Quantitative proteomics analysis of membrane glucocorticoid receptor activation in rainbow trout skeletal muscle

Cortisol modulates energy metabolism promoting the mobilization of glucose and increasing proteolysis to overcome stressful situations in teleost. The cortisol metabolic effects are attributed to genomic mechanisms that involve the interaction of cortisol with its glucocorticoid intracellular receptor. Furthermore, cortisol can also interact with plasma membrane glucocorticoid receptors activating a rapid nongenomic signaling; however, its contribution during the early acute phase stress response in fish is unknown. In the present work, we evaluated the effects of membrane-initiated cortisol actions in vivo in the proteome of rainbow trout (Oncorhynchus mykiss) skeletal muscle. Quantitative iTRAQ analyses were performed to examine proteomic changes in rainbow trout stimulated with physiological concentrations of cortisol and cortisol-BSA, a membrane-impermeable cortisol conjugate. A total of 873 proteins were identified, among which 61 and 47 proteins were differentially expressed under cortisol and cortisol-BSA treatments, respectively. Functional clustering analysis revealed an upregulation of proteins associated with mitochondria and oxidative phosphorylation. These results were validated by Western blot analysis. Additionally, using rainbow trout myotubes, the participation of membrane glucocorticoid receptors in gene expression was evaluated. The results obtained suggest that cortisol acts through a membrane canonical glucocorticoid receptor and mediates the expression of proteins associated with mitochondrial oxidative phosphorylation.