title: A cell-penetrating ester of the neural metabolite lanthionine ketimine stimulates autophagy through the mTORC1 pathway: Evidence for a mechanism of action with pharmacological implications for neurodegenerative pathologies.
abstract: Autophagy is a fundamental cellular recycling process vulnerable to compromise in neurodegeneration. We now report that a cell-penetrating neurotrophic and neuroprotective derivative of the central nervous system (CNS) metabolite, lanthionine ketimine (LK), stimulates autophagy in RG2 glioma and SH-SY5Y neuroblastoma cells at concentrations within or below pharmacological levels reported in previous mouse studies. Autophagy stimulation was evidenced by increased lipidation of microtubule-associated protein 1 light chain 3 (LC3) both in the absence and presence of bafilomycin-A1 which discriminates between effects on autophagic flux versus blockage of autophagy clearance. LKE treatment caused changes in protein level or phosphorylation state of multiple autophagy pathway proteins including mTOR; p70S6 kinase; unc-51-like-kinase-1 (ULK1); beclin-1 and LC3 in a manner essentially identical to effects observed after rapamycin treatment. The LKE site of action was near mTOR because neither LKE nor the mTOR inhibitor rapamycin affected tuberous sclerosis complex (TSC) phosphorylation status upstream from mTOR. Confocal immunofluorescence imaging revealed that LKE specifically decreased mTOR (but not TSC2) colocalization with LAMP2(+) lysosomes in RG2 cells, a necessary event for mTORC1-mediated autophagy suppression, whereas rapamycin had no effect. Suppression of the LK-binding adaptor protein CRMP2 (collapsin response mediator protein-2) by means of shRNA resulted in diminished autophagy flux, suggesting that the LKE action on mTOR localization may occur through a novel mechanism involving CRMP2-mediated intracellular trafficking. These findings clarify the mechanism-of-action for LKE in preclinical models of CNS disease, while suggesting possible roles for natural lanthionine metabolites in regulating CNS autophagy.
authors.affiliation: Veterans Administration-Greater Los Angeles Healthcare System, Los Angeles, USA; David Geffen School of Medicine at the University of California, Los Angeles, USA.
authors.forename: Marni E
authors.initials: ME
authors.lastname: Harris-White
authors.affiliation: Veterans Administration-Greater Los Angeles Healthcare System, Los Angeles, USA; Pepperdine University, Seaver College, Natural Sciences Division, Malibu, CA, USA.
authors.forename: Kathie G
authors.initials: KG
authors.lastname: Ferbas
authors.affiliation: Veterans Administration-Greater Los Angeles Healthcare System, Los Angeles, USA.
authors.forename: Ming F
authors.initials: MF
authors.lastname: Johnson
authors.affiliation: Veterans Administration-Greater Los Angeles Healthcare System, Los Angeles, USA.
authors.forename: Pirooz
authors.initials: P
authors.lastname: Eslami
authors.affiliation: Veterans Administration-Greater Los Angeles Healthcare System, Los Angeles, USA.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Poteshkina
authors.affiliation: Department of Pathology, University of Toledo Medical Center, Toledo, OH 43614, USA.
authors.forename: Kalina
authors.initials: K
authors.lastname: Venkova
authors.affiliation: Department of Pathology, University of Toledo Medical Center, Toledo, OH 43614, USA.
authors.forename: Alexandar
authors.initials: A
authors.lastname: Christov
authors.affiliation: Department of Pathology, University of Toledo Medical Center, Toledo, OH 43614, USA; Department of Neurosciences, University of Toledo Medical Center, Toledo, OH 43614, USA. Electronic address: Kenneth.hensley@utoledo.edu.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hensley
mesh_terms: D000603:Amino Acids, Sulfur / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D000603:Amino Acids, Sulfur; D007166:Immunosuppressive Agents; D036341:Intercellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; C000624653:TSC2 protein, human; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C095114:collapsin response mediator protein-2; C035499:lanthionine ketimine; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
keywords: Autophagy; CRMP2; DPYSL2; Lanthionine ketimine; mTOR complex (mTORC)