Abstract
The ATP-sensitive K+-channels (KATP) are distributed in the tissues coupling metabolism with K+ ions efflux. KATP subunits are encoded by KCNJ8 (Kir6.1), KCNJ11 (Kir6.2), ABCC8 (SUR1), and ABCC9 (SUR2) genes, alternative RNA splicing give rise to SUR variants that confer distinct physiological properties on the channel. An high expression/activity of the sarco-KATP channel is observed in various rat fast-twitch muscles, characterized by elevated muscle strength, while a low expression/activity is observed in the slow-twitch muscles characterized by reduced strength and frailty. Down-regulation of the KATP subunits of fast-twitch fibers is found in conditions characterized by weakness and frailty. KCNJ11 gene knockout mice have reduced glycogen, lean phenotype, lower body fat, and weakness. KATP channel is also a sensor of muscle atrophy. The KCNJ11 gene is located on BTA15, close to a QTL for meat tenderness, it has also a role in glycogen storage, a key mechanism of the postmortem transformation of muscle into meat. The role of KCNJ11 gene in muscle function may underlie an effect of KCNJ11 genotypes on meat tenderness, as recently reported. The fiber phenotype and genotype are important in livestock production science. Quantitative traits including meat production and quality are influenced both by environment and genes. Molecular markers can play an important role in the genetic improvement of animals through breeding strategies. Many factors influence the muscle Warner-Bratzler shear force including breed, age, feeding, the biochemical, and functional parameters. The role of KCNJ11gene and related genes on muscle tenderness will be discussed in the present review.
Highlights
The ATP-sensitive K+-channels (KATP) are widely distributed in the tissues including neurons, vascular, pancreatic beta cells, cardiac, and skeletal muscles (Amoroso et al, 1990; Zhang and Bolton, 1996; Liss and Roeper, 2001; Cole and ClémentChomienne, 2003; Flagg et al, 2010; Olson and Terzic, 2010)
The KATP channels are hetero-octameric complexes of pore-forming inwardly rectifier K+ (Kir6) channel subunits associated with regulatory sulphonylureas receptor (SUR) subunits, members of the ATP binding cassette (ABC) family of membrane proteins
The early developmental period (5–6 days) is dominated by a KATP channel having a conductance of 66 pS, a high open probability of 0.602 which is determined by a reduced mean close time as compared to that recorded in the adult fibers, and an IC50 for ATP and glybenclamide of 123.1 and 3.97 μM, respectively
Summary
The ATP-sensitive K+-channels (KATP) are widely distributed in the tissues including neurons, vascular, pancreatic beta cells, cardiac, and skeletal muscles (Amoroso et al, 1990; Zhang and Bolton, 1996; Liss and Roeper, 2001; Cole and ClémentChomienne, 2003; Flagg et al, 2010; Olson and Terzic, 2010). The early developmental period (5–6 days) is dominated by a KATP channel having a conductance of 66 pS, a high open probability of 0.602 which is determined by a reduced mean close time as compared to that recorded in the adult fibers, and an IC50 for ATP and glybenclamide of 123.1 and 3.97 μM, respectively. The later developmental period (from 56 days) is dominated by a KATP channel having a 71 pS conductance, but a low open probability of 0.222 This adult channel is 3.2 and 73.5 times more sensitive to ATP and glybenclamide than the juvenile channel, respectively (Tricarico et al, 1997b). The sarco-KATP channel activity declines with aging in fast-twitch rat fibers showing surface channel subtypes characterized by low open probability and current density (Tricarico and Camerino, 1994). The age-dependent changes of the KATP channels subtypes may reflect the different metabolic needs of the muscles during development and aging
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