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Proteomic identification of seasonally expressed proteins contributing to heart function and the avoidance of skeletal muscle disuse atrophy in a hibernating mammal

ABSTRACT: Hibernation in mammals such as the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) takes place over 4 to 6 months and is characterized by multi-day bouts of hypothermic torpor (5-7 °C core body temperature) that are regularly interrupted every 1-2 weeks by brief (12-24 hour) normothermic arousal periods called interbout arousals. The goal of our work was to identify the molecular mechanisms which underlie the hibernator’s ability to preserve heart function and avoid the deleterious effects of skeletal muscle disuse atrophy over prolonged periods of inactivity, starvation, and near-freezing body temperatures. To achieve this goal, we performed organelle enrichment of heart and skeletal muscle at five seasonal time points followed by LC-MS-based label-free quantitative proteomics. In both organs we saw a dramatic increase in levels of many proteins as ground squirrels transition from an active state in September to a pre-hibernation state in October. Interestingly, seasonal abundance patterns also identified new candidates for mitigating disuse atrophy in skeletal muscle which include higher levels of DHRS7C, SRL, and RTN2 in December-January torpid, IBA, and March active animals; and higher March active levels of TRIM72 and MPZ. Elevation of these proteins prompted us to perform an ex vivo contractile mechanics analysis of both type 1 (soleus) and type 2 (extensor digitorum longus) muscles in fall active, torpid, and spring active animals. Consistent with our hypotheses, both muscle types showed no deleterious effects despite several months of sedentary activity that would normally result in reduced muscle performance in non-hibernating mammals. An increased understanding of protein expression in natural hibernators may enable novel therapeutic strategies to treat human health concerns such as muscle disuse atrophy and heart disease.

INSTRUMENT(S): Xevo G2-XS QTof

ORGANISM(S): Spermophilus Tridecemlineatus (thirteen-lined Ground Squirrel)

TISSUE(S): Quadriceps, Heart

SUBMITTER: James Checco

LAB HEAD: James Checco

PROVIDER: PXD044532 | Pride | 2023-12-21

REPOSITORIES: Pride

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Project description:Hibernation is energy saving adaptation involving suppression of activity to survive in highly seasonal environments. Immobility and disuse generate muscle loss in most mammalian species. In contrast to other mammals, bears and ground squirrels demonstrate limited muscle atrophy over the physical inactivity of winter hibernation. This suggests that hibernating mammals have adaptive mechanisms to prevent disuse muscle atrophy. To identify common transcriptional program underlying molecular mechanisms preventing muscle loss, we conducted a large-scale gene expression screening in hind limb muscles comparing hibernating and summer active black bears and arctic ground squirrels by the use of custom 9,600 probe cDNA microarrays. The molecular pathway analysis showed an elevated proportion of overexpressed genes involved in all stages of protein biosynthesis and ribosome biogenesis in muscle of both species during hibernation that implies induction of translation at different hibernation states. The induction of protein biosynthesis likely contributes to attenuation of disuse muscle atrophy through prolonged periods of immobility and starvation. This adaptive mechanism allows hibernating mammals to maintain full musculoskeletal function and preserve mobility during and immediately after hibernation, thus promoting survival. The lack of directional changes in genes of protein catabolic pathways does not support the importance of metabolic suppression for preserving muscle mass during winter. Coordinated reduction of multiply genes involved in oxidation reduction and glucose metabolism detected in both species is consistent with metabolic suppression and lower energy demand in skeletal muscle during inactivity of hibernation. Arctic ground squirrels sampled during winter hibernation were compared with the animals sampled during summer. Muscle was hybridized on a custom 9,600 probes nylon membrane microarray platform. Ten in late torpor, four in early arousal, then in late arousal were studied in experiments.

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Proteomic identification of seasonally expressed proteins contributing to heart function and the avoidance of skeletal muscle disuse atrophy in a hibernating mammal

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