Biology subjects

Holzner, M.

Publications and source records attributed to Holzner, M..

4 recordsLinked to original sources

bioRxiv2026

Mapping the MIF-2 Chemokine Interactome Reveals MIF-2-CCL20 Complex Formation in Liver Fibrosis

D-dopachrome tautomerase (D-DT/MIF-2) is an inflammatory cytokine, atypical chemokine (ACK) and member of the macrophage migration-inhibitory factor (MIF) family. While interactions among classical chemokines (CKs) are established, ACK-CK interactions remain underexplored. Here, we screened for MIF-2 binding-partners using a protein array encompassing all CKs and selected ACKs, and validated candidate interactors by surface-plasmon resonance. CCL20/MIP-3 was prioritized based on RNA-sequencing suggesting induction during liver fibrosis. MIF-2/CCL20 complex formation was verified by microscale thermophoresis and interaction interfaces mapped using peptide array and in-silico modeling. The deduced binding-site near the MIF-2 tautomerase pocket was consistent with inhibition of its tautomerase activity by CCL20. We found both proteins abundantly expressed in human liver tissue, with a positive correlation. Pull-down confirmed complex formation and proximity ligation assay demonstrated MIF-2/CCL20 complexes in liver in situ, with higher levels in fibrotic tissue. Functionally, MIF-2/CCL20 complexes suppressed MIF-2-driven CD4 T-cell chemotaxis and fibroblast IL-6 secretion, indicating modulation of immune and stromal responses. This study extends the ACK interactome to MIF-2 and suggests ACK/CK complexes modulate chemokine activities in liver fibrosis.

immunology↗

bioRxiv2025

Illuminating oncogenic KRAS signaling by multi-dimensional chemical proteomics

Mutated KRAS is among the most frequent activating genetic alterations in cancer and drug discovery efforts have led to inhibitors that block its activity. To better understand oncogenic KRAS signaling and the cytostatic effects of drugs, we performed comprehensive dose-dependent proteome-wide target deconvolution, pathway engagement and protein expression characterization of KRAS, MEK, ERK, SHP2 and SOS1 inhibitors in pancreatic (KRAS G12C, G12D) and lung cancer (KRAS G12C) cells. Analysis of the resulting 687,954 dose-response curves available online revealed both common and cell line-specific signaling networks dominated by oncogenic KRAS activity. Time-dose experiments separated early KRAS-MEK-ERK from CDK-mediated signaling that cause cells to exit from the cell cycle. This transition to a quiescent state occurred without substantial proteome re-modelling but extensive changes of protein phosphorylation and ubiquitylation. The collective data highlights the complexity of KRAS signaling in cancer and places a large number of new proteins into this functional context.

cell biology↗

bioRxiv2024

Salmonids exhibit an acute behavioral response to heterothermal environments

Most fish species are ectothermic and rely on behavioral strategies to control their body temperature in heterothermal environments. Both thermotaxis and thermokinesis have been suggested as important underlying mechanisms. However, to what extent these behaviors allow fish to respond to rapid (timescales of minutes) and strong thermal disturbances, like those caused by anthropogenic water releases into natural freshwater systems, is poorly understood. Here, we quantify this response for a salmonid species with a novel laboratory approach coupled with image-based tracking. We exposed brown trout parr (Salmo trutta), acclimated to 12 {degrees}C, to rapidly forming cold- and warm-water interfaces with temperatures ranging from 4 to 20 {degrees}C. We found that fish actively avoided colder water ([≤]8 {degrees}C) through a rapid response that combined thermotaxis and thermokinesis. In contrast, fish did not avoid warmer water and frequently crossed interfaces having temperature contrasts of up to 8 {degrees}C. This study shows that brown trout parr swiftly deploy multiple behavioral strategies to minimize exposure to cold water and take advantage of warm water, illustrating their capability to cope with rapidly occurring thermal alterations.

biophysics↗

bioRxiv2023

The scramblases VMP1 and TMEM41b are required for primitive endoderm specification by targeting WNT signaling

The ER resident proteins VMP1 and TMEM41b share a conserved DedA domain, which confers lipid scramblase activity. Loss of either gene results in embryonic lethality in mice and defects in autophagy and lipid droplet metabolism. We set out to investigate their role in pluripotency and specification. For this purpose, we generated Vmp1 and Tmem41b mutations in mouse embryonic stem cells (ESCs). We observed that ESCs carrying mutations in Vmp1 and Tmem41b show robust self-renewal and an unperturbed pluripotent expression profile but accumulate LC3-positive autophagosomes and lipid droplets consistent with defects in autophagy and lipid metabolism. ESCs carrying combined mutations in Vmp1 and Tmem41b can differentiate into a wide range of embryonic cell types. However, differentiation into primitive endoderm-like cells in culture is impaired, and the establishment of extra- embryonic endoderm stem (XEN) cells is delayed. Mechanistically, we show the deregulation of genes that are associated with WNT signaling. This is further confirmed by cell surface proteome profiling, which identified a significant reduction of the WNT receptor FZD2 at the plasma membrane in Vmp1 and Tmem41b double mutant ESCs. Importantly, we show that transgenic expression of Fzd2 rescues XEN differentiation. Our findings identify the role of the lipid scramblases VMP1 and TMEM41b in WNT signaling during extra-embryonic endoderm development and characterize their distinct and overlapping functions.

developmental biology↗