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Regulation of TORC1 in response to amino acid starvation via lysosomal recruitment of TSC2.

ABSTRACT: TOR complex 1 (TORC1) is a potent anabolic regulator of cellular growth and metabolism. When cells have sufficient amino acids, TORC1 is active due to its lysosomal localization mediated via the Rag GTPases. Upon amino acid removal, the Rag GTPases release TORC1, causing it to become cytoplasmic and inactive. We show here that, upon amino acid removal, the Rag GTPases also recruit TSC2 to the lysosome, where it can act on Rheb. Only when both the Rag GTPases and Rheb are inactive is TORC1 fully released from the lysosome. Upon amino acid withdrawal, cells lacking TSC2 fail to completely release TORC1 from the lysosome, fail to completely inactivate TORC1, and fail to adjust physiologically to amino acid starvation. These data suggest that regulation of TSC2 subcellular localization may be a general mechanism to control its activity and place TSC2 in the amino-acid-sensing pathway to TORC1.

SUBMITTER: Demetriades C

PROVIDER: S-EPMC4346203 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Regulation of TORC1 in response to amino acid starvation via lysosomal recruitment of TSC2.

Demetriades Constantinos C Doumpas Nikolaos N Teleman Aurelio A AA

Cell 20140201 4

TOR complex 1 (TORC1) is a potent anabolic regulator of cellular growth and metabolism. When cells have sufficient amino acids, TORC1 is active due to its lysosomal localization mediated via the Rag GTPases. Upon amino acid removal, the Rag GTPases release TORC1, causing it to become cytoplasmic and inactive. We show here that, upon amino acid removal, the Rag GTPases also recruit TSC2 to the lysosome, where it can act on Rheb. Only when both the Rag GTPases and Rheb are inactive is TORC1 fully ...[more]

PMID: 24529380

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Project description:Streptococcus pyogenes (group A streptococcus [GAS]), a multiple-amino-acid-auxotrophic human pathogen, may face starvation for essential amino acids during various stages of the infection process. Since the response of GAS to such conditions is likely to influence pathogenetic processes, we set out to identify by transcriptional analyses genes and operons that are responsive to amino acid starvation and examined whether functionally meaningful response patterns can be ascertained. We discovered that GAS are capable of mounting a relA-independent amino acid starvation response that involves transcriptional modulation of a wide array of housekeeping genes as well as accessory and dedicated virulence genes. Housekeeping genes that were upregulated during starvation of both wild-type and relA mutant strains included the newly identified T-box members of the aminoacyl-tRNA synthetase genes, the genes for components of the tmRNA-mediated peptide tagging and proteolysis system for abnormal proteins (ssrA, smpB, clpP, and clpC), and the operons for the dnaK and groE groups of molecular chaperones. In addition to upregulation of the genes for oligopeptide permease (opp), intracellular peptidase (pepB), and the two-component regulator covRS reported previously (K. Steiner and H. Malke, Mol. Microbiol. 38:1004-1016, 2000), amino acid starvation stimulated the transcription of the growth phase-associated, virulence-regulatory fas operon, the streptolysin S operon (sag), and the gene for autoinducer-2 production protein (luxS). A prominent feature of operons exhibiting internal transcriptional termination (opp, fas, and sag) was starvation-promoted full-length transcription, a mechanism that improves the efficacy of these systems by increasing the level of coordinate transcription of functionally related genes. Based on these results, a regulatory network with feedback mechanisms is proposed that counteracts the stringent response, links the levels of key rate-limiting enzymes to virulence gene expression, and enables the organism in a dynamic way to take advantage of protein-rich environments provided by its human host. As several of the affected target genes are controlled by more than one regulator, fine modulation may result in accordance with the demands imposed by ecologically different colonization sites upon the adaptive capacity of the pathogen.

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Regulation of TORC1 in response to amino acid starvation via lysosomal recruitment of TSC2.

Publications

Regulation of TORC1 in response to amino acid starvation via lysosomal recruitment of TSC2.

Similar Datasets

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