Biology subjects

Nemeth, E.

Publications and source records attributed to Nemeth, E..

12 recordsLinked to original sources

bioRxiv2026

Anaplasma phagocytophilum Subversion of Host Hepcidin-Ferroportin Iron Nutritional Immunity

Obligatory intracellular bacterium Anaplasma phagocytophilum (Aph) causes an emerging infectious disease called human granulocytic anaplasmosis. Within host cells, Aph proliferates in a membrane-bound vacuole (Aph-vacuole), to which all required nutrients must be routed, including essential iron. Here, using a fluorescent labile iron-binding dye, we found that Aph-vacuoles are enriched with labile iron. Further, ferroportin (Fpn), the only known iron exporter in the plasma membrane of host cells, was increasingly localized to Aph-vacuole post-invasion. Plasma membrane Fpn is tightly regulated by the hormone hepcidin, which binds to Fpn and triggers its ubiquitination and internalization. We found Fpn-GFP mutants deficient in ubiquitination (domain deletion or Y64H) had reduced or absent localization to Aph-vacuoles. Fpn-GFP (D131V) and Fpn-GFP (D039A) mutants that are deficient in iron binding and transport could still localize to Aph-vacuoles, but significantly reduced Aph growth and labile iron in Aph-vacuoles. Aph infection upregulated host cell expression of the hepcidin mRNA and protein. Furthermore, the gene encoding hepcidin is upregulated by inflammation, and we found Aph induced strong IL-6, IL-1{beta}, and TNF- mRNA expression in the host cells. Altogether, these results suggest that Aph induces production of proinflammatory cytokines for autocrine or paracrine hepcidin secretion to trigger the Fpn internalization, which can then be diverted to Aph-vacuoles in a ubiquitination-dependent manner as a mechanism of iron acquisition for thebacteria. This finding illuminates pathogen manipulation of cellular iron export mechanisms, and subversion of host hepcidin-Fpn iron nutritional immunity against pathogens. IMPORTANCEIron is an essential element for both humans and microorganisms, serving as a cofactor in key metabolic processes. Obligatory intracellular bacterium Anaplasma phagocytophilum infects and proliferates within a membrane-bound vacuole (Aph-vacuoles) of neutrophils and endothelial cells, competitively acquiring intracellular iron from the host. Upon exploration of cytoplasmic labile free iron levels and distribution in the A. phagocytophilum-infected and uninfected host cells, we uncovered the unique ability of this bacterium to enrich intravacuolar iron. Ferroportin is the only cellular iron exporter of the host cells, which is regulated by the hepatic hormone hepcidin. Herein, we investigate the role of ferroportin and endogenous hepcidin locally produced by the host cells for iron enrichment in Aph-vacuoles. Ultimately, this study provides new insights into the novel mechanisms of microbial manipulation of host cells to acquire the essential micronutrient iron and overcoming host nutritional immunity, which may facilitate more effective treatment and prevention.

molecular biology↗

bioRxiv2025

The hippocampus as an epistemic forager: When curiosity and reward jointly steer exploration and hippocampal replay

Hippocampal replay is a widely studied phenomenon wherein special neurons of the hippocampus encoding spacial locations - place cells - show a sequential reactivation during periods of immobility, often representing trajectories to or from reward locations, as observed in foraging rodents. Several computational models have been proposed to explain how this phenomenon could contribute to memory consolidation and action planning. However, certain aspects of the mechanism behind hippocampal replay remain unclear, such as why reactivation is biased towards both reward sites and decision points. Here, we propose that both expected reward (satisfying hunger) and expected information gain (satisfying curiosity) contribute to determine the priority of events to be replayed. To test this, we present the Epistemic Replay Algorithm (ERA), which bridges reinforcement learning and active inference into a single computational model. We evaluate the ERA in five experiments spanning three maze types: linear maze, non-stationary maze, double T-maze. Our results first showcase that more curious agents explore more thoroughly while they are still capable of exploiting optimal rewards; and they can adapt faster to changing environments. Further, we find that the ERA model accounts for a larger number of hippocampal replay properties compared to non-curious models, including (i) a broad-to-specific progression of hippocampal replay events; (ii) symmetric replay around decision points; and (iii) the preferential reactivation of both reward sites and decision points. We derive new predictions to further test the model and discuss its implications compared to alternative accounts.

neuroscience↗

bioRxiv2025

Nutritional iron deficiency elicits profound rewiring of red pulp macrophage functions via high FPN and SYK-mediated signaling

Iron deficiency is the most common nutritional disorder worldwide, yet how individual cell types adjust to iron scarcity remains unclear. Splenic red pulp macrophages (RPMs) are essential for systemic iron homeostasis. They manage exceptionally high iron flux by recycling aged red blood cells through erythrophagocytosis, a specialized form of efferocytosis. However, how RPMs adapt their clearance and metabolic programs to iron deficiency remains unexplored. Here, we show that RPMs from mildly anemic, iron-deficient mice exhibit enhanced erythrophagocytic capacity. Proteomic profiling and flow cytometry revealed expansion and activation of lysosomal and mitochondrial networks, accompanied by elevated mitochondrial respiration. This metabolic rewiring and the increase in erythrophagocytosis depended on branched-chain amino acid (BCAA) catabolism. These responses were distinct from alternative macrophage activation states and absent in liver and peritoneal macrophages. Mechanistically, the low hepcidin-high ferroportin axis and SYK kinase activity emerged as drivers of this functional rewiring. Pharmacological inhibition of SYK or BCAA catabolism blunted iron-deficiency-induced erythrophagocytic and mitochondrial adaptations of RPMs. Together, these findings reveal a non-canonical metabolic reprogramming of RPMs that enhances their specialized clearance functions during systemic iron scarcity, raising possiblity that similar signaling circuits may operate in other efferocytic macrophage subsets under altered ferroportin-SYK axis activity.

cell biology↗

bioRxiv2024

Dendritic cells type 1 control the formation, maintenance, and function of tertiary lymphoidstructures in cancer

Tertiary lymphoid structures (TLS) are organized immune cell aggregates that arise in chronic inflammatory conditions. In cancer, TLS are associated with better prognosis and enhanced response to immunotherapy, making these structures attractive therapeutic targets. However, the mechanisms regulating TLS formation and maintenance in cancer are incompletely understood. Using spatial transcriptomics and multiplex imaging across various human tumors, we found an enrichment of mature dendritic cells (DC) expressing high levels of CCR7 in TLS, prompting us to investigate the role of DC in the formation and maintenance of TLS in solid tumors. To address this, we developed a novel murine model of non-small cell lung cancer (NSCLC) that forms mature TLS, containing B cell follicles with germinal centers and T cell zones with T follicular helper cells (TFH) and TCF1+PD-1+ progenitor exhausted CD8+ T cells (Tpex). Here we show that, during the early stages of tumor development, TLS formation relies on IFN{gamma}-driven maturation of the conventional DC type 1 (cDC1) subset, their migration to tumor-draining lymph nodes (tdLN), and recruitment of activated T cells to the tumor site. As tumors progress, TLS maintenance becomes independent of T cell egress from tdLN, coinciding with a significant reduction of cDC1 migration to tdLN. Instead, mature cDC1 accumulate within intratumoral CCR7 ligand-enriched stromal hubs. Notably, timed depletion of cDC1 or disruption of their migration to these stromal hubs after TLS are formed alters TLS maintenance. Importantly, we found that cDC1-mediated antigen presentation to both CD4+ and CD8+ T cells and intact CD40 signaling, is critical for the maintenance of TLS, the preservation of the TFH cell pool, the formation of germinal center and the production of tumor-specific IgG antibodies. These findings underscore the key role of mature cDC1 in establishing and maintaining functional TLS within tumor lesions and highlight the potential for cDC1-targeting therapies as a promising strategy to enhance TLS function and improve anti-tumor immunity in patients with cancer.

immunology↗

bioRxiv2024

Transgenic augmentation of erythroferrone in mice ameliorates anemia in adenine-induced chronic kidney disease

Anemia is a common and disabling complication of chronic kidney disease (CKD). Current therapies can be burdensome, and full correction of anemia is limited by cardiovascular side effects. New approaches that may offer additional therapeutic options are needed. We explored the anti-anemic effects of erythroferrone, an erythroid hormone that induces iron mobilization by suppressing the master iron-regulatory hormone hepcidin. In a preclinical murine model of adenine-induced CKD, transgenic augmentation of erythroferrone mobilized iron, increased hemoglobin concentrations by approximately 2 g/dl, and modestly improved renal function without affecting systemic or renal inflammation, fibrosis, or markers of mineral metabolism. This study supports the concept that therapeutic augmentation of erythroferrone is a promising approach for alleviating CKD-associated anemia.

pathology↗

bioRxiv2024

Essential role of Hepcidin in host resistance to disseminated candidiasis

Candida albicans is a leading cause of life-threatening invasive infections with up to 40% mortality rates in hospitalized individuals despite antifungal therapy. Patients with chronic liver disease are at an increased risk of candidemia, but the mechanisms underlying this susceptibility are incompletely defined. One consequence of chronic liver disease is attenuated ability to produce hepcidin and maintain organismal control of iron homeostasis. To address the biology underlying this critical clinical problem, we demonstrate the mechanistic link between hepcidin insufficiency and candida infection using genetic and inducible hepcidin knockout mice. Hepcidin deficiency led to unrestrained fungal growth and increased transition to the invasive hypha morphology with exposed 1,3, {beta}-glucan that exacerbated kidney injury, independent of the fungal pore-forming toxin candidalysin in immunocompetent mice. Of translational relevance, the therapeutic administration of PR-73, a hepcidin mimetic, improved the outcomes of infection. Thus, we identify hepcidin deficiency as a novel host susceptibility factor against C. albicans and hepcidin mimetics as a potential intervention.

microbiology↗

bioRxiv2024

LIFERING, an E3 ligase, targets the acyl-CoA dehydrogenase-like protein IBR3, for ubiquitination and coordinates cell proliferation and cell death upon DNA damage

Plants rapidly respond to environmental changes to ensure an optimal balance between growth and survival with intact genome. Here, we show that a DNA damage response gene, which we named LIFERING, is under the direct and independent regulation of ATM/ATR-SOG1 and RBR pathways. We demonstrate that LIFERING upon DNA damage plays an essential role in maintaining the balance between cell proliferation and cell death. Downstream of RBR, it is required to maintain proliferation, and in response to DNA damaging agents it initiates a cell death accompanied by rapid elongation and differentiation of the transit amplifying cells in the root meristem. LIFERING is a RING-between-RING E3 ligase; its ligase activity is dependent on the Cys392 residue located in the BRcat domain, responsible for the coordination of zinc ion binding. Using proximity labelling, we identified the acyl-CoA dehydrogenase-like protein IBR3, which is involved in the conversion of indole-3-butyric acid (IBA) to indole-3-acetic acid (IAA), as one of its targets. We provide evidence that IBR3 is ubiquitinated at several Lys residues in the presence of LIFERING. Our findings show that LIFERING rapidly responds to DNA damage and via ubiquitination of IBR3, is likely to be involved in the regulation of free-auxin level, indicating a link between DNA damage response and auxin regulation in the root.

plant biology↗

bioRxiv2023

Targeting PKC alleviates iron overload in diabetes and hemochromatosis

Diabetes is one of the most prevalent chronic diseases worldwide. Iron overload increases the incidence of diabetes and aggravates diabetic complications that cause mortality. Reciprocally, diabetes potentially promotes body iron loading, but the mechanism remains not well understood. In this study, we demonstrated systemic iron excess and the upregulation of iron exporter ferroportin (Fpn) in the enterocytes and macrophages of multiple diabetic mouse models. Increased Fpn expression and iron efflux was also seen in the enterocytes of type 2 diabetic human patients. We further showed that protein kinase C (PKC), which is activated in hyperglycemia, was responsible for the sustained membrane expression of Fpn in physiological and in diabetic settings. For the first time, we identified that PKCs were novel binding proteins and positive regulators of Fpn. Mechanistically, hyperactive PKC promoted exocytotic membrane insertion while inhibited the endocytic trafficking of Fpn in the resting state. PKC also protected Fpn from internalization and degradation by its ligand hepcidin dependent on decreased ubiquitination and increased phosphorylation of Fpn. Importantly, the loss-of-function and pharmacological inhibition of PKC alleviated systemic iron overload in diabetes and hemochromatosis. Our study thus highlights PKC as a novel target in the control of systemic iron homeostasis.

cell biology↗

bioRxiv2023

The hepatokine FGL1 regulates hepcidin and iron metabolism during the recovery from hemorrhage-induced anemia in mice

As a functional component of erythrocyte hemoglobin, iron is essential for oxygen delivery to all tissues in the body. The liver-derived peptide hepcidin is the master regulator of iron homeostasis. During anemia, the erythroid hormone erythroferrone regulates hepcidin synthesis to ensure adequate supply of iron to the bone marrow for red blood cells production. However, mounting evidence suggested that another factor may exert a similar function. We identified the hepatokine FGL1 as a previously undescribed suppressor of hepcidin that is induced in the liver in response to hypoxia during the recovery from anemia and in thalassemic mice. We demonstrated that FGL1 is a potent suppressor of hepcidin in vitro and in vivo. Deletion of Fgl1 in mice results in a blunted repression of hepcidin after bleeding. FGL1 exerts its activity by direct binding to BMP6, thereby inhibiting the canonical BMP-SMAD signaling cascade that controls hepcidin transcription. Key points1/ FGL1 regulates iron metabolism during the recovery from anemia. 2/ FGL1 is an antagonist of the BMP/SMAD signaling pathway.

physiology↗

bioRxiv2021

The Hepcidin Regulator Erythroferrone is a New Member of the Erythropoiesis-Iron-Bone Circuitry

Erythroblast erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis. We report that ERFE expression in osteoblasts is higher compared with erythroblasts, is independent of erythropoietin, and functional in suppressing hepatocyte hepcidin expression. Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. Consistently, Erfe-/- osteoblasts exhibit enhanced mineralization, Sost and Rankl expression, and BMP-mediated signaling ex vivo. The ERFE effect on osteoclasts is mediated through increased osteoblastic RANKL and sclerostin expression, increasing osteoclastogenesis in Erfe-/- mice. Importantly, Erfe loss in {beta}-thalassemic (Hbbth3/+) mice, a disease model with increased ERFE expression, triggers profound osteoclastic bone resorption and bone loss. Together, ERFE exerts an osteoprotective effect by modulating BMP signaling in osteoblasts, decreasing RANKL production to limit osteoclastogenesis, and prevents excessive bone loss during expanded erythropoiesis in {beta}-thalassemia.

physiology↗

bioRxiv2021

Erythroid overproduction of erythroferrone causes iron overload and developmental abnormalities in mice

The hormone erythroferrone (ERFE) is produced by erythroid cells in response to hemorrhage, hypoxia or other erythropoietic stimuli, and suppresses the hepatic production of the iron-regulatory hormone hepcidin, thereby mobilizing iron for erythropoiesis. Suppression of hepcidin by ERFE is thought to be mediated by interference with paracrine BMP signaling that regulates hepcidin transcription in hepatocytes. In anemias with ineffective erythropoiesis, ERFE is pathologically overproduced but its contribution to the clinical manifestations of these anemias is not well understood. We generated three lines of transgenic mice with graded erythroid overexpression of ERFE and showed that they developed dose-dependent iron overload, impaired hepatic BMP signaling and relative hepcidin deficiency. These findings add to the evidence that ERFE is a mediator of iron overload in conditions where ERFE is overproduced, including anemias with ineffective erythropoiesis. At the highest levels of ERFE overexpression the mice manifested decreased perinatal survival, impaired growth, small hypofunctional kidneys, decreased gonadal fat depots and neurobehavioral abnormalities, all consistent with impaired organ-specific BMP signaling during development. Neutralizing excessive ERFE in congenital anemias with ineffective erythropoiesis may not only prevent iron overload but may have additional benefits for growth and development. Key PointsO_LIChronic erythroid overproduction of erythroferrone dose-dependently suppresses hepcidin, causing iron overload even in the absence of anemia C_LIO_LIHigh level overexpression of erythroferrone can cause delayed growth, impaired kidney function and other developmental abnormalities consistent with altered BMP signaling C_LI

physiology↗

bioRxiv2020

Cisplatin is more mutagenic than carboplatin or oxaliplatin at equitoxic concentrations

Platinum-based drugs are a mainstay of cancer chemotherapy. However, their mutagenic effect can increase tumour heterogeneity, contribute to the evolution of treatment resistance, and also induce secondary malignancies. We coupled whole genome sequencing with phenotypic investigations on two cell line models to compare the magnitude and understand the mechanism of mutagenicity of cisplatin, carboplatin and oxaliplatin. Cisplatin induced significantly more base substitution mutations than carboplatin or oxaliplatin when used at equitoxic concentrations on human TK6 or chicken DT40 cells, and also induced the highest number of short insertions and deletions. Assessment through histone H2AX phosphorylation and single cell agarose gel electrophoresis suggested that cisplatin caused more DNA damage than carboplatin or oxaliplatin. The analysis of base substitution spectra revealed that all three tested platinum drugs elicit both a direct mutagenic effect at purine dinucleotides, and an indirect effect of accelerating endogenous mutagenic processes. Whereas the direct mutagenic effect correlated with the level of DNA damage caused, the indirect mutagenic effects were equal. The different mutagenicity and DNA damaging effect of equitoxic platinum drug treatments suggests that DNA damage independent mechanisms significantly contribute to their cytotoxicity. Thus, the comparatively high mutagenicity of cisplatin should be taken into account in the design of chemotherapeutic regimens.

bioinformatics↗