Figure 1.

Amino acid sensing and integration of downstream pathways. Schematic representation of the cellular events during amino acid-deficient and amino acid sufficient conditions. General control nonderepressible-2 kinase senses amino acid insufficiency and orchestrate various homeostatic processes via eIF2 phosphorylation followed by downregulation of global protein synthesis and simultaneously also inhibits mammalian target of rapamycin (mTOR) activation. On the other hand, under the condition of amino acid sufficiency, mTORC1 complex translocates to lysosomal surfaces by virtue of Rag GTPase activation and further initiates protein translation by the release of translation initiation factor eIF4E.