Biology subjects

de Haan, N.

Publications and source records attributed to de Haan, N..

4 recordsLinked to original sources

bioRxiv2026

Salmonella SiiE-mediated apical invasion into colonocytes depends on MUC1 α2,3-linked sialic acids

MUC1 is a highly O-glycosylated cell-bound mucin that plays key roles in intestinal mucosal maintenance and microbe-host interactions. The enteropathogen Salmonella enterica expresses a giant adhesin SiiE, which mediates interaction with MUC1 and apical invasion of epithelial cells in a sialic acid-dependent manner. Here, we investigated the glycan specificity of the SiiE-MUC1 interaction and the expression of glycosylated MUC1 receptor in advanced intestinal epithelial models. Expression of the SiiE adhesin by Salmonella was highest in late logarithmic growth, could be induced by aerobic shock, and was detectable on the bacterial surface and in culture supernatant. Purified SiiE bound multiple O-glycan structures in a MUC1 glycopeptide array, including those bearing terminal sialic acids. Single-cell RNA sequencing of human intestinal epithelium showed that high MUC1 expression correlated with expression of ST3GAL and ST6GALNAC sialyltransferases, indicating the potential presence of both 2,3- and 2,6-linked sialylation in vivo. In HT29-MTX intestinal cultures, both 2,3- and 2,6-linked sialic acids could be detected on the apical surface and 2,3-sialic acid staining colocalized with MUC1. Mass spectrometry-based O-glycomics demonstrated that MUC1 carried predominantly core 1 and core 2 O-glycans decorated with 2,3-linked sialylation. Removal or blocking of 2,3-linked sialic acids abolished Salmonella invasion through the SiiE-MUC1 route. In advanced ex vivo cultures of human ileum and colon, MUC1 was detected in the colon, where regions showed positive staining for 2,3-linked sialic acids, but not in the ileum. After infection of the ex vivo tissues, Salmonella was found in close proximity to 2,3-sialylated colonic MUC1. Together, these findings demonstrate that Salmonella SiiE-mediated apical invasion of colonocytes depends on 2,3-sialylated O-glycans on MUC1. In humans, this pathway might be most relevant during Salmonella invasion in the colon.

microbiology↗

bioRxiv2026

CMAS dampens anti-tumor immunity and associates with response to neoadjuvant immunotherapy in melanoma

Identifying immune-regulatory pathways to predict response is crucial for the efficacy of immune checkpoint blockade (ICB) immunotherapies. Sialylation is upregulated in tumor cells and modulates immune responses in cancer, yet its impact on patient clinical outcome and the spatial organization of the tumor microenvironment remain unclear. Here, using publicly available single-cell RNA sequencing data we show that expression of the sialylation master regulator CMAS in melanoma cells correlates with poorer patient survival. Using a murine melanoma model, we demonstrate that Cmas deletion in tumor cells severely impaired tumor growth and improved anti-tumor lymphoid and myeloid cell responses, increasing tumor cell-intrinsic susceptibility to interferon-gamma-, CD4+ T cell-, and macrophage-mediated killing. Single-cell spatial transcriptomics on neoadjuvant ICB-treated melanoma patient tumor biopsies revealed that CMAS expression in tumor cells inversely correlated with tumor cell proximity to and activation status of T cells and macrophages. Furthermore, expression of CMAS in tumor cells was increased in patients who did not respond to immunotherapy, compared to responders. Overall, our work identifies CMAS as a key modulator of tumor-immune dynamics associated with survival and response to neoadjuvant ICB immunotherapy in melanoma patients.

cancer biology↗

bioRxiv2025

The Ligand Preference of LRP1 is Regulated by O-glycans

Low-density lipoprotein receptor (LDLR) and LDLR-related proteins (LRPs) are endocytic receptors serving as essential physiological regulators of multiple processes including cholesterol clearance, protein reabsorption and neuronal protein trafficking. We originally discovered O-glycans in linkers of the ligand-binding domains of LDLR/LRP receptors and showed that these play critical roles for uptake of LDL by LDLR and albumin by LRP2. Remarkably, these linker O-glycans are introduced exclusively by GALNT11, one out of 20 polypeptide GalNAc-transferase isoenzymes. Here, we investigate the role of linker O-glycans on the large ([~]600 kDa) and widely expressed multiligand LRP1 receptor implicated in diseases including neuropathies. In genetically engineered cell models we activated endogenous full-coding LRP1 with and without O-glycans and demonstrate that while the uptake of certain ligands, such as RAP and ApoE, was unaffected by O-glycans, the uptake of the neurotoxic molecules tau and amyloid beta was altered and in opposite directions. This demonstrates that O-glycans in ligand-binding domains can differentially modulate ligand affinity and specificity of LRP1. Our findings highlight an overlooked regulatory mechanism of endocytic receptors and identify the ligand repertoire of LRP1 as being influenced by O-glycans, with potential implications for neurodegenerative disease.

molecular biology↗

bioRxiv2022

Golgi Fragmentation - One of the Earliest Organelle Phenotypes in Alzheimer's Disease Neurons

Alzheimers disease (AD) is the most common cause of dementia, with no current cure. Consequently, alternative approaches focusing on early pathological events in specific neuronal populations, besides targeting the well-studied Amyloid beta (A{beta}) accumulations and Tau tangles, are needed. In this study, we have investigated disease phenotypes specific to glutamatergic forebrain neurons and mapped the timeline of their occurrence, by implementing familial and sporadic human induced pluripotent stem cell models as well as the 5xFAD mouse model. We recapitulated characteristic late AD disease phenotypes, such as increased A{beta} secretion and Tau hyperphosphorylation, as well as previously well documented mitochondrial and synaptic deficits. Intriguingly, we identified Golgi fragmentation as one of the earliest AD phenotypes, indicating potential impairments in protein processing and post-translational modifications. Computational analysis of RNA sequencing data revealed differentially expressed genes involved in glycosylation and glycan patterns, whilst total glycan profiling revealed minor glycosylation differences. This indicates general robustness of glycosylation besides the observed fragmented morphology. Importantly, we identified that genetic variants in Sortilin-related receptor 1 (SORL1) associated with AD could aggravate the Golgi fragmentation and subsequent glycosylation changes. In summary, we identified Golgi fragmentation as one of the earliest disease phenotypes in AD neurons in various in vivo and in vitro complementary disease models, which can be exacerbated via additional risk variants in SORL1. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/519571v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@98a8eeorg.highwire.dtl.DTLVardef@7aa7b7org.highwire.dtl.DTLVardef@991e33org.highwire.dtl.DTLVardef@8dabb4_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗