Dataset Information

Gmppa defects result in a treatable syndromic myopathy with α-Dystroglycan hyperglycosylation

ABSTRACT: Mutations in GDP-mannose-pyrophosphorylase-A (Gmppa) are associated with a syndromic disorder with deficits such as muscular hypotonia and weakness, achalasia, alacrima, and mental retardation (AAMR-syndrome). Gmppa is catalytically inactive, while its homolog Gmppb converts GTP and mannose-1-phosphate into GDP-mannose, which is a substrate for protein glycosylation. Suggesting that Gmppa is an allosteric inhibitor of Gmppb, Gmppa and Gmppb interact and disruption of Gmppa in mice increases GDP-mannose tissue levels. KO mice develop a myopathic disorder characterized by hyperglycosylation of the sarcolemma-associated protein α-Dystroglycan (α-Dg), while the overall abundance of α-Dg is reduced. This reduction is also observed in skeletal muscle biopsies of AAMR patients and in myoblasts upon knockdown of Gmppa. The knockdown does not impair myoblast differentiation but compromises myotube maintenance. Dietary mannose depletion prevents α-Dg hyperglycosylation and the deterioration of motor functions in mice. Thus our data suggest that the disorder is at least in part preventable.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Leg Muscle

SUBMITTER: Alessandro Ori

LAB HEAD: Alessandro Ori

PROVIDER: PXD014260 | Pride | 2021-04-15

REPOSITORIES: Pride

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Source:

			Action	DRS
	180309_SCS_PF_GMPPA_TMT10_24frHpH_fr1.raw	Raw
	180309_SCS_PF_GMPPA_TMT10_24frHpH_fr10.raw	Raw
	180309_SCS_PF_GMPPA_TMT10_24frHpH_fr11.raw	Raw
	180309_SCS_PF_GMPPA_TMT10_24frHpH_fr12.raw	Raw
	180309_SCS_PF_GMPPA_TMT10_24frHpH_fr13.raw	Raw

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Project description:Phosphomannomutase 2 (PMM2) converts mannose-6-phospahate to mannose-1-phosphate; the substrate for GDP-mannose, a building block of the glycosylation biosynthetic pathway. Pathogenic variants in the PMM2 gene have been shown to be associated with protein hypoglycosylation causing PMM2-congenital disorder of glycosylation (PMM2-CDG). While mannose supplementation improves glycosylation in vitro, but not in vivo, we hypothesized that liposomal delivery of mannose-1-phosphate could increase the stability and delivery of the activated sugar to enter the targeted compartments of cells. Thus, we studied the effect of liposome-encapsulated mannose-1-P (GLM101) on global protein glycosylation and on the cellular proteome in skin fibroblasts from individuals with PMM2-CDG, as well as in individuals with two N-glycosylation defects early in the pathway, namely ALG2-CDG and ALG11-CDG. We leveraged multiplexed proteomics and N-glycoproteomics in fibroblasts derived from different individuals with various pathogenic variants in PMM2, ALG2 and ALG11 genes. Proteomics data revealed a moderate but significant change in the abundance of some of the proteins in all CDG fibroblasts upon GLM101 treatment. On the other hand, N-glycoproteomics revealed the GLM101 treatment enhanced the expression levels of several high-mannose and complex/hybrid glycopeptides from numerous cellular proteins in individuals with defects in PMM2 and ALG2 genes. Both PMM2-CDG and ALG2-CDG exhibited several-fold increase in glycopeptides bearing Man6 and higher glycans and a decrease in Man5 and smaller glycan moieties, suggesting that GLM101 helps in the formation of mature glycoforms. These changes in protein glycosylation were observed in all individuals irrespective of their genetic variants. ALG11-CDG fibroblasts also showed increase in high mannose glycopeptides upon treatment; however, the improvement was not as dramatic as the other two CDG. Overall, our findings suggest that treatment with GLM101 overcomes the genetic block in the glycosylation pathway and can be used as a potential therapy for CDG with enzymatic defects in early steps in protein N-glycosylation.

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Gmppa defects result in a treatable syndromic myopathy with α-Dystroglycan hyperglycosylation

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