Rapamycin (also known as sirolimus) is a potent macrolide compound that functions as an mTOR inhibitor, widely used in cell signaling and autophagy research. It forms a complex with FKBP12, which inhibits the mechanistic target of rapamycin (mTOR), leading to reduced protein synthesis and cell growth. In molecular biology, rapamycin is also used in inducible dimerization systems to control gene expression or protein localization.