mTOR (mechanistic target of rapamycin) is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases.mTOR functions as a serine/threonine protein kinase that regulates cell growth, cell proliferation, cell motility, cell survival, protein synthesis, autophagy, and transcription.mTOR integrates the input from upstream pathways, including insulin, growth factors (such as IGF-1 and IGF-2), and amino acids. mTOR also senses cellular nutrient, oxygen, and energy levels. The mTOR pathway is a central regulator of mammalian metabolism and physiology, with important roles in the function of tissues including liver, muscle, white and brown adipose tissue, and the brain, and is dysregulated in human diseases, such as diabetes, obesity, depression, and certain cancers. MTOR is the catalytic subunit of two structurally distinct complexes: mTORC1 and mTORC2. Both complexes localize to different subcellular compartments, thus affecting their activation and function. As a core component of mTORC2, mTOR also functions as a tyrosine protein kinase that promotes the activation of insulin receptors and insulin-like growth factor 1 receptors. mTORC2 has also been implicated in the control and maintenance of the actin cytoskeleton.