Fig. 4.

The TOR signaling pathways regulates autophagy in mammalian cells and yeast. In mammals, AMPK can be activated by its upstream factors LKB1, TAK1, and CaMKKβ (Yang and Klionsky, 2010). In yeast, Snf1 can be activated by its upstream factors Elm1, Sak1, and Tos3 (Hedbacker and Carlson, 2008). In yeast, the mammalian TSC1 and TSC2 homologs LCB2 and LCB1 (Gable et al., 2000) might form a complex that potentially inhibits TORC1, although this has not been experimentally demonstrated. A putative Akt homolog upstream of LCB2 and LCB1 also needs to be identified in yeast. Green arrows indicate interactions that induce autophagy, red bars indicate inhibition. See the text for details.