Life in Suspended Animation: Role of Chaperone Proteins in Vertebrate and Invertebrate Stress Adaptation

Abstract

When confronted by environmental stress, organisms can employ physiological and biochemical adaptations for survival. These include hibernation, estivation, anhydrobiosis, anaerobiosis, and freeze tolerance. Underlying most of these is strong metabolic rate depression that suppresses rates of ATP-expensive processes like transcription, translation, and protein degradation to achieve major energy savings. Chaperone proteins are crucial to hypometabolism; helping to preserve cell viability and stabilize the proteome over extended periods of time. Two types of chaperones are important to the stress response: heat shock proteins (HSP) and glucose regulated proteins (GRP). Both act to fold new proteins or refold damaged and unfolded proteins, and can also have anti-apoptotic or other protective roles. This review summarizes recent knowledge on the involvement of HSP and GRP in animal responses to environmental stress, showing that chaperone upregulation is a consistent feature of hypometabolism. Hibernating mammals, cold-hardy insects, anoxic turtles, and dehydrated frogs and snails all show upregulation in HSP and GRP gene or protein expression during seasonal or stress-induced dormancies. This widespread chaperone response to environmental stress also provides insights into ways to improve strategies for medical applications such as organ preservation or combating diseases where oxidative and proteotoxic stresses contribute to the condition.