ID: 31334233
Title: CREB3 Transcription Factors: ER-Golgi Stress Transducers as Hubs for Cellular Homeostasis.
Abstract: CREB3 family of transcription factors are ER localized proteins that belong to the bZIP family. They are transported from the ER to the Golgi, cleaved by S1P and S2P proteases and the released N-terminal domains act as transcription factors. CREB3 family members regulate the expression of a large variety of genes and according to their tissue-specific expression profiles they play, among others, roles in acute phase response, lipid metabolism, development, survival, differentiation, organelle autoregulation, and protein secretion. They have been implicated in the ER and Golgi stress responses as regulators of the cell secretory capacity and cell specific cargos. In this review we provide an overview of the diverse functions of each member of the family (CREB3, CREB3L1, CREB3L2, CREB3L3, CREB3L4) with special focus on their role in the central nervous system.

ID: 31612863
Title: Knockdown of CREB3 activates endoplasmic reticulum stress and induces apoptosis in glioblastoma.
Abstract: Glioblastoma is a highly malignant type of central nervous system tumor. In the present study, the results of RNA sequencing indicated that cAMP responsive element binding protein 3 (CREB3) was upregulated in tumor tissues from patients with GBM. The cAMP responsive element binding protein 3 (CREB3) pathway is a major contributor to the malignant progression of glioblastoma. In this study, we explored the mechanisms by which CREB3 regulates the proliferation, invasion and apoptosis of glioblastoma. Pairs of glioblastoma and normal tissues were subjected to RNA sequencing. Then, qRT-PCR and Western blotting were used to detect CREB3 levels in glioblastoma tissues and cell lines, respectively. CREB3 was upregulated in glioblastoma tissues and cell lines. Overexpression of CREB3 promoted the proliferation and invasion of SHG-44 cells, while downregulation of CREB3 inhibited the invasion of U251MG cells. Knockdown of CREB3 also induced apoptosis in U251MG cells and increased the protein levels of BAX, active caspase 3, p-PERK, p-eIF2α and ATF4. An in vivo study in nude mice bearing U251MG cell xenografts confirmed these results. Our findings indicate that CREB3 functions as a tumor promoter in glioblastoma, and thus could serve as a treatment target in glioblastoma patients.

ID: 32666500
Title: POST1/C12ORF49 regulates the SREBP pathway by promoting site-1 protease maturation.
Abstract: Sterol-regulatory element binding proteins (SREBPs) are the key transcriptional regulators of lipid metabolism. The activation of SREBP requires translocation of the SREBP precursor from the endoplasmic reticulum to the Golgi, where it is sequentially cleaved by site-1 protease (S1P) and site-2 protease and releases a nuclear form to modulate gene expression. To search for new genes regulating cholesterol metabolism, we perform a genome-wide CRISPR/Cas9 knockout screen and find that partner of site-1 protease (POST1), encoded by C12ORF49, is critically involved in the SREBP signaling. Ablation of POST1 decreases the generation of nuclear SREBP and reduces the expression of SREBP target genes. POST1 binds S1P, which is synthesized as an inactive protease (form A) and becomes fully mature via a two-step autocatalytic process involving forms B'/B and C'/C. POST1 promotes the generation of the functional S1P-C'/C from S1P-B'/B (canonical cleavage) and, notably, from S1P-A directly (non-canonical cleavage) as well. This POST1-mediated S1P activation is also essential for the cleavages of other S1P substrates including ATF6, CREB3 family members and the α/β-subunit precursor of N-acetylglucosamine-1-phosphotransferase. Together, we demonstrate that POST1 is a cofactor controlling S1P maturation and plays important roles in lipid homeostasis, unfolded protein response, lipoprotein metabolism and lysosome biogenesis.

ID: 36300096
Title: MBTPS1 regulates proliferation of colorectal cancer primarily through its action on sterol regulatory element-binding proteins.
Abstract: Among the main metabolic pathways implicated in cancer cell proliferation are those of cholesterol and fatty acid synthesis, both of which are tightly regulated by sterol regulatory element-binding proteins (SREBPs). SREBPs are activated through specific cleavage by membrane-bound transcription factor protease 1 (MBTPS1), a serine protease that cleaves additional substrates (ATF6, BDNF, CREBs and somatostatin), some of which are also implicated in cell proliferation. The goal of this study was to determine whether MBTPS1 may serve as a master regulator in proliferation of colorectal cancer (CRC). Tumors from CRC patients showed variable levels of MBTPS1 mRNA, which were in positive correlation with the levels of SREBPs and ATF6, and in reverse correlation with BDNF levels. Chemical inhibition of MBTPS1 activity in two CRC-derived cell lines resulted in a marked decrease in the levels of SREBPs, but not of its other substrates and a marked decrease in cell proliferation, which suggested that MBTPS1 activity is critical for proliferation of these cells. In accordance, CRISPR/Cas9 targeted knockout (KO) of the MBTPS1 gene resulted in the survival of only a single clone that presented a phenotype of severely attenuated proliferation and marked downregulation of several energy metabolism pathways. We further showed that survival of the MBTPS1 KO clone was dependent upon significant upregulation of the type-1 interferon pathway, the inhibition of which halted proliferation entirely. Finally, rescue of the MBTPS1 KO cells, resulted in partial restoration of MBTPS1 levels, which was in accordance with partial recovery in proliferation and in SREBP levels. These finding suggest that MBTPS1 plays a critical role in regulating colon cancer proliferation primarily through SREBP-associated lipid metabolism, and as such may serve as a possible therapeutic target in CRC.

ID: 39625813
Title: Karyoptosis as a novel type of UVB-induced regulated cell death.
Abstract: Karyoptosis is a type of regulated cell death (RCD) characterized by explosive nuclear rupture caused by a loss of nuclear membrane integrity, resulting in the release of genomic DNA and other nuclear components into the cytosol and extracellular environment. The mechanism underlying karyoptosis involves a delicate balance between the following forces: the expansion force exerted by the tightly packed DNA in the nucleus, the resistance provided by the nuclear lamina at the inner nuclear membrane (INM), and the tensile force from the cytoskeleton that helps position the nucleus at the center of the cytoplasm, allowing it to remain maximally expanded. In addition, CREB3, a type II integral membrane protein with DNA-binding ability, tethers chromatin to the INM, providing a tightening force through chromatin interactions that prevent nuclear membrane rupture. UVB radiation can trigger this process, inducing CREB3-FL cleavage and producing CREB3-CF. Therefore, UVB acts as an intrinsic factor in the induction of karyoptosis. Importantly, biochemical analysis of RCD markers shows that karyoptosis is distinct from other forms of cell death, such as apoptosis, autophagy, necroptosis, and pyroptosis. This review explores the mechanisms involved in maintaining nuclear membrane integrity and the role of CREB3 in triggering karyoptosis and provides brief suggestions on the potential implications for targeting cancer cells.

ID: 40877583
Title: MBTPS1: a membrane-bound transcription factor protease implicated in the pathogenesis of several skin and skeletal disorders.
Abstract: The MBTPS1 gene, which is located on chromosome 16q24, encodes the membrane-bound transcription factor protease site-1 (MBTPS1), commonly referred to as site-1 protease (S1P). S1P can process a variety of substrates independently or in conjunction with membrane-bound transcription factor protease site-2 (MBTPS2, also known as S2P), including sterol regulatory element binding proteins (SREBPs), activating transcription factor 6 (ATF6) and cyclic-AMP responsive element‑binding protein 3 (CREB3). Variants in the MBTPS1 gene can lead to multiple clinically distinct disorders with different phenotypes, including spondyloepiphyseal dysplasia of Kondo-Fu type (SEDKF), Cataract, alopecia, oral mucosal disorder, and psoriasis-like (CAOP) syndrome, and Silver-Russell-like syndrome (SRS). This review presents the structural and functional characteristics of S1P, enumerates the relevant substrates and elucidates the spectrum of associated disorders resulting from pathogenic variants of MBTPS1, and discusses the correlations investigates the genotype-phenotype correlations underlying these distinct clinical manifestations.

ID: 41053159
Title: Nelfinavir triggers ferroptosis by inducing ER stress mediated downregulation of GPX4/GSH system, upregulation of NRF2/HO-1 axis, and mitochondrial impairment in hepatocellular carcinoma cells.
Abstract: Hepatocellular carcinoma (HCC) is one of the most common malignancies with poor prognosis. Novel therapeutic strategies for HCC are urgently needed. Ferroptosis, an iron and reactive oxygen species (ROS) dependent regulated cell death, emerges to efficiently abrogate the growth and proliferation of HCC cells. The identification of new ferroptosis inducing agents should provide potential therapeutics for more effective management of HCC. Here we have identified nelfinavir, a human immunodeficiency virus (HIV) protease inhibitor as a novel ferroptosis inducer in HCC cells, Hepa1-6 and HepG2. Mechanistically, the induction of ferroptosis by nelfinavir required its induction of ER stress; suppression of ER stress remarkably attenuated mitochondrial impairment and superoxide production, the autophagic degradation of GPX4, and increases in the labile iron pool associated with the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) axis in nelfinavir-treated HCC cells. In a mouse model of HCC xenografts, nelfinavir treatment significantly suppressed tumor growth, and this effect was more pronounced when nelfinavir and sorafenib were administered together. Collectively, we demonstrate that nelfinavir can induce ferroptosis in an ER stress dependent manner, thereby identifying a new inducer of ferroptosis that can potentially be repurposed to treat HCC.

ID: 41077842
Title: Hypoxia-inducible factor 2α overexpression in podocytes ameliorates lipid metabolism disorders in diabetic kidney disease by inhibiting S1P.
Abstract: Background and aims: Lipid accumulation in podocytes is a major driver of diabetic kidney disease (DKD). Hypoxia-inducible factor 2α (HIF-2α) plays an important role in regulating metabolism. The function of HIF-2α in lipid metabolism in podocytes and the progression of DKD remain unclear. Methods: We investigated the effects of HIF-2α on podocyte damage and lipid metabolism using immunofluorescence, flow cytometry, ELISA, and Western blotting. In order to characterize the regulatory effects of HIF-2α, we also used ChIP and dual-luciferase reporter assays to investigate the role of sphingosine kinase 1 (SPHK1), a crucial enzyme in sphingosine-1-phosphate (S1P) synthesis. In vivo, the effect of HIF-2α on lipid metabolism disorders in db/db mice was investigated using the HIF-2α inhibitor PT-2385. Results: Our results revealed that HIF-2α overexpression improved lipid metabolism in DKD by enhancing cholesterol efflux via reduced S1P synthesis in podocytes by 25.69%. Inhibition of HIF-2α expression in the mouse model of diabetes exacerbated podocyte damage and proteinuria. Inhibition of SPHK1 expression rescued HIF-2α knockdown-mediated lipid disorders in podocytes. HIF-2α inhibited the transcription of SPHK1 by binding to the promoter region of SPHK1 and reduced S1P synthesis. Furthermore, we found that FG-4592, a HIF prolyl hydroxylase inhibitor, reduced the total cholesterol level in DKD by activating HIF-2α, thereby protecting against DKD. Conclusion: HIF-2α ameliorated lipid metabolism disorders and podocyte damage in DKD by downregulating S1P, providing a novel insight for HIF-2α against DKD.

ID: 41197884
Title: The hidden hand of endoplasmic reticulum stress in anticancer drug resistance.
Abstract: Endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) play pivotal roles in cancer adaptation and drug resistance. Under stress, dissociation of BiP from ER stress sensors activates three pathways such as PERK, IRE1α, and ATF6, which together promotes tumor cell survival. The PERK-eIF2α-ATF4 axis also suppresses global protein synthesis by inhibiting cyclin D, induces G1 arrest, and selectively enhances pro-survival gene translation. Simultaneously, IRE1α splices XBP1 mRNA to generate XBP1s, augmenting chaperone production, endoplasmic-reticulum-associated degradation (ERAD), and antioxidant defenses, while its RIDD activity selectively degrades mRNAs to alleviate proteotoxic stress. Concurrently, ATF6 traffics to the Golgi, where S1P/S2P cleavage releases ATF6-p50, a transcriptional activator of chaperones and anti-apoptotic genes. Collectively, these adaptive UPR mechanisms enable cancer cell survival, metastasis, and therapeutic resistance under proteotoxic and treatment-induced stress. Therapeutically, targeting the UPR offers dual potential; either inhibiting its pro-survival arms using selective small-molecule inhibitors (e.g., GSK2606414 for PERK, MKC-3946 for IRE1α) or exacerbating ER stress beyond the adaptive threshold to trigger apoptosis. This review critically evaluates how ERS-UPR signaling fosters tumor resilience across diverse malignancies, including breast, prostate, colorectal, and pancreatic cancers, and underscores the need to exploit UPR modulation as a strategy to resensitize tumors to conventional and targeted therapies.

ID: 41303380
Title: New Roles of bZIP-Containing Membrane-Bound Transcription Factors in Chromatin Tethering and Karyoptosis.
Abstract: The nuclear membrane has emerged as a dynamic regulatory platform coordinating genome organization, mechanotransduction, and regulated cell death (RCD). Beyond its barrier function, the nuclear skeleton-comprising lamins, actin-myosin isoforms, nuclear matrix proteins, and the LINC complex-supports nuclear integrity and gene regulation. Recent evidence shows that type II membrane-bound bZIP transcription factors such as cAMP-responsive element-binding protein 3 (CREB3) and CREB3L1 localize to the inner nuclear membrane (INM), linking chromatin tethering with stress signaling. Their stress-induced cleavage by S1P/S2P disrupts chromatin anchoring and, in some contexts, triggers karyoptosis, a novel form of RCD defined by nuclear rupture. These findings position the nuclear envelope (NE) as a mechanosensitive signaling hub with direct implications for disease and therapy. In this review, we provide a comprehensive discussion on how type II membrane-bound bZIP transcription factors and chromatin acting as a nucleoskeleton cooperate to regulate nuclear membrane integrity.

ID: 41317707
Title: Nedd4 family interacting protein 1 (NDFIP1) is a novel target of PF-429242 in promoting autophagy in hepatocellular carcinoma cells.
Abstract: Our previous study demonstrates that PF-429242, an experimental membrane-bound transcription factor site-1 protease (MBTPS1) inhibitor, induces autophagy and exhibits potential anticancer activity in hepatocellular carcinoma (HCC) cells through mechanisms independent of its original target. However, the direct target of PF-429242 is still unclear. Using quantitative proteomics, cellular thermal shift assays, and gene/protein expression analyses, we show that PF-429242 stabilizes Nedd4 family interacting protein 1 (NDFIP1) protein and upregulates its expression at both transcriptional and post-transcriptional levels. Knockdown experiments and pathway analysis confirm that PF-429242-induced autophagy partially occurs via a NDFIP1-dependent pathway. Additionally, NDFIP1 overexpression correlates with improved progression-free survival in HCC patients, as revealed by TCGA and a Taiwanese cohort. In conclusion, this study further identifies NDFIP1 as a novel target of PF-429242, partially responsible for its induction of autophagy in HCC cells. These findings offer a promising therapeutic avenue for treating HCC.

ID: 41317800
Title: A novel brain-derived peptide inhibits microglial pyroptosis through MBTPS1 in neonatal hypoxic-ischemic brain damage.
Abstract: This study aimed to identify whether a novel brain-derived peptide, hypoxic ischemic brain damage-associated peptide (HIBDAP), which was identified by our research group in previous studies through peptidome analysis, has a protective effect on the neonatal brain under hypoxic ischemia (HI), and to elucidate the underlying mechanism in a neonatal hypoxic-ischemic brain damage (HIBD) rat model. The HIBDAP sequence was coupled with the cell-penetrating peptide TAT (YGRKKRRQRRR). Seven days after birth, neonatal rats were subjected to a sham operation or HI. The peptide or an equal volume of normal saline was injected into the left ventricular area with a stereotactic injector. The area of cerebral infarction was assessed via 2,3,5-triphenyl tetrazolium chloride (TTC) staining. Behavioral tests, including the water maze test, suspension test, cliff escape test and step error test, were carried out at 21 days and 3 months after birth. Primary microglias were treated with different concentrations of TAT-HIBDAP. After different durations of oxygen-glucose deprivation (OGD), a Cell Counting Kit-8 (CCK-8) was used to detect the cell survival rate. To screen proteins that interact with this peptide, we labeled this peptide with biotin to perform pull-down and mass spectrometry assays. The mitochondrial membrane-bound transcription factor peptidase (MBTPS1) with the best binding effect of this peptide was selected, and its combination was further verified by immunofluorescence and pull-down. Lentiviral vectors were used to overexpress or knock down MBTPS1 in microglia. The pyroptosis rate was evaluated via a lactate dehydrogenase (LDH) release assay. The morphology of the pyroptotic cells was observed via electron microscopy. The expression of the NLRP-3 inflammasome and downstream inflammatory cytokines was detected via Western blotting. The expression levels of IL-18 and IL-1β in the cell culture supernatants were measured via enzyme-linked immunosorbent assay (ELISA). The average value used was n = 6, and every sample was analyzed three times. A neonatal HIBD rat model in which the left ventricle was injected with TAT-HIBDAP resulted in reduced cerebral infarction size and improved motor, learning and memory-related abilities. HIBDAP suppressed microglial pyroptosis under OGD conditions. The direct relationship between HIBDAP and MBTPS1 was confirmed by pull-down and intracellular immunofluorescence colocalization. In microglia, HIBDAP down regulated the expression of MBTPS1 under OGD conditions. Knocking down MBTPS1 inhibited microglial pyroptosis, and overexpressing MBTPS1 promoted microglial pyroptosis. MBTPS1 overexpression attenuated the effects of HIBDAP on microglial pyroptosis under OGD conditions. The expression levels of NLRP-3, ASC, cleaved-Caspase-1, n-GSDMD, IL-18 and cleaved-IL-1β were significantly decreased in the peptide treatment group, and MBTPS1 overexpression increased their expressions. HIBDAP inhibits microglial pyroptosis by combining with MBTPS1 to inhibit the expression of the NLRP-3/ASC/Caspase-1/GSDMD N-terminus, IL-1β and IL-18 and significantly improves motor, learning and memory-related abilities in neonatal HIBD rats.

ID: 41346334
Title: Effect of ART1 on the efficacy of oxaliplatin in colorectal cancer under high-cholesterol conditions.
Abstract: The growth of colorectal cancer (CRC) can be affected by cholesterol (CHO), which may inhibit the efficacy of oxaliplatin (OXA). A high-fat diet can upregulate phosphorylation by sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P)/sphingosine 1-phosphate receptor 1 (S1PR1) and promote tumour cell proliferation. Moreover, S1P activates signal transducer and activator of transcription 3 (STAT3), which plays a critical role in tumour cell proliferation. Knockdown of arginine-specific single ADP ribosyltransferase 1 (ART1) can delay the growth of CRC and promote the inhibitory effect of OXA on CRC cell proliferation. Consequently, in a high-CHO environment, this study aims to investigate the impact of ART1 knockdown in CRC cells treated with OXA and on the growth of transplanted tumours in mice in vivo. Immunohistochemistry of CRC tissue revealed that, compared with that of normal blood lipids, ART1 expression in CRC tissue from patients with hypercholesterolaemia was higher. Based on CCK8 and EdU assays, we found that ART1 knockdown reduced the proliferation ability of CRC cells and decreased the volume of subcutaneously transplanted tumours in the high-CHO group. Finally, under high-CHO conditions, ART1 knockdown significantly reduced the protein expression levels of SPHK1, S1P, S1PR1, STAT3, and p-STAT3 in CT26 cells and transplanted tumours, as determined by western blotting. These findings suggest that under high-CHO conditions, inhibition of ART1 expression can promote the inhibitory effect of OXA on CT26 cell proliferation, which may be related to the influence of ART1 on STAT3 expression through SPHK1/S1P/S1PR1. This study is of great significance in improving the inhibitory effect of OXA on CRC cell proliferation in a high-CHO environment.

ID: 41354389
Title: Lopinavir/ritonavir induces hepatotoxicity in HepG2 cells through inhibition of the Nrf2 pathway, resulting in oxidative stress, endoplasmic reticulum stress, and cell cycle arrest.
Abstract: Lopinavir/ritonavir (LPV/r), a clinically used protease inhibitor for treating human immunodeficiency virus, is associated with liver injury. In this study, we demonstrated that LPV/r significantly suppressed HepG2 cell viability and increased the secretion of ALT, AST and LDH in the cell supernatant. Flow cytometry analysis revealed that LPV/r induced cell cycle arrest at the G0/G1 phase and triggered apoptosis in HepG2 cells. Furthermore, LPV/r significantly induced oxidative stress and endoplasmic reticulum (ER) stress, evidenced by elevated intracellular reactive oxygen species (ROS) levels, ER vesicular dilation, and alterations in the expression of related proteins. Additionally, LPV/r markedly increased the expression of apoptosis-related proteins. Mechanistically, activation of Nrf2 with tBHQ or overexpression of Nrf2 protein can effectively reverse the suppression of Nrf2/HO-1 expression by LPV/r, thereby reducing ROS accumulation and alleviating LPV/r-induced hepatocyte injury. Collectively, our findings demonstrate that LPV/r suppresses Nrf2 and HO-1 protein, promotes ROS accumulation, which induces oxidative stress and ER stress, ultimately leading to cell apoptosis and G0/G1 phase cell cycle arrest. This research provides novel mechanistic insights into the hepatotoxic effects of LPV/r.

ID: 41408309
Title: CEBPD-mediated SGPP2 upregulation via PERK/ER stress in endothelial cells disrupts S1P homeostasis and impairs angiogenesis in chronic endometritis.
Abstract: Chronic endometritis (CE) is a persistent inflammatory condition associated with adverse pregnancy outcomes. Although impaired endometrial angiogenesis is thought to contribute to its pathogenesis, the underlying molecular mechanisms remain incompletely understood. This study aimed to investigate whether sphingolipid metabolism plays a role in the vascular dysfunction of CE patients. Endometrial samples from control and CE patients were assessed for angiogenesis using immunohistochemistry. Sequencing data of endometrial tissues indicated dysregulation of sphingolipid metabolism in CE patients. ELISA revealed decreased levels of sphingosine-1-phosphate (S1P) in the endometrium of CE patients and in lipopolysaccharide (LPS)-treated human umbilical vein endothelial cells (HUVECs). Functional assays including tube formation, wound healing, and transwell invasion were performed to evaluate the effects of LPS and S1P on HUVECs. Western blotting was used to explore the signaling pathways through which S1P influences HUVECs function after LPS stimulation. RT-qPCR and Western blot analyses further suggested that the reduction in S1P under inflammatory conditions may be attributable to upregulation of sphingosine-1-phosphate phosphatase 2 (SGPP2). Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were employed to detect CEBPD binding to the SGPP2 promoter, and immunofluorescence was used to assess nuclear localization of relevant factors. Knockout experiments were conducted to validate the relationship among CEBPD, SGPP2, and endoplasmic reticulum (ER) stress. Finally, the effect of S1P on pregnancy outcomes was evaluated in a CE mouse model. Microvessel density (MVD) and S1P levels were decreased in both CE patients and the CE mouse model. In HUVECs, LPS suppressed tube formation, migration, and invasion; these effects were reversed by exogenous S1P via the S1PR1-STAT3-VEGFA pathway. SGPP2, an S1P-degrading enzyme, was upregulated in CE endometrial tissues and in LPS-stimulated HUVECs. Mechanistically, the transcription factor CEBPD was shown to directly bind the SGPP2 promoter and promote its expression, a process dependent on PERK-eIF2α-mediated ER stress. In the mouse model, intrauterine administration of S1P attenuated endometrial inflammation, improved angiogenesis, and significantly reduced embryo resorption rates. Our findings delineate a novel pathway linking inflammatory stress to aberrant angiogenesis in endometrium, in which ER stress-driven CEBPD activation transcriptionally upregulates SGPP2, creating a molecular nexus between inflammation and sphingolipid metabolism. This S1P signaling deficit compromises a critical angiogenic pathway necessary for vascular remodeling, which in turn disrupts endometrial receptivity and contributes to CE-associated reproductive failures.

ID: 41865105
Title: Single-nucleus ATAC-seq analysis resolves chromatin and transcriptional features of fibrolamellar carcinoma.
Abstract: Fibrolamellar carcinoma (FLC) is a rare malignancy disproportionately affecting adolescents and young adults with no curative therapy. FLC is characterized by thick stroma, which has long suggested an important role of the tumor microenvironment. Over the past decade, several studies have revealed aberrant chromatin activity and gene expression in FLC. However, an important limitation of these efforts is that they were conducted on bulk tumor samples. Consequently, the cell types that contribute to the different epigenomic and transcriptional features of FLC have remained unknown. In this study we primarily leverage single nucleus ATAC-seq, along with supporting single nucleus RNA-seq, to unveil cell-type specific signal for chromatin activity, microRNAs, transcription factor networks (such as CREB3L1), and super enhancers including those nearby to notable FLC-enriched genes such as CDH11 and SLC16A14. The results provide a high resolution map of chromatin features of FLC, which in turn affords the opportunity to study cell type specific transcriptional reprogramming in the FLC tumor microenvironment.

ID: 42350373
Title: Karyoptosis mediates cell death and neurodegeneration upon proteotoxic stress.
Abstract: Neurodegenerative diseases are frequently associated with proteotoxic stress linked to disease specific proteins. The autophagy-lysosome system provides essential control of proteotoxic stress and its failure can lead to initiation of apoptosis. However, in aging and neurodegenerative diseases apoptosis is insufficient to account for all neuronal death, and several different cell death types have been reported in these contexts. Here we show that karyoptosis, a distinct form of cell death, can be induced by proteotoxic stress and then develops through nuclear degeneration and cellular expulsion of nuclear material. We establish that karyoptosis is regulated by the p38 kinase signalling pathway, which controls stability of the nuclear lamina protein LaminB1 via direct phosphorylation. We demonstrate that karyoptosis affects neurons in models of amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) pathology. Finally, we identify karyoptotic features in post-mortem frontal cortex of FTD and Alzheimer's disease (AD) patients. Together these findings characterise a form of cell death directly linked to proteotoxic stress and nuclear lamina stability that is associated with neurodegeneration.

ID: 42437855
Title: Matrix stiffness induced CREB3L1 activation contributed to skin fibrosis through calcium influx triggered endoplasmic reticulum stress.
Abstract: Skin fibrosis substantially contributes to morbidity and mortality. Fibrotic remodeling, characterized by accumulated and stiffened extracellular matrix, persistently exerts mechanical cues and consistently activates fibroblasts, implying biomechanics as a major driver of fibrosis. However, our understanding towards mechanisms of biomechanics induced fibrosis remained limited. Integrated single-cell sequencing analysis was performed to reveal the atlas of fibrotic skin. ChIP sequencing was performed to reveal the binding sites of CREB3L1. Nanoindenter was used to identify the mechanical properties. Gel contraction assay, wound healing assay, and live cell imaging were conducted to assess the behavior of fibroblasts cultured on hydrogels of different rigidities. Bleomycin induced and mechanical loading induced skin fibrosis models were established on CREB3L1 knockdown and control mice. We identified a mechanosensitive fibroblast cluster that exerts contraction and ECM deposition functions in fibrotic skin, and its transcriptional identity was maintained by CREB3L1. Elevated expression of CREB3L1 was confirmed in human and mouse fibrotic skin. Further analysis showed that CREB3L1 was required for fibroblast activation, including contraction, migration, and ECM accumulation. More importantly, we revealed that matrix stiffness could alter calcium homeostasis, causing calcium influx and endoplasmic reticulum stress. The ER stress state in turn triggered the cleavage of CREB3L1, releasing its luminal domain that function as a profibrotic transcription factor. Inhibiting CREB3L1 could alleviate skin fibrosis both in vivo and in vitro. This study elucidates the molecular mechanism of CREB3L1 mechanosensitive activation in matrix stiffness induced skin fibrosis, and presents a promising therapeutic target for clinical translation.