Impaired turnover of autophagolysosomes in cathepsin L deficiency.
Some of the phenotypes of mice deficient for the lysosomal cysteine endopeptidase cathepsin L (Ctsl) are characterized by large dysmorphic vesicles in the cytoplasm. Specifically, the heart (dilative cardiomyopathy), the thyroid (impaired thyroglobulin processing) and keratinocytes (periodic hair loss and epidermal hyperproliferation) are affected. We hypothesized that the formation of aberrant vesicles is owing to defects in macroautophagy. Therefore, primary mouse embryonic fibroblasts (MEF), which were derived from Ctsl(-/-) animals crossed with mice transgenic for the autophagy marker GFP-LC3, were investigated. Ctsl(-/-) MEF show increased number and size of vesicular structures belonging to the 'acidic' cellular compartment and are also characterized by GFP-LC3. Induction of autophagy by nutrient starvation or rapamycin treatment showed no significant impairment of the initiation of autophagy, the formation of autophagosomes or autophagosome-lysosome fusion in Ctsl(-/-) MEF, but co-localization of GFP-LC3 and Lamp1 revealed unusually large autophagolysosomes filled with Lamp1. Furthermore, the soluble lysosomal enzyme cathepsin D was elevated in Ctsl(-/-) MEF. Thus, degradation of autophagolysosomal content is impaired in the absence of Ctsl. This could slow the turnover of autophagolysosomes and result in accumulation of the dysmorphic and 'acidic' vesicles that were previously described in the context of the pathological phenotypes of Ctsl(-/-) mice.
Institute for Molecular Medicine and Cell Research, Albert Ludwigs University Freiburg, Freiburg, Germany.
Julia
J
Dennemärker
Tobias
T
Lohmüller
Sebastian
S
Müller
Stephanie Vargas
SV
Aguilar
Desmond J
DJ
Tobin
Christoph
C
Peters
Thomas
T
Reinheckel
D000818:Animals; D001343:Autophagy; D015415:Biomarkers / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D056668:Cathepsin L / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D053141:Organelle Size; D010588:Phagosomes / Q000378:metabolism* / Q000473:pathology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
D015415:Biomarkers; D002402:Cathepsin D; D056668:Cathepsin L; D049452:Green Fluorescent Proteins; D051907:Lysosomal Membrane Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1; C480860:Map1lc3b protein, mouse; C534278:Ctsl protein, mouse; C533923:Ctsd protein, mouse