Stress-70 protein induction in Mytilus edulis: Tissue-specific responses to elevated temperature reflect relative vulnerability and physiological function

Abstract

The exposure of organisms to environmental stressors affects the expression levels of certain “stress proteins” that play an important role in protein homeostasis and stress tolerance. We have used an antibody to monitor this response to elevated temperature in the gill, mantle and muscle tissues of the mussel Mytilus edulis. The antibody detected four isoforms of the highly conserved stress-70 family of proteins, which appear homologous with the hsp70, hsc70, hsp72, and grp78 proteins that are detected by the same antibody in humans. Compared with mantle and adductor muscle tissues, gill tissue showed much the greatest increase in levels of both the 70 and 72 kDa proteins. Levels of the 70 and 72 kDa proteins increased for the first 48 hours of heat stress in the gill, and subsequently decreased between 48 and 72 hours. A 78 kDa protein was present in the gill and mantle tissues, but was absent from the adductor muscle. Alternatively, the 70 kDa protein was more abundant in unstressed adductor muscle than in unstressed gill or mantle tissues. Results are discussed in terms of the proposed cellular locations and function of these proteins, the processes contributing to thermally-induced death, and their implications for our understanding of how temperature affects the physiology, ecology and distribution limits of marine organisms.