Biology subjects

Panayotou, G.

Publications and source records attributed to Panayotou, G..

8 recordsLinked to original sources

bioRxiv2026

The loss of Tau in the adult brain triggers neuroplastic, epigenetic and behavioral deficits

INTRODUCTIONAccumulation of pathological Tau precipitates neuronal malfunction in Alzheimers disease (AD). However, the impact of loss of normal Tau function in the adult brain, independently of Tau aggregates, remains unclarified. METHODSWe used a mouse model with conditional mapt knocking-down in forebrain of 5-7 months old animals (cTau-KO), a virus-driven selective Tau knockdown in wild-types (WT) and Tau re-expression approaches, accompanied by neurostructural, epigenetic, proteomic, electrophysiological, neurochemical and behavioral analyses. RESULTSLoss of Tau in the adult brain of cTau-KOs triggers neuronal atrophy and malfunction, epigenetic as well cognitive and mood deficits. Importantly, these perturbations were confirmed by selective Tau loss in WT adult brain and reverted by Tau re-expression or pharmacologically-induced epigenetic correction in cTau-KOs. DISCUSSIONOur findings highlight the contribution of loss of normal Tau function in the adult brain malfunction that could be relevant in diverse brain pathologies beyond AD, associated to Tau and its dysfunction.

neuroscience↗

bioRxiv2025

ERAP1 allotypes 2 and 10 differentially regulate the immunopeptidome of melanocytes

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a polymorphic enzyme that shapes the peptide repertoire presented by MHC class I molecules and can regulate adaptive immune responses in cancer and autoimmunity. Common missense polymorphisms in ERAP1 modulate its activity and are found in specific allotypes in humans. ERAP1 allotypes are linked to predisposition to HLA-associated inflammatory diseases. ERAP1 allotypic variation has been correlated with the development of psoriasis and Bechets disease, through the generation of specific CD8+ T cell populations targeting disease-specific HLAs. Given the established broad effects of ERAP1 activity on the cellular immunopeptidome, we hypothesized that ERAP1 allotypic variation may lead to broad immunopeptidome shifts that underlie antigenic responses. To test this hypothesis, we generated two A375 melanoma cell lines, each one expressing one of the most common, disease-associated, ERAP1 allotypes, namely allotypes 2 or 10. Comparison of the immunopeptidome of these two cell lines showed only minor differences in peptide sequences presented but extensive changes in abundance that included alterations in length distribution, binding affinity and sequence motifs. Our results suggest that enzymatic differences between ERAP1 allotypes are reflected primarily on the quantitative composition of the cellular immunopeptidome. These quantitative changes may constitute a mechanism that underlies ERAP1-allotypic associations with HLA-associated autoimmunity and variable anti-tumor responses.

immunology↗

bioRxiv2024

ERAP1 activity modulates the immunopeptidome but also affects the proteome, metabolism and stress responses in cancer cells

Endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) metabolizes peptides inside the ER and shapes the peptide repertoire available for binding to Major Histocompatibility Complex Class I molecules (MHC-I). Moreover, it may have additional effects on cellular homeostasis, which have not been explored. To address these questions, we used both genetic silencing of ERAP1 expression as well as treatment with a selective allosteric ERAP1 inhibitor to probe changes in the immunopeptidome and proteome of the A375 melanoma cancer cell line. We observed significant immunopeptidome shifts with both methods of functional ERAP1 disruption, which were distinct for each method. Both methods of inhibition led to an enhancement, albeit slight, in tumor cell killing by stimulated human PBMCs and in significant proteomic alterations in pathways related to metabolism and cellular stress. Similar proteomic changes were also observed in the leukemia cell line THP-1. Biochemical analyses suggested that ERAP1 inhibition affected sensitivity to ER stress, reactive oxygen species production and mitochondrial metabolism. Although the proteomics shifts were significant, their potential in shaping immunopeptidome shifts was limited since only 15.8% of differentially presented peptides belonged to proteins with altered expression and only 5.0% of proteins with altered expression were represented in the immunopeptidome shifts. Taken together, our findings suggest that modulation of ERAP1 activity can generate unique immunopeptidomes, mainly due to altered peptide processing in the ER, but also induce changes in the cellular proteome and metabolic state which may have further effects on tumor cells.

biochemistry↗

bioRxiv2021

Allotypic variation in antigen processing controls antigenic peptide generation from SARS-CoV-2 S1 Spike Glycoprotein

Population genetic variability in immune system genes can often underlie variability in immune responses to pathogens. Cytotoxic T-lymphocytes are emerging as critical determinants of both SARS-CoV-2 infection severity and long-term immunity, either after recovery or vaccination. A hallmark of COVID-19 is its highly variable severity and breadth of immune responses between individuals. To address the underlying mechanisms behind this phenomenon we analyzed the proteolytic processing of S1 spike glycoprotein precursor antigenic peptides by 10 common allotypes of ER aminopeptidase 1 (ERAP1), a polymorphic intracellular enzyme that can regulate cytotoxic T-lymphocyte responses by generating or destroying antigenic peptides. We utilized a systematic proteomic approach that allows the concurrent analysis of hundreds of trimming reactions in parallel, thus better emulating antigen processing in the cell. While all ERAP1 allotypes were capable of producing optimal ligands for MHC class I molecules, including known SARS-CoV-2 epitopes, they presented significant differences in peptide sequences produced, suggesting allotype-dependent sequence biases. Allotype 10, previously suggested to be enzymatically deficient, was rather found to be functionally distinct from other allotypes. Our findings suggest that common ERAP1 allotypes can be a major source of heterogeneity in antigen processing and through this mechanism contribute to variable immune responses to COVID-19.

biochemistry↗

bioRxiv2020

Generation of SARS-CoV-2 S1 spike glycoprotein putative antigenic epitopes in vitro by intracellular aminopeptidases

Presentation of antigenic peptides by MHCI is central to cellular immune responses against viral pathogens. While adaptive immune responses versus SARS-CoV-2 can be of critical importance to both recovery and vaccine efficacy, how protein antigens from this pathogen are processed to generate antigenic peptides is largely unknown. Here, we analyzed the proteolytic processing of overlapping precursor peptides spanning the entire sequence of the S1 spike glycoprotein of SARS-CoV-2, by three key enzymes that generate antigenic peptides, aminopeptidases ERAP1, ERAP2 and IRAP. All enzymes generated shorter peptides with sequences suitable for binding onto HLA alleles, but with distinct specificity fingerprints. ERAP1 was the most efficient in generating peptides 8-11 residues long, the optimal length for HLA binding, while IRAP was the least efficient. The combination of ERAP1 with ERAP2 greatly limited the variability of peptide sequences produced. Less than 7% of computationally predicted epitopes were found to be produced experimentally, suggesting that aminopeptidase processing may constitute a significant filter to epitope presentation. These experimentally generated putative epitopes could be prioritized for SARS-CoV-2 immunogenicity studies and vaccine design. We furthermore propose that this in vitro trimming approach could constitute a general filtering method to enhance the prediction robustness for viral antigenic epitopes.

biochemistry↗

bioRxiv2020

High Content Screening and Proteomic Analysis Identify the Kinase Inhibitor BX795 as a Potent Neuroprotective Compound in a Patient-Derived Model of Parkinson's Disease

Combining high throughput screening approaches with induced pluripotent stem cell (iPSC)-based disease modeling represents a promising unbiased strategy to identify therapies for neurodegenerative disorders. Here we applied high content imaging on iPSC-derived neurons from patients with familial Parkinsons disease bearing the G209A (p.A53T) -synuclein (Syn) mutation and launched a screening campaign on a small kinase inhibitor library. We thus identified the multi-kinase inhibitor BX795 that at a single dose effectively restores disease-associated neurodegenerative phenotypes. Proteomics profiling mapped the molecular pathways underlying the protective effects of BX795, comprising a cohort of 118 protein-mediators of the core biological processes of RNA metabolism, protein synthesis, modification and clearance, and stress response, all linked to the mTORC1 signaling hub. In agreement, expression of human p.A53T-Syn in neuronal cells affected key components of the mTORC1 pathway resulting in aberrant protein synthesis that was restored in the presence of BX795 with concurrent facilitation of autophagy. Taken together, we have identified a promising small molecule with neuroprotective actions as candidate therapeutic for PD and other protein conformational disorders.

neuroscience↗

bioRxiv2019

Genetic deletion of Autotaxin from CD11b+ cells decreases the severity of experimental autoimmune encephalomyelitis

Autotaxin (ATX) is a secreted lysophospholipase D catalyzing the extracellular production of lysophosphatidic acid (LPA), a growth factor-like signaling lysophospholipid. ATX and LPA signaling have been incriminated in the pathogenesis of different chronic inflammatory diseases and various types of cancer. In this report, deregulated ATX and LPA levels were detected in the spinal cord and plasma of mice during the development of experimental autoimmune encephalomyelitis (EAE). Among the different sources of ATX expression in the inflamed spinal cord, F4/80+CD11b+ cells, mostly activated macrophages and microglia, were found to express ATX, further suggesting an autocrine role for ATX/LPA in their activation, an EAE hallmark. Accordingly, ATX genetic deletion from CD11b+ cells attenuated the severity of EAE, thus proposing a pathogenic role for the ATX/LPA axis in neuroinflammatory disorders.

immunology↗

bioRxiv2016

The architectural balance of the Ventral Nerve Cord depends on the level of JNK signaling activity

Central Nervous System (CNS) organogenesis is a complex process that obeys precise architectural rules. The impact that nervous system architecture may have on its functionality remains, however, relatively unexplored. To clarify this problem, we analyzed the development of the Drosophila embryonic Ventral Nerve Cord (VNC). VNC morphogenesis requires the tight control of Jun kinase (JNK) signaling, exerted in part via a negative feedback loop mediated by the dual specificity phosphatase Puckered, in a subset of pioneer neurons. Here we show that the JNK pathway autonomously regulates neuronal electrophysiological properties without affecting synaptic vesicle transport. Manipulating, during early embryogenesis, JNK signaling activity in pioneer neurons, directly influences their function as organizers of VNC architecture and, moreover, uncovers a role in the coordination of the embryonic motor circuitry that is required for hatching. Together, our data reveal critical links, mediated by the control of the JNK signaling cascade by Puckered, between the structural organization of the VNC and its functional optimization.

developmental biology↗