title: Endosomal/lysosomal processing of gangliosides affects neuronal cholesterol sequestration in Niemann-Pick disease type C.
abstract: Niemann-Pick disease type C (NPC) is a severe neurovisceral lysosomal storage disorder caused by defects in NPC1 or NPC2 proteins. Although numerous studies support the primacy of cholesterol storage, neurons of double-mutant mice lacking both NPC1 and an enzyme required for synthesis of all complex gangliosides (β1,4GalNAc transferase) have been reported to exhibit dramatically reduced cholesterol sequestration. Here we show that NPC2-deficient mice lacking this enzyme also exhibit reduced cholesterol, but that genetically restricting synthesis to only a-series gangliosides fully restores neuronal cholesterol storage to typical disease levels. Examining the subcellular locations of sequestered compounds in neurons lacking NPC1 or NPC2 by confocal microscopy revealed that cholesterol and the two principal storage gangliosides (GM2 and GM3) were not consistently co-localized within the same intracellular vesicles. To determine whether the lack of GM2 and GM3 co-localization was due to differences in synthetic versus degradative pathway expression, we generated mice lacking both NPC1 and lysosomal β-galactosidase, and therefore unable to generate GM2 and GM3 in lysosomes. Double mutants lacked both gangliosides, indicating that each is the product of endosomal/lysosomal processing. Unexpectedly, GM1 accumulation in double mutants increased compared to single mutants consistent with a direct role for NPC1 in ganglioside salvage. These studies provide further evidence that NPC1 and NPC2 proteins participate in endosomal/lysosomal processing of both sphingolipids and cholesterol.
authors.affiliation: Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Zhou
authors.forename: Cristin
authors.initials: C
authors.lastname: Davidson
authors.forename: Robert
authors.initials: R
authors.lastname: McGlynn
authors.forename: Gloria
authors.initials: G
authors.lastname: Stephney
authors.forename: Kostantin
authors.initials: K
authors.lastname: Dobrenis
authors.forename: Marie T
authors.initials: MT
authors.lastname: Vanier
authors.forename: Steven U
authors.initials: SU
authors.lastname: Walkley
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D052119:Lysosomal-Associated Membrane Protein 2 / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal / Q000379:methods; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D000077296:Niemann-Pick C1 Protein; D052556:Niemann-Pick Disease, Type C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D005732:Gangliosides; D047908:Intracellular Signaling Peptides and Proteins; D052119:Lysosomal-Associated Membrane Protein 2; D000077296:Niemann-Pick C1 Protein; C106831:Npc1 protein, mouse; C497045:Npc2 protein, mouse; D011506:Proteins; D033921:Vesicular Transport Proteins; D002784:Cholesterol; D001616:beta-Galactosidase