Figure 1. The regulation of mammalian target of rapamycin (mTOR) by the LKB1/AMPK signaling pathway.

Environmental stress leads to the activation of AMP-activated protein kinase (AMPK) by liver kinase B1 (LKB1), which subsequently activates hamartin (TSC1)/tuberin (TSC2) complex. The activation of this pathway down-regulates mTOR activity, which leads to cell growth arrest. mTOR activity can also be regulated by growth factors through the PI3K/PTEN/AKT pathway.