Biology subjects

Rademacher, C.

Publications and source records attributed to Rademacher, C..

11 recordsLinked to original sources

bioRxiv2026

Biological recognition of mirror-image glycans

Recent synthesis of essential enzymes, such as DNA and RNA polymerases with opposite chirality, has boosted the feasibility of creating mirror-image life. Such life, if ever produced, will undoubtedly be coated by a dense display of glycans (glycoproteins, glycolipids, polysaccharides) built from enantiomers of common monosaccharides. Recognition of mirror-image glycans by extant glycan-binding proteins (GBPs) may be critical for colonization by or immune response to mirror life organisms. We evaluated recognition of enantiomers of common glycans by a diverse set of purified GBPs (plant and human derived), antibodies (including IgM from human plasma), mammalian cells (including immune cells), and organs in live animals. We found that GBP binding to enantiomers of naturally prevalent glycans is widespread. Notably, L-glucose and L-galactose interact with fucose-binding lectins, including DC-SIGN, a C-type lectin expressed on immune cells. These interactions can be inhibited by soluble "natural" glycan ligands and enantiomeric ones confirming specificity. Binding of L-glycans to diverse immune cell repertoires revealed preferences for specific glycan enantiomers. IgM antibodies from human serum showed donor-specific recognition of L-glycans. We propose that the recognition of L-glycans by extant GBPs arises from their co-evolution over millennia with the L-glycans that are present in the glycocalyx of many microorganisms.

biochemistry↗

bioRxiv2025

Covalent activation of the C-type lectin DC-SIGN

Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN) is a C-type lectin receptor expressed on antigen-presenting cells, crucial for pathogen recognition and immune modulation. The shallow and polar carbohydrate binding site of DC-SIGN presents challenges for ligand design. Here, we explored covalent modification targeting specific lysine residues as a novel strategy to modulate DC-SIGN function. Screening a lysine-targeted electrophilic fragment library using orthogonal functional assays identified two potent activators. Structural analyses via NMR spectroscopy, mass spectrometry and computational modeling confirmed structural perturbations of the carbohydrate recognition domain and revealed distinct mechanisms of activation. While both activators significantly enhanced DC-SIGNs affinity for monosaccharide ligands, one compound induced oligomerization via covalent coupling and non-covalent secondary site interactions, whereas the other selectively modified lysine K373 directly within the primary carbohydrate-binding site. These findings demonstrate the potential of lysine-targeted covalent compounds as a novel therapeutic strategy for modulating DC-SIGN function and potentially C-type lectins in general. Table of contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=50 SRC="FIGDIR/small/674704v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1b44543org.highwire.dtl.DTLVardef@2f3feaorg.highwire.dtl.DTLVardef@d48e1org.highwire.dtl.DTLVardef@2baee1_HPS_FORMAT_FIGEXP M_FIG C_FIG We introduce the first covalent activators of a C-type lectin. Using GCI, NMR, MS/MS and computational modeling, we delineate mechanisms from a functional electrophile-first screen on DC-SIGN that yields two modes: NHS-ester 11 modifies K379 to induce CRD oligomerization via a secondary site, and squarate 33 modifies K373 in the carbohydrate site to strengthen glycan binding.

pharmacology and toxicology↗

bioRxiv2025

A cryptic pocket allosterically modulates oligosaccharide binding to DC-SIGN

DC-SIGN is a C-type lectin receptor expressed on antigen-presenting cells, crucial for pathogen recognition and immune modulation. Here, we identify and characterize a previously unrecognized cryptic allosteric pocket in DC-SIGN using molecular dynamics simulations, NMR spectroscopy, cryogenic electron microscopy and biochemical assays. Rotation of the gatekeeper residue M270 exposes the pocket whose occupancy modulates glycan binding. Mutations M270F and T314A mimic the occupied and unoccupied states of this pocket, respectively, shifting the conformational equilibrium of -helix 2 and altering oligosaccharide affinity via the extended carbohydrate binding site. While Ca{superscript 2} coordination at the canonical binding site remains unaffected, our data reveal a complex interplay between the Ca{superscript 2} binding sites and the canonical and extended glycan binding surfaces. These findings uncover a hierarchical allosteric mechanism that enables selective tuning of glycan affinity and suggest the cryptic pocket as a novel target for drug discovery in C-type lectins.

biochemistry↗

bioRxiv2025

Langerhans Cell-targeted mRNA Delivery: A Strategy for Dose-Sparing and Enhanced Anti-Tumor Immunity

Despite the success of mRNA therapeutics, challenges remain in optimizing immune responses and minimizing side effects. Cell-specific antigen delivery may help reduce required doses and improve vaccine efficacy. In this study, we report on the first targeted delivery system for mRNA to a specific subset of skin-resident antigen-presenting cells - Langerhans cells. By functionalizing lipid nanoparticles (LNPs) with a langerin-specific glycomimetic ligand, we achieve selective mRNA delivery to both murine and human primary Langerhans cells with minimal off-target uptake, at the same time resulting in significantly increased mRNA translation. This targeted mRNA delivery not only enhances antigen presentation and T cell responses but also enables dose-sparing and superior anti-tumor immunity compared to conventional immunization in a B16-OVA tumor model. Importantly, our platforms high compatibility with various lipid nanoparticle formulations offers a flexible and precise tool for skin-directed mRNA delivery.

immunology↗

bioRxiv2025

Langerhans Cell-targeted Protein Delivery Enhances Antigen-Specific Cellular Immune Response

Targeted antigen delivery to immune cells, particularly dendritic cells, has emerged as a promising strategy to enhance therapeutic efficacy of vaccines, while minimizing adverse effects associated with conventional immunization. In this study, we use our previously described small glycomimetic molecule that selectively recognizes the Langerhans cell (LC)-specific surface receptor Langerin and demonstrate specific delivery of protein antigens to these specialized dendritic cells. Our results show that Langerin-mediated antigen delivery significantly enhances the immune response in vivo, resulting in increased expansion and activation of antigen-specific T cells, compared to immunization with unmodified antigen. We demonstrate the feasibility of our LC-targeted platform for immune cell-specific immunization with protein antigen and underscore the potential of LCs as an access point for next-generation vaccines and immunotherapies.

immunology↗

bioRxiv2021

Information transfer in mammalian glycan-based communication

Glycan-binding proteins, so-called lectins, are exposed on mammalian cell surfaces and decipher the information encoded within glycans translating it into biochemical signal transduction pathways in the cell. These glycan-lectin communication pathways are complex and difficult to analyse. However, quantitative data with single cell resolution provides means to disentangle the associated signalling cascades. We chose C-Type lectin receptors (CLRs) expressed on immune cells as a model system to study their capacity to transmit information encoded in glycans of incoming particles. Lectin receptor NF{kappa}B-reporter cell lines expressing DC-SIGN, MCL, dectin-1, dectin-2, and mincle, as well as TNFR and TLR-1&2 in monocytic cell lines were characterized by comparing their efficiency to transmit glycan-encoded information. The information content was measured by following NF{kappa}B dependent GFP expression. While most receptors did transmit information to NF{kappa}B efficiently, we found dectin-2 to be an inefficient signalling receptor. Yet upon closer analysis we show that the sensitivity of the dectin-2 signal transduction pathway (EC50) can be enhanced by overexpression of its co-receptor FcR{gamma}, while its transmitted information cannot. In this context, we expanded our investigation towards the integration of multiple signal transduction pathways, which is crucial during pathogen recognition. We show how lectin receptors using a similar signal transduction pathway (dectin-1 and dectin-2) are being integrated; by striking a compromise between the lectins. By using dectin-2 and other lectins as example we demonstrate how cellular heterogeneity and the receptor itself determine the efficiency and therefore outcome of the signal transduction pathways.

cell biology↗

bioRxiv2020

The impact of Staphylococcus aureus cell wall glycosylation on langerin recognition and Langerhans cell activation

Staphylococcus aureus is the leading cause of skin and soft tissue infections. It remains incompletely understood how skin-resident immune cells respond to S. aureus invasion and contribute to an effective immune response. Langerhans cells (LCs), the only professional antigen-presenting cell type in the epidermis, sense S. aureus through their pattern-recognition receptor langerin, triggering a pro-inflammatory response. Langerin specifically recognizes the {beta}-1,4-linked N-acetylglucosamine ({beta}-GlcNAc) modification, which requires the glycosyltransferase TarS, on the cell wall glycopolymer Wall Teichoic Acid (WTA). Recently, an alternative WTA glycosyltransferase, TarP, was identified in methicillin-resistant S. aureus strains belonging to clonal complexes (CC) 5 and CC398. TarP also modifies WTA with {beta}-GlcNAc but at the C-3 position of the WTA ribitol phosphate (RboP) subunit. Here, we aimed to unravel the impact of {beta}-GlcNAc linkage position for langerin binding and LC activation. In addition, we performed structure-binding studies using a small panel of unique chemically-synthesized WTA molecules to assess langerin-WTA binding requirements. Using FITC-labeled recombinant human langerin and genetically-modified S. aureus strains, we observed that langerin similarly recognized bacteria that produce either TarS- or TarP-modified WTA. Furthermore, using chemically-synthesized WTA, representative of the different S. aureus WTA glycosylation patterns, established that {beta}-GlcNAc is sufficient to confer langerin binding. Functionally, tarP-expressing S. aureus induce increased cytokine production and maturation of in vitro-generated LCs compared to tarSexpressing S. aureus. Overall, our data suggest that LCs are able to sense all {beta}-GlcNAc-WTA producing S. aureus strains, likely performing an important role as first responders upon S. aureus skin invasion.

microbiology↗

bioRxiv2020

Molecular Mechanism of the pH-Dependent Calcium Affinity in Langerin

The C-type lectin receptor langerin plays a vital role in the mammalian defense against invading pathogens. Its function hinges on the affinity to its co-factor Ca2+ which in turn is regulated by the pH. We studied the structural consequences of protonating the allosteric pH-sensor histidine H294 by molecular dynamics simulations (total simulation time: about 120 {micro}s) and Markov models. We discovered a mechanism in which the signal that the pH has dropped is transferred to the Ca2+-binding site without transferring the initial proton. Instead, protonation of H294 unlocks a conformation in which a protonated lysine side-chain forms a hydrogen bond with a Ca2+-coordinating aspartic acid. This destabilizes Ca2+ in the binding pocket, which we probed by steered molecular dynamics. After Ca2+-release, the proton is likely transferred to the aspartic acid and stabilized by a dyad with a nearby glutamic acid, triggering a conformational transition and thus preventing Ca2+-rebinding.

molecular biology↗

bioRxiv2018

A specific, glycomimetic Langerin ligand for human Langerhans cell targeting

Langerhans cells are a subset of dendritic cells residing in the epidermis of the human skin. As such, they are key mediators of immune regulation and have emerged as prime targets for novel transcutaneous cancer vaccines. Importantly, the induction of protective T cell immunity by these vaccines requires the efficient and specific delivery of both tumor-associated antigens and adjuvants. Langerhans cells uniquely express Langerin (CD207), an endocytic C-type lectin receptor. Here, we report the discovery of a specific, glycomimetic Langerin ligand employing a heparin-inspired design strategy that integrated NMR spectroscopy and molecular docking. The conjugation of these glycomimetics to liposomes enabled the specific and efficient targeting of Langerhans cells in the human skin. This delivery platform provides superior versatility and scalability over antibody-based approaches and thus addresses current limitations of dendritic cell-based immunotherapies.

immunology↗

bioRxiv2017

Wall teichoic acid is a pathogen-associated molecular pattern of Staphylococcus aureus that is recognized by langerin (CD207) on skin Langerhans cells

Staphylococcus aureus is a major cause of skin and soft tissue infections and aggravator of the inflammatory skin disease atopic dermatitis (AD). Epicutaneous exposure to S. aureus induces Th17 responses through skin Langerhans cells (LCs), which paradoxically contribute to host defense but also to AD pathogenesis. The underlying molecular mechanisms of the association between S. aureus and skin inflammation are poorly understood. Here, we demonstrate that human LCs directly interact with S. aureus through the pattern-recognition receptor langerin (CD207). Human, but not mouse, langerin interacts with S. aureus through the conserved {beta}-N-acetylglucosamine (GlcNAc) modifications on wall teichoic acid (WTA), thereby discriminating S. aureus from other staphylococcal species. Importantly, the specific S. aureus WTA glycoprofile strongly influences the level of Th1-and Th17-polarizing cytokines that are produced by in vitro generated LCs. Finally, in a murine epicutaneous infection model, S. aureus induced a more pronounced influx of inflammatory cells and pro-inflammatory cytokine transcripts in skin of human langerin transgenic mice compared to wild-type mice. Our findings provide molecular insight into the unique pro-inflammatory capacities of S. aureus in relation to inflammatory skin disease.

microbiology↗

bioRxiv2017

Discovery of BAZ2A Bromodomain Ligands

The bromodomain adjacent to zinc finger domain protein 2A (BAZ2A) is implicated in aggressive prostate cancer. The BAZ2A bromodomain is a challenging target because of the shallow pocket of its natural ligand, the acetylated side chain of lysine. Here, we report the successful screening of a library of nearly 1500 small molecules by high-throughput docking and force field-based binding-energy evaluation. For seven of the 20 molecules selected in silico, evidence of binding to the BAZ2A bromodomain is provided by ligand-observed NMR spectroscopy. Two of these compounds show a favorable ligand efficiency of 0.42 kcal/mol per non-hydrogen atom in a competition-binding assay. The crystal structures of the BAZ2A bromodomain in complex with four fragment hits validate the predicted binding modes. The binding modes of compounds 1 and 3 are compatible with ligand growing for optimization of affinity for BAZ2A and selectivity against the close homologue BAZ2B.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC=\"FIGDIR/small/122317_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (36K):\norg.highwire.dtl.DTLVardef@aba498org.highwire.dtl.DTLVardef@c32ddeorg.highwire.dtl.DTLVardef@1f85fc0org.highwire.dtl.DTLVardef@15671bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗