Biology subjects

Kummer, L.

Publications and source records attributed to Kummer, L..

4 recordsLinked to original sources

bioRxiv2025

Mouse Models Uniformly Featuring Human-like Lesions Harboring Drug-tolerant Mycobacterium tuberculosis

Mouse models have been key to studies of tuberculosis pathogenesis and drug efficacy, but many, such as those employing BALB/c mice, fail to reproduce the full range of heterogenous microniches observed in well-structured human lesions, which feature hypoxic caseous cores of necrotic debris surrounded by infected foamy macrophages. The granuloma presents a variety of environments differing in levels of oxygen, ions, nutrients, and intra versus extracellular residence, which determine the physiological state of the infecting bacillus and its susceptibility to immune or drug control. Recently, alternative mouse strains such as C3HeB/FeJ have allowed the study of infection and treatment in the context of these varied environments but exhibit substantial inconsistency in development of human-like lesions, both within and between individual mice. Building on the observation that inducible nitric oxide synthase (Nos2)-deficient mice consistently develop hypoxic necrotic lesions, we have established two simplified models with infection by the aerosol route. The first uses the slightly attenuated M. tuberculosis R1Rv strain, which produces a progressive infection that is contained at a high stable burden by an adaptive immune response. In the second model, vaccination with the attenuated {Delta}RD1, pantothenate auxotroph mc2 6230 protects from an otherwise lethal infection with virulent M. tuberculosis Erdman. This model reflects most contemporary tuberculosis infections, which take place in the context of a pre-existing immune response from vaccination. Both variations uniformly develop well-structured hypoxic necrotic lesions harboring drug tolerant bacteria. These refined models will be useful in studies of M. tuberculosis infection and treatment.

microbiology↗

bioRxiv2024

Characterization of Collaborative Cross mouse founder strain CAST/EiJ as a novel model for lethal COVID-19

Mutations in SARS-CoV-2 variants of concern (VOCs) have expanded the viral host range beyond primates, and a limited range of other mammals, to mice, affording the opportunity to exploit genetically diverse mouse panels to model the broad range of responses to infection in patient populations. Here we surveyed responses to VOC infection in genetically diverse Collaborative Cross (CC) founder strains. Infection of wild-derived CC founder strains produced a broad range of viral burden, disease susceptibility and survival, whereas most other strains were resistant to disease despite measurable lung viral titers. In particular, CAST/EiJ, a wild-derived strain, developed high lung viral burdens, more severe lung pathology than seen in other CC strains, and a dysregulated cytokine profile resulting in morbidity and mortality. These inbred mouse strains may serve as a valuable platform to evaluate therapeutic countermeasures against severe COVID-19 and other coronavirus pandemics in the future.

immunology↗

bioRxiv2021

Engineering single pan-specific ubiquibodies for targeted degradation of all forms of endogenous ERK protein kinase

Ubiquibodies (uAbs) are a customizable proteome editing technology that utilizes E3 ubiquitin ligases genetically fused to synthetic binding proteins to steer otherwise stable proteins of interest (POIs) to the proteasome for degradation. The ability of engineered uAbs to accelerate the turnover of exogenous or endogenous POIs in a posttranslational manner offers a simple yet robust tool for dissecting diverse functional properties of cellular proteins as well as for expanding the druggable proteome to include tumorigenic protein families that have yet-to-be successfully drugged by conventional inhibitors. Here, we describe the engineering of uAbs comprised of a highly modular human E3 ubiquitin ligase, human carboxyl terminus of Hsc70-interacting protein (CHIP), tethered to different designed ankyrin repeat proteins (DARPins) that bind to nonphosphorylated (inactive) and/or doubly phosphorylated (active) forms of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Two of the resulting uAbs were found to be global ERK degraders, pan-specifically capturing all endogenous ERK1/2 protein forms and redirecting them to the proteasome for degradation in different cell lines, including MCF7 breast cancer cells. Taken together, these results demonstrate how the substrate specificity of an E3 ubiquitin ligase can be reprogrammed to generate designer uAbs against difficult-to-drug targets, enabling a modular platform for remodeling the mammalian proteome.

synthetic biology↗

bioRxiv2020

Crystal structure of the human oxytocin receptor

The peptide hormone oxytocin modulates socioemotional behaviour and sexual reproduction via the centrally expressed oxytocin receptor (OTR) across several species. Here, we report the crystal structure of human OTR in complex with retosiban, a non-peptide antagonist developed as an oral drug for the prevention of preterm labour. Our structure reveals insights into the detailed interactions between the G-protein coupled receptor (GPCR) and an OTR-selective antagonist. The observation of an extrahelical cholesterol molecule, binding in an unexpected location between helix IV and V, provides a structural rationale for its allosteric effect and critical influence on OTR function. Furthermore, our structure in combination with experimental data allows the identification of a conserved neurohypophyseal receptor-specific coordination site for Mg2+ that acts as potent positive allosteric modulator for agonist binding. Together these results further our molecular understanding of the oxytocin/vasopressin receptor family and will facilitate structure-guided development of new therapeutics.

biochemistry↗