SialidaseNeu3action on GM1 ganglioside is neuroprotective in GM1 Gangliosidosis
GM1 gangliosidosis is a neurodegenerative disorder caused by mutations in theGLB1gene, which encodes lysosomalb-galactosidase. The enzyme deficiency blocks GM1 ganglioside catabolism, leading to accumulation of GM1 ganglioside and asialo-GM1 ganglioside (GA1 glycolipid) in brain. This disease can present in varying degrees of severity, with the level of residualb-galactosidase activity primarily determining the clinical course.Glb1null mouse models, which completely lackb-galactosidase expression, exhibit a less severe form of the disease than expected from the comparable deficiency in humans, suggesting a potential species difference in the GM1 ganglioside degradation pathway. We hypothesized this difference may involve the sialidase NEU3, which acts on GM1 ganglioside to produce GA1 glycolipid. To test this hypothesis, we generatedGlb1/Neu3double knockout (DKO) mice. These mice had a significantly shorter lifespan, increased neurodegeneration, and more severe ataxia thanGlb1KO mice.Glb1/Neu3DKO mouse brains exhibited an increased GM1 ganglioside to GA1 glycolipid ratio compared withGlb1KO mice, indicating that Neu3 mediated GM1 ganglioside to GA1 glycolipid conversion inGlb1KO mice. The expression of genes associated with neuroinflammation and glial responses were enhanced inGlb1/Neu3DKO mice compared withGlb1KO mice. Mouse Neu3 more efficiently converted GM1 ganglioside to GA1 glycolipid than human NEU3 did. Our findings highlight Neu3's role in ameliorating the consequences ofGlb1deletion in mice, provide insights into NEU3's differential effects between mice and humans in GM1 gangliosidosis, and offer a potential therapeutic approach for reducing toxic GM1 ganglioside accumulation in GM1 gangliosidosis patients. Overall design: Compare gene expression profile between Control and DKO mice.