TFEBulous control of traffic by mTOR.

EMBO J 30 16, 3242–3258 (2011); published online July 29 2011 Cell growth is accompanied by the synthesis of macromolecules and biogenesis of organelles. The protein kinase mTOR (mechanistic or mammalian target of rapamycin) controls these processes by sensing availability of growth signals. The targeting of macromolecules and trafficking of cargo-containing vesicles into appropriate cellular compartments are also important processes that are highly controlled during growth versus stress conditions. In this issue of , Peña-Llopis demonstrate that mTOR complex 1 (mTORC1) could regulate endocytosis by controlling the expression of endosomal proteins such as the vacuolar (V)-ATPases. mTORC1 performs this novel function by modulating the phosphorylation and activity of the transcription factor EB (TFEB), which is required for expression of genes involved in autophagosome and lysosome biogenesis. This study, along with a related study in by Settembre , reveals how growth signals mediated by mTOR and other protein kinases such as mitogen-activated protein kinase (MAPK) can converge on TFEB to direct endosome biogenesis and trafficking.