SAT654 Regulation Of The Melanocortin-4 Receptor (mc4r) By Attractin Like Protein 1 (alp1)

Disclosure: P. Buscaglia: None. J. Sebag: None. The Melanocortin-4 Receptor (MC4R) plays a central role in the regulation of energy homeostasis. Mutations in MC4R are responsible for up to 6% of early onset obesity in humans and deletion of MC4R in mice results in severe obesity due to hyperphagia. MC4R is a GPCR expressed in different region of the brains including the paraventricular nucleus of the hypothalamus. Stimulation of MC4R by its agonist αMSH and inhibition by its endogenous inverse agonist AGRP result in inhibition or stimulation of food intake respectively. MC4R is known to interact with two single transmembrane proteins, the Melanocortin Receptor Accessory Protein 2 (MRAP2) and Attractin Like Protein 1 (ALP1). Whereas MRAP2 has been shown to promote MC4R signaling in vitro and in vivo, the pharmacological and physiological relevance of ALP1 for MC4R signaling and actions is not known. To determine if ALP1 alters MC4R signaling, we measured αMSH-stimulated cAMP production in cells transfected with MC4R alone or with either ALP1 or MRAP2. We found that ALP1 increases MC4R signaling to a larger extent than MRAP2. We also showed that ALP1 inhibits β-arrestin recruitment to MC4R, thus likely preventing desensitization of the receptor. To assess the physiological importance of ALP1, we generated an ALP1(Flox) mouse and bred it to MC4R(CRE) mice. Deletion of ALP1 in MC4R neurons resulted in increased body weight compared to MC4R(CRE) control on standard diet. This increase in body weight was further exacerbated when animals were fed a high fat diet. In conclusion our results suggest that ALP1 regulates MC4R signaling and that deletion of ALP1 from MC4R neurons causes weight gain that may be due to decreased MC4R activity. Presentation: Saturday, June 17, 2023