GCN2 is required to maintain core body temperature in mice during acute cold.
Non-shivering thermogenesis in the brown adipose tissue (BAT) of rodents requires macronutrients to fuel the generation of heat during hypothermic conditions. Therefore, it is critical to identify signaling pathways which aid in nutrient delivery within this thermogenic tissue. To understand the contribution of the integrated stress response (ISR) in directing adaptive thermogenesis, we examined the role of the kinase activity of general control nonderepressible 2 (GCN2) within the BAT during acute cold exposure. We hypothesized that under hypothermic conditions, GCN2 maintains thermogenesis via ISR gene targets such as fibroblast growth factor 21 (FGF21), that triggers thermogenic uncoupling in BAT. In alignment with our hypothesis, both female and male mice either lacking GCN2 or administered a small molecule inhibitor of GCN2 were profoundly intolerant to acute cold stress. However, while GCN2 deletion in male mice impeded liver-derived FGF21 expression, it did not affect FGF21 levels in females, suggesting an alternative role for GCN2 in the maintenance of thermogenesis. Within the BAT, acute cold exposure increased ISR target genes and thermogenic genes regardless of GCN2 status and sex. RNA sequencing in BAT during cold exposure revealed a gene signature that identified actomyosin mechanics and transmembrane transport as the top two processes requiring GCN2. The top gene signature included cytoskeletal and class II myosin heavy chain genes critical for maximal thermogenesis during cold stress. The second gene signature included amino acid transporters which corresponded with higher circulating amino acids. In conclusion, we identify a novel role for GCN2 activation during acute cold exposure to facilitate mechanosensitive cell signaling and use of amino acids for adaptive thermogenesis.