MTOR and obesity due to melanocortin 4 receptor deficiency: mTOR forms two distinct complexes, mTORC1 and mTORC2; raptor and PRAS40 are the specific subunits of mTORC1, whereas rictor, mSIN1, and Protor1/2 are the specific subunits of the mTORC2 complex.86,87 mTORC1 and mTORC2 act differently in the PI3K/AKT/mTOR signaling pathway and both are closely associated with the pathogenesis of obesity (Fig. 2).