title: Mice deficient in Neu4 sialidase exhibit abnormal ganglioside catabolism and lysosomal storage.
abstract: Mammalian sialidase Neu4, ubiquitously expressed in human tissues, is located in the lysosomal and mitochondrial lumen and has broad substrate specificity against sialylated glycoconjugates. To investigate whether Neu4 is involved in ganglioside catabolism, we transfected beta-hexosaminidase-deficient neuroglia cells from a Tay-Sachs patient with a Neu4-expressing plasmid and demonstrated the correction of storage due to the clearance of accumulated GM2 ganglioside. To further clarify the biological role of Neu4, we have generated a stable loss-of-function phenotype in cultured HeLa cells and in mice with targeted disruption of the Neu4 gene. The silenced HeLa cells showed reduced activity against gangliosides and had large heterogeneous lysosomes containing lamellar structures. Neu4(-/-) mice were viable, fertile and lacked gross morphological abnormalities, but showed a marked vacuolization and lysosomal storage in lung and spleen cells. Lysosomal storage bodies were also present in cultured macrophages preloaded with gangliosides. Thin-layer chromatography showed increased relative level of GD1a ganglioside and a markedly decreased level of GM1 ganglioside in brain of Neu4(-/-) mice suggesting that Neu4 may be important for desialylation of brain gangliosides and consistent with the in situ hybridization data. Increased levels of cholesterol, ceramide and polyunsaturated fatty acids were also detected in the lungs and spleen of Neu4(-/-) mice by high-resolution NMR spectroscopy. Together, our data suggest that Neu4 is a functional component of the ganglioside-metabolizing system, contributing to the postnatal development of the brain and other vital organs.
authors.affiliation: Department of Medical Genetics, CHU Sainte-Justine, CHUM, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Volkan
authors.initials: V
authors.lastname: Seyrantepe
authors.forename: Maryssa
authors.initials: M
authors.lastname: Canuel
authors.forename: Stéphane
authors.initials: S
authors.lastname: Carpentier
authors.forename: Karine
authors.initials: K
authors.lastname: Landry
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Durand
authors.forename: Feng
authors.initials: F
authors.lastname: Liang
authors.forename: Jibin
authors.initials: J
authors.lastname: Zeng
authors.forename: Aurore
authors.initials: A
authors.lastname: Caqueret
authors.forename: Roy A
authors.initials: RA
authors.lastname: Gravel
authors.forename: Sergio
authors.initials: S
authors.lastname: Marchesini
authors.forename: Claudia
authors.initials: C
authors.lastname: Zwingmann
authors.forename: Jacques
authors.initials: J
authors.lastname: Michaud
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Morales
authors.forename: Thierry
authors.initials: T
authors.lastname: Levade
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Pshezhetsky
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001921:Brain / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D002384:Catalysis; D005677:G(M1) Ganglioside / Q000032:analysis / Q000378:metabolism; D005678:G(M2) Ganglioside / Q000032:analysis / Q000378:metabolism; D005732:Gangliosides / Q000032:analysis / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008168:Lung / Q000201:enzymology / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009439:Neuraminidase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D013154:Spleen / Q000201:enzymology / Q000648:ultrastructure; D014018:Tissue Distribution; D001619:beta-N-Acetylhexosaminidases / Q000235:genetics
chemical_list: D005732:Gangliosides; D005678:G(M2) Ganglioside; D005677:G(M1) Ganglioside; C481539:Neu4 protein, mouse; D009439:Neuraminidase; D001619:beta-N-Acetylhexosaminidases