Co-activation of Akt, Nrf2, and NF-κB Signals under UPRER in Torpid Myotis Ricketti Bats for Survival.

Bats hibernate to survive stressful conditions. Examination of whole cell and mitochondrial proteomes of the liver of Myotis ricketti revealed that torpid bats had endoplasmic reticulum unfolded protein response (UPRER), global reduction in glycolysis, enhancement of lipolysis, and selective amino acid metabolism. Compared to active bats, torpid bats had higher amounts of phosphorylated serine/threonine kinase (p-Akt) and UPRER markers such as PKR-like endoplasmic reticulum kinase (PERK) and activating transcription factor 4 (ATF4). Torpid bats also had lower amounts of the complex of Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappa B) (p65)/I-kappa B alpha. Cellular redistribution of 78 kDa glucose-regulated protein (GRP78) and reduced binding between PERK and GRP78 were also seen in torpid bats. Evidence of such was not observed in fasted, cold-treated, or normal mice. These data indicated that bats activate Akt, Nrf2, and NF-kappa B via the PERK-ATF4 regulatory axis against endoplasmic reticulum stresses during hibernation. Huang et al. use proteomics to examine liver and liver mitochondria of hibernating bats. The authors observe the unfolded protein response in endoplasmic reticulum and co-activation of survival signaling pathways in torpid bats and provide further insight into physiological adaptations that allow bats to survive a long period of hibernation.