Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology

Niamh X Cawley; Anna T Lyons; Daniel Abebe; Rachel Luke; Julia Yerger; Rebecca Telese; Christopher A Wassif; Joan E Bailey-Wilson; Forbes D Porter

doi:10.3390/ijms23095082

Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology

Int J Mol Sci. 2022 May 3;23(9):5082. doi: 10.3390/ijms23095082.

Authors

Niamh X Cawley¹, Anna T Lyons¹, Daniel Abebe², Rachel Luke¹, Julia Yerger¹, Rebecca Telese¹, Christopher A Wassif¹, Joan E Bailey-Wilson³, Forbes D Porter¹

Affiliations

¹ Division of Translational Medicine, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
² Research Animal Management Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
³ Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Department of Health and Human Services, Baltimore, MD 21224, USA.

Abstract

Complex asparagine-linked glycosylation plays key roles in cellular functions, including cellular signaling, protein stability, and immune response. Previously, we characterized the appearance of a complex asparagine-linked glycosylated form of lysosome-associated membrane protein 1 (LAMP1) in the cerebellum of Npc1^-/- mice. This LAMP1 form was found on activated microglia, and its appearance correlated both spatially and temporally with cerebellar Purkinje neuron loss. To test the importance of complex asparagine-linked glycosylation in NPC1 pathology, we generated NPC1 knock-out mice deficient in MGAT5, a key Golgi-resident glycosyl transferase involved in complex asparagine-linked glycosylation. Our results show that Mgat5^-/-:Npc1^-/- mice were smaller than Mgat5^+/+:Npc1^-/- mice, and exhibited earlier NPC1 disease onset and reduced lifespan. Western blot and lectin binding analyses of cerebellar extracts confirmed the reduction in complex asparagine-linked glycosylation, and the absence of the hyper-glycosylated LAMP1 previously observed. Western blot analysis of cerebellar extracts demonstrated reduced calbindin staining in Mgat5^-/-:Npc1^-/- mice compared to Mgat5^+/+:Npc1^-/- mutant mice, and immunofluorescent staining of cerebellar sections indicated decreased levels of Purkinje neurons and increased astrogliosis in Mgat5^-/-:Npc1^-/- mice. Our results suggest that reduced asparagine-linked glycosylation increases NPC1 disease severity in mice, and leads to the hypothesis that mutations in genes involved in asparagine-linked glycosylation may contribute to disease severity progression in individuals with NPC1. To examine this with respect to MGAT5, we analyzed 111 NPC1 patients for two MGAT5 SNPs associated with multiple sclerosis; however, we did not identify an association with NPC1 phenotypic severity.

Keywords: LAMP1; MGAT5; N-linked glycosylation; Niemann–Pick disease; Purkinje neuron; disease severity score; type C.

MeSH terms

Animals
Asparagine / metabolism
Asparagine / pharmacology
Glycosylation
Humans
Mice
Mice, Inbred BALB C
N-Acetylglucosaminyltransferases* / metabolism
Niemann-Pick Disease, Type C* / metabolism
Niemann-Pick Disease, Type C* / pathology

Substances

Asparagine
Mgat5 protein, human
N-Acetylglucosaminyltransferases
alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase

Grants and funding

This work was supported by the intramural research programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Human Genome Research Institute.