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MRAP2 regulates energy homeostasis by promoting primary cilia localization of MC4R
Adelaide Bernard, … , Jeremy F. Reiter, Christian Vaisse
Adelaide Bernard, … , Jeremy F. Reiter, Christian Vaisse
Published January 24, 2023
Citation Information: JCI Insight. 2023;8(2):e155900. https://doi.org/10.1172/jci.insight.155900.
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Research Article Endocrinology Metabolism

MRAP2 regulates energy homeostasis by promoting primary cilia localization of MC4R

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Abstract

The G protein–coupled receptor melanocortin-4 receptor (MC4R) and its associated protein melanocortin receptor–associated protein 2 (MRAP2) are essential for the regulation of food intake and body weight in humans. MC4R localizes and functions at the neuronal primary cilium, a microtubule-based organelle that senses and relays extracellular signals. Here, we demonstrate that MRAP2 is critical for the weight-regulating function of MC4R neurons and the ciliary localization of MC4R. More generally, our study also reveals that GPCR localization to primary cilia can require specific accessory proteins that may not be present in heterologous cell culture systems. Our findings further demonstrate that targeting of MC4R to neuronal primary cilia is essential for the control of long-term energy homeostasis and suggest that genetic disruption of MC4R ciliary localization may frequently underlie inherited forms of obesity.

Authors

Adelaide Bernard, Irene Ojeda Naharros, Xinyu Yue, Francois Mifsud, Abbey Blake, Florence Bourgain-Guglielmetti, Jordi Ciprin, Sumei Zhang, Erin McDaid, Kellan Kim, Maxence V. Nachury, Jeremy F. Reiter, Christian Vaisse

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Figure 2

MRAP2 localizes MC4R to the IMCD3 primary cilium.

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MRAP2 localizes MC4R to the IMCD3 primary cilium.
(A) Representative wid...
(A) Representative widefield micrographs of IMCD3 cells transiently transfected with GFP-tagged melanocortin receptors alone (left), or cotransfected with MRAP1-FLAG (center) or MRAP2-FLAG (right). Cells are stained for cilia (AcTub, magenta), GFP-tagged melanocortin receptors (yellow), MRAP1- or MRAP2-FLAG (white), and nuclei (Hoechst 33342, cyan). MC4R-GFP and MRAP2-FLAG colocalize at the primary cilium (top panel). Scale bars: 5 μm (low-magnification images) and 2 μm (inserts). (B) Melanocortin receptor enrichment at the cilium when transfected without MRAP (blue), with MRAP1 (purple), or with MRAP2 (magenta). MRAP2 expression increases ciliary localization of MC2R, MC3R, MC4R, and MC5R but not MC1R. MRAP1 coexpression has no effect on ciliary localization. n = 20–40 ciliated cells per condition were imaged and analyzed. Ciliary and cell body intensity of melanocortin receptors and MRAPs was measured using Fiji. Enrichment at the cilium is expressed as: (integrated density at the cilium)/(integrated density in the cell body). Enrichment > 1 indicates higher localization of GFP-tagged melanocortin receptor or MRAP at the primary cilium than at the cell body. Data are from 3 different replicates and are represented as a superplot, with their mean and SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 using ordinary 2-way ANOVA, with Tukey’s multiple-comparison test performed on replicate averages.

Copyright © 2023 American Society for Clinical Investigation
ISSN 2379-3708

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