Melanocortin 2 Receptor Accessory Protein 2 (MRAP2)

MRAP2 is a conserved homologue of MRAP. MRAP2 was an MCR accessory protein important in the functional expression of one or more of the MCRs. The MRAP2-FLAG protein is ~27 and 29 kDa. The 29 kDa isoform is a glycosylated form as treatment with endoglycosidases and/or mutagenesis of the putative N-glycosylation site resulted in its disappearance. Co-immunoprecipitation studies demonstrated that MRAP2 interacts with the MC2R, homodimerises and can heterodimerise with MRAP. MRAP2 enhances the cell surface expression of the MC2R in transfected cells and enables signalling of the MC2R and cAMP generation in response to ACTH. MRAP2 therefore joins MRAP in a new melanocortin accessory protein family. The interplay between these 2 small transmembrane proteins on MC2R function may provide further insight to melanocortin receptor regulation.