Biology subjects

Thoms, S.

Publications and source records attributed to Thoms, S..

6 recordsLinked to original sources

bioRxiv2026

Mitochondrial PEX14 supports peroxisome biogenesis

Peroxisomes are essential for cellular homeostasis and human health due to their central metabolic and physiological functions. The peroxisomal membrane protein PEX14 is indispensable for matrix protein import into peroxisomes. Recent studies support a hybrid model in which pre-peroxisomal vesicles originating from both, mitochondria and the endoplasmic reticulum, fuse to generate peroxisomes. PEX14 has repeatedly been observed at mitochondria in biogenesis disease models or upon protein overexpression, but such localization has generally been interpreted as aberrant mislocalization. Whether endogenous PEX14 naturally localizes to mitochondria and contributes to peroxisome biogenesis has remained unknown. Here, using high-content and super-resolution microscopy, we demonstrate that endogenous PEX14 localizes to the mitochondrial outer membrane. We show that ectopically expressed PEX14 accumulates at mitochondria, and PEX14 variants unable to access mitochondria and restricted to peroxisomes fail to rescue the PEX14 knockout phenotype. Vice versa, a mitochondria-targeted PEX14 variant supports peroxisome biogenesis. Our results identify the physiological mitochondrial pool of PEX14 in human cells and establish it as an essential intermediate in de novo peroxisome biogenesis.

cell biology↗

bioRxiv2026

dSTORMQuant: A Python Package for Post-Processing and Quantitative Analysis of SMLM datasets

SummarySingle-molecule localization microscopy techniques, such as (direct) stochastic optical reconstruction microscopy ((d)STORM) and photo-activated localization microscopy (PALM) enable the visualization of subcellular molecular organization beyond the diffraction limit of conventional light microscopy. Not only is data acquisition rather slow, but the downstream analysis of localization datasets often remains computationally challenging and time-consuming. Consequently, the complexity and duration of data processing often limit experiments to the acquisition and analysis of only small numbers of cells or regions of interest, thereby restricting the statistical power and biological reliability of SMLM studies. To address this limitation, we developed an open-source Python-based package for automated, high-throughput post-processing and quantitative analysis of SMLM localization data, enabling efficient and straightforward handling of extensive datasets with minimal manual intervention. Availability and implementationdSTORMQuant (source code and documentation) are freely available on GitHub at https://github.com/BCMM-Bielefeld-University/dSTORMQuant under GPL v3 license.

bioinformatics↗

bioRxiv2025

Peroxisome protein import deficiency causes heart failure in mouse and human

Peroxisomes are ubiquitous cellular organelles with potentially vital roles in lipid and reactive oxygen metabolism. The metabolic demands of the heart are substantial; however, the contribution of peroxisomes to cardiac development, health, and their role in heart failure (HF) remain largely unexplored. We developed and examined a mouse and an engineered human myocardium (EHM) model with a deficiency in cardiac peroxisome biogenesis to investigate the role of peroxisomes in cardiac function and pathology. In the EHM, loss of peroxisome protein import and subsequent peroxisomal metabolic impairment trigger mitochondrial damage and compromise cellular respiration and energy production. Peroxisome dysfunction results in incoherent electrical conduction, defective Ca2+-handling, and ultimately presentation of a HF phenotype with pathological force generation. These phenotypes are mirrored in an orthogonal murine model system with defective cardiac peroxisome biogenesis. Preload-dependent deficits in force generation due to insufficient energy supply are eventually fatal. Thus, peroxisomes play an important role in sustaining normal heart operations. Vice versa, peroxisome maintenance is compromised in pressure overload-induced HF, establishing peroxisomes as potential modulators of pathology and targets of therapy.

cell biology↗

bioRxiv2024

Defining the high-translational readthrough stop codon context

Translational termination is not entirely efficient and competes with elongation, which might result in translational readthrough (TR). TR occurs when a near-cognate tRNA binds to a stop codon, (mis)interpreting it as a sense codon and producing a C-terminal extension of the protein. This process is influenced by the stop codon itself and the surrounding nucleotide sequence, known as the stop codon context (SCC). To investigate the role of these cis-acting elements beyond the high-TR motif UGA CUA G, this study examines specific positions within the SCC, both upstream and downstream of the motif, that contribute to variations in basal and aminoglycoside-induced TR. In particular, we identified a surprisingly large influence of the upstream nucleotide positions -9 and -8 (relative to the stop codon) and positions +11 and +12 on readthrough levels, revealing a complex interplay between nucleotides in the expanded SCC. These findings support our understanding of translational termination and may benefit the development of pharmacological therapy for diseases caused by premature stop codon mutations.

molecular biology↗

bioRxiv2022

mTOR pathway inhibition stimulates pharmacologically induced nonsense suppression

A large number of human genetic diseases result from premature termination codons (PTCs) caused by splicing defects, insertions, deletions or point mutations also termed nonsense mutations. Nonsense mutations are the source of various genetic diseases, ranging from rare neuro-metabolic disorders to relatively common inheritable cancer syndromes and muscular dystrophies. Over the years, a wide spectrum of studies has shown that certain antibiotics and other synthetic molecules can act as nonsense mutation suppressors, by inducing readthrough of the stop-codon leading to the expression of a full-length protein. Unfortunately, most readthrough-inducing agents have limited effects and are toxic. Thus, efforts are made to improve the clinical outcome of nonsense mutation suppressors. Here we show that the mTOR pathway is involved in antibiotic-mediated readthrough of nonsense mutations at the level of protein translation initiation. We demonstrate that inhibition of the mTOR translation-initiation-controlling eIF4E branch induces antibiotic-mediated nonsense mutation readthrough, paving the way to the development of a novel therapeutic strategy for enhancing the restoration of these disease-causing mutated transcripts.

cell biology↗

bioRxiv2020

Peroxisomes contribute to intracellular calcium dynamics

Peroxisomes communicate with other cellular compartments by transfer of various metabolites. However, whether peroxisomes are sites for calcium handling and exchange has remained contentious. Here we generated sensors for assessment of peroxisomal calcium and applied them for single cell-based calcium imaging in HeLa cells and cardiomyocytes. We found that peroxisomes in HeLa cells take up calcium upon depletion of intracellular calcium stores and upon calcium influx across the plasma membrane. Further, we show that peroxisomes of neonatal rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes can take up calcium in a controlled manner. Our results indicate that peroxisomal and cytosolic calcium signals are tightly interconnected. Hence, peroxisomes may play an important role in shaping cellular calcium dynamics by serving as buffers or sources of intracellular calcium.

biochemistry↗