Location Matters

Sci. Signal.  17 Jun 2008:
Vol. 1, Issue 24, pp. ec225
DOI: 10.1126/scisignal.124ec225

The signaling pathway through which cells modulate protein synthesis and cell growth in response to amino acids has been tricky to unravel. Sancak et al. add a key piece to the puzzle with experiments that reveal a role for a group of small guanosine triphosphatases (GTPases) known as Rag proteins. RagC associates with the mTORC1 protein kinase complex, a key regulator of cell growth. This interaction of Rag proteins with mTORC1 appears to be necessary and sufficient to convey nutrient availability signals when cells are exposed to amino acids. The physical interaction of Rag proteins with mTORC1 appears not to regulate activity of mTOR but to influence its localization within the endomembrane system of the cell.

Y. Sancak, T. R. Peterson, Y. D. Shaul, R. A. Lindquist, C. C. Thoreen, L. Bar-Peled, D. M. Sabatini, The Rag GTPases bind raptor and mediate amino acid signaling to mTORC1. Science 320, 1496-1501 (2008). [Abstract] [Full Text]