Determination of the Interaction and Pharmacological Modulation of MCHR1 Signaling by the C-Terminus of MRAP2 Protein

Jing Xu,Xiao-Mei Yang,Shan Bian,Xiaowei Lei,Chao Zhang,Yue Zhai,Bopei Jiang,Tao Zan,Li-Na Jin,Meng Wang,Zhe Kuang,Cong Zhang,Shangyun Liu,Qingfeng Li

doi:10.3389/fendo.2022.848728

Abstract

Melanin concentrating hormone (MCH), an orexigenic neuropeptide, is primarily secreted by the hypothalamus and acts on its receptor, the melanin-concentrating hormone receptor 1 (MCHR1), to regulate appetite and energy homeostasis. The Melanocortin Receptor Accessory Protein 2 (MRAP2), a small single transmembrane protein broadly expressed in multiple tissues, has been defined as a vital endocrine modulator of five melanocortin receptors (MC1R–MC5R) and several other GPCRs in the regulation of central neuronal activities and peripheral energy balance. Here, we demonstrated the interaction between MRAP2 and MCHR1 by immunoprecipitation and bimolecular fluorescent assay and found that MRAP2 could inhibit MCHR1 signaling in vitro. A series of functional truncations of different regions further identified that the C-terminal domains of MRAP2 protein were required for the pharmacological modulation of intracellular Ca2+ coupled cascades and membrane transport. These findings elucidated the broad regulatory profile of MRAP2 protein in the central nervous system and may provide implications for the modulation of central MCHR1 function in vivo.

Highlights

Hypothalamus functions as one of the most important neuronal cores for the integration of a variety of physiological signals from the periphery to modulate secretion of multiple peptidic pituitary hormones involved in maintaining energy homeostasis and proper feeding behavior
We found that MCHR1 and melanocortin receptor accessory protein 2 (MRAP2) co-expressed in most of neuronal cells in the central nervous system (Figure 1C)
We further proved that MRAP2 functioned as a wide modulator of GPCRs and more receptors would be identified as MRAP2 partners in the near future

Summary

Introduction

Hypothalamus functions as one of the most important neuronal cores for the integration of a variety of physiological signals from the periphery to modulate secretion of multiple peptidic pituitary hormones involved in maintaining energy homeostasis and proper feeding behavior. It has been shown that MRAP2 potentiates melanocortin-4 receptor (MC4R) signaling in several species [6, 8, 9] and plays a key role in GPCR signaling to regulate the dynamic neuronal appetite and food intake. Both MRAP2- and MC4Rdeficient backgrounds develop severe obesity syndrome in human and murine models [6, 8, 10, 11]. Given that MRAP2 regulates the activity of several other metabolicrelated GPCRs besides MC4R, such as PKRs [12], OX1R [13], and GHSR1a [14], and the regulatory regions for these GPCRs are specific [13, 15], we speculate that the absence of hyperphagia in MRAP2 knockout mice could arise from the coordinated modulation of the MRAP2 protein on multiple endogenous metabolic-related GPCR signaling pathways

Methods

Results

Conclusion