Percorrer por autor "Aerts, Johannes M."
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- LIMP-2 deficiency-associated glycolipid abnormalities in micePublication . da Silva Gaspar, Paulo Jorge Miranda; Marques, André R.A.; Ferraz, Maria J.; Damme, Markus; Krame, Gertjan; Mirzaian, Mina; Gijbels, Marion; Ottenhoff, Roelef; van Roomen, Cindy; Overkleeft, Herman S.; Schwake, Michael; Heybrock, Saskia; Macário, Maria Carmo; Saftig, Paul; Aerts, Johannes M.Glucocerebrosidase (GCase) catalyzes the lysosomal degradation of glucosylceramide (GlcCer). GCase deficiency results in Gaucher disease (GD), a lysosomal storage disorder with characteristic hepatosplenomegaly. Transport of GCase to lysosomes is mediated by the lysosomal integral membrane protein type 2 (LIMP-2). Deficiency of LIMP-2 leads to reduced cellular GCase levels and manifests as Action Myoclonic Renal Failure Syndrome (AMRF). We investigated the cause for the markedly different symptomatology of GD and AMRF. In tissues of Limp2 − /− mice no prominent abnormalities in lysosomal enzymes were noted except for variable deficiency of GCase, as measured with enzymatic activity assay and detection of active GCase molecules with an activity-based probe. Noteworthy, in LIMP-2-deficient mice, residual GCase is remarkably high in leukocytes. GCase deficiency in tissues does not correlate with increases in GlcCer, but rather with increases in glucosylsphingosine (GlcSph) and glucosylated cholesterol (GlcChol), both glucosylated metabolites derived from GlcCer. Isolated lysosomes from hepatocytes of Limp2 − /− mice revealed no prominent abnormalities in lysosomal matrix proteins except GCase. The Limp2 − /− tritosomes showed clear increases in GlcSph and GlcChol but not in GlcCer. In conclusion, our data imply a critical role of LIMP-2 in glycosphingolipid homeostasis. Despite low GCase levels striking GlcCer accumulation is avoided in tissues of LIMP-2 deficient mice.
- Lysosomal Storage Diseases. For Better or Worse: Adapting to Defective Lysosomal Glycosphingolipid BreakdownPublication . Aerts, Johannes M.; Ferraz, Maria J.; Mirzaian, Mina; Gaspar, Paulo; Oussoren, Saskia V.; Wisse, Patrick; Kuo, Chi-Lin; Lelieveld, Lindsey T.; Kytidou, Kassiani; Hazeu, Marc D.; Boer, Daphne E.C.; Meijer, Rianne; van der Lienden, Martijn J.C.; Chao, Daniela H.M.; Gabriel, Tanit L.; Aten, Jan; Overkleeft, Herman S.; van Eijk, Marco; Boot, Rolf G.; Marques, André R.A.The cellular recycling of glycosphingolipids (GSLs) is mediated by specific lysosomal glycosidases. Inherited deficiencies in these enzymes cause lysosomal storage disorders. Some of the common disorders are Gaucher disease (GD) and Fabry disease (FD) resulting from the defects in lysosomal glucocerebrosidase (GBA) degrading glucosylceramide and α‐galactosidase A (GLA) degrading globotriaosylceramide. Here, GSL accumulation in tissues slows down with age despite ongoing lysosomal turnover of endogenous and endocytosed GSLs. Biochemical adaptations might explain this phenomenon. One crucial adaptation is the deacylation of accumulating GSLs in lysosomes by acid ceramidase. The soluble bases glucosylsphingosine in GD and globotriaosylsphingosine in FD are capable of leaving lysosomes and cells. In the case of GD, a further adaptation involves the cytosol‐faced enzyme GBA2. This enzyme allows extra‐lysosomal degradation of GlcCer while possibly generating glucosylated cholesterol. The beneficial and harmful effects of these adaptations are discussed.