The late endosome is essential for mTORC1 signaling.
The multisubunit mTORC1 complex integrates signals from growth factors and nutrients to regulate protein synthesis, cell growth, and autophagy. To examine how endocytic trafficking might be involved in nutrient regulation of mTORC1, we perturbed specific endocytic trafficking pathways and measured mTORC1 activity using S6K1 as a readout. When early/late endosomal conversion was blocked by either overexpression of constitutively active Rab5 (Rab5CA) or knockdown of the Rab7 GEF hVps39, insulin- and amino acid-stimulated mTORC1/S6K1 activation were inhibited, and mTOR localized to hybrid early/late endosomes. Inhibition of other stages of endocytic trafficking had no effect on mTORC1. Overexpression of Rheb, which activates mTOR independently of mTOR localization, rescued mTORC1 signaling in cells expressing Rab5CA, whereas hyperactivation of endogenous Rheb in TSC2-/- MEFs did not. These data suggest that integrity of late endosomes is essential for amino acid- and insulin-stimulated mTORC1 signaling and that blocking the early/late endosomal conversion prevents mTOR from interacting with Rheb in the late endosomal compartment.
Flinn
Rory J
RJ
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Yan
Ying
Y
Goswami
Sumanta
S
Parker
Peter J
PJ
Backer
Jonathan M
JM
D000818:Animals; D011992:Endosomes / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes; D009479:Neuropeptides / Q000378:metabolism*; D011506:Proteins; D000076205:Ras Homolog Enriched in Brain Protein; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000378:metabolism*; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
D046912:Multiprotein Complexes; D009479:Neuropeptides; D011506:Proteins; C490211:RHEB protein, human; D000076205:Ras Homolog Enriched in Brain Protein; C490213:Rheb protein, mouse; C000624653:TSC2 protein, human; D014157:Transcription Factors; C000624654:Tsc2 protein, mouse; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; C427755:RAB5C protein, human; D020559:Monomeric GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins