title: Characterization ofDrosophila Saposin-relatedmutants as a model for lysosomal sphingolipid storage diseases.
abstract: Sphingolipidoses are inherited diseases belonging to the class of lysosomal storage diseases (LSDs), which are characterized by the accumulation of indigestible material in the lysosome caused by specific defects in the lysosomal degradation machinery. While some LSDs can be efficiently treated by enzyme replacement therapy (ERT), this is not possible if the nervous system is affected due to the presence of the blood-brain barrier. Sphingolipidoses in particular often present as severe, untreatable forms of LSDs with massive sphingolipid and membrane accumulation in lysosomes, neurodegeneration and very short life expectancy. The digestion of intralumenal membranes within lysosomes is facilitated by lysosomal sphingolipid activator proteins (saposins), which are cleaved from a prosaposin precursor. Prosaposin mutations cause some of the severest forms of sphingolipidoses, and are associated with perinatal lethality in mice, hampering studies on disease progression. We identify theDrosophilaprosaposin orthologue Saposin-related (Sap-r) as a key regulator of lysosomal lipid homeostasis in the fly. Its mutation leads to a typical spingolipidosis phenotype with an enlarged endolysosomal compartment and sphingolipid accumulation as shown by mass spectrometry and thin layer chromatography.Sap-rmutants show reduced viability with ∼50% survival to adulthood, allowing us to study progressive neurodegeneration and analyze their lipid profile in young and aged flies. Additionally, we observe a defect in sterol homeostasis with local sterol depletion at the plasma membrane. Furthermore, we find that autophagy is increased, resulting in the accumulation of mitochondria in lysosomes, concomitant with increased oxidative stress. Together, we establishDrosophila Sap-rmutants as a lysosomal storage disease model suitable for studying the age-dependent progression of lysosomal dysfunction associated with lipid accumulation and the resulting pathological signaling events.
authors.affiliation: LIMES-Institute, Program Unit Development & Genetics, Laboratory for Molecular Developmental Biology, University of Bonn, Carl-Troll-Strasse 31, 53115 Bonn, Germany m.hoch@uni-bonn.de sellin@uni-bonn.de.
authors.forename: Julia
authors.identifier: 0000-0001-5354-2872
authors.initials: J
authors.lastname: Sellin
authors.affiliation: LIMES-Institute, Program Unit Membrane Biology & Lipid Biochemistry, c/o Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Schulze
authors.affiliation: LIMES-Institute, Program Unit Development & Genetics, Laboratory for Molecular Developmental Biology, University of Bonn, Carl-Troll-Strasse 31, 53115 Bonn, Germany.
authors.forename: Marie
authors.initials: M
authors.lastname: Paradis
authors.affiliation: LIMES-Institute, Program Unit Development & Genetics, Laboratory for Molecular Developmental Biology, University of Bonn, Carl-Troll-Strasse 31, 53115 Bonn, Germany.
authors.forename: Dominic
authors.initials: D
authors.lastname: Gosejacob
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
authors.forename: Cyrus
authors.initials: C
authors.lastname: Papan
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
authors.forename: Andrej
authors.initials: A
authors.lastname: Shevchenko
authors.affiliation: University of Osnabrück, Department of Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrueck, Germany.
authors.forename: Olympia Ekaterina
authors.initials: OE
authors.lastname: Psathaki
authors.affiliation: University of Osnabrück, Biology, EM unit, Barbarastraße 11, 49076 Osnabrueck, Germany.
authors.forename: Achim
authors.identifier: 0000-0002-8845-6859
authors.initials: A
authors.lastname: Paululat
authors.affiliation: LIMES-Institute, Program Unit Development & Genetics, Laboratory for Molecular Developmental Biology, University of Bonn, Carl-Troll-Strasse 31, 53115 Bonn, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Thielisch
authors.affiliation: LIMES-Institute, Program Unit Membrane Biology & Lipid Biochemistry, c/o Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
authors.forename: Konrad
authors.initials: K
authors.lastname: Sandhoff
authors.affiliation: LIMES-Institute, Program Unit Development & Genetics, Laboratory for Molecular Developmental Biology, University of Bonn, Carl-Troll-Strasse 31, 53115 Bonn, Germany m.hoch@uni-bonn.de sellin@uni-bonn.de.
authors.forename: Michael
authors.identifier: 0000-0003-3941-5679
authors.initials: M
authors.lastname: Hoch
mesh_terms: D000143:Acids / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004195:Disease Models, Animal; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics*; D016464:Lysosomal Storage Diseases / Q000235:genetics* / Q000503:physiopathology; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D009043:Motor Activity; D009154:Mutation / Q000235:genetics*; D009410:Nerve Degeneration / Q000473:pathology / Q000503:physiopathology; D018384:Oxidative Stress; D010743:Phospholipids / Q000378:metabolism; D021381:Protein Transport; D049231:Saposins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013106:Sphingolipidoses / Q000235:genetics* / Q000503:physiopathology; D013107:Sphingolipids / Q000378:metabolism; D013261:Sterols / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000143:Acids; D029721:Drosophila Proteins; D010743:Phospholipids; D049231:Saposins; D013107:Sphingolipids; D013261:Sterols
keywords: Drosophila; Lipid profiling; Lysosomal storage diseases; Lysosomes; Sphingolipid degradation; Sphingolipidoses