A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ)
The neuromuscular junction (NMJ) is the site where the motor neuron innervates skeletal muscle, enabling muscular contraction. Congenital myasthenic syndromes (CMS) arise when mutations in any of the approximately 35 known causative genes cause impaired neuromuscular transmission at the NMJ, resulti...
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2024-10-01
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| author | Stephen Henry Holland Ricardo Carmona-Martinez Kaela O’Connor Daniel O’Neil Andreas Roos Sally Spendiff Hanns Lochmüller |
| author_facet | Stephen Henry Holland Ricardo Carmona-Martinez Kaela O’Connor Daniel O’Neil Andreas Roos Sally Spendiff Hanns Lochmüller |
| author_sort | Stephen Henry Holland |
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| description | The neuromuscular junction (NMJ) is the site where the motor neuron innervates skeletal muscle, enabling muscular contraction. Congenital myasthenic syndromes (CMS) arise when mutations in any of the approximately 35 known causative genes cause impaired neuromuscular transmission at the NMJ, resulting in fatigable muscle weakness. A subset of five of these CMS-causative genes are associated with protein glycosylation. Glutamine-fructose-6-phosphate transaminase 1 (Gfpt1) is the rate-limiting enzyme within the hexosamine biosynthetic pathway (HBP), a metabolic pathway that produces the precursors for glycosylation. We hypothesized that deficiency in Gfpt1 expression results in aberrant or reduced glycosylation, impairing the proper assembly and stability of key NMJ-associated proteins. Using both in vitro and in vivo Gfpt1-deficient models, we determined that the acetylcholine receptor delta subunit (AChRδ) has reduced expression and is hypo-glycosylated. Using laser capture microdissection, NMJs were harvested from Gfpt1 knockout mouse muscle. A lower-molecular-weight species of AChRδ was identified at the NMJ that was not detected in controls. Furthermore, Gfpt1-deficient muscle lysates showed impairment in protein O-GlcNAcylation and sialylation, suggesting that multiple glycan chains are impacted. Other key NMJ-associated proteins, in addition to AChRδ, may also be differentially glycosylated in Gfpt1-deficient muscle. |
| format | Article |
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| institution | OA Journals |
| issn | 2218-273X |
| language | English |
| publishDate | 2024-10-01 |
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| spelling | doaj-art-e5f54fce7e5a4e9f9e07f148b22656752025-08-20T02:11:12ZengMDPI AGBiomolecules2218-273X2024-10-011410125210.3390/biom14101252A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ)Stephen Henry Holland0Ricardo Carmona-Martinez1Kaela O’Connor2Daniel O’Neil3Andreas Roos4Sally Spendiff5Hanns Lochmüller6Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaChildren’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaChildren’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaChildren’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaDr. Eric Poulin Center for Neuromuscular Disorders, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1N 6N5, CanadaChildren’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaChildren’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, CanadaThe neuromuscular junction (NMJ) is the site where the motor neuron innervates skeletal muscle, enabling muscular contraction. Congenital myasthenic syndromes (CMS) arise when mutations in any of the approximately 35 known causative genes cause impaired neuromuscular transmission at the NMJ, resulting in fatigable muscle weakness. A subset of five of these CMS-causative genes are associated with protein glycosylation. Glutamine-fructose-6-phosphate transaminase 1 (Gfpt1) is the rate-limiting enzyme within the hexosamine biosynthetic pathway (HBP), a metabolic pathway that produces the precursors for glycosylation. We hypothesized that deficiency in Gfpt1 expression results in aberrant or reduced glycosylation, impairing the proper assembly and stability of key NMJ-associated proteins. Using both in vitro and in vivo Gfpt1-deficient models, we determined that the acetylcholine receptor delta subunit (AChRδ) has reduced expression and is hypo-glycosylated. Using laser capture microdissection, NMJs were harvested from Gfpt1 knockout mouse muscle. A lower-molecular-weight species of AChRδ was identified at the NMJ that was not detected in controls. Furthermore, Gfpt1-deficient muscle lysates showed impairment in protein O-GlcNAcylation and sialylation, suggesting that multiple glycan chains are impacted. Other key NMJ-associated proteins, in addition to AChRδ, may also be differentially glycosylated in Gfpt1-deficient muscle.https://www.mdpi.com/2218-273X/14/10/1252glutamine-fructose-6-phosphate transaminase 1 (Gfpt1)congenital myasthenic syndrome (CMS)neuromuscular junction (NMJ)O-GlcNAcylationacetylcholine receptor delta subunit (AChRδ)glycosylation |
| spellingShingle | Stephen Henry Holland Ricardo Carmona-Martinez Kaela O’Connor Daniel O’Neil Andreas Roos Sally Spendiff Hanns Lochmüller A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) Biomolecules glutamine-fructose-6-phosphate transaminase 1 (Gfpt1) congenital myasthenic syndrome (CMS) neuromuscular junction (NMJ) O-GlcNAcylation acetylcholine receptor delta subunit (AChRδ) glycosylation |
| title | A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) |
| title_full | A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) |
| title_fullStr | A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) |
| title_full_unstemmed | A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) |
| title_short | A Deficiency in Glutamine-Fructose-6-Phosphate Transaminase 1 (Gfpt1) in Skeletal Muscle Results in Reduced Glycosylation of the Delta Subunit of the Nicotinic Acetylcholine Receptor (AChRδ) |
| title_sort | deficiency in glutamine fructose 6 phosphate transaminase 1 gfpt1 in skeletal muscle results in reduced glycosylation of the delta subunit of the nicotinic acetylcholine receptor achrδ |
| topic | glutamine-fructose-6-phosphate transaminase 1 (Gfpt1) congenital myasthenic syndrome (CMS) neuromuscular junction (NMJ) O-GlcNAcylation acetylcholine receptor delta subunit (AChRδ) glycosylation |
| url | https://www.mdpi.com/2218-273X/14/10/1252 |
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