Biology subjects

Ros, U.

Publications and source records attributed to Ros, U..

4 recordsLinked to original sources

bioRxiv2026

Low-order MLKL oligomers induce irregular membrane defects in necroptosis

MLKL is a key executioner of necroptosis, a lytic form of regulated cell death associated with inflammatory pathologies. Upon activation by RIPK3-mediated phosphorylation, MLKL oligomerizes and translocates to the plasma membrane to induce permeabilization through yet unknown mechanisms. By imaging single particles of MLKL at the plasma membrane of necroptotic cells, here we show that, upon activation, MLKL transitions from a diffuse cytosolic distribution to discrete, low-mobility assemblies before cell bursting. This is accompanied by oligomerization into a mixture of species ranging from monomers up to hexamers. We directly visualize MLKL-induced membrane damage using atomic force microscopy imaging in supported bilayers, which reveals the formation of irregular membrane openings whose edges are only partially decorated with protein. Our findings support a mechanism in which low-order self-assemblies of MLKL disrupt plasma membrane integrity and stabilize membrane defect edges without organizing into defined pore structures, in contrast to membrane permeabilization in other forms of cell death. This reframes necroptosis execution and dissects membrane insertion of MLKL oligomers for potential targeting.

biophysics↗

bioRxiv2026

A cell death-independent role for MLKL in TGF-β receptor recycling in Marfan syndrome

Marfan syndrome (MFS) causes thoracic aortic aneurysm through mutations in the fibrillin-1 gene and subsequent dysregulated TGF-{beta} signalling. Mixed lineage kinase domain-like protein (MLKL) executes necroptosis after RIPK3-dependent phosphorylation, but also functions in endosomal trafficking. Here we show that MLKL phosphorylation sustains TGF-{beta} receptor recycling and aortic wall integrity without causing cell death. Phosphorylation-dead MLKLS345A/S347A (MlklAA) mice developed aortic root dilation with disorganised collagen architecture and a secretory-pathway proteomic signature. Crossing them with Fbn1C1039G/+ MFS mice aggravated aortic dilation, disrupted collagen fibril ultrastructure and prolyl/lysyl hydroxylation, and caused lethal rupture under angiotensin II. Complete MLKL deficiency reproduced this phenotype. Phosphorylated MLKL was increased in MFS aortas, yet cleaved caspase-3, TUNEL positivity, smooth muscle cell content and leukocyte infiltration were unchanged. In smooth muscle cells, MLKL depletion dysregulated collagen-modifying enzymes, altered TGF-{beta}-driven matrix remodelling and impaired RAB11-dependent TGF{beta}R1 recycling. These findings suggest that phosphorylation-dependent, non-lytic functions of MLKL may contribute to the maintenance of thoracic aortic integrity in MFS.

cell biology↗

bioRxiv2021

Systematic assessment of the accuracy of subunit counting in biomolecular complexes using automated single molecule brightness analysis

Analysis of single molecule brightness allows subunit counting of high-order oligomeric biomolecular complexes. Although the theory behind the method has been extensively assessed, systematic analysis of the experimental conditions required to accurately quantify the stoichiometry of biological complexes remains challenging. In this work, we develop a high-throughput, automated computational pipeline for single molecule brightness analysis that requires minimal human input. We use this strategy to systematically quantify the accuracy of counting under a wide range of experimental conditions in simulated ground-truth data and then validate its use on experimentally obtained data. Our approach defines a set of conditions under which subunit counting by brightness analysis is designed to work optimally and helps establishing the experimental limits in quantifying the number of subunits in a complex of interest. Finally, we combine these features into a powerful, yet simple, software that can be easily used for the stoichiometry analysis of such complexes.

biophysics↗

bioRxiv2019

Ferroptotic pores induce Ca2+ fluxes and ESCRT-III activation to modulate cell death kinetics

Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca2+ fluxes during ferroptosis correlate with the activation of ESCRT-III-mediated membrane repair, which counterbalances the kinetics of cell death and modulates the inflammatory signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained high levels of cytosolic Ca2+ prior to plasma membrane disruption are a common feature of regulated necrosis and position ESCRT-III as a general protective mechanism in these inflammatory cell death pathways.

cell biology↗