title: Phosphorylation of eIF2α triggered by mTORC1 inhibition and PP6C activation is required for autophagy and is aberrant in PP6C-mutated melanoma.
abstract: Amino acid deprivation promotes the inhibition of the kinase complex mTORC1 (mammalian target of rapamycin complex 1) and activation of the kinase GCN2 (general control nonrepressed 2). Signaling pathways downstream of both kinases have been thought to independently induce autophagy. We showed that these two amino acid-sensing systems are linked. We showed that pharmacological inhibition of mTORC1 led to activation of GCN2 and phosphorylation of the eukaryotic initiation factor 2α (eIF2α) in a mechanism dependent on the catalytic subunit of protein phosphatase 6 (PP6C). Autophagy induced by pharmacological inhibition of mTORC1 required PP6C, GCN2, and eIF2α phosphorylation. Although some of the PP6C mutants found in melanoma did not form a strong complex with PP6 regulatory subunits and were rapidly degraded, these mutants paradoxically stabilized PP6C encoded by the wild-type allele and increased eIF2α phosphorylation. Furthermore, these PP6C mutations were associated with increased autophagy in vitro and in human melanoma samples. Thus, these data showed that GCN2 activation and phosphorylation of eIF2α in response to mTORC1 inhibition are necessary for autophagy. Additionally, we described a role for PP6C in this process and provided a mechanism for PP6C mutations associated with melanoma.
authors.affiliation: Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Jordan
authors.initials: J
authors.lastname: Wengrod
authors.affiliation: Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Ding
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Weiss
authors.affiliation: Department of Population Health, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhong
authors.affiliation: Department of Dermatology, New York University School of Medicine, New York, NY 10016, USA. NYU Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Iman
authors.initials: I
authors.lastname: Osman
authors.affiliation: Department of Medicine, New York University School of Medicine, New York, NY 10016, USA. NYU Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016, USA. Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA. Lawrence.gardner@nyumc.org.
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Gardner
mesh_terms: D000596:Amino Acids / Q000172:deficiency; D001343:Autophagy / Q000502:physiology*; D045744:Cell Line, Tumor; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D000076222:Mechanistic Target of Rapamycin Complex 1; D008545:Melanoma / Q000235:genetics* / Q000503:physiopathology*; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors*; D009154:Mutation / Q000235:genetics; D010749:Phosphoprotein Phosphatases / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D046912:Multiprotein Complexes; D014415:Tunicamycin; C529271:EIF2AK4 protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; C106079:protein phosphatase 6; D020123:Sirolimus