title: Disruption of the autophagy-lysosome pathway is involved in neuropathology of the nclf mouse model of neuronal ceroid lipofuscinosis.
abstract: Variant late-infantile neuronal ceroid lipofuscinosis, a fatal lysosomal storage disorder accompanied by regional atrophy and pronounced neuron loss in the brain, is caused by mutations in the CLN6 gene. CLN6 is a non-glycosylated endoplasmic reticulum (ER)-resident membrane protein of unknown function. To investigate mechanisms contributing to neurodegeneration in CLN6 disease we examined the nclf mouse, a naturally occurring model of the human CLN6 disease. Prominent autofluorescent and electron-dense lysosomal storage material was found in cerebellar Purkinje cells, thalamus, hippocampus, olfactory bulb and in cortical layer II to V. Another prominent early feature of nclf pathogenesis was the localized astrocytosis that was evident in many brain regions and the more widespread microgliosis. Expression analysis of mutant Cln6 found in nclf mice demonstrated synthesis of a truncated protein with a reduced half-life. Whereas the rapid degradation of the mutant Cln6 protein can be inhibited by proteasomal inhibitors, there was no evidence for ER stress or activation of the unfolded protein response in various brain areas during postnatal development. Age-dependent increases in LC3-II, ubiquitinated proteins, and neuronal p62-positive aggregates were observed, indicating a disruption of the autophagy-lysosome degradation pathway of proteins in brains of nclf mice, most likely due to defective fusion between autophagosomes and lysosomes. These data suggest that proteasomal degradation of mutant Cln6 is sufficient to prevent the accumulation of misfolded Cln6 protein, whereas lysosomal dysfunction impairs constitutive autophagy promoting neurodegeneration.
authors.affiliation: Department of Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Thelen
authors.forename: Markus
authors.initials: M
authors.lastname: Damme
authors.forename: Markus
authors.initials: M
authors.lastname: Daμμe
authors.forename: Michaela
authors.initials: M
authors.lastname: Schweizer
authors.forename: Christian
authors.initials: C
authors.lastname: Hagel
authors.forename: Andrew M S
authors.initials: AM
authors.lastname: Wong
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Cooper
authors.forename: Thomas
authors.initials: T
authors.lastname: Braulke
authors.forename: Giovanna
authors.initials: G
authors.lastname: Galliciotti
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology; D001284:Atrophy; D001343:Autophagy; D002531:Cerebellum / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D059865:Endoplasmic Reticulum Stress; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016254:Mutagenesis, Insertional; D009472:Neuronal Ceroid-Lipofuscinoses / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009830:Olfactory Bulb / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000378:metabolism; D057149:Ubiquitinated Proteins / Q000378:metabolism; D056811:Unfolded Protein Response
chemical_list: C486722:Cln6 protein, mouse; C490981:Gtf2h1 protein, mouse; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D057149:Ubiquitinated Proteins; D049452:Green Fluorescent Proteins; D051758:Transcription Factor TFIIH; D046988:Proteasome Endopeptidase Complex