Biology subjects

Kolbe, T.

Publications and source records attributed to Kolbe, T..

5 recordsLinked to original sources

bioRxiv2025

tRNA thiolation defects disrupt cellular proteostasis and tissue homeostasis in mammals

Sulfur modification of tRNA wobble uridines is an evolutionarily conserved mechanism that ensures efficient protein synthesis. In humans, loss of this anticodon modification due to mutations in CTU2 (cytosolic thiouridylase 2) causes DREAM-PL syndrome, a severe congenital disorder often leading to early postnatal death. However, the mechanisms by which loss of tRNA thiolation drives pathology remain unclear. Here, we show that loss of CTU2 triggers significant cellular proteostasis defects in patient cells and model cell lines. Structural and biochemical analyses reveal that the pathogenic CTU2L63P mutation destabilizes the CTU1/CTU2 complex and abolishes tRNA binding and thiolation. Acute loss of CTU2 caused codon-specific ribosome pausing at A-ending codons decoded by thiolated tRNAs, and decreased ribosome occupancy of A-rich transcripts in a dosage-dependent manner. Codon-biased mRNAs transcribed from genes critical for ciliogenesis are predicted to be most affected, linking their reduced translation to DREAM-PL etiology in humans. Surprisingly, Ctu2L63P mice display severe thiolation defects, but develop normally, are viable and fertile. Our findings highlight the importance of functional tRNA thiolation for organismal health in humans and identify species-specific vulnerabilities during embryonic development in mammals.

cell biology↗

bioRxiv2025

Pro- and anti-inflammatory macrophages adjust UCP2 protein levels based on their intrinsic metabolism and available metabolites

The immune and metabolic responses of macrophages are closely linked, and mitochondria play a key role in polarizing them into pro-inflammatory (classical) and anti-inflammatory (alternative) states. Mitochondrial uncoupling protein 2 (UCP2) is involved in regulating macrophage inflammation and glucose metabolism; however, its regulatory mechanisms are unclear. We found that inflammatory stimuli reduce UCP2 expression and oxygen consumption rates (OCR), indicating mitochondrial suppression. Conversely, IL-4-activated macrophages displayed higher UCP2 levels and enhanced respiration. Under glucose deprivation, LPS-stimulated macrophages retained mitochondrial activity despite lower UCP2 levels. Pyruvate emerged as a key regulator of UCP2, blocking its mitochondrial entry reduced UCP2 expression. Additionally, hypoxia markedly decreased UCP2 levels in IL-4-activated macrophages, suggesting that hypoxia contributes to UCP2 suppression in pro-inflammatory macrophages. Notably, pro-inflammatory macrophages exhibit reduced reliance on UCP2 due to suppressed mitochondrial respiration. Pyruvate regulates UCP2 expression, highlighting the connection between glycolysis and mitochondrial metabolism. These findings may inform therapeutic strategies for diseases involving immune dysregulation.

biophysics↗

bioRxiv2025

Understanding Influenza A Virus particles detaching from reconstructed cell surfaces

Influenza infection is a multistage process that involves the trafficking of viral particles across the cell membrane. Before endocytosis, virions target the membrane by binding hemagglutinin ligands to sialic acid residues on cell receptors. After budding, neuraminidase cleaves these residues, enabling virions to detach from the infected cell surface. ln this paper, we examine detachment dynamics through simulations and the-oretical analysis. We explain experimental findings showing that the time required for virions to detach can decrease as the single-trajectory average number of bridges increases-a counterintuitive result specific to neuraminidase activity. Furthermore, we demonstrate that the detachment time is not governed by a Poisson distribution but depends on multiple factors, including ligand-receptor reaction rates, virion size, and receptor diffusion constant. These results clarify how biochemical parameters regulate the residence time of virions at the cell surface. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/668852v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@2ae5d4org.highwire.dtl.DTLVardef@56e756org.highwire.dtl.DTLVardef@16de32dorg.highwire.dtl.DTLVardef@15dda8f_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2025

Sequential PIDD1 auto-processing is essential for ploidy control in liver and heart

Polyploidization refers to the balanced increase in gene copy number and is a feature of specialized cells in different mammalian tissues, including the liver and the heart. During organogenesis, hepatocytes and cardiomyocytes undergo scheduled polyploidization events to increase their cellular or nuclear DNA content. This is thought to improve cellular output and enable for rapid genetic adaptation in response to stress. Yet, excessive increases in ploidy can also be disadvantageous and increase the risk of genome instability. Hence, a dedicated machinery, the PIDDosome multi-protein complex, has evolved to prevent exacerbated increases in DNA content. Using targeted mutagenesis in mice, we show that the PIDDosome controls hepatocyte ploidy in a cell-autonomous manner and that sequential and quantitative auto-processing of PIDD1 is key for accurate control of ploidy in postnatal development of liver and heart. Stoichiometric imbalances in bioactive PIDD1-fragments impair p53-dependent and independent cell cycle arrest responses during organogenesis, as well as caspase-2-dependent apoptosis caused by centrosome amplification. Strikingly, targeted mutagenesis of the caspase cleavage motif in the critical E3-ligase controlling p53 protein levels, Mdm2, impairs ploidy control in hepatocytes, but not in cardiomyocytes, indicative of the existence of alternative caspase-2 substrates that help to restrict ploidy in the heart.

cell biology↗

bioRxiv2021

Effect of different ambient temperatures on reproductive outcome and wellbeing of lactating females in two mouse strains

Ambient temperature is an important non-biotic environmental factor influencing immunological and oncological parameters in laboratory mice. It is under discussion which temperature is more appropriate and whether the commonly used room temperature in rodent facilities of about 21{degrees}C represents a chronic cold stress or the 30{degrees}C of the thermoneutral zone constitutes heat stress for the animals. In this study we selected the physiological challenging period of lactation to investigate the influence of a cage temperature of 20{degrees}C, 25{degrees}C, and 30{degrees}C, respectively, on reproductive performance and stress hormone levels in two frequently used mouse strains. We found that more pups were weaned from B6D2F1 hybrids compared to C57BL/6N mothers and that the number of weaned pups was strongly reduced if mothers of both strains were kept at 30{degrees}C. Furthermore, at 30{degrees}C mothers and pups showed reduced body weight at weaning and offspring had longer tails. Despite pronounced temperature effects on reproductive parameters, we did not find any impact on adrenocortical activity in breeding and control mice. Independent of the ambient temperature however, we found that females raising pups showed elevated levels of fecal corticosterone metabolites (FCMs) compared to controls. Increased levels of stress hormone metabolites were measured specially around birth and during the third week of lactation. Our results provide no evidence for reduced or improved wellbeing of lactating mice at different ambient temperatures, but we found that a 30{degrees}C cage temperature impairs reproductive performance.

physiology↗