The Mammalian Target of Rapamycin Complex 1 (mTORC1): An Ally of M. tuberculosis in Host Cells

The serine/threonine protein kinase mammalian target of rapamycin (mTOR) is a conserved member of the phosphoinositide 3-kinase (PI3K)-related kinase family. It is the key component of two distinct multi-subunit complexes called mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Besides mTOR, the catalytic subunit, the two complexes share two additional subunits: the mammalian lethal with Sec13 protein 8 (mLST8, also known as GβL), which stabilizes mTOR, and the DEP-domain-containing mTOR-interacting protein (Deptor), which inhibits mTOR. Moreover, mTORC1 is characterized by the presence of the regulatory-associated protein of mTOR (Raptor, also known as RPTOR), which is involved in mTORC1 localization and substrate recruitment, and the proline-rich AKT substrate of 40 kDa (PRAS40, also known as AKT1S1), an insulin-responsive mTORC1 inhibitor. mTORC2 contains mSIN1, Protor, and the rapamycin-insensitive companion of mTOR (Rictor), a protein that may have analogous function to Raptor. Among the most recent reviews on the structure and function of the two complexes, the reader is referred to [1]. The primary functions of mTORC1 and mTORC2 are distinct: mTORC1 controls cell growth, while mTORC2 controls cell survival and proliferation [2]. Here, we focus on mTORC1, which has been studied in the context of tuberculosis pathogenesis.