Biology subjects

Stylianakis, E.

Publications and source records attributed to Stylianakis, E..

6 recordsLinked to original sources

bioRxiv2026

OTUB1 controls marginal zone B-cell development by stabilizing RelA in a CD40-dependent manner

Ubiquitin-dependent regulation of NF-{kappa}B signaling is essential for B-cell homeostasis and fate decisions, yet the contribution of specific deubiquitinating enzymes remains incompletely defined. OTUB1, a lysine-48-specific deubiquitinase, has been broadly implicated in immune regulation, including control of NF-{kappa}B signaling and prevention of immune hyperactivation. Previous studies have demonstrated that B cell-specific deletion of OTUB1 leads to B cell hyperplasia, increased antibody production, and lupus-like autoimmunity, highlighting its importance in maintaining B cell tolerance and immune homeostasis. Using B cell-specific OTUB1-deficient mice, we show that loss of OTUB1 leads to a marked expansion of marginal zone (MZ) B cells and their precursor populations in the spleen, accompanied by an activated phenotype and enhanced proliferative responses, particularly upon CD40 stimulation. OTUB1 deficiency results in altered CD40-induced NF-{kappa}B signaling, characterized by enhanced I{kappa}B degradation and increased nuclear accumulation of p50-containing NF-{kappa}B complexes, despite reduced RelA stability. Mechanistically, we show that OTUB1 interacts with RelA, restricting its lysine-48-linked ubiquitination and proteasomal degradation, thereby stabilizing this key transcription factor. Collectively, these findings identify RelA as a novel OTUB1 target and uncover an additional layer of ubiquitin-dependent control of NF-{kappa}B signaling that governs splenic B-cell homeostasis and marginal zone B-cell development.

immunology↗

bioRxiv2026

A streamlined spectral cytometry method for FAD and NADH autofluorescence analysis in immunometabolic studies

Abstract/SummaryWe present a streamlined protocol that enables the characterization of the metabolic state of immune cell populations through their distinct NADH/FAD autofluorescence fingerprints using a FACSymphony A5 spectral cytometer. We demonstrate the utility of this approach by profiling the metabolic status of diverse splenic B-cell subsets and assessing metabolic changes associated with their activation state.

immunology↗

bioRxiv2026

Treg-derived IκBζ promotes their conversion into Th2-like effectors and drives type 2 inflammation via BATF

Regulatory T cells (Treg cells) maintain peripheral immune tolerance but display considerable plasticity in peripheral tissues. The molecular mechanisms governing their function and plasticity, particularly under inflammatory conditions, remain poorly defined. Here, we identify the NF-{kappa}B-associated transcriptional cofactor I{kappa}B{zeta} as a critical regulator of Treg cell plasticity and function. Enforced expression of I{kappa}B{zeta} in Treg cells triggered the excessive expansion of functionally impaired Treg cells, resulting in lymphadenopathy, splenomegaly, and systemic type 2 inflammation, most prominently in the lung. Mechanistically, I{kappa}B{zeta} modified BATF expression and function, thereby driving the cell-intrinsic production of Th2-associated cytokines by Treg cells. Conversely, Treg-specific deletion of I{kappa}B{zeta} constrained IL-33-mediated expansion of tissue Treg cells and surprisingly attenuated type 2 inflammation. Thus, I{kappa}B{zeta} functions as a molecular switch that reprograms regulatory T cells into Th2-like Treg cells, thereby perturbing peripheral immune tolerance. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/707402v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1ef0b17org.highwire.dtl.DTLVardef@c12eaaorg.highwire.dtl.DTLVardef@decc86org.highwire.dtl.DTLVardef@1458767_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Aging-Associated Microbiota Drives Treg Dysfunction via TNF Signaling

Aging is associated with a chronic, low-grade inflammatory state referred to as inflammaging, which contributes to impaired immune regulation and increased susceptibility to disease. While regulatory T (Treg) cells are key mediators of immune homeostasis, their role in the context of age-related inflammation remains poorly understood. Here we demonstrate that age-related changes in the microbiota promote impaired Treg cell function, resulting in the differentiation of inflammatory T cells. In agreement, we find that aged germ-free (GF) mice exhibited a more balanced immune profile, where the Treg cells are functional and pro-inflammatory mediators are reduced, suggesting that microbial exposure is essential for the establishment of inflammaging. Furthermore, we show that the use of old microbiota in young animals was sufficient to induce pro-inflammatory T cell responses and impaired mucosal Treg cell proliferation, while young microbiota restored Treg cell function in old animals. Mechanistically, we show that exposure to aged microbiota was associated with sustained TNF signaling, elevated oxidative stress, DNA damage, and increased expression of senescence markers such as {gamma}H2AX and p16 in Treg cells. These findings uncover a microbiota-TNF-dependent mechanism by which age-associated microbial dysbiosis drives Treg cell dysfunction and promotes immune aging, highlighting the therapeutic potential of microbiota-targeted strategies to restore immune homeostasis in the elderly.

immunology↗

bioRxiv2025

B cells maintain the homeostasis of splenic marginal zone antigen-presenting cells to promote the anti-viral CD8+ T cell response

Natural killer and CD8+ T cells are critical in the elimination of blood-borne viruses such as cytomegalovirus (CMV); however, the role of B cells in this process is less clear. Here, using the murine CMV (MCMV) infection model, we demonstrated that the B cell-deficient mice mounted a weaker primary virus-specific CD8+ T cell response than their wild-type counterparts, which was associated with increased viral transcription. Notably, we found that the contribution of B cells to the CD8+ T-cell-mediated anti-viral response was not associated with their ability to generate antibodies but with their ability to sustain Langerin+ type 1 conventional dendritic cells (cDC1s), a dendritic cells (DC) subset known for being involved in viral and bacterial clearance in the marginal zone of the spleen. Furthermore, we found that the presence of Langerin+ cDC1s is dependent on B cells expressing lymphotoxin (LT{beta}) to maintain CD169+ marginal metallophilic macrophages (MMMs). We further discovered, using ligand-receptor interaction analyses, that the communication between MMMs and Langerin+ cDC1s was mediated via VCAM1 - ITGA4/ITGB1 interaction. Thus, our data reveals that B cell regulate the development of MMMs in the spleen via LT{beta} expression and consequently sustain Langerin+ cDC1s homeostasis for effective initiation of an anti-viral CD8+ T cell response. Overall, our study offers a new perspective on how B cells maintain the homeostasis of antigen-presenting cells in the splenic marginal zone and thus indirectly affect the virus-specific CD8+ T cell response, which could potentially be extended to other infectious and autoimmune diseases as well as tumors.

immunology↗

bioRxiv2022

Mouse HP1γ regulates TRF1 expression and telomere stability

AimsTElomeric Repeat-containing RNA are long non-coding RNAs generated from the telomeres. TERRAs are essential for the establishment of heterochromatin marks at telomeres, which serve for the binding of Heterochromatin Protein 1 (HP1), a protein family of epigenetic modifiers involved with chromatin compaction and gene silencing. While HP1{gamma} is enriched on gene bodies of actively transcribed human and mouse genes, it is unclear if its transcriptional role is important for HP1{gamma} function in telomere cohesion and telomere maintenance. We aimed to study the effect of mouse HP1{gamma} on the transcription of telomere factors and molecules that can affect telomere maintenance. Main methodsWe investigated the telomere function of HP1{gamma} by using deficient mouse embryonic fibroblasts (MEFs) deriving from 13.5 embryonic day embryos compared to their litter mate controls. We used gene expression analysis of HP1{gamma} deficient MEFs and validated the molecular and mechanistic consequences of HP1{gamma} loss by telomere FISH, immunofluorescence, RT-qPCR and DNA-RNA Immunoprecipitation (DRIP). Key findingsLoss of HP1{gamma} in primary MEFs leads to a downregulation of various telomere and telomere-accessory transcripts, including shelterin protein TRF1. Its downregulation is associated with increased telomere replication stress and DNA damage ({gamma}H2AX), effects more profound in females. We suggest that the source for the impaired telomere maintenance is a consequence of increased telomeric DNA-RNA hybrids and TERRAs arising at and from mouse chromosomes 18 and X. SignificanceOur results suggest an important transcriptional control by mouse HP1{gamma} of various telomere factors including TRF1 protein and TERRAs that has profound consequences on telomere stability, with a potential sexually dimorphic nature.

cell biology↗