title: Loss of AP-5 results in accumulation of aberrant endolysosomes: defining a new type of lysosomal storage disease.
abstract: Adaptor proteins (AP 1-5) are heterotetrameric complexes that facilitate specialized cargo sorting in vesicular-mediated trafficking. Mutations in AP5Z1, encoding a subunit of the AP-5 complex, have been reported to cause hereditary spastic paraplegia (HSP), although their impact at the cellular level has not been assessed. Here we characterize three independent fibroblast lines derived from skin biopsies of patients harbouring nonsense mutations in AP5Z1 and presenting with spastic paraplegia accompanied by neuropathy, parkinsonism and/or cognitive impairment. In all three patient-derived lines, we show that there is complete loss of AP-5 ζ protein and a reduction in the associated AP-5 µ5 protein. Using ultrastructural analysis, we show that these patient-derived lines consistently exhibit abundant multilamellar structures that are positive for markers of endolysosomes and are filled with aberrant storage material organized as exaggerated multilamellar whorls, striated belts and 'fingerprint bodies'. This phenotype can be replicated in a HeLa cell culture model by siRNA knockdown of AP-5 ζ. The cellular phenotype bears striking resemblance to features described in a number of lysosomal storage diseases (LSDs). Collectively, these findings reveal an emerging picture of the role of AP-5 in endosomal and lysosomal homeostasis, illuminates a potential pathomechanism that is relevant to the role of AP-5 in neurons and expands the understanding of recessive HSPs. Moreover, the resulting accumulation of storage material in endolysosomes leads us to propose that AP-5 deficiency represents a new type of LSDs.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK, jh228@cam.ac.uk.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hirst
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
authors.forename: James R
authors.initials: JR
authors.lastname: Edgar
authors.affiliation: Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S_1127, Institut du Cerveau et de la Moelle épinière, Paris F-75013, France, Ecole Pratique des Hautes Etudes, Paris F-75014, France.
authors.forename: Typhaine
authors.initials: T
authors.lastname: Esteves
authors.affiliation: Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S_1127, Institut du Cerveau et de la Moelle épinière, Paris F-75013, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Darios
authors.affiliation: Sanford Children's Health Research Center, Barrow Neurological Institute and Ronald A. Matricaria Institute of Molecular Medicine, Phoenix Children's Hospital, Sioux Falls, SD, USA.
authors.forename: Marianna
authors.initials: M
authors.lastname: Madeo
authors.affiliation: Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Jaerak
authors.initials: J
authors.lastname: Chang
authors.affiliation: Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Ricardo H
authors.initials: RH
authors.lastname: Roda
authors.affiliation: Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S_1127, Institut du Cerveau et de la Moelle épinière, Paris F-75013, France, APHP, Department of Genetics, Pitié-Salpêtrière Hospital, Paris F-75013, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Dürr
authors.affiliation: Département de Neurologie, Hôpital de Hautepierre, Strasbourg, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Anheim
authors.affiliation: Genetics of Neurodegenerative and Metabolic Diseases Unit, IRCCS-Fondazione Istituto Neurologico Carlo Besta, Milan 20133, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Gellera
authors.affiliation: Department of Neurology, Vanderbilt Brain Institute and Centre for Human Genetics Research, Vanderbilt University School of Medicine, 1161 21th Avenue South, Nashville, TN, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Human Genetics and Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, FL, USA.
authors.forename: Stephan
authors.initials: S
authors.lastname: Züchner
authors.affiliation: Genetics of Neurodegenerative and Metabolic Diseases Unit, IRCCS-Fondazione Istituto Neurologico Carlo Besta, Milan 20133, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Mariotti
authors.affiliation: Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S_1127, Institut du Cerveau et de la Moelle épinière, Paris F-75013, France, Ecole Pratique des Hautes Etudes, Paris F-75014, France, APHP, Department of Genetics, Pitié-Salpêtrière Hospital, Paris F-75013, France.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Stevanin
authors.affiliation: Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Blackstone
authors.affiliation: Sanford Children's Health Research Center, Barrow Neurological Institute and Ronald A. Matricaria Institute of Molecular Medicine, Phoenix Children's Hospital, Sioux Falls, SD, USA, Barrow Neurological Institute & Ronald A. Matricaria Institute for Molecular Medicine, Phoenix Children's Hospital, Phoenix, AZ and Department of Child Health, University of Arizona College of Medicine, Phoenix, AZ.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Kruer
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Robinson
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics*; D000368:Aged; D011992:Endosomes / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D055785:Gene Knockdown Techniques; D056726:Genetic Association Studies; D006367:HeLa Cells; D006801:Humans; D016464:Lysosomal Storage Diseases / Q000235:genetics* / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference
chemical_list: C570280:AP5B1 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D011506:Proteins; C520412:SPG11 protein, human