Biology subjects

Gueven, B.

Publications and source records attributed to Gueven, B..

3 recordsLinked to original sources

bioRxiv2025

A microprotein encoded by FERMT3 modulates endothelial cell protein catabolism and induces p53-mediated cell cycle arrest and senescence

BackgroundHuman endothelial cells express numerous microproteins (miPs) encoded by small open reading frames (smORFs) distributed throughout the genome, yet the biological functions of most remain unknown. This study set out to characterize a novel 69 amino acid miP encoded by a smORF located within the coding sequence of the FERM domain containing kindlin-3 transcript (miP-FERMT3). MethodsConfocal microscopy was used to determine the subcellular localization of miP-FERMT3 in endothelial cells and its interaction partners were determined by mass spectrometry and immunoblotting. RNA sequencing identified transcriptional alterations induced by miP-FERMT3 overexpression. Cell proliferation and cell cycle stages were assessed by live cell imaging, EdU incorporation and flow cytometry, while senescence was examined by senescence-associated {beta}-galactosidase staining, live cell imaging and RT-qPCR-based measurement of telomere length. ResultsIn endothelial cells miP-FERMT3 localized mainly to centriole subdistal appendages, where it interacted with proteins involved in ubiquitin- and proteasome-dependent protein catabolism, including PSMD9, CUL2 and TRIM8. Consistent with these interactions, cells expressing miP-FERMT3 exhibited increased global protein ubiquitination, enhanced centrosomal neddylation and elevated proteasomal activity. MiP-FERMT3 also promoted the nuclear accumulation of p53, which subsequently repressed FOXM1 expression, leading to the downregulation of genes required for cell-cycle progression and upregulation of genes involved in cell cycle inhibition, resulting in cell-cycle arrest. Cells expressing the miP also demonstrated multiple hallmarks of cellular senescence, including enlarged size, DNA damage, increased senescence-associated {beta}-galactosidase activity, telomere shortening and paracrine pro-inflammatory activation of naive endothelial cells. Analyses of independent murine and human transcriptomic and proteomic aging datasets further revealed that FERMT3 expression and protein abundance increase with age. ConclusionsThese findings identify miP-FERMT3 as a novel regulator of protein catabolism and p53-dependent cell cycle arrest and cellular senescence in endothelial cells. Given the aging-associated upregulation of FERMT3 in mouse and human endothelial cells, increased miP-FERMT3 expression may contribute to the onset of vascular senescence as a hallmark of aging.

cell biology↗

bioRxiv2025

Microprotein miP-PSTPIP2 affects cytoskeleton dynamics to modulate endothelial cell endocytosis, barrier function and migration

BackgroundA large number of microproteins (miPs) encoded by small open reading frames (smORFs) are expressed in endothelial cells, yet their function remains largely unknown. In this study, we characterized a novel 46-amino-acid miP encoded by a smORF within the proline-serine-threonine phosphatase interacting protein 2 (PSTPIP2) transcript that was upregulated under inflammatory conditions and we refer to as miP-PSTPIP2. MethodsImmunoprecipitation coupled with mass spectrometry-based proteomics, immunoblotting, immunofluorescence and proximity ligation assays were used to identify and validate miP-PSTPIP2 interacting proteins in human endothelial cells. The impact of adenovirus-mediated overexpression of miP-PSTPIP2 on endocytosis, cytoskeleton dynamics and abundance of proteins involved in these processes was investigated by confocal microscopy and immunoblotting. Live cell imaging was used to assess endothelial cell migration and vascular permeability. ResultsmiP-PSTPIP2 physically associated with caveolar proteins, proteins involved in the regulation of cytoskeleton dynamics, intracellular transport, clathrin adaptor activity, as well as nuclear proteins. Human endothelial cells overexpressing miP-PSTPIP2 demonstrated enhanced endocytosis and transcytosis of transferrin as well as low-density lipoprotein. Mechanistically, miP-PSTPIP2 modulated Arp2/3-mediated actin nucleation and branching, which are required for dynamic cytoskeleton rearrangements. Moreover, altered cytoskeleton dynamics in miP-PSTPIP2-expressing endothelial cells resulted in impaired cell migration as well as increased permeability and monocyte trans-endothelial migration. ConclusionsmiP-PSTPIP2 is an inflammation-induced endothelial miP that regulates Arp2/3-dependent actin dynamics, thereby enhancing lipid uptake and leukocyte permeability. Its upregulation under inflammatory conditions suggests a contributory role in endothelial dysfunction and vascular inflammation.

cell biology↗

bioRxiv2025

Immunomodulatory endothelial cells contribute to T cell recruitment and activation through antigen presentation on MHC class II

AimsA subset of endothelial cells referred to as immunomodulatory endothelial cells (IMEC) has been proposed to regulate T cell responses in atherosclerosis, but their phenotype and function remain poorly understood. Here, we characterized the inflammation-induced emergence of IMEC and their crosstalk with T cells. Methods and ResultsAn in vitro model to study IMEC was established and characterized using flow cytometry and proteomics. Single-cell transcriptome data from human atherosclerotic arteries as well as single cell transcriptome and endothelial cell-specific translatome data from a murine atherogenesis model were used to determine pathophysiological relevance. Immunopeptidomics was performed to detect antigen presentation. T cell chemotaxis, adhesion and activation were assessed through flow cytometry and microscopy. IMEC were induced by treating human endothelial cells with interleukin-1{beta}, interferon-{gamma}, and transforming growth factor-{beta}2. These cells expressed lower levels of classical endothelial cell markers but expressed major histocompatibility complex (MHC) class II, proteins involved in antigen processing and presentation (CD83, CD80 and CD86) and pro-inflammatory cytokines as well as chemokines, including CXCL9. An endothelial cell subpopulation with similar immunomodulatory features was identified in a mouse model of accelerated atherogenesis as well as in human atheromas. Conditioned medium from IMEC enhanced the migration of peripheral blood mononuclear cells and induced T cell chemotaxis, the latter being partially inhibited by antagonizing CXCL9. Proteins related to glycosaminoglycan degradation were significantly downregulated in IMEC which was relevant inasmuch as the glycocalyx plays a key role in the establishment of chemokine gradients. Indeed, the accumulation of heparan sulfates in IMEC contributed to the adhesion of T cells. Notably, IMEC that had been exposed to monocyte lysates presented 627 peptide antigens on MHC class II and induced T cell activation. ConclusionOur data demonstrate the role of IMEC as non-professional antigen-presenting cells that potentially contribute to T cell-mediated immune responses in cardiovascular disease. Translational PerspectiveThis study characterizes immunomodulatory endothelial cells (IMEC) as critical mediators of vascular inflammation through their capacity to process and present exogenous antigens and activate T cells. Induced by pro-atherogenic cytokines (IFN-{gamma}, IL-1{beta}, TGF-{beta}2), IMEC upregulate MHC class II and costimulatory molecules, promote leukocyte chemotaxis, and enhance T cell adhesion through surface heparan sulfate. The identification of IMEC-like populations in both murine models and human atherosclerotic plaques indicates a conserved immunological function in atherogenesis. These findings position IMEC as novel, non-professional antigen-presenting cells and potential therapeutic targets to modulate vascular immune responses in atherosclerotic cardiovascular disease.

immunology↗