GHRL and obesity due to melanocortin 4 receptor deficiency: Recent evidence also indicates that melanocortin 2 receptor accessory protein 2 (MRAP2) modulates the ghrelin receptor GHSR1a by suppressing its constitutive activity, enhancing its G protein-dependent signaling, and preventing β-arrestin recruitment and signaling in response to ghrelin [36,38], suggesting potential therapeutic implications for obesity.