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.