As hypothesized, this mouse became obese. Finally, Barsh produced recombinant Agrp protein that was then tested by Gantz and his team at U-M on the cloned human melanocortin receptors expressed in cell lines. It was found to be a very potent inhibitor of hormone action at the melanocortin-4 receptor. Agrp occurs in all humans, but it is not known if levels vary. The melanocortin-4 receptor is one of five cell surface receptors for the melanocortin hormones.
Cells use hormones to communicate with each other.
Within the hypothalamus, these hormones cause a feeling of satiety by stimulating the melanocortin-4 receptor. It is believed that this new protein, Agrp , can block the action of these hormones at the melanocortin-4 receptor, thus preventing the individual from feeling full. Gantz says researchers now must determine what stimulates the release of Agrp and if Agrp circulates in the bloodstream or just acts locally in the brain.