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

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 5

MRAP2 is required in the adult PVN for MC4R ciliary localization.

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MRAP2 is required in the adult PVN for MC4R ciliary localization. (A) Ex...
(A) Experimental design. Mrap2fl/fl Mc4rgfp mice were injected unilaterally with AAV encoding mCherry-IRES-Cre (n = 4, 8-week-old females) and analyzed 3 weeks following injection. (B) Representative low-magnification image of PVN, mCherry (magenta), and nuclei (Hoescht, cyan). Orange squares indicate higher-magnification images depicted in C. Scale bar: 200 μm. (C) Higher-magnification images of inserts from B (orange squares). Immunofluorescence staining of MRAP2 (white) of the control contralateral and experimental, ipsilateral PVN with mCherry (magenta), and nuclei (Hoescht, cyan). Arrows indicate MRAP2+ cilia, absent from mCherry-expressing cells. Scale bar: 50 μm. (D) Immunofluorescence staining of control, contralateral PVN, and experimental, ipsilateral PVN for, on the left, mCherry (magenta) and nuclei (Hoescht, cyan); in the center, ADCY3 (white); and, on the right, MC4R-GFP (yellow). White squares indicate regions imaged for higher-magnification images in the middle and right. ADCY3 is not altered by loss of MRAP2, while MC4R localization to neuronal primary cilia is abrogated by loss of MRAP2. Arrows indicate MC4R+ cilia. Scale bars: 20 μm. (E) Quantification of the total number of cilia (ADCY3+) and MC4R+ cilia per image in the control, contralateral PVN, and experimental, ipsilateral PVN. (F) Quantification of the percentage of MC4R+ cilia remaining in the ipsi-AAV–injected side compared with the contralateral side. Data are represented as mean ± SEM; *P < 0.05, **P < 0.01 using 2 way ANOVA with Sidak’s multiple-comparison test (E) and 2-tailed Student’s t test (F).