Alg mannosyltransferases: From functional and structural analyses to the lipid-linked oligosaccharide pathway reconstitution

Wang, Ning; Li, Shengtao; Xiang, Meng-Hai; Gao, Xiao‐Dong

doi:10.1016/j.bbagen.2022.130112

Cited by 7 publications

(4 citation statements)

References 40 publications

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“…To consider the mechanism of F304S modifier activity on DHDDS, it is necessary to understand glycosylation pathways. The protein N-glycosylation and other protein glycosylation pathways require more than 35 enzymes and are crucial for function in all cells of the body [57][58][59][60][61]. During N-glycosylation, GlcNAc 2 Man 9 Glc 3 carbohydrate complexes are gradually assembled on an ER transmembrane lipid carrier (dolichol-P) and finally transferred to specific asparagine residues on target proteins.…”

Section: Discussionmentioning

confidence: 99%

Inherited Retinal Degeneration Caused by Dehydrodolichyl Diphosphate Synthase Mutation–Effect of an ALG6 Modifier Variant

Monson,

Cideciyan,

Roman

et al. 2024

IJMS

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Modern advances in disease genetics have uncovered numerous modifier genes that play a role in the severity of disease expression. One such class of genetic conditions is known as inherited retinal degenerations (IRDs), a collection of retinal degenerative disorders caused by mutations in over 300 genes. A single missense mutation (K42E) in the gene encoding the enzyme dehydrodolichyl diphosphate synthase (DHDDS), which is required for protein N-glycosylation in all cells and tissues, causes DHDDS-IRD (retinitis pigmentosa type 59 (RP59; OMIM #613861)). Apart from a retinal phenotype, however, DHDDS-IRD is surprisingly non-syndromic (i.e., without any systemic manifestations). To explore disease pathology, we selected five glycosylation-related genes for analysis that are suggested to have disease modifier variants. These genes encode glycosyltransferases (ALG6, ALG8), an ER resident protein (DDOST), a high-mannose oligosaccharyl transferase (MPDU1), and a protein N-glycosylation regulatory protein (TNKS). DNA samples from 11 confirmed DHDDS (K42E)-IRD patients were sequenced at the site of each candidate genetic modifier. Quantitative measures of retinal structure and function were performed across five decades of life by evaluating foveal photoreceptor thickness, visual acuity, foveal sensitivity, macular and extramacular rod sensitivity, and kinetic visual field extent. The ALG6 variant, (F304S), was correlated with greater macular cone disease severity and less peripheral rod disease severity. Thus, modifier gene polymorphisms may account for a significant portion of phenotypic variation observed in human genetic disease. However, the consequences of the polymorphisms may be counterintuitively complex in terms of rod and cone populations affected in different regions of the retina.

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Section: Discussionmentioning

confidence: 99%

Inherited Retinal Degeneration Caused by Dehydrodolichyl Diphosphate Synthase Mutation–Effect of an ALG6 Modifier Variant

Monson,

Cideciyan,

Roman

et al. 2024

IJMS

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“…The core of N-glycan Glc3Man9GlcNAc2 formation is the precursor for N-glycan biosynthesis, which catalyzed by ALG family through the α-1,2 α-1,3 and α-1,6 linkages of mannose [35,36]. The ALGs and glycan products have been implicated in physiological and pathological processes [37,38]. ALG9 Mutation carriers develop kidney and liver cysts [39].…”

Section: Discussionmentioning

confidence: 99%

High-mannose glycosylation of ITGAM regulates the development and differentiation of trophoblast in the placenta

Cui

Wang

Pei

et al. 2023

Preprint

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Background Development of placenta and differentiation of trophoblast is a hallmark event for successful pregnancy. Trophoblast stem (TS) cells proliferate and differentiate into TS-like cytotrophoblasts (CTBs), further formulate the differentiated subtypes, syncytiotrophoblasts (STBs) and invasive extravillous tropholoblasts (EVTs). Defective differentiation of TS-like CTBs is associated with severe gestational diseases. Protein glycosylation is an essential form of posttranslational modification. However, glycosylation-related mechanism controlling TS-like CTBs differentiation remains unknown. This study aims to investigate the function of high-mannose type glycans and ALG3 on TS-like CTBs differentiation. Furthermore, the mechanism of high-mannose and ITGAM during TS-like CTBs differentiation were explored.Methods Employing lectin microarray, the glycosylation expression traits were compared in the villi of miscarriage patients and healthy women. The expression of high-mannose and ALG3 were investigated by immunoblotting and immunofluorescence assays. The glycosylation proteins were screened by pull down and LC-MS/MS detection. Signaling pathway were screened by the human phosphokinase antibody array. The differentiation of TS-like CTBs were measured by immunoblotting and immunofluorescence assays.Results Lectin microarray results revealed that increased level of high-mannose type glycans on the TS-like CTBs of miscarriage patients compared with normal pregnancy women. Meantime, ALG3 levels increased in TS-like CTBs of miscarriage patients. Upregulating high-mannose type glycans by ALG3 hampered TS-like CTBs differentiated into STBs and EVTs, and arrested TS-like CTBs in the property stage. Furthermore, high level of high-mannose type glycans on ITGAM inhibited the binding of ITGAM and Fn, inactivating the p-STAT1 signaling pathway, further inhibiting TS-like CTBs differentiation potential.Conclusions These findings reveal that high-mannose type glycans, especially on ITGAM, hampered binding of ITGAM and Fn, which leads to the impaired TS-like CTBs differentiation by p-STAT1 signaling pathway. The present study provides novel insight into the function and mechanism of α1,3-linked high-mannose type glycans in TS-like CTBs differentiation in human placenta, which can also be used as a glycol molecular target for the treatment of miscarriage.

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“…Before attachment to protein, the N-glycan is synthesized as a lipid-linked oligosaccharide (LLO). Most eukaryotes share a common fourteen sugar Glc3Man9GlcNAc2 (G3M9GN2, where Glc (G), Man (M) and GlcNAc (GN) are glucose, mannose and N-acetylglucosamine, respectively) precursor oligosaccharide whose stepwise assembly is catalyzed by the Alg (asparagine-linked glycosylation) glycosyltransferases 5 , 6 . These glycosyltransferase reactions are topologically distinct 7 .…”

Section: Introductionmentioning

confidence: 99%

Rft1 catalyzes lipid-linked oligosaccharide translocation across the ER membrane

Chen,

Pei,

et al. 2024

Nat Commun

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The eukaryotic asparagine (N)-linked glycan is pre-assembled as a fourteen-sugar oligosaccharide on a lipid carrier in the endoplasmic reticulum (ER). Seven sugars are first added to dolichol pyrophosphate (PP-Dol) on the cytoplasmic face of the ER, generating Man5GlcNAc2-PP-Dol (M5GN2-PP-Dol). M5GN2-PP-Dol is then flipped across the bilayer into the lumen by an ER translocator. Genetic studies identified Rft1 as the M5GN2-PP-Dol flippase in vivo but are at odds with biochemical data suggesting Rft1 is dispensable for flipping in vitro. Thus, the question of whether Rft1 plays a direct or an indirect role during M5GN2-PP-Dol translocation has been controversial for over two decades. We describe a completely reconstituted in vitro assay for M5GN2-PP-Dol translocation and demonstrate that purified Rft1 catalyzes the translocation of M5GN2-PP-Dol across the lipid bilayer. These data, combined with in vitro results demonstrating substrate selectivity and rft1∆ phenotypes, confirm the molecular identity of Rft1 as the M5GN2-PP-Dol ER flippase.

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Alg mannosyltransferases: From functional and structural analyses to the lipid-linked oligosaccharide pathway reconstitution

Cited by 7 publications

References 40 publications

Inherited Retinal Degeneration Caused by Dehydrodolichyl Diphosphate Synthase Mutation–Effect of an ALG6 Modifier Variant

Inherited Retinal Degeneration Caused by Dehydrodolichyl Diphosphate Synthase Mutation–Effect of an ALG6 Modifier Variant

High-mannose glycosylation of ITGAM regulates the development and differentiation of trophoblast in the placenta

Rft1 catalyzes lipid-linked oligosaccharide translocation across the ER membrane

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