PerspectiveCell Biology

Growth Signaling from Inside

Science  04 Nov 2011:
Vol. 334, Issue 6056, pp. 611-612
DOI: 10.1126/science.1214355

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Summary

All cells have the ability to sense whether nutrients are scarce or abundant so that appropriate anabolic or catabolic programs can be initiated. A key sensor of nutrient status in eukaryotes is target of rapamycin (TOR) (1), an enzyme that phosphorylates a subset of proteins that function in cell growth and metabolism (2). In mammalian cells, TOR associates with accessory proteins to form mammalian TOR complex 1 (mTORC1) (3). Amino acids are potent activators of mTORC1 (4, 5), but it has not been clear how mTORC1 senses amino acids within the cell. On page 678 of this issue, Zoncu et al. (6) describe how sensing amino acids occurs inside the lumen of lysosomes, the main degradative organelles in the cell.