose uptake, and the prevention of fiber damage and contractile dysfunction during fatigue. The extent of the cytoprotective capabilities of the KATP channel vary tremendously between muscles with different muscle fiber type composition. Semi-quantitative measurement of Kir6.2 subunit content showed that variances exist in KATP channel content between fiber types and between different muscles. These differences may be related to the extent of importance of the channel's function in a specific muscle. The highest Kir6.2 content was observed in the most glycolytic fiber types and in the more glycolytic muscles studied, and it is these muscles and fiber types which appear to be most dependent on functional KATP channels for their cytoprotective role.