Identification and functional analysis of six melanocortin-4-receptor-like (MC4R-like) mutations in goldfish (Carassius auratus)

Melanocortin receptor-4 (MC4R) belongs to the G protein-coupled receptor family, characterized by a classical structure of seven transmembrane domains (7TMD). They play an important role in food intake and weight regulation. In the present study, we identified melanocortin-4-receptor-like (caMC4RL) mutants of goldfish from the Qian River in the Qin Ling region and characterized their functional properties, including the constitutive activities of the mutants, ligand-induced cAMP and ERK1/2 accumulation, and AMPK activation. The results show that six caMC4RL mutants were identified in goldfish from the Qian River in the Qin Ling region, and are located in the conserved position of the Cyprinidae MC4Rs. The mutations (E57K, P296S, and R302T/K) result in the loss of Gs signaling function. The mutations (P296 and R302T/K) exhibited biased signaling in response to ACTH stimulation in the MAPK/ERK pathway. In addition, the E57K mutant may play a role in weight regulation and could serve as molecular markers for molecular breeding. These data will provide fundamental information for functional studies of teleost GPCR mutants and MC4R isoforms.