The effect of cold stress on heat shock proteins in nauplii (larvae) of the brine shrimp, Artemia franciscana

Abstract

Heat shock proteins (HSPs) are highly conserved and present in organisms under normal physiological conditions and function in protein folding, degradation and localization. HSPs are also synthesized in response to environmental stressors such as heat, anoxia, desiccation and cold. These molecular chaperones protect other proteins from irreversible denaturation during stress, thereby maintaining proteostasis and allowing cells to survive unfavorable conditions. Artemia franciscana, commonly known as brine shrimp, are micro-crustaceans that live in harsh aquatic environments and experience high salinity, extreme temperatures, variable water levels, and hypoxia. In anticipation of stressful conditions, A. franciscana alter their life cycle by releasing cysts that enter diapause. Nauplii (larvae) emerge after diapause termination or when favorable conditions return. The effect of cold shock on three HSPs, HSP90, HSP70 and HSP40 was studied in the nauplii of A. franciscana during 6 h of cold-shock at 1C and 6 h of recovery from cold shock at 27C. Immunoprobing of western blots containing cell-free protein extracts of stressed nauplii showed that the amounts of HSP90 and HSP40 decreased and increased, respectively, during recovery from cold shock, while the level of HSP70 was not altered in response to cold stress. The changes in HSP90 and HSP40 suggest their role in cold stress tolerance, however additional research, such as the use of RNA interference (RNAi), is required to explore how these proteins protect A. franciscana during cold stress. This study is important because it contributes to the understanding of stress physiology and how organisms cope with cold.