Biology subjects

Zandberg, W. F.

Publications and source records attributed to Zandberg, W. F..

3 recordsLinked to original sources

bioRxiv2026

Intestinal epithelial Casd1 influences mucus sialic acid O-acetylation and tissue damage susceptibility toward large-intestinal mucosal insults.

The intestinal mucus network, primarily composed of O-glycosylated MUC2 mucin polymers, is essential for protecting the gastrointestinal tract from microbial threats. Sialic acid (Sia), a terminal monosaccharide on complex O-glycans, plays a key role in maintaining mucus integrity and is frequently modified by Casd1-dependent O-acetylation (OAc). Despite its prevalence, the biological significance of sialic acid OAc (OAc-Sia) modifications in human and murine mucus remains unclear. We hypothesized that OAc-Sia variants on mucus interact with the microbiota and are required for optimal mucus barrier function and host-microbe homeostasis in the colon. To test this, we profiled OAc-Sia on human and mouse MUC2 in situ using viral-derived probes with bacterial FISH and confocal microscopy; generated intestinal epithelial cell (IEC)-specific Casd1 null mice (IEC Casd1-/-); performed sialylomic and O-glycomic HPLC-MS analyses; assessed microbial communities by 16S rRNA sequencing with quantitative microbial profiling (QMP); and evaluated disease susceptibility using DSS colitis and Citrobacter rodentium infection models. Results revealed that both human and murine mucins are extensively O-acetylated and interact with the microbiota, suggesting biological relevance. IEC Casd1-/- mice were viable and displayed a complete loss of mucin OAc-Sia, indicating Casd1 is the sole contributor to OAc-status. Unexpectedly, mucus function was intact in IEC Casd1-/- mice, with no difference in structure or quality vs. WT co-housed littermates.16S rRNA analysis showed a modest but significant sex-specific reduction of microbial loads in male IEC Casd1-/-mice, and a clear trend toward reduced Turicibacter spp. vs. WT mice in both male and females, without impacting overall short-chain fatty acid (SCFA) production. DSS treatment led to more severe and extensive tissue damage in IEC Casd1-/- mice. C. rodentium infection led to increased damage in the cecum and distal colon of IEC Casd1-/- mice without affecting pathogen load, suggesting that OAc-Sia status has a role in tolerance defense. These findings establish intestinal epithelial Sia O-acetylation as a component dispensable for mucus and host-microbe homeostasis at baseline, but important in limiting damage to mucosal inflammatory insults.

cell biology↗

bioRxiv2025

The complete {lambda}-carrageenan depolymerization cascade from a marine Pseudoalteromonad revealed by structural analysis of the enzymes.

Carrageenans are a complex group of polysaccharides derived from the cell walls of red macroalgae. They are an abundant, yet recalcitrant nutrient source for most marine heterotrophic bacteria. Some member species of the Pseudoalteromonas genus are effective at metabolizing carrageenan. However, the enzymatic pathway for {lambda}-carrageenan, one of the most sulfated naturally occurring polysaccharides, remains unknown. Using detailed structural analysis by X-ray crystallography we reveal the sophisticated and cyclic enzymatic cascade deployed by Pseudoalteromonas distincta (strain U2A) to utilize {lambda}-carrageenan. The cascade incorporates ten glycoside hydrolases and five sulfatases that are specific for {lambda}-carrageenan and cooperate to completely deconstruct this polysaccharide, thus yielding galactose monosaccharides for subsequent energy production. The detailed molecular understanding of {lambda}-carrageenan depolymerisation provided includes structural evidence for a lesser described sulfatase catalytic mechanism and elucidation of a distinct catabolic cascade that is unique from previously described carrageenan metabolic pathways. This insight also holds potential for the application of enzymatic logic in the generation of high value products from abundant natural biopolymers, such as carrageenans.

biochemistry↗

bioRxiv2021

Carbohydrate sulfation as a mechanism for fine-tuning Siglec ligands

The immunomodulatory family of Siglecs recognize sialic acid-containing glycans as self, which is exploited in cancer for immune-evasion. The biochemical nature of Siglec ligands remains incompletely understood with emerging evidence suggesting the importance of carbohydrate sulfation. Here, we investigate how specific sulfate modifications affect Siglec ligands by overexpressing eight carbohydrate sulfotransferases (CHSTs) in five cell lines. Overexpression of three CHSTs (CHST1, CHST2, or CHST4) significantly enhances the binding of numerous Siglecs. Unexpectedly, two other CHSTs (Gal3ST2 and Gal3ST3) diminish Siglec binding, suggesting a new mode to modulate Siglec ligands via sulfation. Results are cell type dependent, indicating that the context in which sulfated glycans are presented is important. Moreover, pharmacological blockade of N- and O-glycan maturation reveals a cell type-specific pattern of importance for either class of glycan. Production of a highly homogenous CD33 (Siglec-3) fragment enabled a mass spectrometry-based binding assay to determine 10-fold and 3-fold enhanced affinity for Neu5Ac2-3(6-O-sulfo)Gal{beta}1-4GlcNAc and Neu5Ac2-3Gal{beta}1-4(6-O- sulfo)GlcNAc, respectively, over Neu5Ac2-3Gal{beta}1-4GlcNAc. CD33 showed significant additivity in affinity (36-fold) for the disulfated ligand, Neu5Ac2-3(6-O-sulfo)Gal{beta}1-4(6-O-sulfo)GlcNAc. Moreover, overexpression of both CHST1 and CHST2 in cells greatly enhanced the binding of several Siglecs, including CD33. Finally, we reveal that CHST1 is upregulated in numerous cancers, correlating with poorer survival rates and sodium chlorate sensitivity for the binding of Siglecs to cancer cell lines. These results provide new insights into carbohydrate sulfation as a modification that is a general mechanism for tuning Siglec ligands on cells, including in cancer.

immunology↗