Cell Death & Disease

Nerve growth factor (NGF) exerts neuroprotective effects in the retina, and accumulating evidence indicates that microglia represent a key cellular target of NGF/TrkA signaling. However, evidence showing that the NGF/TrkA signaling in microglia is required for downstream neuroprotective actions remains unresolved. Here, we directly addressed this question by pharmacologically depleting microglia and assessing the impact on NGF pathway activity and retinal integrity. Adult C57BL/6J mice were treated with the CSF1R inhibitor PLX5622 for three weeks, resulting in a robust ([~]77%) depletion of retinal microglia. Microglial ablation induced marked structural and cellular alterations, including significant loss of retinal ganglion cells (RGCs) and thinning of retinal layers, in the absence of any other lesion or insult. Residual microglia exhibited layer-specific phenotypic changes, with a phagocytic profile in the ganglion cell layer and a more ramified morphology in the outer plexiform layer. Strikingly, microglial depletion led to a profound decrease of NGF signaling, with a strong reduction in total and phosphorylated TrkA, and decreased p75NTR levels, in retinal extracts. The amount of TrkA expression is strongly correlated with microglial levels, supporting a primary role of microglia in sustaining NGF signaling in the retina. Together, these findings demonstrate that microglia are required for NGF/TrkA signaling and identify these cells as essential mediators of NGF-dependent neuroprotection in the retina.

Recurrent hypoglycemia increases cognitive impairment in diabetes mellitus patients. Following cerebral neuron injury, endothelial cells provide morphological, metabolic and immune support to damaged neurons. We investigated the inflammatory mechanism involved in hippocampal neuron degeneration. Behavioral experiments, including the open field test (OFT) and the Morris water maze test, were performed to measure cognitive changes. Using a vascular ring experiment, we evaluated vasodilation of the carotid artery. ZBP1 expression was knocked down after transfection with small interfering RNA in a brain endothelial cell line (bEnd3). In this study, PANoptosis, a recently defined form of programmed cell death (PCD), was found to be increased by hypoglycemia in the hippocampus of type 2 diabetic mice in vivo and by low glucose in bEnd3 cells in vitro. ZBP1 knockdown decreased PANoptosis induced by low-glucose stimulation in high-glucose-cultivated bEnd3 cells. RNA transcriptomics sequencing revealed that AGE-RAGE signaling significantly changed after ZBP1 was knocked down in bEnd3 cells. Corresponding biochemical data confirmed that ZBP1 knockdown regulated the advanced glycation end products (AGEs)-Receptor for Advanced Glycation End Products (RAGE) axis in bEnd3 cells. We present the first evidence that hypoglycemia impaired cognition in mice with type 2 diabetes by activating brain endothelial ZBP1-mediated PANoptosis via the AGE-RAGE axis. ARTICLE HIGHLIGHTSO_LIPANoptosis, a newly defined form of programmed cell death, is induced in the hippocampus after recurrent hypoglycemia in male db/db mice. C_LIO_LIZBP1, a sensor of the PANoptosome, was activated in low glucose cultured brain endothelial cells. C_LIO_LIHypoglycemia impairs vasodilation and cognitive function in type 2 diabetic mice. C_LIO_LIOur study indicates that inhibiting ZBP1-PANoptosis and the AGE-RAGE axis may be a potential approach to prevent hypoglycemia-induced cognitive degeneration in individuals with type 2 diabetes. C_LI

Altered iron homeostasis has long been implicated in Parkinson's Disease (PD), although the mechanisms have not been clear. Given the critical role of PD-related activating mutations in LRRK2 (leucine-rich repeat protein kinase 2) within membrane trafficking pathways we examined the impact of a homozygous mutant LRRK2G2019S on iron homeostasis within the RAW macrophage cell line with high iron capacity. Proteomics analysis revealed a dysregulation of iron-related proteins in steady state with highly elevated levels of ferritin light chain and a reduction of ferritin heavy chain. LRRK2G2019S mutant cells showed efficient ferritinophagy upon iron chelation, but upon iron overload there was a near complete block in the degradation of the ferritinophagy adaptor NCOA4. These conditions lead to an accumulation of phosphorylated Rab8 at the plasma membrane, which is selectively inhibited by LRRK type II kinase inhibitors. Iron overload then leads to increased oxidative stress and ferroptotic cell death. These data implicate LRRK2 as a key regulator of iron homeostasis and point to the need for an increased focus on the mechanisms of iron dysregulation in PD.

Macrophages/osteoclasts are highly fusogenic cells that interact closely with bone-metastatic breast cancer cells. These cancer cells adapt to bone microenvironments by undergoing osteomimicry, acquiring bone-like phenotypes. Exploration using human breast cancer-bone metastases dataset revealed that a small population of epithelial breast cancer cells express osteoclast-like and osteomimicry genes at the single-cell level. Cell fusion and cell-in-cell (CIC) processes are two uncommon yet prognostically significant mechanisms in cancer. We showed that co-culture between murine breast cancer cells and osteoclasts yielded a unique osteoclast phenotype through dynamic cell-in-cell (CIC) interactions and fusion-like behaviours between pre-osteoclasts/mature osteoclasts and breast tumor cells, resulting in osteoclast-tumor hybrid-like cells. These tumor cell interactions characterized by membrane retention and nuclear adjacency to host nuclei were consistently observed throughout osteoclast differentiation. Single-cell sequencing analysis and interpretative assays on hybrid-like cells revealed altered extracellular matrix (ECM) modification processes, immunoregulatory, and cancer-associated pathways compared to unfused osteoclasts. Tumor cells co-cultured with osteoclasts expressed hematopoietic and osteoclast-lineage factors more strongly than tumor cells cultured alone with their effects amplified under direct cell-cell contact. The presence of these hybrid-like cells was validated in human breast cancer-bone metastases. We propose that disseminated bone-tropic breast cancer cells were stimulated by osteoclasts to undergo a non-canonical, dynamic osteoclast differentiation and CIC formation to form hybrid-like cells that may facilitate bone metastatic lesions.

Mitochondria engage in extensive communication with other organelles through membrane contacts. Perturbed mitochondria-organelle interactions are indicated in a variety of neurodegenerative diseases, but the underlying mechanisms remain poorly understood. Here, we report a new class of mitochondria-organelle communication: autophagosome/autophagic vacuole (AV)-mitochondria (Mito) contact, which exhibits hyper-tethering in tauopathy neurons, consequently hampering AV retrograde transport. Such defects are attributed to accelerated turnover of the contact release factor TBC1D15, triggered by mitochondrial bioenergetic deficit-induced hyperactivity of the AMP-activated protein kinase (AMPK). Increasing TBC1D15 levels or repressing AMPK activity normalizes AV-Mito contact release and restores retrograde transport of AVs, thereby increasing autophagic cargo clearance and reducing tau burden in tauopathy axons. Furthermore, overexpression of TBC1D15 enhances autophagic clearance and attenuates tau pathology, alleviating neurodegeneration and cognitive dysfunction in tauopathy mice. Taken together, our study provides new insights into AV-Mito contact dysregulation in tauopathy-related autophagy failure, laying the groundwork for the development of potential therapeutics to combat tauopathy diseases.

B7-H3 (CD276) is an immune checkpoint molecule frequently overexpressed in hepatocellular carcinoma (HCC) and represents a promising therapeutic target. However, its roles in tumor cell adhesion, metastatic behavior and immune evasion--particularly in interactions with natural killer (NK) cells--remain incompletely understood. In the present study, B7-H3 was depleted using small interfering RNA and CRISPR/Cas9 in epithelial (Huh7 and HepG2) and mesenchymal (SNU449) HCC cell lines. Tumor cell survival, apoptosis, adhesion, migration and invasion were evaluated using functional assays. Expression of adhesion molecules and immune checkpoint proteins was assessed by flow cytometry and western blotting. Oncogenic signaling pathways were analyzed by examining phosphorylation of Akt, ERK, FAK and STAT3. NK cell-mediated cytotoxicity was assessed using primary human NK cells. B7-H3 depletion reduced clonogenic survival and increased apoptosis in mesenchymal HCC cells under anchorage-independent conditions. Loss of B7-H3 impaired cell adhesion, migration and invasion, accompanied by downregulation of PTGFRN, E-cadherin, integrin 3 and integrin V, and reduced cell-to-cell aggregation under anchorage-independent conditions. B7-H3 depletion also decreased surface expression of PD-L1, PD-L2 and CD47. Notably, B7-H3-deficient cells exhibited enhanced susceptibility to primary NK cell-mediated cytotoxicity. Mechanistically, B7-H3 promoted tumorigenic signaling through Akt/S6, MVP/ERK and FAK/Src pathways in epithelial cells, and through FAK/Src and JAK2/STAT3 pathways in mesenchymal cells. Together, these findings reveal previously unrecognized roles for B7-H3 in coordinating adhesion and NK immune evasion in HCC, and support its therapeutic targeting for next-generation immunotherapies.

Pregnancy is a unique period regarding immune cell regulation. Within the placenta, maternal immune cells play a central role in immune surveillance and tissue remodeling. However, regulatory mechanisms of systemic immunity during pregnancy are less clear. Here, we show that neutrophil function is altered in pregnant mice (E13.5), indicated by increased slow rolling velocity and reduced adhesion. Mechanistically, PreImplantation factor (PIF), a 15 amino acid peptide which is produced by human and murine trophoblast cells of the placenta, is continuously secreted into the maternal circulation and plays a key role in modulating neutrophil function via blocking the voltage-gated potassium channel KV1.3. This resulted in impaired intracellular Ca2+ signaling and subsequently disturbance of neutrophil post-arrest modifications and a higher susceptibility to physiological shear forces in vivo and in vitro. Furthermore, PIF-mediated KV1.3 blockade impaired E-selectin-mediated release of S100A8/A9 and phagocytosis. Taken together, we have identified PIF as an important modulator of neutrophil function during pregnancy suggesting a critical role in regulating innate immune responses throughout gestation.

Extracellular vesicles (EVs) contribute to the damage caused by traumatic brain injury (TBI) and can cross the blood-brain barrier (BBB). We analyzed plasma-derived EVs from human TBI patients to identify factors potentially contributing to TBI pathology. EVs were isolated using membrane affinity (ExoEasy) and size exclusion chromatography (iZone), both yielding CD9(+) and CD63(+) EVs with minimal contamination by serum albumin and apolipoprotein. Immunoblotting detected GFAP in TBI but not control EVs, indicating astrocyte-derived EVs crossing the BBB. Proteomic analysis and immunoblotting of EVs from TBI samples identified C-reactive protein and 14-3-3 proteins, which were not detected in control EVs, indicating inflammation associated with TBI. Lipidomic analysis showed ceramide enrichment in TBI EVs, validated by anti-ceramide immunoprecipitation. In a mouse closed head-controlled cortical impact model, brain EVs similarly showed elevated ceramide, confirming ceramide-rich EV release after TBI. Immunocytochemistry localized acid sphingomyelinase (ASM), a ceramide-generating enzyme, to ependymal cilia, suggesting these sites as a potential source of EVs. This was further supported by the detection of ASM in both brain- and plasma-derived EVs, along with the ciliary marker Arl13b in the brain. To assess function, we treated murine neuronal (N2a) cells with TBI EVs. Transcriptomics and STRING analyses revealed enrichment of mitochondrial-associated transcripts. Immunoblotting showed increased p53 and voltage-dependent anion channel 1 (VDAC1), which mediate ceramide-induced apoptosis. Seahorse assays showed that TBI EVs suppressed glycolysis, as indicated by reduced ECAR, while mitochondrial respiration (OCR) remained unchanged. LDH assays further indicated that TBI EVs were more neurotoxic than control EVs. Together, these findings identify ceramide-rich EVs as plasma biomarkers of TBI-induced inflammation, potential mediators of neuronal mitochondrial dysfunction, and pharmacological targets to prevent TBI-induced damage.

3-mercaptopyruvate sulfurtransferase (3-MST) is a mammalian enzyme that contributes to hydrogen sulfide and reactive sulfur species generation. Here we show that 3-MST is markedly upregulated in colorectal cancer stem cells (CSCs) and functions as a critical metabolic support mechanism for this therapy-resistant tumor cell population. CSCs exhibit low proliferation rate, high membrane rigidity and a metabolically restrained phenotype characterized by low oxidative phosphorylation rate, combined with a reduced rate of glycolysis. Genetic or pharmacological inhibition of 3-MST further suppresses cellular bioenergetics in CSCs, and this bioenergetic collapse impairs CSC proliferation, spheroid formation, migration and promotes cell death and attenuates tumor growth. Integrated transcriptomic, proteomic, metabolomic, and lipidomic analyses reveal extensive metabolic remodeling of the CSCs following 3-MST inhibition, including disruption of the glycolysis-TCA axis and marked remodeling of membrane lipid composition, including enrichment of ceramides and sphingolipids and increased incorporation of polyunsaturated phospholipids, resulting in increased membrane fluidity. 3-MST inhibition induced an activation of integrated stress pathways, proteotoxic stress responses and inflammatory signaling, linking the metabolic failure of CSCs to the induction of mixed-mode cell death. These findings identify 3-MST as a metabolic vulnerability in colorectal CSCs. Targeting this enzyme may be a translatable strategy to eliminate therapy-resistant tumor stem cell populations.

Autophagy is a critical homeostatic mechanism in podocytes, maintaining cellular integrity under stress and proteostatic challenges. Dysregulation of autophagy has been implicated in different glomerular diseases such as diabetes and membranous glomerulonephropathy (MGN), yet the underlying molecular drivers remain incompletely understood. We identified microRNA-378a (miR-378a), previously found upregulated in MGN, as a functional enhancer of autophagic flux in human podocytes and tubular epithelial cells. While miR-378a did not directly alter transcription of canonical autophagy genes (ATG2A, ATG5, ATG7, ATG12), it increased autophagic flux through suppression of mTOR phosphorylation at Ser2448. Given that NPNT is a miR-378a target and a key glomerular basement membrane component, we investigated its role in autophagy regulation. NPNT knockdown reduced ATG2A, ATG7, and BCN1 expression, but paradoxically increased autophagic flux, independent of mTOR, accompanied by enhanced ERK1/2 phosphorylation. These findings reveal a dual-layered regulatory network in which miR-378a promotes autophagy via mTOR inhibition, whereas NPNT modulates autophagy probably through MAPK-dependent signaling. Our results highlight the complex interplay between miRs, extracellular matrix components, and intracellular signaling pathways in podocyte autophagy. Dysregulation of these pathways in kidney disease may reflect both adaptive and maladaptive responses, providing mechanistic insights and potential therapeutic targets to preserve glomerular filtration barrier integrity in immune-mediated kidney disease.

Platelets are blood cells that play a critical role in hemostasis and thrombosis. Serum albumin, which constitutes approximately 50% of plasma proteins, has traditionally been considered non-interactive with platelets and not involved in platelet function. Here, using a molecular force sensor and platelet adhesion and aggregation assays, we show that serum albumin, if denatured, specifically binds to integrin IIb{beta}3 in platelets and transmits platelet contractile forces, regulating platelet activation, adhesion and aggregation as effectively as fibrinogen (the clotting factor I). 0.1% ethanol or 10 {micro}M hydrogen peroxide, physiologically attainable in blood through alcohol intake or disease-elevated oxidative stress, are sufficient to denature albumin into a functional platelet ligand. These findings revealed albumin as a previously unrecognized but important regulator of platelet functions, with broad implications for the thrombotic risk in the context of physiological conditions that induce albumin denaturation.

Alzheimers disease (AD) is the most prevalent form of dementia, characterized by progressive memory loss, cognitive decline, and emotional dysregulation. Adult hippocampal neurogenesis (AHN) critically contributes to cognition and mood but undergoes precipitous decline during AD progression. Here, we investigated whether enhancing AHN through genetic expansion of endogenous neural stem cells (NSC) ameliorates AD-related phenotypes. Using lentiviral overexpression of the cell cycle regulators Cdk4 and CyclinD1 in the dentate gyrus of 3xTg-AD mouse, we show that enhancing AHN partially rescues hippocampal-specific cognitive functions, namely: spatial navigation and exploratory behavior. These findings show that endogenous NSC can be exploited to ameliorate hippocampal cognitive functions in AD, providing additional evidence for exploiting AHN as a promising therapeutic target for neurodegenerative disease.

Well- and dedifferentiated liposarcomas (WDLPS and DDLPS) are characterized by extensive copy- number alterations rather than recurrent gene-inactivating mutations, obscuring the molecular mechanisms that drive disease progression and, critically, the transition from well-differentiated to the more aggressive dedifferentiated tumor states. Despite marked differences in clinical behavior and prognosis, the regulatory events underlying adipocytic lineage destabilization in DDLPS remain poorly understood. Here, we establish an in vivo model of retroperitoneal liposarcoma in Xenopus tropicalis through early embryonic mosaic perturbation of p53 and Rb pathway components. Combined disruption reproducibly induced retroperitoneal WDLPS development, demonstrating that pathway-level deregulation of the MDM2-p53 and CDK4-Rb axes is sufficient to initiate liposarcoma development in vivo. Strikingly, additional perturbation of transcriptional co-activator ep300 in this context resulted in increased tumor dedifferentiation, yielding lesions composed of spatially coexisting well- and dedifferentiated adipocytic states. In contrast, direct targeted disruption of downstream adipogenic regulators recurrently lost in human DDLPS, including cebpa, g0s2, and dgat2, failed to induce dedifferentiation in the same genetic context in vivo. These findings indicate that dedifferentiation cannot be explained by loss of downstream adipocytic effectors alone but instead reflects destabilization of higher-order regulatory programs governing adipocytic identity. Together, these results establish an in vivo model that closely reflects the clinical situation on a pathway level and provides initial mechanistic insight into how adipocytic differentiation may become destabilized during disease progression. This framework offers a foundation for future studies leveraging higher-order and multi-omic approaches to dissect the molecular processes underlying the WDLPS-to-DDLPS transition.

To elucidate how cancer cells generate resistance and defined forms of tissue structure in response to therapeutic stress, we tracked the temporal dynamics of life cycle of polyploid giant cancer cells (PGCCs) induced by the mitotic destabilizer vincristine (VCR). Live-cell fluorescence imaging revealed that VCR activated a distinct endoreplication-based life cycle, which replaced canonical mitosis. PGCCs exhibited reduced proliferative activity, enhanced epithelial-mesenchymal transition (EMT), progressive acquisition of blastomere-like features, and broad multilineage differentiation potential. Both PGCC populations and single PGCC-derived progeny displayed time- and dose-dependent acquisition of malignant traits in vitro and tumorigenic capacity in vivo. PGCC-derived spheroids exhibited ability to differentiate into the cells of origin from three germ layers. Importantly, pre-budding PGCCs induced by higher VCR concentrations exhibited enhanced ability for glandular structure formation and tissue differentiation. Morphologically, the nuclei of PGCC-derived spheroids underwent growth in size, formation of luminal structure, and followed by maturation of lumen. Mechanistically, PGCCs entered a senescent state characterized by elevated senescence-associated secretory phenotype (SASP)-manifested by rich proinflammatory cytokines. Notably, silencing IL1{beta}, IL6, or IL8, or pharmacological inhibition of their receptors, suppressed PGCC formation, budding, EMT, and blastomere-like reprogramming into structured tissue. Our studies provide novel mechanistic insights into early embryogenesis and tumorigenesis at the tissue structural developmental level.

The proteasome is an essential multiprotein complex whose inhibition can lead to apoptosis. Ferroptosis is a non-apoptotic cell death mechanism whose fundamental regulation continues to be elucidated. How proteasome function regulates ferroptosis sensitivity is poorly understood and difficult to study given the essential nature of the proteasome. Here, we isolated the effects of proteasome inhibition on ferroptosis by combining direct cell death imaging, cell death pathway-specific inhibitors, and mathematical modeling. We find that proteasome inhibition enhances sensitivity to ferroptosis induced by glutathione peroxidase 4 (GPX4) inhibition while simultaneously promoting resistance to ferroptosis induced by system x - inhibition. Sensitization to GPX4 inhibition requires protein synthesis but not the apoptosis execution machinery and is opposed by the activating transcription factor 4 (ATF4) stress response pathway. This work demonstrates a complex role for proteasome function in ferroptosis regulation and establishes new methods to dissect cross-talk between ferroptosis and essential cellular processes.

Longitudinal bone growth occurs through endochondral ossification, which is accompanied by the differentiation of chondrocytes in the growth plate. Disruption in chondrocyte maturation can lead to skeletal growth abnormalities, such as those observed in Kabuki syndrome type 1 (KS1), a genetic disorder caused by heterozygous pathogenic variants in the KMT2D gene. KS1 patients exhibit postnatal growth deficiency, craniofacial hypoplasia, and skeletal deformities, yet the mechanisms underlying these phenotypic manifestations remain poorly understood. Our study investigated the effects of KMT2D deficiency on chondrocyte maturation and identified premature chondrocyte hypertrophy as a key driver of skeletal abnormalities in KS1. We previously observed reduced femur and tibia length in a KS1 mouse model, along with altered growth plate architecture, particularly affecting the heights of the proliferative and hypertrophic zones. Here, we show that KMT2D-deficient chondrocytes exhibit accelerated differentiation and early senescence upon exposure to supraphysiological oxygen levels (20% O2). These pathological changes were linked to increased mitochondrial reactive oxygen species (ROS) production likely caused by deficiencies in electron transport chain function, leading to oxidative stress and premature hypertrophy. Pharmacological ROS neutralization or hypoxic conditions mitigated these effects, restoring normal chondrocyte differentiation and preventing premature ossification. These findings demonstrate that KMT2D loss induces oxidative stress-driven chondrocyte hypertrophy, disrupting the balance of cartilage growth and ossification. Our study provides crucial mechanistic insights into KS1-associated skeletal abnormalities and suggests mitochondrial ROS regulation as a potential therapeutic avenue.

Development of motoneurons from stem cells is characterized by a change from glycolytic to oxidative metabolism. Since this transition remains poorly understood, we examined it at five distinct differentiation stages from hiPSC to motoneuron. While a direct comparison of hiPSCs and mature motoneurons confirmed the expected glycolytic-to-oxidative shift, the intermediate stages showed that the conversion was not monotonic. After an initial drop of glycolysis at the hiPSC-to-neuroepithelial transition, late neuroepithelial cells showed intermittent peaks of the glycolytic marker lactate dehydrogenase A and the metabolic regulator TIGAR. Furthermore, the lactate-produced-to-glucose-consumed ratio remained elevated. A fully oxidative phenotype was only assumed upon progress from neural progenitors to motoneurons, portrayed by a definitive drop of the lactate-produced-to-glucose-consumed ratio, an increase of mitochondrial membrane charging, and shifts from lactate dehydrogenase A to B, from pyruvate dehydrogenase to anaplerotic pyruvate carboxylase, and from Mitofusin 1 to 2. Together, our data show that metabolic maturation in human motoneurons does not occur as a simple switch. Instead, it unfolds through distinct stages in a directional yet nonlinear manner.

Osteosarcoma is a malignant bone tumor with a high risk of metastatic relapse and poor outcomes due to primary and acquired chemoresistance. This highlights the medical need to develop effective targeted approaches to overcome chemoresistance. Recent studies have revealed the roles of metabolic reprogramming and mitochondria-nucleus crosstalk in osteosarcoma progression, indicating the potential of these cellular processes as therapeutic targets. The complex formed by mitochondrial apoptosis-inducing factor (AIF) and coiled-coil-helix-coiled-coil-helix domain-containing protein 4 (CHCHD4) orchestrates the import and oxidative folding of cysteine-rich, nuclear-encoded proteins, thereby regulating key mitochondrial functions and metabolism. Here, we identified mitoxantrone as an inhibitor of the AIF/CHCHD4 mitochondrial import machinery and revealed a new mitoxantrone-induced metabolic vulnerability in some osteosarcoma cell line models, characterized by intracellular glutamine accumulation and an increase in nucleotide synthesis. As a result, synergy was found between mitoxantrone and the glutaminase inhibitor telaglenastat in both in vitro and in vivo osteosarcoma models. Collectively, our findings position the AIF/CHCHD4 complex as a druggable therapeutic target and provide a combination strategy for mitoxantrone/telaglenastat treatment to overcome metabolic adaptations and chemoresistance in osteosarcoma. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/716303v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1229e58org.highwire.dtl.DTLVardef@1c9af45org.highwire.dtl.DTLVardef@120d2borg.highwire.dtl.DTLVardef@11e8216_HPS_FORMAT_FIGEXP M_FIG C_FIG

Transactive response DNA binding protein 43 kDa (TDP-43) pathology, is a central molecular hallmark of amyotrophic lateral sclerosis (ALS). However, the underlying triggers are incompletely understood. Here, we show that infection with herpes simplex virus (HSV) induces molecular hallmarks of ALS in various in vitro and in vivo models and is associated with an increased risk of ALS in human population data. German healthcare provider data (n = 238,440) and herpesvirus serology of an ALS patient and control cohort (n = 1,100) showed that HSV infection elevated the ALS risk by 210% and odds by [~]65%, respectively. On a molecular level, HSV infection promoted TDP-43 pathology in neuronal cell models, human iPSC-derived motoneurons and cerebral organoids, mice, and human tissue sections. This effect was triggered by HSV-1 or 2, but not by several other related herpesviruses. Mechanistically, the infected cell protein 0 (ICP0) of HSV-1/2 drives TDP-43 pathology by disturbance of promyelocytic leukemia nuclear bodies (PML-NBs), thereby abrogating TDP-43 SUMO2/3ylation. Taken together, we reveal a previously unrecognized association between HSV infection and ALS and clarify the underlying molecular mechanism that drives TDP-43 pathology. Our data may guide future studies into therapeutic and prophylactic interventions against ALS.

Photoreceptor (PR) loss causes vision loss in many blinding diseases, and effective therapies to prevent this cell loss are lacking. Aspartate aminotransferases (GOTs), located in the cytosol (GOT1) and mitochondria (GOT2), are key components of the malate-aspartate shuttle, which transfers reducing equivalents from cytosol to mitochondria. Previous work has implicated the GOTs as potential modulators of blinding retinal disease. To determine the roles of GOT1 and GOT2 in rod PRs, we generated rod PR-specific Got1 or Got2 conditional knockout mice (Got1 or Got2 cKO). We previously showed that Got1 cKO causes PR degeneration and is accompanied by NADH accumulation and a decreased retinal NAD+/NADH ratio. Here, we show that NADH oxidation via metabolic or genetic means prolongs PR survival in Got1 cKO animals, implicating NADH accumulation, or reductive stress, as a key driver of PR degeneration. In contrast, Got2 cKO causes minimal PR degeneration and alterations in retinal NADH and the NAD+/NADH ratio that oppose reductive stress. Interestingly, GOT2, but not GOT1, is decreased in multiple models of PR degeneration, including retinal detachment (RD) where the NAD+/NADH ratio favors a reductive state. Notably, loss of Got2 in PRs demonstrates a neuroprotective effect after experimental RD suggesting decreased GOT2 expression may be part of a stress response to promote PR survival. Overall, this study illustrates the differential dependence on the GOTs for PR health, provides evidence that an overly reductive environment is detrimental to PR survival, and identifies GOT2 as a novel therapeutic target with potentially broad application in blinding diseases.