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Figure S5. The mammalian target of rapamycin (mTOR) pathway in relation to autophagy. (A) mTOR is a kinase which phosphorylates p70S6K and 4E-BP1 (Schmelzle and Hall, 2000), which are involved in translational control. Rapamycin inhibits mTOR, which leads to induction of autophagy. The effect of rapamycin can be seen by a decrease in phosphorylation of the substrates of mTOR, which are p70S6K and 4E-BP1. Decrease in p70S6K phosphorylation leads to a reduction in phosphorylation of S6 ribosomal protein (S6P) (Schmelzle and Hall, 2000). Physiologically, autophagy can be induced by starvation which inhibits mTOR activity, and this effect is relieved by nutrients. mTOR is also regulated by growth factor signalling through the phosphatidylinositol-3-kinase (PI3K) pathway. Rheb is upstream of mTOR which facilitates mTOR activity during PI3K signalling (Manning and Cantley, 2003), thereby reducing autophagy (Ravikumar et al., 2004). (B) COS-7 cells treated with or without 10 mM LiCl, 0.2 µM rapamycin (rap), or 100 µM L-690,330 for 24 h were analyzed for mTOR activity by immunofluorescence with antibody against phospho-S6P using a confocal microscope. Bar, 20 µm.