Hypothalamic C2-domain protein involved in MC4R trafficking and control of energy balance
C2CD5 is involved in the regulation of MC4R trafficking and energy balance in mice, but the relevance to human obesity treatment is unclear.
Where it sits
this study against the rest of the melanotan 1 corpusSummary and findings
This study investigates the role of C2CD5 in the regulation of MC4R trafficking and energy balance in mice. The research involved wild type and C2CD5 knockout mice fed different diets, assessing body weight, energy expenditure, and feeding behavior following Melanotan (MTII) injection. Findings suggest that C2CD5 is involved in MC4R endocytosis and may impact body weight regulation.
Abstract
<h4>ABSTRACT</h4> <h4>Objective</h4> Rates of overweight and obesity epidemic have risen significantly in the past few decades, and 34% of adults and 15-20% of children and adolescents in the United States are now obese. Melanocortin receptor 4 (MC4R), contributes to appetite control in hypothalamic neurons and is a target for future anti-obesity treatments (such as setmelanotide) or novel drug development effort. Proper MC4R trafficking regulation in hypothalamic neurons is crucial for normal neural control of homeostasis and is altered in obesity and in presence of lipids. The mechanisms underlying altered MC4R trafficking in the context of obesity is still unclear. Here, we discovered that C2CD5 expressed in the hypothalamus is involved in the regulation of MC4R endocytosis. This study unmasked a novel trafficking protein nutritionally regulated in the hypothalamus providing a novel target for MC4R dependent pathways involved in bodyweight homeostasis and Obesity. <h4>Methods</h4> To evaluate the expression of C2cd5, we first used in situ hybridization and RNAscope technology in combination with electronic microscopy. For in vivo , we characterized the energy balance of wild type (WT) and C2CD5 whole-body knockout (C2CD5KO) mice fed normal chow (NC) and/or western-diet (high-fat/high-sucrose/cholesterol) (WD). To this end, we performed comprehensive longitudinal assessment of bodyweight, energy balance (food intake, energy expenditure, locomotor activity using TSE metabolic cages), and glucose homeostasis. In addition, we evaluated the consequence of loss of C2CD5 on feeding behavior changes normally induced by MC4R agonist (Melanotan, MTII) injection in the paraventricular hypothalamus (PVH). For in vitro approach, we tease out the role of C2CD5 and its calcium sensing domain C2 in MC4R trafficking. We focused on endocytosis of MC4R using an antibody feeding experiment (in a neuronal cell line - Neuro2A (N2A) stably expressing HA-MC4R-GFP; against HA-tag and analyzed by flux cytometry). <h4>Results</h4> We found that 1) the expression of hypothalamic C2CD5 is decreased in diet-induced obesity models compared to controls, 2) mice lacking C2CD5 exhibit an increase in food intake compared to WT mice, 3) C2CD5 interacts with endocytosis machinery in hypothalamus, 4) loss of functional C2CD5 (lacking C2 domain) blunts MC4R endocytosis in vitro and increases MC4R at the surface that fails to respond to MC4R ligand, and, 5) C2CD5KO mice exhibit decreased acute responses to MTII injection into the PVH. <h4>Conclusions</h4> Based on these, we conclude that hypothalamic C2CD5 is involved in MC4R endocytosis and regulate bodyweight homeostasis. These studies suggest that C2CD5 represents a new protein regulated by metabolic cues and involved in metabolic receptor endocytosis. C2CD5 represent a new target and pathway that could be targeted in Obesity.
Background
The paper addresses the biological question of how the trafficking of the melanocortin-4 receptor (MC4R) is regulated and its implications for energy balance. Previous studies have indicated that MC4R plays a critical role in energy homeostasis, but the specific mechanisms of its trafficking have not been fully elucidated. Understanding these mechanisms could provide insights into metabolic disorders, making this study relevant.
Methods
The study employs a rodent model to investigate the role of a hypothalamic C2-domain protein in MC4R trafficking. The sample size and specific dosing regimen are not reported in the abstract. Primary outcome measures focus on the trafficking dynamics of MC4R, while secondary measures may include assessments of energy balance.
Results
Not reported in abstract.
Interpretation
Without specific results reported, it is challenging to compare this study's findings to existing literature. The absence of numeric data limits the ability to assess the clinical significance of any observed effects. Potential confounds include the use of a rodent model, which may not fully translate to human physiology, and the lack of detailed methodology.
Key findings
- Not reported in abstract.
Limitations
- Not reported in abstract.