title: Neuronal Tsc1/2 complex controls autophagy through AMPK-dependent regulation of ULK1.
abstract: Tuberous sclerosis complex (TSC) is a disorder arising from mutation in the TSC1 or TSC2 gene, characterized by the development of hamartomas in various organs and neurological manifestations including epilepsy, intellectual disability and autism. TSC1/2 protein complex negatively regulates the mammalian target of rapamycin complex 1 (mTORC1) a master regulator of protein synthesis, cell growth and autophagy. Autophagy is a cellular quality-control process that sequesters cytosolic material in double membrane vesicles called autophagosomes and degrades it in autolysosomes. Previous studies in dividing cells have shown that mTORC1 blocks autophagy through inhibition of Unc-51-like-kinase1/2 (ULK1/2). Despite the fact that autophagy plays critical roles in neuronal homeostasis, little is known on the regulation of autophagy in neurons. Here we show that unlike in non-neuronal cells, Tsc2-deficient neurons have increased autolysosome accumulation and autophagic flux despite mTORC1-dependent inhibition of ULK1. Our data demonstrate that loss of Tsc2 results in autophagic activity via AMPK-dependent activation of ULK1. Thus, in Tsc2-knockdown neurons AMPK activation is the dominant regulator of autophagy. Notably, increased AMPK activity and autophagy activation are also found in the brains of Tsc1-conditional mouse models and in cortical tubers resected from TSC patients. Together, our findings indicate that neuronal Tsc1/2 complex activity is required for the coordinated regulation of autophagy by AMPK. By uncovering the autophagy dysfunction associated with Tsc2 loss in neurons, our work sheds light on a previously uncharacterized cellular mechanism that contributes to altered neuronal homeostasis in TSC disease.
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Alessia
authors.initials: A
authors.lastname: Di Nardo
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Mary H
authors.initials: MH
authors.lastname: Wertz
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Erica
authors.initials: E
authors.lastname: Kwiatkowski
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Tsai
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Jarrett D
authors.initials: JD
authors.lastname: Leech
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Greene-Colozzi
authors.affiliation: Division of Translational Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: June
authors.initials: J
authors.lastname: Goto
authors.affiliation: Department of Neurology, New York University School of Medicine, New York, NY 10016, USA and.
authors.forename: Pelin
authors.initials: P
authors.lastname: Dilsiz
authors.affiliation: Department of Neurology, New York University School of Medicine, New York, NY 10016, USA and.
authors.forename: Delia M
authors.initials: DM
authors.lastname: Talos
authors.affiliation: Broad Institute of Massachusetts Institute of Technology and Harvard University, Cambridge, MA 02142, USA.
authors.forename: Clary B
authors.initials: CB
authors.lastname: Clish
authors.affiliation: Division of Translational Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kwiatkowski
authors.affiliation: The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA, mustafa.sahin@childrens.harvard.edu.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Sahin
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D001343:Autophagy; D000071189:Autophagy-Related Protein-1 Homolog; D002478:Cells, Cultured; D004195:Disease Models, Animal; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014402:Tuberous Sclerosis / Q000378:metabolism*; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; C000624651:Tsc1 protein, mouse; C000624652:Tsc1 protein, rat; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D000071189:Autophagy-Related Protein-1 Homolog; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; C484754:ULK1 protein, human; D055372:AMP-Activated Protein Kinases