The structure of mTOR complexes at a glance

Mechanistic target of rapamycin (mTOR) is a Ser/Thr kinase and is structurally and functionally conserved from yeast to mammals. mTOR exists in two distinct protein complexes: mTORC1 (mTOR complex 1) and mTORC2 (mTOR complex 2). The mTORC1 and mTORC2 are master regulators for important cellular processes, including cell growth and proliferation. The dysregulation of the two complexes involves human diseases, such as tumorigenesis, diabetes and neurological disorders. The structural information of mTOR complexes has been limited by technical difficulties for two decades. However, the breakthrough of cryo-electron microscopy (cryo-EM) has made it possible to visualize the assembly and regulation of the ~1 megadalton dynamic complexes. Here we summarize the recent advances in structural studies of mTOR complexes. The structures will provide a framework to understand the past and future biochemical and functional studies, and be valuable for structure-guided drug design.