Biology subjects

Hagelueken, G.

Publications and source records attributed to Hagelueken, G..

15 recordsLinked to original sources

bioRxiv2026

Evolutionary algorithms accelerate de novo design of potent Nectin-4-specific cancer biologics

Recent advances in AI-based structural biology have made de novo protein binder design increasingly effective, yet performance remains highly target dependent. For instance, the cancer surface antigen Nectin-4, an immunoglobulin-like cell adhesion protein, proved particularly challenging for RFdiffusion-based minibinder generation, yielding substantially fewer high-quality candidates than related targets. To address this bottleneck, we integrated an evolutionary genetic algorithm (GA) with AI-driven design. GA selection with tunable stringency was coupled with diversification via partial diffusion or direct sequence editing, enabling efficient exploration of sequence-structure space and rapid enrichment of promising candidates. This AI-GA pipeline quickly produced large and diverse minibinder panels with very good in silico quality metrics and is compatible with inputs from multiple design algorithms. Pooled, large-scale experimental screening identified highly stable Nectin-4 minibinders with single-digit nanomolar down to subnanomolar affinities. Lead binders were further engineered into Nectin-4-specific flow cytometry detection reagents and potent bispecific T cell engagers, demonstrating functional activity beyond binding. Together, these results show that evolutionary refinement can unlock challenging targets and accelerate de novo protein design for next-generation cancer biologics.

bioengineering↗

bioRxiv2026

NLRP3 activators disrupt the endocytic AP2 complex and plasma membrane signaling

Organellar perturbations are linked to NLRP3 inflammasome activation, however, it remains unclear whether unrelated agonists converge on a common upstream pathway. Here, we traced intracellular organelle and protein movements by differential ultracentrifugation combined with mass spectrometry-based proteomics. We show that NLRP3 activators uniformly disrupt the endocytic Adaptor Protein 2 (AP2) complex, whereas other subcellular rearrangements are stimulus-specific. We discovered Dynasore as a K-efflux-independent NLRP3 activator that engages this signaling node irrespective of endocytosis inhibition. Pharmacological and genetic perturbation of AP2 renders cells unresponsive to extracellular cues, blunting GPCR signaling, cAMP production, and chemotaxis, thereby enforcing a frozen signaling state that propagates NLRP3 inflammasome activation. Collectively, our study reveals a common surveillance checkpoint linking impaired plasma membrane signaling to the execution of inflammation and cell death. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/707400v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@178eb1dorg.highwire.dtl.DTLVardef@193cb02org.highwire.dtl.DTLVardef@1f50080org.highwire.dtl.DTLVardef@1f3e3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Inhibition of NLRP3 by a CNS-penetrating indazole scaffold

Low-grade inflammation is a hallmark of ageing and a key cause of age-related impairments and diseases1. The NOD-like receptor NLRP3 senses a variety of danger signals and environmental insults, resulting in pro-inflammatory response, inflammasome formation and pyroptosis2,3. Its aberrant activation has been linked to many acute and chronic diseases ranging from atherosclerosis to Alzheimers disease and cancer, making NLRP3 an attractive therapeutic target4,5. Here we report the discovery, characterization, and structure of an indazole-based NLRP3 antagonist, BAL-1516, which potently inhibits inflammasome formation in monocytes and microglia. The cryo-electron microscopy structure of BAL-1516 bound to NLRP3 reveals a previously undescribed compound binding site at a surface groove of the nucleotide-binding domain with contacts to the FISNA and WHD subdomains. The characteristic feature of BAL compound binding is the formation of three hydrogen bonds to the peripheral {beta}-strand of the triple-ATPase; two from the indazoles nitrogen atoms and a third from the compounds linker region. Additional phenyl and thiazole moieties render the compound hydrophobic, allowing excellent blood-brain barrier penetration. The compound binding site is highly specific for NOD-like receptors, and the optimized compound BAL-1516 is able to directly bind mouse NLRP3 despite two conservative residue changes in the binding interface. The BAL compounds represent a first-in-class family of NLRP3 inhibitors, providing a broad design space, including covalent and degradative properties, for the development of NLRP3-directed therapeutics. The innate immune system contains cytosolic proteins that sense cellular stress caused by bacterial, viral and fungal infections or sterile inflammation, to control cellular integrity2. NLRP3 is a well-studied member of the nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) that is involved in the activation of the inflammasome, a multiprotein complex that mediates inflammation6. Upon detection of stress or pathogen-associated signals, NLRP3 triggers the activation of caspase-1, which leads to the production of pro-inflammatory cytokines such as IL-1{beta} and IL-18, driving inflammatory responses and ultimately pyroptotic cell death. In the context of neuroinflammation, NLRP3 plays a significant role in the pathogenesis of various neurodegenerative diseases, including Alzheimers disease, Parkinsons disease, and multiple sclerosis7. Research into targeting NLRP3 signalling with CNS-penetrating molecules holds potential for developing therapeutic strategies to alleviate neuroinflammatory conditions and to slow the progression of neurodegenerative diseases.

immunology↗

bioRxiv2025

Development of AI-designed protein binders for detection and targeting of cancer cell surface proteins

Artificial intelligence (AI)-based protein design opens new avenues for the rapid generation of new research tools and therapeutics, but experimental validation lags behind the computational design throughput. Here, we present a scalable workflow for the discovery and validation of AI-designed protein binders. Leveraging the RFdiffusion protein design pipeline with a custom filter for stable alpha-helical bundle folds, we construct libraries of thousands of AI-binders against cancer-associated surface proteins. Mammalian cell-surface and phage display screening yield multiple high-affinity PD-L1 binders but fewer hits for CD276 (B7-H3) and VTCN1 (B7-H4), reflecting the target-dependent efficiency of RFdiffusion in generating high-quality designs. Using our experimentally validated AI-designed binder libraries, we benchmark freely available structure prediction models. We find that interface predicted template modelling (ipTM) scores by Chai-1 with ESM embedding correlate well with experimental success and even predict deleterious effects of binding interface mutations. To demonstrate the versatility of AI-binders as research tools, we deploy them in CAR-T cells and also assemble them with fluorophore-labeled streptavidin into tetravalent quattrobinders, which achieve antibody-comparable staining of endogenous PD-L1 by flow cytometry. With high production yields and accessible structural models, AI-designed quattrobinders are versatile and cost-effective research tools amenable to community-driven validation and optimization.

bioengineering↗

bioRxiv2025

Specificity and Mechanism of tRNA cleavage by the AriB Toprim nuclease of the PARIS bacterial immune system

Transfer RNA molecules have been recently recognized as widespread targets of bacterial immune systems. Translation inhibition through tRNA cleavage or modification inhibits phage propagation, thereby protecting the bacterial population. To counteract this, some viruses encode their own tRNA molecules, allowing infection to take place. The AriB effector of the PARIS defence system is a Toprim nuclease previously shown to target the E. coli tRNALys(UUU), but not a tRNALys(UUU) variant encoded by bacteriophage T5. We demonstrate here that the T5-tRNALys(UUU) is required but not sufficient to bypass PARIS immunity. Combining tRNA-sequencing, genetics, phage infection and in vitro biochemical data, we reveal that the E. coli tRNAThr(UGU), is another prime target of AriB and tRNAAsn(GUU) represents a secondary, yet biologically relevant, target of the PARIS effector. Activated AriB protein cleaves these targets in vitro, and the cleavage reaction is not dependent on the presence of specific tRNA modifications. We show that the overexpression of phage T5 tRNALys(UUU), tRNAThr(UGU) and tRNAAsn(GUU) variants is sufficient to inhibit PARIS anti-viral defence. Finally, we propose a model for tRNA recognition by the AriB dimer and provide molecular details of its nuclease activity and specificity.

microbiology↗

bioRxiv2024

Sensing endogenous RNA in living human cells using a CRISPR-activated protease

Most techniques used to detect specific mRNAs in eukaryotic cells require to extract nucleic acids and thereby kill the cells. A programmable sensor for monitoring endogenous transcripts in living cells, in contrast, would enable to enrich living cells based on a specific transcription or splicing event, and studying these cells by live microscopy or sequencing methods requiring intact cells. We have engineered CRISPR-READ, a live cell RNA detector based on the CRISPR-associated Lon protease CalpL and a cA4-producing Type III CRISPR system. Upon RNA-programmable RNA sensing, CRISPR-READ produces an orthogonal second messenger, which leads to the cleavage of a dual FRET / localization reporter compatible with FACS sorting and live microscopy. Using this genetically encoded sensing circuit as a readout for a genome-wide CRISPR perturbation screen, we identified an extended Type-I interferon signaling cascade; RNA-Seq on sensor-sorted cells enabled unbiased identification of correlated stochasticity in gene expression across single cells.

bioengineering↗

bioRxiv2024

The SAVED domain of the type III CRISPR protease CalpL is a ring nuclease

Prokaryotic CRISPR-Cas immune systems detect and cleave foreign nucleic acids. In type III CRISPR-Cas systems, the Cas10 subunit of the activated recognition complex synthesizes cyclic oligoadenylates (cOAs), second messengers that activate downstream ancillary effector proteins. Once the viral attack has been weathered, elimination of extant cOA is essential to limit the antiviral response and to allow cellular recovery. Various families of ring nucleases have been identified, specializing in the degradation of cOAs either as standalone enzymes or as domains of effector proteins. Here we describe the ring nuclease activity inherent in the SAVED domain of the cA4-activated CRISPR Lon protease CalpL. We characterize the kinetics of cA4 cleavage and identify key catalytic residues. We demonstrate that cA4-incuced oligomerization of CalpL is essential not only for activation of the protease, but is also required for nuclease activity. Further, the nuclease activity of CalpL poses a limitation to the protease reaction, indicating a mechanism for regulation of the CalpL/T/S signaling cascade. This work is the first demonstration of a catalytic SAVED domain and gives new insights into the dynamics of transcriptional adaption in CRISPR defense systems which are not aimed at abortive infection but rather at a reversible adaption to phage attack.

biochemistry↗

bioRxiv2023

Pyroptosis inhibiting nanobodies block Gasdermin D pore formation

Gasdermin D (GSDMD) is a key mediator of pyroptosis, a pro-inflammatory form of cell death occurring downstream of inflammasome activation as part of the innate immune defence. Upon cleavage by inflammatory caspases, the N-terminal domain of GSDMD forms pores in the plasma membrane resulting in cytokine release and eventually cell death. Targeting GSDMD is an attractive way to dampen inflammation. In this study, six GSDMD targeting nanobodies were characterized in terms of their binding affinity, stability, and effect on GSDMD pore formation. Three of the nanobodies inhibited GSDMD pore formation in a liposome leakage assay, although caspase cleavage was not perturbed. We determined the crystal structure of human GSDMD in complex with two nanobodies at 1.9 [A] resolution, providing detailed insights into the GSDMD-nanobody interactions and epitope binding. The pore formation is sterically blocked by one of the nanobodies that binds to the oligomerization interface of the N-terminal domain in the multi-subunit assembly. Our biochemical and structural findings provide new tools for studying inflammasome biology and build a framework for the design of novel GSDMD targeting drugs.

biochemistry↗

bioRxiv2023

Conformational coupling of the sialic acid TRAP transporter HiSiaQM with its substrate binding protein HiSiaP

The tripartite ATP-independent periplasmic (TRAP) transporters use an extra cytoplasmic substrate binding protein (SBP) to transport a wide variety of substrates in bacteria and archaea. The SBP can adopt an open or closed state depending on the presence of substrate. The two transmembrane domains of TRAP transporters form a monomeric elevator whose function is strictly dependent on the presence of a sodium ion gradient. Insights from experimental structures, structural predictions and molecular modeling have suggested a conformational coupling between the membrane elevator and the substrate binding protein. Here, we use a disulfide engineering approach to lock the TRAP transporter HiSiaPQM from Haemophilus influenzae in different conformational states. The SBP, HiSiaP, was locked in its substrate-bound form and the transmembrane elevator, HiSiaQM, was locked in either its predicted inward- or outward-facing states. We characterized the disulfide-locked variants and used single-molecule total internal reflection fluorescence (TIRF) microscopy to study their interactions. Our experiments demonstrate that the SBP and the transmembrane elevator are indeed conformationally coupled, meaning that the open and closed state of the SBP recognize specific conformational states of the transporter and vice versa.

biochemistry↗

bioRxiv2022

A conserved isoleucine in the binding pocket of RIG-I controls immune tolerance to mitochondrial RNA

RIG-I is a cytosolic receptor of viral RNA essential for the immune response to numerous RNA viruses. Accordingly, RIG-I must sensitively detect viral RNA yet tolerate abundant self-RNA species. The basic binding cleft and an aromatic amino acid of the RIG-I C-terminal domain(CTD) mediate high-affinity recognition of 5triphosphorylated and 5base-paired RNA(dsRNA). Here, we found that, while 5unmodified hydroxyl(OH)-dsRNA demonstrated residual activation potential, 5-monophosphate(5p)-termini, present on most cellular RNAs, prevented RIG-I activation. Determination of CTD/dsRNA co-crystal structures and mutant activation studies revealed that the evolutionarily conserved I875 within the CTD sterically inhibits 5p-dsRNA binding. RIG-I(I875A) was activated by both synthetic 5p-dsRNA and endogenous long dsRNA within the polyA-rich fraction of total cellular RNA. RIG-I(I875A) specifically interacted with a long, highly structured, polyA-bearing, non-coding mitochondrial(mt) RNA, and depletion of mtRNA from total RNA abolished its activation. Altogether, our study demonstrates that avoidance of 5p-RNA recognition is crucial to preventing mtRNA-triggered RIG-I-mediated autoinflammation.

immunology↗

bioRxiv2021

SAVED by a toxin: Structure and function of the CRISPR Lon protease.

CRISPR antiviral defense systems such as the well-known DNA-targeting Cas9- and the more complex RNA-targeting type III systems are widespread in bacteria and archea 1, 2. The type III systems can orchestrate a complex antiviral response that is initiated by the synthesis of cyclic oligoadenylates (cOAs) upon foreign RNA recognition 3-5. These second messenger molecules bind to the CARF (CRISPR associated Rossmann-fold) domains of dedicated effector proteins that are often DNAses, RNAses, or putative transcription factors 6. The activated effectors interfere with cellular pathways of the host, inducing cell death or a dormant state of the cell that is better suited to avoid propagation of the viral attack 7, 8. Among a large set of proteins that were predicted to be linked to the type III systems 9, 10, the CRISPR-Lon protein caught our attention. The protein was predicted to be an integral membrane protein containing a SAVED-instead of a CARF-domain as well as a Lon protease effector domain. Here, we report the crystal structure of CRISPR-Lon. The protein is a soluble monomer and indeed contains a SAVED domain that accommodates cA4. Further, we show that CRISPR-Lon forms a stable complex with the 34 kDa CRISPR-T protein. Upon activation by cA4, CRISPR-Lon specifically cleaves CRISRP-T, releasing CRISPR-T23, a 23 kDa fragment that is structurally very similar to MazF toxins and is likely a sequence specific nuclease. Our results describe the first cOA activated proteolytic enzyme and provide the first example of a SAVED domain connected to a type III CRISPR defense system. The use of a protease as a means to unleash a fast response against a threat has intriguing parallels to eukaryotic innate immunity.

biochemistry↗

bioRxiv2021

The structure of HiSiaQM defines the architecture of tripartite ATP-independent periplasmic (TRAP) transporters

Tripartite ATP-independent periplasmic (TRAP) transporters are widespread in bacteria and archaea and provide important uptake routes for many metabolites 1-3. They consist of three structural domains, a soluble substrate-binding protein (P-domain), and two transmembrane domains (Q- and M-domains) that form a functional unit 4. While the structures of the P-domains are well-known, an experimental structure of any QM-domain has been elusive. HiSiaPQM is a TRAP transporter for the monocarboxylate sialic acid, which plays a key role in the virulence of pathogenic bacteria 5. Here, we present the first cryo-electron microscopy structure of the membrane domains of HiSiaPQM reconstituted in lipid nanodiscs. The reconstruction reveals that TRAP transporters consist of 15 transmembrane helices and are structurally related to elevator-type transporters, such as GltPh and VcINDY 6, 7. Whereas the latter proteins function as multimers, the idiosyncratic Q-domain of TRAP transporters enables the formation of a monomeric elevator architecture. Structural and mutational analyses together with an AlphaFold 8 model of the tripartite (PQM) complex reveal the structural and conformational coupling of the substrate-binding protein to the transporter domains. Furthermore, we characterize high-affinity VHHs that bind to the periplasmic side of HiSiaQM and inhibit sialic acid uptake in vivo. Thereby, they also confirm the orientation of the protein in the membrane. Our study provides the first structure of any binding-protein dependent secondary transporter and provides starting points for the development of specific inhibitors.

biochemistry↗

bioRxiv2021

Directionality of PYD filament growth determined by the transition of NLRP3 nucleation seeds to ASC elongation

Inflammasomes sense intrinsic and extrinsic danger signals to trigger inflammatory responses and pyroptotic cell death. Homotypic pyrin domain (PYD) interactions of inflammasome forming Nod-like receptors with the adaptor protein ASC mediate oligomerization into helical filamentous assemblies. These supramolecular organizing centers recruit and activate caspase-1, which results in IL-1{beta} family cytokine maturation and pyroptotic cell death. The molecular details of the critical step in signal transduction of inflammasome signaling, however, remain ill-defined. Here, we describe the cryo-EM structure of the human NLRP3 PYD filament at 3.6 [A] resolution. We identify a unique pattern of highly polar interface residues that form the homomeric interactions leading to characteristic filament ends that we designate as A- and B-end, respectively. Coupling a titration polymerization assay to cryo-EM, we demonstrate that the ASC adaptor protein elongation on NLRP3 PYD filament seeds is unidirectional, associating exclusively to the B-end of the NLRP3 filament. Notably, NLRP3 and ASC PYD filaments exhibit the same symmetry in rotation and axial rise per subunit, allowing for a continuous transition between NLRP3 as the nucleation seed and ASC as the elongator. Integrating the directionality of filament growth, we present a molecular model of the ASC speck consisting of active NLRP3-NEK7, ASC, and Caspase-1 proteins.

immunology↗

bioRxiv2021

Cryo-EM structure of the NLRP3 decamer bound to the cytokine release inhibitory drug CRID3

NLRP3 is an intracellular sensor protein whose activation by a broad spectrum of exogenous and endogenous stimuli leads to inflammasome formation and pyroptosis. The mechanisms leading to NLRP3 activation and the way how antagonistic small molecules function remain poorly understood. Here we report the cryo-electron microscopy structures of full-length NLRP3 in its native form and complexed with the inhibitor CRID3 (also named MCC950). Inactive, ADP-bound NLRP3 is a decamer composed of homodimers of intertwined LRR domains that assemble back-to-back as pentamers with the NACHT domain located at the apical axis of this spherical structure. Molecular contacts between the concave sites of two opposing LRRs are mediated by an acidic loop extending from an LRR transition segment. Binding of CRID3 significantly stabilizes the NACHT and LRR domains relative to each other, allowing structural resolution of 3.9-4.2 [A]. CRID3 binds into a cleft, connecting four subdomains of the NACHT with the transition LRR. Its central sulfonylurea group interacts with the Walker A motif of the NLRP3 nucleotide-binding domain and is sandwiched between two arginines from opposing sites, explaining the specificity of NLRP3 for this chemical entity. With the determination of the binding site of this lead therapeutic, specific targeting of NLRP3 for the treatment of autoinflammatory and autoimmune diseases and rational drug optimization are within reach.

immunology↗

bioRxiv2020

Triggering closure of a sialic acid TRAP transporter substrate binding protein through binding of natural or artificial substrates

The pathogens Vibrio cholerae and Haemophilus influenzae use tripartite ATP-independent periplasmic transporters (TRAPs) to scavenge sialic acid from host tissues. They use it as a nutrient or to evade the innate immune system by sialylating surface lipopolysaccharides. An essential component of TRAP transporters is a periplasmic substrate binding protein (SBP). Without substrate, the SBP has been proposed to rest in an open-state, which is not recognised by the transporter. Substrate binding induces a conformational change of the SBP and it is thought that this closed state is recognised by the transporter, triggering substrate translocation. Here we use real time single molecule FRET experiments and crystallography to investigate the open- to closed-state transition of VcSiaP, the SBP of the sialic acid TRAP transporter from V. cholerae. We show that the conformational switching of VcSiaP is strictly substrate induced, confirming an important aspect of the proposed transport mechanism. Two new crystal structures of VcSiaP provide insights into the closing mechanism. While the first structure contains the natural ligand, sialic acid, the second structure contains an artificial peptide in the sialic acid binding site. Together, the two structures suggest that the ligand itself stabilises the closed state and that SBP closure is triggered by physically bridging the gap between the two lobes of the SBP. Finally, we demonstrate that the affinity for the artificial peptide substrate can be substantially increased by varying its amino acid sequence and by this, serve as a starting point for the development of peptide-based inhibitors of TRAP transporters.

biophysics↗