Protein synthesis is lowered while 20S proteasome activity is maintained following acclimation to low temperature in juvenile spotted wolffish (Anarhichas minor Olafsen)

The effects of temperature on protein metabolism have been studied mostly with respect to protein synthesis. Temperature generally has a parabolic effect on protein synthesis with a maximum rate being observed at optimal growth temperature. The effect of temperature on protein degradation is poorly understood. The 20S proteasome is mainly responsible for the degradation of short-lived and oxidatively modified proteins and has been recently identified as a potentially good proxy for protein degradation in fish. The aim of this experiment was to examine the relationships between the rate of protein synthesis, activity of the 20S proteasome, oxidative stress markers and antioxidant capacity in white muscle of juvenile spotted wolffish (Anarhichas minor) acclimated at three temperatures (4, 8 and 12 degrees C). The rate of protein synthesis was lower at 4 degrees C than at 8 degrees C while it was intermediate at 12 degrees C. Despite the decrease of protein synthesis at low temperature, the activity of 20S proteasome activity was maintained high in fish acclimated at lower temperature (4 degrees C), reaching levels 130% of that of fish acclimated at 8 degrees C when measured at a common temperature. The oxidative stress markers TBARS and protein-carbonyl content did not change among temperature groups, but reduced glutathione concentration was higher in cold-acclimated fish, suggesting a higher antioxidant capacity in this group. Our data suggest that lower growth rate in cold temperature results from both high 20S proteasome activity and a reduced rate of protein synthesis.