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In vivo evidence for lysosome depletion and impaired autophagic clearance in hereditary spastic paraplegia type SPG11

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Item Type:Article
Title:In vivo evidence for lysosome depletion and impaired autophagic clearance in hereditary spastic paraplegia type SPG11
Creators Name:Varga, R.E. and Khundadze, M. and Damme, M. and Nietzsche, S. and Hoffmann, B. and Stauber, T. and Koch, N. and Hennings, J.C. and Franzka, P. and Huebner, A.K. and Kessels, M.M. and Biskup, C. and Jentsch, T.J. and Qualmann, B. and Braulke, T. and Kurth, I. and Beetz, C. and Hübner, C.A.
Abstract:Hereditary spastic paraplegia (HSP) is characterized by a dying back degeneration of corticospinal axons which leads to progressive weakness and spasticity of the legs. SPG11 is the most common autosomal-recessive form of HSPs and is caused by mutations in SPG11. A recent in vitro study suggested that Spatacsin, the respective gene product, is needed for the recycling of lysosomes from autolysosomes, a process known as autophagic lysosome reformation. The relevance of this observation for hereditary spastic paraplegia, however, has remained unclear. Here, we report that disruption of Spatacsin in mice indeed causes hereditary spastic paraplegia-like phenotypes with loss of cortical neurons and Purkinje cells. Degenerating neurons accumulate autofluorescent material, which stains for the lysosomal protein Lamp1 and for p62, a marker of substrate destined to be degraded by autophagy, and hence appears to be related to autolysosomes. Supporting a more generalized defect of autophagy, levels of lipidated LC3 are increased in Spatacsin knockout mouse embryonic fibrobasts (MEFs). Though distinct parameters of lysosomal function like processing of cathepsin D and lysosomal pH are preserved, lysosome numbers are reduced in knockout MEFs and the recovery of lysosomes during sustained starvation impaired consistent with a defect of autophagic lysosome reformation. Because lysosomes are reduced in cortical neurons and Purkinje cells in vivo, we propose that the decreased number of lysosomes available for fusion with autophagosomes impairs autolysosomal clearance, results in the accumulation of undegraded material and finally causes death of particularly sensitive neurons like cortical motoneurons and Purkinje cells in knockout mice.
Keywords:Autophagy, Cultured Cells, Cerebellum, Hereditary Spastic Paraplegia, Inbred C57BL Mice, Knockout Mice, Lysosomes, Motor Cortex, Proteins, Purkinje Cells, Animals, Mice
Source:PLoS Genetics
Publisher:Public Library of Science
Page Range:e1005454
Date:18 August 2015
Official Publication:https://doi.org/10.1371/journal.pgen.1005454
PubMed:View item in PubMed

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