Skeletal muscle of torpid Richardson's ground squirrels (Urocitellus richardsonii) exhibits a less active form of citrate synthase associated with lowered lysine succinylation

This study investigated the regulation of citrate synthase in the muscle tissue of a small mammalian hibernator through comparison of functional and structural properties. The results demonstrated a significant decrease in the Vmax of purified torpid CS compared to the control euthermic enzyme (1.2-1.7 fold greater in the control) that was evident over a wide range of temperatures (8, 22 and 37 °C) that are encountered by the enzyme in hibernation. This was also reflected in the specific activity of the enzyme in crude muscle protein extracts. Analyzing the purified CS through immunoblotting demonstrated that the enzyme contained noticeably less lysine succinylation in the torpid state (about 50% of euthermic levels) and this was correlated with an increase in total levels of SIRT5, the enzyme responsible for mediating desuccinylation in the mitochondria (2.2 fold increase). Taken together, the results of this study support the idea that CS is inhibited during hibernation in the ground squirrel skeletal muscle and that this alteration could be mediated by decreases in succinylation.PMID:34186087 | DOI:10.1016/j.cryobiol.2021.06.006

Source: Cryobiology - June 29, 2021 Category: Biology Authors: Stuart R Green Kenneth B Storey Source Type: research