Meeting Abstract
An unavoidable consequence of aerobic metabolism is the production of reactive oxygen species (ROS). While ROS are important molecular signals in cells, excess ROS cause damage to cellular components such as lipids and proteins. While there is general agreement that mitochondria are the primary sources of ROS, it is not clear how variation in mitochondrial density or metabolic rate among tissues influences ROS-induced damage and rates of protein synthesis. Fish skeletal muscle is comprised of highly aerobic red muscle and highly anaerobic white muscle, offering an excellent model system in which to evaluate the role of tissue aerobic capacity on ROS-induced damage. The present study characterizes protein and lipid oxidative damage, as well as markers of protein degradation and measurements of protein synthesis rates, in red and white muscle of the pinfish, Lagodon rhomboides. Red muscle had a greater mitochondrial volume density and had more oxidative damage than white muscle, including elevated protein carbonylation and lipid peroxidation. Protein degradation in muscle occurs via the lysosomal-autophagy or ubiquitin-proteasome pathways and has been shown to be tissue dependent. Lysosomal degradation markers and autophagosome volume density were greater in white muscle, while ubiquitin expression and 20S proteasome activity were significantly greater in red muscle. However, ubiquitin ligase expression was significantly higher in white muscle. Red muscle also had a higher basal metabolic rate and higher rates of protein synthesis, presumably due to the higher mitochondrial volume density and the associated increase in oxidative damage. Together these results support the concept that a consequence of an elevated aerobic capacity is greater costs associated with protein synthesis.
