title: Growth factor signaling to mTORC1 by amino acid-laden macropinosomes.
abstract: The rapid activation of the mechanistic target of rapamycin complex-1 (mTORC1) by growth factors is increased by extracellular amino acids through yet-undefined mechanisms of amino acid transfer into endolysosomes. Because the endocytic process of macropinocytosis concentrates extracellular solutes into endolysosomes and is increased in cells stimulated by growth factors or tumor-promoting phorbol esters, we analyzed its role in amino acid-dependent activation of mTORC1. Here, we show that growth factor-dependent activation of mTORC1 by amino acids, but not glucose, requires macropinocytosis. In murine bone marrow-derived macrophages and murine embryonic fibroblasts stimulated with their cognate growth factors or with phorbol myristate acetate, activation of mTORC1 required an Akt-independent vesicular pathway of amino acid delivery into endolysosomes, mediated by the actin cytoskeleton. Macropinocytosis delivered small, fluorescent fluid-phase solutes into endolysosomes sufficiently fast to explain growth factor-mediated signaling by amino acids. Therefore, the amino acid-laden macropinosome is an essential and discrete unit of growth factor receptor signaling to mTORC1.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Sei
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Regina
authors.initials: R
authors.lastname: Pacitto
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109 Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109.
authors.forename: Yao
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109 Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109.
authors.forename: Ken
authors.initials: K
authors.lastname: Inoki
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109 jswan@umich.edu.
authors.forename: Joel A
authors.initials: JA
authors.lastname: Swanson
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes / Q000502:physiology*; D010873:Pinocytosis; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000502:physiology*
chemical_list: D000596:Amino Acids; D046912:Multiprotein Complexes; D010982:Platelet-Derived Growth Factor; D016173:Macrophage Colony-Stimulating Factor; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases