Purification and characterization of NADP-isocitrate dehydrogenase from skeletal muscle of Urocitellus richardsonii

Abstract

NADP-dependent isocitrate dehydrogenase (NADP-IDH, EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate with the concomitant production of NADPH. NADPH plays important roles in many biosynthesis pathways, maintenance of proper oxidation-reduction balance, and protection against oxidative damage. This present study investigated the dynamic nature of NADP-IDH during hibernation by purifying it from the skeletal muscle of Richardson's ground squirrel (Urocitellus richardsonii) and analyzing its structural and functional changes in response to hibernation. Kinetic parameters of puri ed NADP-IDH from euthermic and hibernating ground squirrel skeletal muscle were characterized at 22°C and 5°C. Relative to euthermic muscle, NADP-IDH in hibernating muscle had a higher a nity for its substrate, isocitrate at 22°C, whereas at 5°C, there was a signi cant decrease in isocitrate a nity. Western blot analysis revealed greater serine and threonine phosphorylation in hibernator NADP-IDH as compared to euthermic NADP-IDH. In addition, Bioinformatic analysis predicted the presence of 18 threonine and 21 serine phosphorylation sites on squirrel NADP-IDH. The structural and functional changes in NADP-IDH indicate the ability of the organism to reduce energy consumption during hibernation, while emphasizing increased NADPH production, and thus antioxidant activity, during torpor arousal cycles.

Torpor‐responsive microRNAs in the heart of the Monito del monte, Dromiciops gliroides

“…In contrast to homeotherms who suffer deleterious arrythmias during hypothermia, heterotherms can maintain cardiac function at low T b despite increased blood viscosity and peripheral resistance via reversible cardiac hypertrophy and improved contractility. [10][11][12] Additionally, hibernators utilize tissue preservation strategies including chaperone proteins and antioxidant defenses to prepare for oxidative stress during arousal, [13][14][15][16][17][18][19] as well as various transcription factors to regulate gene expression. [20][21][22][23][24][25] Understanding the molecular mechanisms mammalian hibernators utilize to survive the stresses associated with torpor and arousal could potentially be applied to human medicine, particularly in the development of therapeutics for ischemia/reperfusion injuries and improved organ transplantation.…”