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In the molecular complexity that reigns in our body with the aim of controlling all its processes, Weight and appetite are undoubtedly one of the most complicated to keep under control.. Now, an international team of scientists has shed light about a molecular mechanism that acts as a master modulator, changing the way our brain processes hunger and satiety signals. Something that can give rise to new medications such as the famous Ozempic. The study. Published in the journal Nature, this research focuses on a key player in our metabolism: the melanocortin-4 receptor or MCR4. In this way, you can think that MCR4 is the “guardian of appetite” because it is nothing more than a protein present in our neurons that, when activated, tells us that we are satiated and that it is time to burn energy and reduce food intake. However, the operation is not as simple as the switch that turns the light on or off in our house. This is where its lesser-known, but crucial, partner comes into play: the MRAP2 accessory protein. The big change. Until now, it was known that the MRAP2 protein interacts with MC4R, but the consequences of this relationship were not fully understood. The new research reveals that MRAP2 has a drastic effect on the behavior of the appetite guardian and this is where the role it may have as a therapeutic target comes into play. What was known until now is that MC4R receptors tend to clump together on the surface of cells, forming “oligomers” or, to simplify, working in pairs or groups. Now the study shows that when MRAP2 enters the scene, it breaks these bonds and forces the MC4R receptors to act as “monomers”, that is, alone. A priori, the fact of going from being paired to acting alone may be insignificant, but the consequences it has are enormous and completely modify the recipient’s response to stimuli. Boosts the main signal. This is one of the effects caused by the MRAP2 interaction in this equation. Specifically, it has been seen that when it is in a monomeric state, MC4R becomes much more efficient in activating signaling pathways mediated by the G protein. This means that, with the same amount of stimulus (the α-MSH hormonewhich makes us feel satiated), the cell’s response is considerably stronger. Cancels stop signal. Normally, after activation, the receptors recruit a protein called β-arrestin2, which acts as a brake: it stops signaling and causes the receptor to be internalized, removing it from the cell surface to “reset” the system. Surprisingly, MRAP2 impairs this process. It hinders the recruitment of β-arrestin2, which in turn reduces the internalization of the receptor, so its ligands can bind to it in a much simpler way. The receiver on the front line. By preventing the receptor from entering the cell, MRAP2 allows MC4R to remain on the cell surface longer, ready to continue receiving signals. It’s like keeping a soldier on the front lines of battle instead of sending him to rest. In summary, MRAP2 acts as a “tuner” that modifies the MC4R receptor, biasing its function toward more potent and sustained G protein-mediated effects, while disabling its own braking system. The importance. Once this process has been understood, we move on to its importance in the clinic. The first thing that has been seen is that mutations in the MRAP2 gene are associated with cases of severe obesity in humans. This study provides for the first time the detailed molecular mechanism that explains why. Bottom line, if MRAP2 isn’t working properly, the MC4R “appetite keeper” doesn’t get that extra boost, becoming less efficient and contributing to an energy imbalance. These findings open a new avenue for drug development. Instead of looking for molecules that simply activate or deactivate MC4R, one could now think of therapies that modulate the interaction between MC4R and MRAP2. We could design treatments that mimic the effect of MRAP2 to enhance the satiety signal in people with obesity, offering a much more sophisticated approach tailored to the biology of our body. More drugs. Right now on the market we have different treatments that are focused on those people who have the most problems losing weight. We talk especially about GLP-1 agonists such as Ozempic or Mounjaro, which have given good results. But on the horizon we can see that they will not be alone and many others will arrive. Images | i yunmai Drew Hays In Xataka | Solving one of the great myths of losing weight: if “walking quickly” works by itself to lose weight