Biology subjects

Brunner, A.

Publications and source records attributed to Brunner, A..

10 recordsLinked to original sources

bioRxiv2026

De novo Design of Macrocyclic Molecular Glues

The engineering of induced proximity has transformed drug discovery, yet the development of molecular glues remains largely serendipitous and restricted to the retrospective optimisation of accidental discoveries. Here, we present EvoBind-multimer, a deep learning framework for the de novo design of molecular glues directly from protein sequences. Unlike structure-based docking, our method generates small macrocyclic peptides that bridge user-defined protein pairs without requiring prior interface knowledge or existing ligands. We applied this framework to recruit the E3 ligase VHL to two challenging oncoproteins: KRAS and BRD4. Live-cell NanoBRET demonstrated robust design-induced proximity for both pairs. Mechanistic validation demonstrated that the generated macrocycles form functional VHL-target ternary complexes capable of driving Cullin-RING ligase-dependent proteasomal degradation and downstream signalling shutdown. Finally, evaluation in patient-derived xenograft neuroblastoma tumoroids revealed that ternary complex processing is deeply context-dependent: identical macrocycles acted as potent degraders in one patient model, yet functioned as stabilising "LOCKTACs" in another, driving VHL-dependent target sequestration without turnover. By enabling the de novo design of induced proximity from sequence alone, EvoBind-multimer provides a route towards designing new protein functions.

bioinformatics↗

bioRxiv2025

Loose coupling between Ca2+ channels and release sensors as a synaptic correlate of higher order brain function

In the mature neocortex, functionally distinct areas are built by the same archetypes of neurons, but depending on the area, these neurons and their synapses are engaged in very different functions, ranging from lower order processing of sensory information to higher order associations and cognitive functions. We found significant differences in the functional presynaptic nanoarchitectures of the same types of pyramidal neuron synapses, depending on whether they are located in the prefrontal cortex (PFC) or in the primary somatosensory cortex (S1). Synapses in PFC operated with loose microdomain coupling as opposed to tight nanodomain coupling in S1. These differences were associated with significant differences in synaptic timing, efficacy and plasticity between areas. Our data suggest that the mature neocortex uses tuning of synaptic topographies to specialize seemingly identical types of neurons for their required function. They suggest that microdomain coupling in pyramidal neuron synapses could be a presynaptic structure-function correlate of higher order neocortical functions.

neuroscience↗

bioRxiv2024

Nanoscale 3D DNA tracing reveals the mechanism of self-organization of mitotic chromosomes

How genomic DNA is folded during cell division to form the characteristic rod-shaped mitotic chromosomes essential for faithful genome inheritance is a long-standing open question in biology. Here, we use nanoscale DNA-tracing in single dividing cells to directly visualize how the 3D fold of genomic DNA changes during mitosis, at scales from single loops to entire chromosomes. Our structural analysis reveals a characteristic genome scaling minimum at 6-8 Mbp in mitosis. Combined with data-driven modeling and molecular perturbations, we can show that very large and strongly overlapping loops formed by Condensins are the fundamental structuring principle of mitotic chromosomes. These loops compact chromosomes locally and globally to the limit set by chromatin self-repulsion. The characteristic length, density and increasingly overlapping structure of mitotic loops we observe in 3D, fully explain how the rod-shaped mitotic chromosome structure emerges by self-organization during cell division.

cell biology↗

bioRxiv2024

Quantitative imaging of loop extruders rebuilding interphase genome architecture after mitosis

How cells establish the interphase genome organization after mitosis is incompletely understood. Using quantitative and super-resolution microscopy, we show that the transition from a Condensin to a Cohesin-based genome organization occurs dynamically over two hours. While a significant fraction of Condensins remains chromatin-bound until early Gl, Cohesin-STAGl and its boundary factor CTCF are rapidly imported into daughter nuclei in telophase, immediately bind chromosomes as individual complexes and are sufficient to build the first interphase TAD structures. By contrast, the more abundant Cohesin-STAG2 accumulates on chromosomes only gradually later in Gl, is responsible for compaction inside TAD structures and forms paired complexes upon completed nuclear import. 0ur quantitative time-resolved mapping of mitotic and interphase loop extruders in single cells reveals that the nested loop architecture formed by sequential action of two Condensins in mitosis is seamlessly replaced by a less compact, but conceptually similar hierarchically nested loop architecture driven by sequential action of two Cohesins.

cell biology↗

bioRxiv2023

A liquid-like coat mediates chromosome clustering during mitotic exit

SummaryThe individualization of chromosomes during early mitosis and their clustering upon exit from cell division are two key transitions that ensure efficient segregation of eukaryotic chromosomes. Both processes are regulated by the surfactant-like protein Ki-67, but how Ki-67 achieves these diametric functions has remained unknown. Here, we report that Ki-67 radically switches from a chromosome repellent to a chromosome attractant during anaphase. We show that Ki-67 dephosphorylation during mitotic exit and the simultaneous exposure of a conserved basic patch induce the RNA-dependent formation of a liquid-like condensed phase on the chromosome surface. Experiments and coarse-grained simulations support a model in which the coalescence of chromosome surfaces driven by phase separation promote clustering of chromosomes. Our study reveals how the switch of Ki-67 from a surfactant to a liquid-like condensed phase can generate the mechanical forces during genome segregation that are required for re-establishing nuclear-cytoplasmic compartmentalization after mitosis.

cell biology↗

bioRxiv2023

An array of signal-specific MoYpd1 isoforms determines full virulence in the pathogenic fungus Magnaporthe oryzae

Magnaporthe oryzae is placed first on a list of the worlds top ten plant pathogens with the highest scientific and economic importance. The pathogen is highly evolved to sense environmental changes quickly to invade different tissues of its host plant successfully. Here, we found alternative splicing (AS) as a previously unknown mechanism of how the pathogen may handle rapidly changing situations during in planta growth. The AS facilitates the production of multiple mRNAs and, consequently, protein isoforms with distinct biological functions from a single gene. The locus MGG_07173 occurs only once in the genome of M. oryzae and encodes the phosphotransfer protein MoYpd1p, which plays an important role in the high osmolarity glycerol (HOG) signaling pathway for osmoregulation. Originating from this locus, at least three MoYPD1 isoforms are produced in a signal-specific manner. The transcript levels of these MoYPD1-isoforms were individually affected by external stress, which is equally present in host plant tissues. Potassium salt (KCI) stress raised MoYPD1_T0 and MoYPD1_T2 abundance, whereas osmotic stress by sorbitol elevates MoYPD1_T1 levels. In line with this, signal-specific nuclear translocation of green fluorescent protein-fused MoYpd1p isoforms in response to stress was observed. The protein isoforms MoYpd1p_T0 and MoYpd1p_T2 were detected in the nucleus following KCl treatment, whereas MoYpd1p_T1 did likewise upon sorbitol stress. Mutant strains that produce only one of the MoYpd1p isoforms are less virulent, suggesting a combination thereof is required to invade the host successfully. Using in silico protein-protein interaction studies, we were able to assign different roles to respective isoforms in the HOG signaling pathway and predicted interactions with other signaling pathways. In summary, we demonstrate the signal-specific production of MoYpd1p isoforms that individually increase signal diversity and orchestrate virulence in the rice blast fungus M. oryzae. Authors summaryThe worlds population rises rapidly and a major problem is the global food security. Magnaporthe oryzae is placed first on a list of the worlds top ten plant pathogens with the highest scientific and economic importance since it causes blast, the most devastating disease of cultivated rice, which is the major food source for more than half of the world population. In this study, we demonstrate signal-specific production of a signaling protein, MoYpd1p, and show for the first time that the isoforms individually increase signal diversity and orchestrate virulence in the rice blast fungus M. oryzae. These results will help to better understand the molecular basis of pathogenicity of the rice blast fungus and consequently open the door to develop new strategies for plant protection and food security. In addition, our study is a valuable contribution to the basic research area of signaling mechanisms in in filamentous pathogenic fungi, and will thus be of high interest for a broad readership of the scientific community.

microbiology↗

bioRxiv2022

Genetically encoded multimeric tags for intracellular protein localisation in cryo-EM

Cryo-electron tomography is a powerful label-free tool for visualizing biomolecules in their native cellular context at molecular resolution. However, the precise localisation of biomolecules of interest in the tomographic volumes is challenging. Here, we present a tagging strategy for intracellular protein localisation based on genetically encoded multimeric particles (GEMs). We show the applicability of drug-controlled GEM labelling of endogenous proteins in cryo-electron tomography and cryo-correlative fluorescence imaging in human cells.

cell biology↗

bioRxiv2020

REEP4 is recruited to the inner nuclear membrane by ELYS and promotes nuclear pore complex formation

Nuclear pore complexes (NPCs) are channels within the nuclear envelope that mediate nucleocytoplasmic transport. NPCs assemble either into the closed nuclear envelope during interphase or concomitantly with nuclear envelope reformation during anaphase. Both, interphase and post-mitotic NPC biogenesis require local deformation of membrane. Yet, the factors that control proper membrane remodeling for post-mitotic NPC assembly are unknown. Here, we report that the reticulon homology domain-protein REEP4 localizes not only to high-curvature membrane of the cytoplasmic endoplasmic reticulum (ER) but also to the inner nuclear membrane (INM). We show that REEP4 is recruited to the INM by the NPC biogenesis factor ELYS and promotes NPC assembly. REEP4 contributes mainly to anaphase NPC assembly, suggesting that REEP4 has an unexpected role in coordinating nuclear envelope reformation with post-mitotic NPC biogenesis.

cell biology↗

bioRxiv2020

The first AI-based mobile application for antibiotic resistance testing

Antimicrobial resistance is a major global health threat and its development is promoted by antibiotic misuse. While disk diffusion antibiotic susceptibility testing (AST, also called antibiogram) is broadly used to test for antibiotic resistance in bacterial infections, it faces strong criticism because of inter-operator variability and the complexity of interpretative reading. Automatic reading systems address these issues, but are not always adapted or available to resource-limited settings. We present the first artificial intelligence (AI)-based, offline smartphone application for antibiogram analysis. The application captures images with the phones camera, and the user is guided throughout the analysis on the same device by a user-friendly graphical interface. An embedded expert system validates the coherence of the antibiogram data and provides interpreted results. The fully automatic measurement procedure of our applications reading system achieves an overall agreement of 90% on susceptibility categorization against a hospital-standard automatic system and 98% against manual measurement (gold standard), with reduced inter-operator variability. The applications performance showed that the automatic reading of antibiotic resistance testing is entirely feasible on a smartphone. Moreover our application is suited for resource-limited settings, and therefore has the potential to significantly increase patients access to AST worldwide.

microbiology↗

bioRxiv2018

MaxQuant.Live enables global targeting of more than 25,000 peptides

Mass spectrometry (MS)-based proteomics is often performed in a shotgun format, in which as many peptide precursors as possible are selected from full or MS1 scans so that their fragment spectra can be recorded in MS2 scans. While achieving great proteome depths, shotgun proteomics cannot guarantee that each precursor will be fragmented in each run. In contrast, targeted proteomics aims to reproducibly and sensitively record a restricted number of precursor/fragment combinations in each run, based on pre-scheduled mass-to-charge and retention time windows. Here we set out to merge these two concepts by a global targeting approach in which an arbitrary number of precursors of interest are detected in real-time, followed by standard fragmentation or advanced peptide-specific analyses. We made use of a fast application programming interface to a quadrupole Orbitrap instrument and real-time recalibration in mass, retention time and intensity dimensions to predict precursor identity. MaxQuant.Live is freely available (www.maxquant.live) and has a graphical user interface to specify many pre-defined data acquisition strategies. Acquisition speed is as fast as with the vendor software and the power of our approach is demonstrated with the acquisition of breakdown curves for hundreds of precursors of interest. We also uncover precursors that are not even visible in MS1 scans, using elution time prediction based on the auto-adjusted retention time alone. Finally, we successfully recognized and targeted more than 25,000 peptides in single LC-MS runs. Global targeting combines the advantages of two classical approaches in MS-based proteomics, while greatly expanding the analytical toolbox.

bioinformatics↗