Functional characterization of melanocortin-3 receptor in rainbow trout (Oncorhynchus mykiss)

The melanocortin-3 receptor (MC3R) is an important regulator of energy homeostasis and inflammation in mammals. However, its function in teleost fish needs to be further explored. In this study, we characterized rainbow trout MC3R (rtMC3R), which encoded a putative protein of 331 amino acids. Phylogenetic and chromosomal synteny analyses showed that rtMC3R was closely related to bony fishes. Quantitative PCR (qPCR) revealed that the transcripts of rtMC3R were highly expressed in the brain and muscle. The cellular function of rtMC3R was further verified by the signal-pathway-specific luciferase reporter assays. Four agonists such as alpha-MSH, beta-MSH, ACTH (1-24), and NDP-MSH can active rtMC3R, increasing the production of intracellular cAMP and upregulating MAPK/ERK signals. Moreover, we found that rtMC3R stimulated with alpha-MSH and NDP-MSH can significantly inhibit the NF-kappa B signaling pathway. This research will be helpful for further studies on the function of MC3R in rainbow trout, especially the role of energy metabolism and immune regulation.

Automated summary

This study characterized the rainbow trout MC3R and found its close relation to mammalian MC3R. The transcripts of rtMC3R were highly expressed in the brain and muscle. rtMC3R can be activated by agonists and modulate multiple signal pathways, while inhibiting the NF-kappa B signaling pathway.