title: Abnormal gangliosides are localized in lipid rafts in Sanfilippo (MPS3a) mouse brain.
abstract: Allogenic stem cell transplantation can reduce lysosomal storage of heparan sulfate-derived oligosaccharides by up to 27 % in Sanfilippo MPS3a brain, but does not reduce the abnormal storage of sialolactosylceramide (G(M3)) or improve neurological symptoms, suggesting that ganglioside storage is in a non-lysosomal compartment. To investigate this further we isolated the Triton X100-insoluble at 4 °C, lipid raft (LR) fraction from a sucrose-density gradient from cerebral hemispheres of a 7 month old mouse model of Sanfilippo MPS3a and age-matched control mouse brain. HPLC/MS/MS analysis revealed the expected enrichment of normal complex gangliosides, ceramides, galatosylceramides and sphingomyelin enrichment in this LR fraction. The abnormal HS-derived oligosaccharide storage material was in the Triton X100-soluble at 4 °C fractions (8-12),whereas both GM3 and sialo[GalNAc]lactosylceramide (GM2) were found exclusively in the LR fraction (fractions 3 and 4) and were >90 % C18:0 fatty acid, suggesting a neuronal origin. Further analysis also revealed a >threefold increase in the late-endosome marker bis (monoacylglycerol) phosphate (>70 % as C22:6/22:6-BMP) in non-LR fractions 8-12 whereas different forms of the proposed BMP precursor, phosphatidylglycerol (PG) were in both LR and non-LR fractions and were less elevated in MPS3a brain. Thus heparan sulfate-derived oligosaccharide storage is associated with abnormal lipid accumulation in both lysosomal (BMP) and non-lysosomal (GM3 and GM2) compartments.
authors.affiliation: University of Chicago, Chicago, IL, USA. dawg@uchicago.edu
authors.forename: G
authors.initials: G
authors.lastname: Dawson
authors.forename: M
authors.initials: M
authors.lastname: Fuller
authors.forename: K M
authors.initials: KM
authors.lastname: Helmsley
authors.forename: J J
authors.initials: JJ
authors.lastname: Hopwood
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D005678:G(M2) Ganglioside / Q000378:metabolism; D005679:G(M3) Ganglioside / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D008246:Lysophospholipids / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D050178:Monoglycerides / Q000378:metabolism; D009084:Mucopolysaccharidosis III / Q000378:metabolism*; D053719:Tandem Mass Spectrometry
chemical_list: D005679:G(M3) Ganglioside; D005732:Gangliosides; D008246:Lysophospholipids; D050178:Monoglycerides; C012786:bis(monoacylglyceryl)phosphate; D005678:G(M2) Ganglioside