The amino acid sensitive TOR pathway from yeast to mammals

Abstract 

The target of rapamycin (TOR) is an ancient effector of cell growth that integrates signals from growth factors and nutrients. Two downstream effectors of mammalian TOR, the translational components S6K1 and 4EBP1, are commonly used as reporters of mTOR activity. The conical signaling cascade initiated by growth factors is mediated by PI3K, PKB, TSC1/2 and Rheb. However, the process through which nutrients, i.e., amino acids, activate mTOR remains largely unknown. Evidence exists for both an intracellular and/or a membrane bound sensor for amino acid mediated mTOR activation. Research in eukaryotic models, has implicated amino acid transporters as nutrient sensors. This review describes recent advances in nutrient signaling that impinge on mTOR and its targets including hVps34, class III PI3K, a transducer of nutrient availability to mTOR.

Keywords: mTOR, Amino acid transport, Leucine, hVPS34

Abbreviations: HEAT domains, Huntington, EF3, A subunit of PP2A, and TOR1 Domains, FAT, Frap, ATM, and TRAP PIKK like domains, FAT/C, FAT domain C-terminal, FRB, FKBP12-Rapamycin Binding domain, NRD, Negative Regulatory Domain