Melanocortin 4 receptor

Melanocortin 4 receptor (MC4R) is a protein that in humans is encoded by the MC4R gene located on chromosome 18 (18q22). It is a part of the melanocortin receptor family and plays a critical role in regulating energy homeostasis, appetite, and body weight. Mutations in the MC4R gene are associated with some forms of obesity and are the most common genetic cause of human obesity.

Structure

The MC4R is a G protein-coupled receptor that interacts with alpha-melanocyte-stimulating hormone (α-MSH). It is primarily expressed in the central nervous system, particularly in the hypothalamus, an area of the brain involved in the regulation of feeding behavior and energy expenditure.

Function

The primary function of MC4R is to regulate energy balance. Activation of MC4R by its ligand, α-MSH, leads to a decrease in appetite and an increase in energy expenditure. Conversely, inhibition of MC4R increases food intake. This receptor is a critical downstream target of the leptin-melanocortin pathway, which is important for the regulation of body weight and metabolism.

Clinical Significance

Mutations in the MC4R gene can lead to a dysfunction in the receptor, which may result in hyperphagia (excessive eating) and obesity. Such mutations are a common cause of monogenic obesity, which is obesity resulting from mutations in a single gene. Individuals with defective MC4R may exhibit early-onset obesity, increased lean body mass, and increased bone density.

Treatment and Research

Research into MC4R has led to the development of several potential treatments for obesity that target this receptor. These include MC4R agonists, which mimic the action of α-MSH, potentially reducing appetite and promoting weight loss. Clinical trials are ongoing to evaluate the efficacy and safety of these treatments.

See Also

• Leptin
• G protein-coupled receptor
• Obesity
• Hypothalamus