o:3199 Remodeling of skeletal muscle myosin metabolic states in hibernating mammals en Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis. Animals; Hibernation physiology; Energy Metabolism; Skeletal Muscle Myosinsmetabolism; Ursidaemetabolism physiology; Adenosine Triphosphate metabolism; Muscle, Skeletal metabolism physiology; Muscle Fibers, Skeletal metabolism; Proteomics 1552099 10.7554/eLife.94616 2024-07-08T14:20:54.015Z 44 yes 46 Christopher T. A. Lewis University of Copenhagen 0000-0003-4477-422X Elise G. Melhedegaard University of Copenhagen person Marija M. Ognjanovic University of Copenhagen person Mathilde S. Olsen University of Copenhagen person Jenni Laitila University of Copenhagen person Robert A. E. Seaborne University of Copenhagen / King's College London person Magnus Gronset University of Copenhagen person Changxin Zhang University of Michigan person Hiroyuki Iwamoto Japan Synchrotron Radiation Research Institute person Anthony L. Hessel University of Muenster / Accelerated Muscle Biotechnologies Consultants person Michel N. Kuehn University of Muenster / Accelerated Muscle Biotechnologies Consultants person Carla Merino Biosfer Teslab person Nuria Amigo Biosfer Teslab person Ole Frobert Aarhus University / Örebro University person Sylvain Giroud University of Veterinary Medicine Vienna / Northern Michigan University person 0000-0001-6621-7462 James F. Staples University of Western Ontario person Anna V. Goropashnaya University of Alaska Fairbanks person Vadim B. Fedorov University of Alaska Fairbanks person Brian Barnes University of Alaska Fairbanks person Oivind Toien University of Alaska Fairbanks person 0000-0001-5967-2483 Kelly Drew University of Alaska Fairbanks person Ryan J. Sprenger University of British Columbia person Julien Ochala University of Copenhagen person application/pdf 4067908 https://phaidra.vetmeduni.ac.at/o:3199 no yes 16 70 1552253 eLife 26 13 eLife Sciences Publications Ltd 2024