Global N-linked Glycosylation is Not Significantly Impaired in Myoblasts in Congenital Myasthenic Syndromes Caused by Defective Glutamine-Fructose-6-Phosphate Transaminase 1 (GFPT1).
Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first enzyme of the hexosamine biosynthetic pathway. It transfers an amino group from glutamine to fructose-6-phosphate to yield glucosamine-6-phosphate, thus providing the precursor for uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) synthesis. UDP-GlcNAc is an essential substrate for all mammalian glycosylation biosynthetic pathways and N-glycan branching is especially sensitive to alterations in the concentration of this sugar nucleotide. It has been reported that GFPT1 mutations lead to a distinct sub-class of congenital myasthenic syndromes (CMS) termed "limb-girdle CMS with tubular aggregates". CMS are hereditary neuromuscular transmission disorders in which neuromuscular junctions are impaired. To investigate whether alterations in protein glycosylation at the neuromuscular junction might be involved in this impairment, we have employed mass spectrometric strategies to study the N-glycomes of myoblasts and myotubes derived from two healthy controls, three GFPT1 patients, and four patients with other muscular diseases, namely CMS caused by mutations in DOK7, myopathy caused by mutations in MTND5, limb girdle muscular dystrophy type 2A (LGMD2A), and Pompe disease. A comparison of the relative abundances of bi-, tri-, and tetra-antennary N-glycans in each of the cell preparations revealed that all samples exhibited broadly similar levels of branching. Moreover, although some differences were observed in the relative abundances of some of the N-glycan constituents, these variations were modest and were not confined to the GFPT1 samples. Therefore, GFPT1 mutations in CMS patients do not appear to compromise global N-glycosylation in muscle cells.
Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. q.chen11@imperial.ac.uk.
Qiushi
Q
Chen
John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne NE1 3BZ, UK. juliane.mueller@ncl.ac.uk.
Juliane S
JS
Müller
Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. p.pang05@imperial.ac.uk.
Poh-Choo
PC
Pang
John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne NE1 3BZ, UK. shlaval@outlook.com.
Steve H
SH
Laval
Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. s.haslam@imperial.ac.uk.
Stuart M
SM
Haslam
John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne NE1 3BZ, UK. Hanns.Lochmuller@newcastle.ac.uk.
Hanns
H
Lochmüller
Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. a.dell@imperial.ac.uk.
Anne
A
Dell
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002478:Cells, Cultured; D042967:Electron Transport Complex I / Q000235:genetics; D005260:Female; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000235:genetics*; D006031:Glycosylation; D006801:Humans; D008297:Male; D008875:Middle Aged; D024101:Mitochondrial Proteins / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D020294:Myasthenic Syndromes, Congenital / Q000235:genetics / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism*; D011499:Protein Processing, Post-Translational
C511692:DOK7 protein, human; D024101:Mitochondrial Proteins; D009124:Muscle Proteins; C481838:MT-ND5 protein, human; C497511:GFPT1 protein, human; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing); D042967:Electron Transport Complex I
congenital myasthenic syndromes; glutamine-fructose-6-phosphate transaminase 1; glycosylation; mass spectrometry