Biology subjects

Geiger, R.

Publications and source records attributed to Geiger, R..

10 recordsLinked to original sources

bioRxiv2026

Structural modeling and experimental validation define the MxA-Thogotovirus nucleoprotein interface that drives restriction and escape

The human MxA (myxovirus resistance protein A) host restriction factor inhibits orthomyxoviruses, such as Thogotovirus (THOV) and influenza A virus (IAV), by binding to their nucleoproteins. Despite being discovered over six decades ago, how MxA interacts with viral targets remains unclear. Earlier studies using evolutionary analysis and mutagenesis showed that the MxA L4 loop, especially a hydrophobic aromatic amino acid at residue 561, is crucial for binding THOV nucleoprotein (NP) and restricting THOV. Here, we combined previous insights with structure prediction methods, molecular dynamics simulations, and experimental validation to define the human MxA L4 loop binding interface to THOV NP. We also evaluated the stability of MxA L4-NP binding through classical all-atom molecular dynamics simulations. Our model revealed MxA L4 binding to a surface-exposed site on THOV NP, including residues previously linked to viral escape from MxA restriction, even though this information was not used to guide our modeling efforts. This MxA-THOV NP interface is distinct from NPs RNA-binding or oligomerization surfaces. Our molecular dynamics simulations also agree with earlier data indicating that F561Y enhances MxA binding to THOV NP, whereas F561W reduces it and F561V ablates it entirely. Based on this model, we predicted specific variants in human MxA or THOV NP that could result in increased host restriction or viral escape. We tested these predictions using a viral minireplicon assay to validate our model. Our efforts will guide vital viral surveillance studies and the development of MxA-based antivirals. (240) Significance StatementThe interferon-stimulated MxA protein encodes a critical barrier to zoonotic spillover of orthomyxoviruses, restricting infection by binding viral nucleoprotein (NP). Despite being among the best-studied interferon-stimulated genes (ISGs), the specific host-viral interaction surface involved in binding or restriction is poorly understood. We address this hurdle using structural modeling and molecular dynamics simulations to generate a model of the biochemical interactions between MxA and Thogotovirus NP. Our model is consistent with previous work identifying mutations that strengthen or weaken the binding interaction. We validate this model using in vitro analysis of predicted mutations at the host-virus interface. Our model provides a framework for additional mutational studies, surveillance of viruses poised for zoonosis, and rational antiviral design. (115)

microbiology↗

bioRxiv2026

Droplet single-cell CRISPR screens identify regulators of T cell-mediated target-cell killing

Cytotoxic CD8 T cells kill target cells through brief cell-cell encounters, but pooled genetic screens cannot readily link perturbations in individual T cells to the fate of the target cells they engage. We developed droplet single-cell CRISPR screening to pair individual primary human CD8 T cells with cancer cells, measure rapid target-cell death, and recover sgRNAs from phenotype-defined droplets. Applied across primary T cells from multiple donors, the platform recovered regulators of T cell receptor signaling, synapse formation, granule exocytosis and cytotoxic differentiation, and identified negative regulators of killing, including established inhibitory nodes such as PTEN, RASA2 and FOXO1, together with AFAP1L2 and components of the mTORC1 pathway. Validation across bispecific engager and TCR-engineered settings showed that selected hits modulate target-cell killing across recognition modalities and tumor models. Unexpectedly, perturbation of RPTOR or RHEB enhanced cytotoxic execution while reducing mTORC1 output, increasing AKT phosphorylation, and attenuating anabolic programs. Transient pharmacologic mTORC1 inhibition reproduced this rapid-killing state and improved antitumor activity after adoptive transfer. These results establish an interaction-resolved pooled genetic strategy for mapping cytotoxicity regulators and reveal that transient modulation of mTORC1 can shift T cells from anabolic growth toward rapid cytotoxic execution to enhance antitumor activity.

immunology↗

bioRxiv2025

Structural atlas of Pakpunavirus P7-1 reveals determinants of virion stability and genome ejection

Bacteriophages of the Pakpunavirus genus exhibit broad host range and potent bacteriolytic activity, making them promising candidates for clinical use. Here, we present a structural atlas of the therapeutic phage Pakpunavirus P7-1, a component of a phage cocktail targeting Pseudomonas aeruginosa that has undergone Phase 1/2 clinical trials. We determined the near-atomic structure of the extended virion and obtained a medium-resolution reconstruction of the contracted tail. Atomic models were built for 20 structural proteins comprising the icosahedral capsid, neck, contractile tail, and baseplate. We identified six upward-pointing Short Tail Fibers that stabilize the extended sheath and six highly flexible Long Tail Fibers likely involved in host recognition. Ordered fragments of the Tape Measure Protein revealed six copies inside the tail tube, forming a 3-helix cork at the tail tip. Sheath contraction repositions the baseplate, projecting all twelve tail fibers outward, yet contraction alone is insufficient to trigger genome ejection.

biochemistry↗

bioRxiv2025

Targeting FOXA1 and FOXA2 Disrupts the Lineage-Specific Oncogenic Output Program in Prostate Cancer

Activation of the androgen receptor (AR) is the key lineage-specific oncogenic pathway and the primary therapeutic target in prostate cancer. While AR signaling is enabled by the pioneer transcription factor FOXA1, its homolog FOXA2 is specifically expressed in advanced lineage plasticity prostate cancers that have lost the AR signaling axis. However, their roles and utility as drug targets remain incompletely characterized. Here, we show an unexpected collaboration of FOXA1 and FOXA2 in mediating AR-independent cell proliferation in different lineage plasticity cancer subtypes. Conversely, joint loss-of-function or pharmacologic disruption of FOXA1 and FOXA2 leads to the collapse of lineage-specific oncogenic transcription factors followed by cell cycle arrest. In summary, our findings uncover a druggable dependency for AR-positive and - negative prostate cancers.

cancer biology↗

bioRxiv2025

TRIM24 Degradation Counteracts Adaptation to Androgen Receptor Inhibition in Prostate Cancer

The androgen receptor (AR) is the primary therapeutic target in prostate cancer. While androgen deprivation therapy (ADT) and androgen receptor signaling inhibitors (ARSi) are effective, the disease eventually progresses to fatal castration-resistant prostate cancer (CRPC). That said, little is known about the mechanisms in residual disease that initiates tumor relapse upon ADT/ARSi. Here, we discover a crucial role for TRIM24 in supporting the survival of residual cell clusters primed for tumor relapse in vivo. Consequently, reducing TRIM24 with bifunctional degraders (dTRIM24) significantly delays or even prevents the emergence of CRPC in the context of AR reactivation and lineage plasticity. dTRIM24 not only inhibits AR signaling but also counteracts adaptive pathways engaged by AR inhibition itself, such as STAT3 activation and EMT. Our findings underscore the potential of TRIM24 as an effective and druggable target for preventing prostate cancer progression under AR inhibition. SignificanceDespite advances in targeting AR signaling in prostate cancer, tumor relapse remains a major concern. Here, we provide evidence that more durable responses can be achieved by pharmacologically degrading TRIM24. At the molecular level, TRIM24 degradation inhibits both AR signaling and adaptive pathways that enable tumor relapse.

cancer biology↗

bioRxiv2022

Myc controls IL-15-driven expansion and translational machinery of NK cells

Myc is a pleiotropic transcription factor involved in cancer, cell proliferation, and metabolism. Its regulation and function in Natural Killer (NK) cells, which are innate cytotoxic lymphocytes important to control viral infections and cancer, remain poorly defined. Here we show that mice deficient for Myc in NK cells presented a severe reduction in these lymphocytes. Myc was required for NK cell development and expansion in response to the key cytokine interleukin (IL)-15, which induced Myc through transcriptional and posttranslational mechanisms. Mechanistically, Myc ablation in vivo largely impacted NK cells ribosomagenesis, reducing their translation and expansion capacities. Similar results were obtained by inhibiting MYC in human NK cells. Impairing translation by pharmacological intervention phenocopied the consequences of deleting or blocking MYC in vitro. Notably, mice lacking Myc in NK cells exhibited defective anticancer immunity, which reflected their decreased numbers of mature NK cells exerting suboptimal cytotoxic functions. These results indicate that MYC is a central node in NK cells, connecting IL-15 to translational fitness, expansion, and anticancer immunity.

immunology↗

bioRxiv2022

Integrated Multi-omics Analyses of NFKB1 patients B cells points towards an up regula-tion of NF-κB network inhibitors

The transcription factor NF-{kappa}B plays a pivotal role in the adaptive immune response. Pathogenic variants in NFKB1 are the most common genetic etiology of common variable immunodeficiency (CVID). Patients frequently present with impaired terminal B cell differentiation, autoimmunity, and hyperinflammatory immune dysregulation. NF-{kappa}B signaling and target gene expression are expected to be dysregulated in NFKB1-mutated patients. Here, we performed a multi-omics characterization of B cells from a cohort of clinically affected and unaffected NFKB1 mutation carriers. Our analysis identified specific epigenetic dysregulation and gene expression differences on B cells from NFKB1-mutated patients. We observed an aberrant expression of negative regulators of NF-{kappa}B signaling in NFKB1 mutation carriers, which may be a key factor for the autoinflammatory phenotype of these patients. Moreover, our analysis points towards a dysregulation of XBP1 and BCL3, key players of B cell activation and proliferation at different stages of B cell differentiation. The reduced expression of negative regulators of the NF-{kappa}B network is likely to be one of several mechanisms responsible for the aberrant NF-{kappa}B signaling, which impairs the maintenance of a normal humoral immune response. In summary, our findings highlight epigenetic and gene expression changes in B cells associated with NFKB1 mutations. Our data give insight into future therapeutic opportunities for patients with NFKB1 (haplo)insufficiency.

immunology↗

bioRxiv2020

A Genome-wide CRISPR-Cas9 Screen Identifies Host Factors Essential for Optimal Plasmodium Liver Stage Development.

Prior to initiating symptomatic malaria, a single Plasmodium sporozoite infects a hepatocyte and develops into thousands of merozoites, in part by scavenging host resources. We show that host microtubules dynamically reorganize around the developing liver stage (LS) parasite. Using a genome-wide CRISPR-Cas9 screen, we identified host regulators of cytoskeleton organization, vesicle trafficking, ER/Golgi stress and lipid biogenesis that regulate Plasmodium LS development. These novel regulators of infection, including Centromere Protein J (CENPJ), led us to interrogate how microtubule organizing centers (MTOCs) are regulated during infection. Foci of {gamma}-tubulin localized to the parasite periphery; depletion of CENPJ exacerbated this re-localization and increased infection. Further, we show that the Golgi acts as a non-centrosomal MTOC by organizing {gamma}-tubulin and stimulating microtubule nucleation at the parasite periphery. Collectively, we show that the Plasmodium LS recruits the host Golgi to form MT mediated conduits along which host organelles are recruited to the PVM, to support liver stage development. Our findings suggest many host-targeted pharmacological inhibitors may inhibit LS infection.

cell biology↗

bioRxiv2020

ADA2 is a lysosomal DNase regulating the type-I interferon response

Deficiency of adenosine deaminase 2 (DADA2) is a severe, congenital syndrome, which manifests with hematologic, immunologic and inflammatory pathologies. DADA2 is caused by biallelic mutations in ADA2, but the function of ADA2, and the mechanistic link between ADA2 deficiency and the severe inflammatory phenotype remains unclear. Here, we show that monocyte-derived proteomes from DADA2 patients are highly enriched in interferon response proteins. Using immunohistochemistry and detailed glycan analysis we demonstrate that ADA2 is post-translationally modified for sorting to the lysosomes. At acidic, lysosomal pH, ADA2 acts as a novel DNase that degrades cGAS/Sting-activating ligands. Furthermore, we define a clear structure-function relationship for this acidic DNase activity. Deletion of ADA2 increased the production of cGAMP and type I interferons upon exposure to dsDNA, which was reverted by ADA2 overexpression or deletion of STING. Our results identify a new level of control in the nucleic acid sensing machinery and provide a mechanistic explanation for the pathophysiology of autoinflammation in DADA2. One Sentence SummaryADA2 is a lysosomal nuclease controlling nucleic acid sensing and type I interferon production.

immunology↗

bioRxiv2019

Pseudomonas aeruginosa lectin LecB impairs keratinocyte fitness by abrogating growth factor signalling

Lectins are glycan-binding proteins with no catalytic activity and ubiquitously expressed in nature. Numerous bacteria employ lectins to efficiently bind to epithelia, thus facilitating tissue colonisation. Wounded skin is one of the preferred niches for Pseudomonas aeruginosa, which has developed diverse strategies to impair tissue repair processes and promote infection.\n\nHere, we analyse the effect of the P. aeruginosa fucose-binding lectin LecB on human keratinocytes and demonstrate that it triggers events in the host, upon binding to fucosylated residues on cell membrane receptors, that extend beyond its role as an adhesion molecule. We found that LecB associates with several growth factor receptors and dampens their signalling pathways, leading to the arrest of cell cycle. Additionally, we describe a novel LecB-triggered mechanism to downregulate host cell receptors by showing that LecB leads to insulin-like growth factor receptor 1 internalisation, without receptor activation, and subsequent missorting towards intracellular endosomal compartments.\n\nOverall, these data highlight that LecB is a multitask virulence factor that, through subversion of several host pathways, has a profound impact on keratinocyte proliferation and survival.

cell biology↗