Abstract:
I examined the effects of oxidative stress and changes in temperature on heat shock protein (Hsp) levels in cold-adapted and cold-acclimated fishes. Adaptation of Antarctic notothenioids to cold temperature is correlated with high levels of Hsps, thought to minimize cold-induced protein denaturation. Hsp70 levels were measured in red- and white-blooded Antarctic notothenioid fishes exposed to their critical thermal maximum (CTMax), 4°C warm acclimated, and notothenioids from different latitudes. I determined the effect of cold acclimation on Hsp levels and the role of sirtuins in regulating Hsp expression and changes in metabolism in threespine stickleback, Gasterosteus aculeatus, cold-acclimated to 8°C. Levels of Hsps do not increase in Antarctic notothenioids exposed to their CTMax, and warm acclimation reduced levels of Hsp70. Hsp70 levels were higher in Antarctic notothenioids compared to a temperate notothenioid and higher in white-blooded notothenioids compared to red-blooded notothenioids, despite higher oxidative stress levels in red-blooded fish, suggesting Hsp70 does not mitigate oxidative stress. Cold acclimation of stickleback resulted in tissue-specific increases in some Hsps and sirtuins. My research indicates that cold acclimation increases Hsp levels, and moderate increases in temperature reduce Hsp levels in cold-adapted fishes. Together, these data lend support to the hypothesis that cold denatures proteins.
