Biology subjects

Kopitman, E.

Publications and source records attributed to Kopitman, E..

4 recordsLinked to original sources

bioRxiv2025

Cell surface ATP6V1B2 marks a subset of persistent senescent cells with increased resistance to apoptosis

Accumulation of senescent cells promotes ageing and age-related diseases. While senescent cells are heterogenous and increasingly persistent in vivo with age, the mechanisms underlying their heterogeneity, resistance to apoptosis, and tissue accumulation remain insufficiently understood. Here we report that in response to DNA damage, a subset of senescent cells upregulates the v-type ATPase subunit, ATP6V1B2 (V1B2) on the cell surface. This upregulation is associated with altered lysosomal activity and changes in intracellular pH. Heterogeneity of senescent cells marked by cell surface V1B2 (csV1B2) is present in naturally occurring senescent cells within both ageing and fibrotic lungs. Senescent cells expressing csV1B2 show an age-independent transcriptional signature associated with DNA repair and resistance to apoptosis. Consistent with this, we show that csV1B2 expression correlates with senescent cell resistance to ABT-737-induced apoptosis in culture. Our study identifies a subset of senescent cells, marked by csV1B2, with a distinct signature of apoptosis resistance. Understanding the functional heterogeneity of senescent cells and the mechanisms accountable for persistence of specific subpopulations in tissues may facilitate the development of improved senotherapeutic strategies for age-related diseases.

cell biology↗

bioRxiv2025

Single-cell quantification of senescence burden reveals cell type-specific ageing dynamics across organs

Cellular senescence, a hallmark of ageing, drives tissue dysfunction by promoting inflammation and fuelling disease. Yet, the dynamics of senescent cell accumulation across tissues and their cell type identity remain poorly understood. Here, we introduce the first, single-cell, protein-level approach, combining multiple senescence markers for the identification and quantification of senescent cells across multiple tissues in mice and in human PBMCs. Applying this method, we reveal widespread but heterogeneous changes in senescence marker expression across cell types and tissues. The cells we identify as senescent displayed transcriptomic senescence signatures, providing a direct molecular link between protein- and mRNA-level detection of senescence. Importantly, senescence accumulation was strongly coordinated within organs but showed little correlation across them, supporting the idea of a tissue specific progression of ageing. These findings refine our understanding of the tissue-specific dynamics of senescence accumulation with age, and provide a framework for evaluating diverse therapeutic interventions.

cell biology↗

bioRxiv2025

TECPR2 maintains mitochondrial homeostasis in neurodegeneration

HSAN9 is a rare progressive neurodegenerative disease in children linked to bi-allelic loss-of-function mutations in the TECPR2 gene. TECPR2 is a multi-domain protein harboring N-terminal WD repeats and C-terminal TECPR repeats, followed by a functional LIR motif that serves in autolysosomal targeting. Here, we show that the lack of TECPR2 leads to impairment of mitophagy that can be recovered by the expression of its C-terminal domain. Accordingly, we uncover severe mitochondrial dysfunction and accumulation of mitochondrial content in primary fibroblasts derived from an HSAN9 patient, and in embryonic fibroblasts and dorsal root ganglia derived from an HSAN9 mouse model. Strikingly, these mitochondrial defects are mediated by a mitochondrial stress through activation of the integrated stress response (ISR), whereas mitochondrial function is recovered by pharmaceutical or genetic suppression of ISR. Our findings provide a new link between mitophagy and ISR in mitochondrial homeostasis during neurodegeneration.

cell biology↗

bioRxiv2024

A new cellular platform for studying autophagy

Atg8 proteins play a crucial role in autophagy. There is a single Atg8 isoform in yeast, while mammals have up to seven homologs categorized into LC3s and GABARAPs. The GABARAP subfamily consists of GABARAP, GABARAPL1, and GABARAPL2/GATE16, implicated in various stages along the pathway. However, the intricacies among GABARAP proteins are complex and require a more precise delineation. Here, we introduce a new cellular platform to study autophagy using CRISPR/Cas9-mediated tagging of endogenous genes of the GABARAP subfamily with different fluorescent proteins. This platform allows robust examination of autophagy by flow cytometry of cell populations and monitoring of GABARAP homologs at single-cell resolution using fluorescence microscopy. Strikingly, the simultaneous labeling of the different endogenous GABARAPs allows the identification and isolation of autophagosomes differentially marked by these proteins. Using this system, we found that the different GABARAPs are associated with different autophagosomes. We argue that this new cellular platform will be crucial in studying the unique roles of individual GABARAP proteins in autophagy and other putative cellular processes.

cell biology↗