bims-meglyc 2025-09-21 papers

Issue of 2025–09–21
three papers selected by
Silvia Radenkovic, UMC Utrecht

HGG Adv. 2025 Sep 16. pii: S2666-2477(25)00120-4. [Epub ahead of print] 100517

Aberrant N-glycosylation may be a therapeutic target in carriers of a common and highly pleiotropic variant in the manganese transporter ZIP8.

Vartika Tomar, John Kang, Ruxian Lin, Steven R Brant, Mark Lazarev, Caitlin Tressler, Kristine Glunde, Natasha Zachara, Joanna Melia.

The treatment of defective glycosylation in clinical practice has been limited to patients with rare and severe phenotypes associated with congenital disorders of glycosylation (CDG). Carried by approximately 5% of the human population, the discovery of the highly pleiotropic, missense variant in a manganese transporter ZIP8 has exposed under-appreciated roles for Mn homeostasis and aberrant Mn-dependent glycosyltransferases activity leading to defective N-glycosylation in complex human diseases. Here, we test the hypothesis that aberrant N-glycosylation contributes to disease pathogenesis of ZIP8 A391T-associated Crohn's disease. Analysis of N-glycan branching in intestinal biopsies demonstrates perturbation in active Crohn's disease and a genotype-dependent effect characterized by increased truncated N-glycans. A mouse model of ZIP8 391-Thr recapitulates the intestinal glycophenotype of patients carrying ZIP8 variants. Borrowing from therapeutic strategies employed in the treatment of patients with CDGs, oral monosaccharide therapy with N-acetylglucosamine ameliorates the epithelial N-glycan defect, bile acid dyshomeostasis, intestinal permeability, and susceptibility to chemical-induced colitis in a mouse model of ZIP8 391-Thr. Together, these data support ZIP8 391-Thr alters N-glycosylation to contribute to disease pathogenesis, challenging the clinical paradigm that CDGs are limited to patients with rare diseases. Critically, the defect in glycosylation can be targeted with monosaccharide supplementation, providing an opportunity for genotype-driven, personalized medicine.

Keywords: Crohn’s disease; N-glycosylation; SLC39A8; ZIP8; manganese

DOI: https://doi.org/10.1016/j.xhgg.2025.100517

MicroPubl Biol. 2025 ;2025

Dissecting the impact of N-acetylmannosamine (ManNAc) on ganglioside levels in a sialin-deficient cell model.

Marya S Sabir, Marjan Huizing, William A Gahl, Frances M Platt, May Christine V Malicdan.

Lysosomal free sialic acid storage disorder (FSASD) is an ultra-rare neurodegenerative condition caused by mutations in SLC17A5 , which encodes the lysosomal sialic acid exporter, sialin. Deficiency of sialin leads to lysosomal accumulation of unconjugated ("free") sialic acid. This study investigated the ability of N-acetylmannosamine (ManNAc), a precursor of sialic acid, to rescue glycosphingolipid (GSL) sialylation in a SLC17A5-deficient HEK-293T model system. Our findings reveal that while ManNAc supplementation may enhance sialic acid biosynthesis, it does not fully restore ganglioside sialylation to wild-type levels, highlighting the essential role of lysosomal sialic acid recycling in maintaining GSL sialylation homeostasis.

DOI: https://doi.org/10.17912/micropub.biology.001733

MAbs. 2025 Dec;17(1): 2561823

ManNAc attenuates Man5 glycoform abundance through GNE-mediated metabolic channeling of UDP-GlcNAc to N-glycosylation modifications via CMP-Neu5Ac biosynthesis.

N-glycosylation, a critical quality attribute of monoclonal antibodies, plays a pivotal role in regulating pharmacokinetics and pharmacodynamics through high-mannose (Man5) glycoform modulation. While our previous work demonstrated that N-acetyl-D-mannosamine (ManNAc) supplementation effectively reduces Man5 levels without compromising antibody yield or other critical quality attributes, the mechanistic basis remained unclear. This study systematically investigates ManNAc's regulatory mechanism through a multi-parametric analysis. Cellular uptake studies revealed a 3-day latency period preceding Man5 reduction post-ManNAc administration. Subsequent transcriptional profiling showed no significant alterations in Man5-associated enzyme expression (Mgat1, Mgat2, Man2a1, SLC35A3), while metabolomic analysis demonstrated marked elevation of intracellular ManNAc, uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc), and cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac) levels. Mechanistic studies revealed two critical findings: (1) Chinese hamster ovary cells exhibit minimal endogenous N-acetyl-D-glucosamine-2-epimerase expression, and (2) CMP-Neu5Ac exerts potent inhibition on glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase (GNE) activity in vitro, despite ManNAc's lack of transcriptional regulation on GNE. We propose a metabolic flux redirection model, where ManNAc-derived CMP-Neu5Ac accumulation inhibits GNE activity, thereby shunting UDP-GlcNAc from sialic acid biosynthesis toward N-glycosylation pathways to reduce Man5 levels. This work not only identifies UDP-GlcNAc substrate limitation as a key constraint in antibody glycosylation but also establishes exogenous monosaccharide supplementation as a novel metabolic engineering strategy for Man5 optimization. These findings provide critical mechanistic insights for precision glycoengineering of therapeutic antibodies.

Keywords: Cytidine-5’-monophospho-N-acetylneuraminic acid; N-acetyl-D-mannosamine; glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine enzyme; high mannose; monoclonal antibodies; uridine-diphosphate-N-acetylglucosamine

DOI: https://doi.org/10.1080/19420862.2025.2561823