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Mammalian target of rapamycin complex 1 (mTORC1) monitors cellular amino acid changes for function, but the molecular mediators of this process remain to be fully defined. Here, we report that depletion of cellular amino acids, either alone or in combination, leads to the ubiquitination of mTOR, which inhibits mTORC1 kinase activity by preventing substrate recruitment. Mechanistically, amino acid depletion causes accumulation of uncharged tRNAs, thereby stimulating GCN2 to phosphorylate FBXO22, which in turn accrues in the cytoplasm and ubiquitinates mTOR at Lys2066 in a K27-linked manner. Accordingly, mutation of mTOR Lys2066 abolished mTOR ubiquitination in response to amino acid depletion, rendering mTOR insensitive to amino acid starvation both in vitro and in vivo. Collectively, these data reveal a novel mechanism of amino acid sensing by mTORC1 via a previously unknown GCN2-FBXO22-mTOR pathway that is uniquely controlled by uncharged tRNAs. [Display omitted] • Amino acid depletion leads to mTOR ubiquitination through the tRNA-GCN2-FBXO22 axis • GCN2 phosphorylates FBXO22 at T127 to cause cytoplasmic retention of FBXO22 • FBXO22-mediated mTOR ubiquitination at K2066 prevents mTORC1 substrate recruitment • mTOR ubiquitination regulates amino acid sensing by mTORC1 in vitro and in vivo Ge et al. unravel a novel mechanism of amino acid sensing by mTORC1, in which amino acid depletion-caused accumulation of uncharged tRNAs stimulates GCN2 to phosphorylate FBXO22, which in turn accrues in the cytoplasm and ubiquitinates mTOR at K2066 to inhibit mTORC1 kinase activity by preventing substrate recruitment. [ABSTRACT FROM AUTHOR]

The biofilm formation of Pseudomonas aeruginosa (P. aeruginosa) is regulated by a phenomenon of quorum sensing (QS). With 5-hydroxyl-3,4-halogenated-5 H -furan-2-ones as beginning, analogs bearing alkyl chains, vinyl bromide, or aromatic rings were designed and synthesized. The minimum inhibitory concentration (MIC) of the compounds against P. aeruginosa was assayed and the biofilm inhibition ratio was determined at different concentrations lower than the MIC. C-5 aromatic substituted furanones showed remarkable biofilm formation as well as inhibition of virulence factor production in P. aeruginosa. Fluorescence report analysis identified the QS regulatory mechanism of the most active compound 29. This study provides us a novel candidate for combating drug resistant bacteria strains by merely inhibiting biofilm formation. Without suppressing the regular life cycle of the bacteria, bacterial resistance mechanisms may not be activated. Unlabelled Image [ABSTRACT FROM AUTHOR]