title: Identification of an AMPK phosphorylation site in Drosophila TSC2 (gigas) that regulate cell growth.
abstract: AMP-activated protein kinase (AMPK) is an important metabolic regulator that mediates cellular adaptation to diverse stresses. One of the AMPK substrates, tuberous sclerosis complex 2 (TSC2), was suggested to mediate AMPK-induced silencing of mTOR complex 1 (mTORC1) signaling that is critical for cell growth. However, it is not known whether the AMPK-dependent TSC2 phosphorylation, originally observed in mammalian cells, is conserved in invertebrates. Here we show that energy depletion inhibits mTORC1 signaling through the AMPK-TSC2 axis in Drosophila S2 cells. We have discovered an AMPK phosphorylation site in TSC2-like genes from many different invertebrate species including Drosophila. The site (Ser1338 in Drosophila TSC2) is specifically and efficiently phosphorylated by AMPK in vitro. To evaluate the functional role of this phosphorylation site in vivo, we generated transgenic flies that can express identical amount of either wild-type or phosphorylation-resistant mutant Drosophila TSC2 in a tissue-specific manner. In response to transgenic Sestrin induction, which causes ectopic AMPK activation and subsequent mTORC1 inhibition, wild-type Drosophila TSC2 synergistically reduced tissue growth in the dorsal epithelium of Drosophila wings. However, phosphorylation-resistant mutant Drosophila TSC2 was unable to show such a growth-inhibiting effect, suggesting that this phosphorylation is important for AMPK-dependent regulation of cell growth.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA. myungjin@umich.edu.
authors.forename: Myungjin
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA. leeju@umich.edu.
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Lee
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000378:metabolism; D009928:Organ Specificity; D010766:Phosphorylation; D016415:Sequence Alignment; D012694:Serine / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014921:Wings, Animal / Q000196:embryology / Q000254:growth & development
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D046912:Multiprotein Complexes; C117726:gig protein, Drosophila; D012694:Serine; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases
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