Stimulation of Acid Sphingomyelinase Activity by Lysosomal Lipids and Sphingolipid Activator Proteins
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Thomas Linke
Abstract
Acid sphingomyelinase is a watersoluble, lysosomal glycoprotein that catalyzes the degradation of membrane bound sphingomyelin into phosphorylcholine and ceramide. Sphingomyelin itself is an important component of the extracellular leaflet of various cellular membranes. The aim of the present investigation was to study sphingomyelin hydrolysis as a membrane bound process. We analyzed the degradation of sphingomyelin by recombinant, highly purified acid sphingomyelinase in a detergentfree, liposomal assay system. In order to mimic the in vivo intralysosomal conditions as closely as possible a number of negatively charged, lysosomally occuring lipids including bis(monoacylglycero)phosphate and phosphatidylinositol were incorporated into substratecarrying liposomes. Dolichol and its phosphate ester dolicholphosphate were also included in this study. Bis(monoacylglycero)phosphate and phosphatidylinositol were both effective stimulators of sphingomyelin hydrolysis. Dolichol and dolicholphosphate also significantly increased sphingomyelin hydrolysis. The influence of membrane curvature was investigated by incorporating the substrate into small (SUVs) and large unilamellar vesicles (LUVs) with varying mean diameter. Degradation rates were substantially higher in SUVs than in LUVs. Surface plasmon resonance experiments demonstrated that acid sphingomyelinase binds strongly to lipid bilayers. This interaction is significantly enhanced by anionic lipids such as bis(monoacylglycero)phosphate. Under detergent free conditions only the sphingolipid activator protein SAPC had a pronounced influence on sphingomyelin degradation in both neutral and negatively charged liposomes, catalyzed by highly purified acid sphingomyelinase, while SAPA, B and D had no noticeable effect on sphingomyelin degradation.
Copyright © 2001 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Highlight: Glycobiology
- O-Glycosylation of the Mucin Type
- Glycoproteins from Insect Cells: Sialylated or Not?
- Congenital Disorders of Glycosylation: Glycosylation Defects in Man and Biological Models for Their Study
- Mitochondrial Single-Stranded DNA-Binding Proteins: in Search for New Functions
- Do Rodent and Human Brains Have Different N-Glycosylation Patterns?
- The Liver Flukes Fasciola gigantica and Fasciola hepatica Express the Leucocyte Cluster of Differentiation Marker CD77 (Globotriaosylceramide) in Their Tegument
- Cloning and Expression of Drosophila melanogaster UDP-GlcNAc:?-3-D-Mannoside ? 1,2-N-Acetylglucosaminyltransferase I
- Pathways of Mucin O-Glycosylation in Normal and Malignant Rat Colonic Epithelial Cells Reveal a Mechanism for Cancer-Associated Sialyl-Tn Antigen Expression
- 6-O-Sulfo De-N-Acetylsialyl Lewis X as a Novel High-Affinity Ligand for Human L-Selectin: Total Synthesis and Structural Characterization
- Segregation of Gangliosides GM1 and GD3 on Cell Membranes, Isolated Membrane Rafts, and Defined Supported Lipid Monolayers
- Structural Characterization of Fucose-Containing Oligosaccharides by High-Performance Liquid Chromatography and Matrix-Assisted Laser Desorption/ Ionization Time-of-Flight Mass Spectrometry
- Anencephaly: Structural Characterization of Gangliosides in Defined Brain Regions
- Acidic Glycerol Lipids of Trichomonas vaginalis and Tritrichomonas foetus
- Stimulation of Acid Sphingomyelinase Activity by Lysosomal Lipids and Sphingolipid Activator Proteins
- Biosynthesis of N-Acetylneuraminic Acid in Cells Lacking UDP-N-Acetylglucosamine 2-Epimerase/ N-Acetylmannosamine Kinase
- Synthesis of Nucleotide-Activated Oligosaccharides by ?-Galactosidase from Bacillus circulans
- Elucidation of the Role of Functional Amino Acid Residues of the Small Sialidase from Clostridium perfringens by Site-Directed Mutagenesis
- Biosynthesis of Lipid-Linked Oligosaccharides in Yeast: the ALG3 Gene Encodes the Dol-P-Man:Man5GlcNAc2-PP-Dol Mannosyltransferase
- Intra- and Intermolecular Triplex DNA Formation in the Murine c-myb Proto-Oncogene Promoter Are Inhibited by Mithramycin
- Experimental Regulation of STAT Gene Expression Reveals an Involvement of STAT5 in Interleukin-4-Driven Cell Proliferation
