Showing papers in "EMBO Reports in 2020"

Mitochondrial DNA in inflammation and immunity

Abstract: Mitochondria are cellular organelles that orchestrate a vast range of biological processes, from energy production and metabolism to cell death and inflammation. Despite this seemingly symbiotic relationship, mitochondria harbour within them a potent agonist of innate immunity: their own genome. Release of mitochondrial DNA into the cytoplasm and out into the extracellular milieu activates a plethora of different pattern recognition receptors and innate immune responses, including cGAS-STING, TLR9 and inflammasome formation leading to, among others, robust type I interferon responses. In this Review, we discuss how mtDNA can be released from the mitochondria, the various inflammatory pathways triggered by mtDNA release and its myriad biological consequences for health and disease.

Antibiotic resistance and persistence-Implications for human health and treatment perspectives.

Abstract: Antimicrobial resistance (AMR) and persistence are associated with an elevated risk of treatment failure and relapsing infections. They are thus important drivers of increased morbidity and mortality rates resulting in growing healthcare costs. Antibiotic resistance is readily identifiable with standard microbiological assays, and the threat imposed by antibiotic resistance has been well recognized. Measures aiming to reduce resistance development and spreading of resistant bacteria are being enforced. However, the phenomenon of bacteria surviving antibiotic exposure despite being fully susceptible, so-called antibiotic persistence, is still largely underestimated. In contrast to antibiotic resistance, antibiotic persistence is difficult to measure and therefore often missed, potentially leading to treatment failures. In this review, we focus on bacterial mechanisms allowing evasion of antibiotic killing and discuss their implications on human health. We describe the relationship between antibiotic persistence and bacterial heterogeneity and discuss recent studies that link bacterial persistence and tolerance with the evolution of antibiotic resistance. Finally, we review persister detection methods, novel strategies aiming at eradicating bacterial persisters and the latest advances in the development of new antibiotics.

Mitochondrial transfer from MSCs to T cells induces Treg differentiation and restricts inflammatory response

Abstract: Mesenchymal stem cells (MSCs) have fueled ample translation for the treatment of immune-mediated diseases. They exert immunoregulatory and tissue-restoring effects. MSC-mediated transfer of mitochondria (MitoT) has been demonstrated to rescue target organs from tissue damage, yet the mechanism remains to be fully resolved. Therefore, we explored the effect of MitoT on lymphoid cells. Here, we describe dose-dependent MitoT from mitochondria-labeled MSCs mainly to CD4+ T cells, rather than CD8+ T cells or CD19+ B cells. Artificial transfer of isolated MSC-derived mitochondria increases the expression of mRNA transcripts involved in T-cell activation and T regulatory cell differentiation including FOXP3, IL2RA, CTLA4, and TGFβ1, leading to an increase in a highly suppressive CD25+ FoxP3+ population. In a GVHD mouse model, transplantation of MitoT-induced human T cells leads to significant improvement in survival and reduction in tissue damage and organ T CD4+ , CD8+ , and IFN-γ+ expressing cell infiltration. These findings point to a unique CD4+ T-cell reprogramming mechanism with pre-clinical proof-of-concept data that pave the way for the exploration of organelle-based therapies in immune diseases.

The evolving landscape around genome editing in agriculture: Many countries have exempted or move to exempt forms of genome editing from GMO regulation of crop plants.

Abstract: The EU and New Zealand are the only legislations where genome-edited plants are considered and regulated as GMOs while many other countries move to exempt genome-edited crops.

PINK1 phosphorylates Drp1S616 to regulate mitophagy-independent mitochondrial dynamics.

Abstract: Impairment of PINK1/parkin-mediated mitophagy is currently proposed to be the molecular basis of mitochondrial abnormality in Parkinson's disease (PD). We here demonstrate that PINK1 directly phosphorylates Drp1 on S616. Drp1S616 phosphorylation is significantly reduced in cells and mouse tissues deficient for PINK1, but unaffected by parkin inactivation. PINK1-mediated mitochondrial fission is Drp1S616 phosphorylation dependent. Overexpression of either wild-type Drp1 or of the phosphomimetic mutant Drp1S616D , but not a dephosphorylation-mimic mutant Drp1S616A , rescues PINK1 deficiency-associated phenotypes in Drosophila. Moreover, Drp1 restores PINK1-dependent mitochondrial fission in ATG5-null cells and ATG7-null Drosophila. Reduced Drp1S616 phosphorylation is detected in fibroblasts derived from 4 PD patients harboring PINK1 mutations and in 4 out of 7 sporadic PD cases. Taken together, we have identified Drp1 as a substrate of PINK1 and a novel mechanism how PINK1 regulates mitochondrial fission independent of parkin and autophagy. Our results further link impaired PINK1-mediated Drp1S616 phosphorylation with the pathogenesis of both familial and sporadic PD.

Cristae undergo continuous cycles of membrane remodelling in a MICOS-dependent manner.

Abstract: The mitochondrial inner membrane can reshape under different physiological conditions. How, at which frequency this occurs in living cells, and the molecular players involved are unknown. Here, we show using state-of-the-art live-cell stimulated emission depletion (STED) super-resolution nanoscopy that neighbouring crista junctions (CJs) dynamically appose and separate from each other in a reversible and balanced manner in human cells. Staining of cristae membranes (CM), using various protein markers or two lipophilic inner membrane-specific dyes, further revealed that cristae undergo continuous cycles of membrane remodelling. These events are accompanied by fluctuations of the membrane potential within distinct cristae over time. Both CJ and CM dynamics depended on MIC13 and occurred at similar timescales in the range of seconds. Our data further suggest that MIC60 acts as a docking platform promoting CJ and contact site formation. Overall, by employing advanced imaging techniques including fluorescence recovery after photobleaching (FRAP), single-particle tracking (SPT), live-cell STED and high-resolution Airyscan microscopy, we propose a model of CJ dynamics being mechanistically linked to CM remodelling representing cristae membrane fission and fusion events occurring within individual mitochondria.

NBR1-mediated p62-liquid droplets enhance the Keap1-Nrf2 system.

Abstract: p62/SQSTM1 is a multivalent protein that has the ability to cause liquid-liquid phase separation and serves as a receptor protein that participates in cargo isolation during selective autophagy. This protein is also involved in the non-canonical activation of the Keap1-Nrf2 system, a major oxidative stress response pathway. Here, we show a role of neighbor of BRCA1 gene 1 (NBR1), an autophagy receptor structurally similar to p62/SQSTM1, in p62-liquid droplet formation and Keap1-Nrf2 pathway activation. Overexpression of NBR1 blocks selective degradation of p62/SQSTM1 through autophagy and promotes the accumulation and phosphorylation of p62/SQSTM1 in liquid-like bodies, which is required for the activation of Nrf2. NBR1 is induced in response to oxidative stress, which triggers p62-mediated Nrf2 activation. Conversely, loss of Nbr1 suppresses not only the formation of p62/SQSTM1-liquid droplets, but also of p62-dependent Nrf2 activation during oxidative stress. Taken together, our results show that NBR1 mediates p62/SQSTM1-liquid droplet formation to activate the Keap1-Nrf2 pathway.

Acetyltransferase GCN5 regulates autophagy and lysosome biogenesis by targeting TFEB.

Abstract: Accumulating evidence highlights the role of histone acetyltransferase GCN5 in the regulation of cell metabolism in metazoans. Here, we report that GCN5 is a negative regulator of autophagy, a lysosome-dependent catabolic mechanism. In animal cells and Drosophila, GCN5 inhibits the biogenesis of autophagosomes and lysosomes by targeting TFEB, the master transcription factor for autophagy- and lysosome-related gene expression. We show that GCN5 is a specific TFEB acetyltransferase, and acetylation by GCN5 results in the decrease in TFEB transcriptional activity. Induction of autophagy inactivates GCN5, accompanied by reduced TFEB acetylation and increased lysosome formation. We further demonstrate that acetylation at K274 and K279 disrupts the dimerization of TFEB and the binding of TFEB to its target gene promoters. In a Tau-based neurodegenerative Drosophila model, deletion of dGcn5 improves the clearance of Tau protein aggregates and ameliorates the neurodegenerative phenotypes. Together, our results reveal GCN5 as a novel conserved TFEB regulator, and the regulatory mechanisms may be involved in autophagy- and lysosome-related physiological and pathological processes.

YTHDF1-mediated translation amplifies Wnt-driven intestinal stemness

Abstract: N6-methyladenosine (m6 A) mRNA methylation has emerged as an important player in many biological processes by regulating gene expression. However, its roles in intestinal stem cell (ISC) homeostasis remain largely unknown. Here, we report that YTHDF1, an m6 A reader, is highly expressed in ISCs and its expression is upregulated by Wnt signaling at the translational level. Whereas YTHDF1 is dispensable for normal intestinal development in mice, genetic ablation of Ythdf1 dramatically blocks Wnt-driven regeneration and tumorigenesis with reduced ISC stemness. Mechanistically, YTHDF1 facilitates the translation of Wnt signaling effectors including TCF7L2/TCF4, while this process is enhanced during Wnt activation to augment β-catenin activity. Targeting YTHDF1 in ISCs of established tumors leads to tumor shrinkage and prolonged survival. Collectively, our studies unveil YTHDF1 as an amplifier of Wnt/β-catenin signaling at the translational level, which is required for the maintenance of ISCs during regeneration and tumorigenesis.

SARS-CoV-2 evades immune detection in alveolar macrophages

Abstract: Respiratory infections, like the current COVID-19 pandemic, target epithelial cells in the respiratory tract. Alveolar macrophages (AMs) are tissue-resident macrophages located within the lung. They play a key role in the early phases of an immune response to respiratory viruses. AMs are likely the first immune cells to encounter SARS-CoV-2 during an infection, and their reaction to the virus will have a profound impact on the outcome of the infection. Interferons (IFNs) are antiviral cytokines and among the first cytokines produced upon viral infection. In this study, AMs from non-infectious donors are challenged with SARS-CoV-2. We demonstrate that challenged AMs are incapable of sensing SARS-CoV-2 and of producing an IFN response in contrast to other respiratory viruses, like influenza A virus and Sendai virus, which trigger a robust IFN response. The absence of IFN production in AMs upon challenge with SARS-CoV-2 could explain the initial asymptotic phase observed during COVID-19 and argues against AMs being the sources of pro-inflammatory cytokines later during infection.

Cell cycle dynamics of lamina-associated DNA.

Abstract: In mammalian interphase nuclei, more than one thousand large genomic regions are positioned at the nuclear lamina (NL). These lamina-associated domains (LADs) are involved in gene regulation and may provide a backbone for the folding of interphase chromosomes. Little is known about the dynamics of LADs during interphase, in particular at the onset of G1 phase and during DNA replication. We developed an antibody-based variant of the DamID technology (named pA-DamID) that allows us to map and visualize genome-NL interactions with high temporal resolution. Application of pA-DamID combined with synchronization and cell sorting experiments reveals that LAD-NL contacts are generally rapidly established early in G1 phase. However, LADs on the distal ~25 Mb of most chromosomes tend to contact the NL first and then gradually detach, while centromere-proximal LADs accumulate gradually at the NL. Furthermore, our data indicate that S-phase chromatin shows transiently increased lamin interactions. These findings highlight a dynamic choreography of LAD-NL contacts during interphase progression and illustrate the usefulness of pA-DamID to study the dynamics of genome compartmentalization.

Respiratory supercomplexes enhance electron transport by decreasing cytochrome c diffusion distance

Abstract: Respiratory chains are crucial for cellular energy conversion and consist of multi-subunit complexes that can assemble into supercomplexes. These structures have been intensively characterized in various organisms, but their physiological roles remain unclear. Here, we elucidate their function by leveraging a high-resolution structural model of yeast respiratory supercomplexes that allowed us to inhibit supercomplex formation by mutation of key residues in the interaction interface. Analyses of a mutant defective in supercomplex formation, which still contains fully functional individual complexes, show that the lack of supercomplex assembly delays the diffusion of cytochrome c between the separated complexes, thus reducing electron transfer efficiency. Consequently, competitive cellular fitness is severely reduced in the absence of supercomplex formation and can be restored by overexpression of cytochrome c. In sum, our results establish how respiratory supercomplexes increase the efficiency of cellular energy conversion, thereby providing an evolutionary advantage for aerobic organisms.

Ageing, metabolism and the intestine

Abstract: The intestinal epithelium serves as a dynamic barrier to the environment and integrates a variety of signals, including those from metabolites, commensal microbiota, immune responses and stressors upon ageing. The intestine is constantly challenged and requires a high renewal rate to replace damaged cells in order to maintain its barrier function. Essential for its renewal capacity are intestinal stem cells, which constantly give rise to progenitor cells that differentiate into the multiple cell types present in the epithelium. Here, we review the current state of research of how metabolism and ageing control intestinal stem cell function and epithelial homeostasis. We focus on recent insights gained from model organisms that indicate how changes in metabolic signalling during ageing are a major driver for the loss of stem cell plasticity and epithelial homeostasis, ultimately affecting the resilience of an organism and limiting its lifespan. We compare findings made in mouse and Drosophila and discuss differences and commonalities in the underlying signalling pathways and mechanisms in the context of ageing.

Schistosomal extracellular vesicle-enclosed miRNAs modulate host T helper cell differentiation.

Abstract: During the chronic stage of Schistosoma infection, the female lays fertile eggs, triggering a strong anti-parasitic type 2 helper T-cell (Th2) immune response. It is unclear how this Th2 response gradually declines even though the worms live for years and continue to produce eggs. Here, we show that Schistosoma mansoni downregulates Th2 differentiation in an antigen-presenting cell-independent manner, by modulating the Th2-specific transcriptional program. Adult schistosomes secrete miRNA-harboring extracellular vesicles that are internalized by Th cells in vitro. Schistosomal miRNAs are found also in T helper cells isolated from Peyer's patches and mesenteric lymph nodes of infected mice. In T helper cells, the schistosomal miR-10 targets MAP3K7 and consequently downmodulates NF-κB activity, a critical transcription factor for Th2 differentiation and function. Our results explain, at least partially, how schistosomes tune down the Th2 response, and provide further insight into the reciprocal geographic distribution between high prevalence of parasitic infections and immune disorders such as allergy. Furthermore, this worm-host crosstalk mechanism can be harnessed to develop diagnostic and therapeutic approaches for human schistosomiasis and Th2-associated diseases.

Hexokinase 2 displacement from mitochondria-associated membranes prompts Ca2+ -dependent death of cancer cells.

Abstract: Cancer cells undergo changes in metabolic and survival pathways that increase their malignancy. Isoform 2 of the glycolytic enzyme hexokinase (HK2) enhances both glucose metabolism and resistance to death stimuli in many neoplastic cell types. Here, we observe that HK2 locates at mitochondria-endoplasmic reticulum (ER) contact sites called MAMs (mitochondria-associated membranes). HK2 displacement from MAMs with a selective peptide triggers mitochondrial Ca2+ overload caused by Ca2+ release from ER via inositol-3-phosphate receptors (IP3Rs) and by Ca2+ entry through plasma membrane. This results in Ca2+ -dependent calpain activation, mitochondrial depolarization and cell death. The HK2-targeting peptide causes massive death of chronic lymphocytic leukemia B cells freshly isolated from patients, and an actionable form of the peptide reduces growth of breast and colon cancer cells allografted in mice without noxious effects on healthy tissues. These results identify a signaling pathway primed by HK2 displacement from MAMs that can be activated as anti-neoplastic strategy.

A conserved ATG2-GABARAP family interaction is critical for phagophore formation.

Abstract: The intracellular trafficking pathway, macroautophagy, is a recycling and disposal service that can be upregulated during periods of stress to maintain cellular homeostasis. An essential phase is the elongation and closure of the phagophore to seal and isolate unwanted cargo prior to lysosomal degradation. Human ATG2A and ATG2B proteins, through their interaction with WIPI proteins, are thought to be key players during phagophore elongation and closure, but little mechanistic detail is known about their function. We have identified a highly conserved motif driving the interaction between human ATG2 and GABARAP proteins that is in close proximity to the ATG2-WIPI4 interaction site. We show that the ATG2A-GABARAP interaction mutants are unable to form and close phagophores resulting in blocked autophagy, similar to ATG2A/ATG2B double-knockout cells. In contrast, the ATG2A-WIPI4 interaction mutant fully restored phagophore formation and autophagy flux, similar to wild-type ATG2A. Taken together, we provide new mechanistic insights into the requirements for ATG2 function at the phagophore and suggest that an ATG2-GABARAP/GABARAP-L1 interaction is essential for phagophore formation, whereas ATG2-WIPI4 interaction is dispensable.

Androgen receptor-regulated circFNTA activates KRAS signaling to promote bladder cancer invasion.

Abstract: The androgen receptor (AR) has been linked to bladder cancer (BCa) progression, but if this involves circular RNAs (circRNAs) remains unclear. Here, we find that AR alters the levels of circRNA-FNTA (circFNTA) to increase BCa cell invasion and chemo-resistance. Mechanistically, AR represses the RNA editing gene ADAR2 via direct binding to its 5' promoter region to increase circFNTA levels, which then sponges the microRNA miR-370-3p to increase the expression of its host gene FNTA. This AR-mediated ADAR2/circFNTA/miR-370-3p/FNTA pathway then activates KRAS signaling to alter BCa cell invasion and chemo-sensitivity to cisplatin. A clinical BCa sample survey shows that circFNTA expression is elevated in BCa tissues, and results from a BCa mouse model indicate that depletion of circFNTA leads to the suppression of BCa metastases and increased cisplatin chemo-sensitivity. Together, based on our results using multiple BCa cell lines and an in vivo mouse model we suggest that targeting this newly identified AR/ADAR2/circFNTA/miR-370-3p/FNTA/KRAS axis may lead to the development of therapies to suppress BCa metastasis and to increase its chemo-sensitivity.

Stimulation of glycolysis promotes cardiomyocyte proliferation after injury in adult zebrafish.

Abstract: Cardiac metabolism plays a crucial role in producing sufficient energy to sustain cardiac function. However, the role of metabolism in different aspects of cardiomyocyte regeneration remains unclear. Working with the adult zebrafish heart regeneration model, we first find an increase in the levels of mRNAs encoding enzymes regulating glucose and pyruvate metabolism, including pyruvate kinase M1/2 (Pkm) and pyruvate dehydrogenase kinases (Pdks), especially in tissues bordering the damaged area. We further find that impaired glycolysis decreases the number of proliferating cardiomyocytes following injury. These observations are supported by analyses using loss-of-function models for the metabolic regulators Pkma2 and peroxisome proliferator-activated receptor gamma coactivator 1 alpha. Cardiomyocyte-specific loss- and gain-of-function manipulations of pyruvate metabolism using Pdk3 as well as a catalytic subunit of the pyruvate dehydrogenase complex (PDC) reveal its importance in cardiomyocyte dedifferentiation and proliferation after injury. Furthermore, we find that PDK activity can modulate cell cycle progression and protrusive activity in mammalian cardiomyocytes in culture. Our findings reveal new roles for cardiac metabolism and the PDK-PDC axis in cardiomyocyte behavior following cardiac injury.

Mitochondrial protein biogenesis in the synapse is supported by local translation.

Abstract: Synapses are the regions of the neuron that enable the transmission and propagation of action potentials on the cost of high energy consumption and elevated demand for mitochondrial ATP production The rapid changes in local energetic requirements at dendritic spines imply the role of mitochondria in the maintenance of their homeostasis Using global proteomic analysis supported with complementary experimental approaches, we show that an essential pool of mitochondrial proteins is locally produced at the synapse indicating that mitochondrial protein biogenesis takes place locally to maintain functional mitochondria in axons and dendrites Furthermore, we show that stimulation of synaptoneurosomes induces the local synthesis of mitochondrial proteins that are transported to the mitochondria and incorporated into the protein supercomplexes of the respiratory chain Importantly, in a mouse model of fragile X syndrome, Fmr1 KO mice, a common disease associated with dysregulation of synaptic protein synthesis, we observed altered morphology and respiration rates of synaptic mitochondria That indicates that the local production of mitochondrial proteins plays an essential role in synaptic functions

USP1 deubiquitinates Akt to inhibit PI3K-Akt-FoxO signaling in muscle during prolonged starvation.

Abstract: PI3K-Akt-FoxO-mTOR signaling is the central pathway controlling growth and metabolism in all cells. Ubiquitination of the protein kinase Akt prior to its phosphorylation is required for PI3K-Akt activity. Here, we found that the deubiquitinating (DUB) enzyme USP1 removes K63-linked polyubiquitin chains on Akt to restrict PI3K-Akt-FoxO signaling in mouse muscle during prolonged starvation. DUB screening platform identified USP1 as a direct DUB for Akt, and USP1 depletion in mouse muscle increased Akt ubiquitination, PI3K-Akt-FoxO signaling, and glucose uptake during fasting. Co-immunoprecipitation and mass spectrometry identified disabled homolog-2 (Dab2), the tuberous sclerosis complex TSC1/TSC2, and PHLPP1 as USP1 bound proteins. During starvation, Dab2 is essential for Akt recruitment to USP1-TSC1-PHLPP1 complex, and for PI3K-Akt-FoxO inhibition. Surprisingly, USP1 limits TSC1 levels to sustain mTOR-mediated basal protein synthesis rates and maintain its own protein levels. We propose that Dab2 recruits Akt to USP1-TSC1-PHLPP1 complex to efficiently terminate the transmission of growth signals when cellular energy level is low.

Chemokines and galectins form heterodimers to modulate inflammation.

Abstract: Chemokines and galectins are simultaneously upregulated and mediate leukocyte recruitment during inflammation. Until now, these effector molecules have been considered to function independently. Here, we tested the hypothesis that they form molecular hybrids. By systematically screening chemokines for their ability to bind galectin-1 and galectin-3, we identified several interacting pairs, such as CXCL12 and galectin-3. Based on NMR and MD studies of the CXCL12/galectin-3 heterodimer, we identified contact sites between CXCL12 β-strand 1 and Gal-3 F-face residues. Mutagenesis of galectin-3 residues involved in heterodimer formation resulted in reduced binding to CXCL12, enabling testing of functional activity comparatively. Galectin-3, but not its mutants, inhibited CXCL12-induced chemotaxis of leukocytes and their recruitment into the mouse peritoneum. Moreover, galectin-3 attenuated CXCL12-stimulated signaling via its receptor CXCR4 in a ternary complex with the chemokine and receptor, consistent with our structural model. This first report of heterodimerization between chemokines and galectins reveals a new type of interaction between inflammatory mediators that can underlie a novel immunoregulatory mechanism in inflammation. Thus, further exploration of the chemokine/galectin interactome is warranted.

TBK1-mediated phosphorylation of LC3C and GABARAP-L2 controls autophagosome shedding by ATG4 protease.

Abstract: Autophagy is a highly conserved catabolic process through which defective or otherwise harmful cellular components are targeted for degradation via the lysosomal route. Regulatory pathways, involving post-translational modifications such as phosphorylation, play a critical role in controlling this tightly orchestrated process. Here, we demonstrate that TBK1 regulates autophagy by phosphorylating autophagy modifiers LC3C and GABARAP-L2 on surface-exposed serine residues (LC3C S93 and S96; GABARAP-L2 S87 and S88). This phosphorylation event impedes their binding to the processing enzyme ATG4 by destabilizing the complex. Phosphorylated LC3C/GABARAP-L2 cannot be removed from liposomes by ATG4 and are thus protected from ATG4-mediated premature removal from nascent autophagosomes. This ensures a steady coat of lipidated LC3C/GABARAP-L2 throughout the early steps in autophagosome formation and aids in maintaining a unidirectional flow of the autophagosome to the lysosome. Taken together, we present a new regulatory mechanism of autophagy, which influences the conjugation and de-conjugation of LC3C and GABARAP-L2 to autophagosomes by TBK1-mediated phosphorylation.

Epstein-Barr virus-derived circular RNA LMP2A induces stemness in EBV-associated gastric cancer.

Abstract: Cancer stem cells (CSCs) are cancer-initiating cells that are not only a source of tumorigenesis but also the cause of tumour progression, metastasis and therapy resistance. EBV-associated gastric cancer (EBVaGC) is a distinct subtype of gastric cancer with unique clinicopathological and molecular features. However, whether CSCs exist in EBVaGC, and the tumorigenic mechanism of EBV, remains unclear. Here, NOD/SCID mice were injected subcutaneously with the EBVaGC cell line SNU719 and treated with 5-fluorouracil weekly. Successive generations of xenografts yielded a highly malignant EBVaGC cell line, SNU-4th, which displays properties of CSCs and mainly consists of CD44+ CD24- cells. In SNU-4th cells, an EBV-encoded circRNA, ebv-circLMP2A, expression increased and plays crucial roles in inducing and maintaining stemness phenotypes through targeting miR-3908/TRIM59/p53 axis. Additionally, high expression of ebv-circLMP2A is significantly associated with metastasis and poor prognosis in patients with EBVaGC. These findings not only provide evidence for the existence of CSCs in EBVaGC and elucidate the pathogenic mechanism of ebv-circLMP2A in EBVaGC, but also provide a promising therapeutic target for EBVaGC.

CrRLK1L receptor-like kinases HERK1 and ANJEA are female determinants of pollen tube reception.

Abstract: Communication between the gametophytes is vital for angiosperm fertilisation. Multiple CrRLK1L‐type receptor kinases prevent premature pollen tube burst, while another CrRLK1L protein, FERONIA (FER), is required for pollen tube reception in the female gametophyte. We report here the identification of two additional CrRLK1L homologues, HERCULES RECEPTOR KINASE 1 (HERK1) and ANJEA (ANJ), which act redundantly to promote pollen tube growth arrest at the synergid cells. HERK1 and ANJ localise to the filiform apparatus of the synergid cells in unfertilised ovules, and in herk1 anj mutants, a majority of ovules remain unfertilised due to pollen tube overgrowth, together indicating that HERK1 and ANJ act as female determinants for fertilisation. As in fer mutants, the synergid cell‐specific, endomembrane protein NORTIA (NTA) is not relocalised after pollen tube reception; however, unlike fer mutants, reactive oxygen species levels are unaffected in herk1 anj double mutants. Both ANJ and HERK1 associate with FER and its proposed co‐receptor LORELEI (LRE) in planta. Together, our data indicate that HERK1 and ANJ act with FER to mediate female–male gametophyte interactions during plant fertilisation.

Muscle-derived GDF15 drives diurnal anorexia and systemic metabolic remodeling during mitochondrial stress.

Abstract: Mitochondrial dysfunction promotes metabolic stress responses in a cell-autonomous as well as organismal manner. The wasting hormone growth differentiation factor 15 (GDF15) is recognized as a biomarker of mitochondrial disorders, but its pathophysiological function remains elusive. To test the hypothesis that GDF15 is fundamental to the metabolic stress response during mitochondrial dysfunction, we investigated transgenic mice (Ucp1-TG) with compromised muscle-specific mitochondrial OXPHOS capacity via respiratory uncoupling. Ucp1-TG mice show a skeletal muscle-specific induction and diurnal variation of GDF15 as a myokine. Remarkably, genetic loss of GDF15 in Ucp1-TG mice does not affect muscle wasting or transcriptional cell-autonomous stress response but promotes a progressive increase in body fat mass. Furthermore, muscle mitochondrial stress-induced systemic metabolic flexibility, insulin sensitivity, and white adipose tissue browning are fully abolished in the absence of GDF15. Mechanistically, we uncovered a GDF15-dependent daytime-restricted anorexia, whereas GDF15 is unable to suppress food intake at night. Altogether, our evidence suggests a novel diurnal action and key pathophysiological role of mitochondrial stress-induced GDF15 in the regulation of systemic energy metabolism.

SIRT2-dependent IDH1 deacetylation inhibits colorectal cancer and liver metastases.

Abstract: Protein lysine acetylation affects colorectal cancer (CRC) distant metastasis through multiple pathways. In a previous proteomics screen, we found that isocitrate dehydrogenase 1 (IDH1) is hyperacetylated in CRC primary tumors and liver metastases. Here, we further investigate the function of IDH1 hyperacetylation at lysine 224 in CRC progression. We find that IDH1 K224 deacetylation promotes its enzymatic activity and the production of α-KG, and we identify sirtuin-2 (SIRT2) as a major deacetylase for IDH1. SIRT2 overexpression significantly inhibits CRC cell proliferation, migration, and invasion. IDH1 acetylation is modulated in response to intracellular metabolite concentration and regulates cellular redox hemostasis. Moreover, IDH1 acetylation reversely regulates HIF1α-dependent SRC transcription which in turn controls CRC progression. Physiologically, our data indicate that IDH1 deacetylation represses CRC cell invasion and migration in vitro and in vivo, while the hyperacetylation of IDH1 on K224 is significantly correlated to distant metastasis and poor survival of colorectal cancer patients. In summary, our study uncovers a novel mechanism through which SIRT2-dependent IDH1 deacetylation regulates cellular metabolism and inhibits liver metastasis of colorectal cancer.

Mitophagy regulates integrity of mitochondria at synapses and is critical for synaptic maintenance.

Abstract: Synaptic mitochondria are particularly vulnerable to physiological insults, and defects in synaptic mitochondria are linked to early pathophysiology of Alzheimer's disease (AD) Mitophagy, a cargo-specific autophagy for elimination of dysfunctional mitochondria, constitutes a key quality control mechanism However, how mitophagy ensures synaptic mitochondrial integrity remains largely unknown Here, we reveal Rheb and Snapin as key players regulating mitochondrial homeostasis at synapses Rheb initiates mitophagy to target damaged mitochondria for autophagy, whereas dynein-Snapin-mediated retrograde transport promotes clearance of mitophagosomes from synaptic terminals We demonstrate that synaptic accumulation of mitophagosomes is a feature in AD-related mutant hAPP mouse brains, which is attributed to increased mitophagy initiation coupled with impaired removal of mitophagosomes from AD synapses due to defective retrograde transport Furthermore, while deficiency in dynein-Snapin-mediated retrograde transport recapitulates synaptic mitophagy stress and induces synaptic degeneration, elevated Snapin expression attenuates mitochondrial defects and ameliorates synapse loss in AD mouse brains Taken together, our study provides new insights into mitophagy regulation of synaptic mitochondrial integrity, establishing a foundation for mitigating AD-associated mitochondria deficits and synaptic damage through mitophagy enhancement

Arginine methylation-dependent LSD1 stability promotes invasion and metastasis of breast cancer.

Abstract: Histone lysine demethylase 1 (LSD1), the first identified histone demethylase, is overexpressed in multiple tumor types, including breast cancer. However, the mechanisms that cause LSD1 dysregulation in breast cancer remain largely unclear. Here, we report that protein arginine methyltransferase 4 (PRMT4 or CARM1) dimethylates LSD1 at R838, which promotes the binding of the deubiquitinase USP7, resulting in the deubiquitination and stabilization of LSD1. Moreover, CARM1- and USP7-dependent LSD1 stabilization plays a key role in repressing E-cadherin and activating vimentin transcription through promoter H3K4me2 and H3K9me2 demethylation, respectively, which promotes invasion and metastasis of breast cancer cells. Consistently, LSD1 arginine methylation levels correlate with tumor grade in human malignant breast carcinoma samples. Our findings unveil a unique mechanism controlling LSD1 stability by arginine methylation, also highlighting the role of the CARM1-USP7-LSD1 axis in breast cancer progression.

Healthy soils for healthy plants for healthy humans

Abstract: The microbiota of the human gut and the plant rhizome are similar in many ways and intricately connected with each other. A healthy plant therefore affects human microbiota and human health.

Prostate cancer cell-intrinsic interferon signaling regulates dormancy and metastatic outgrowth in bone

Abstract: The latency associated with bone metastasis emergence in castrate-resistant prostate cancer is attributed to dormancy, a state in which cancer cells persist prior to overt lesion formation. Using single-cell transcriptomics and ex vivo profiling, we have uncovered the critical role of tumor-intrinsic immune signaling in the retention of cancer cell dormancy. We demonstrate that loss of tumor-intrinsic type I IFN occurs in proliferating prostate cancer cells in bone. This loss suppresses tumor immunogenicity and therapeutic response and promotes bone cell activation to drive cancer progression. Restoration of tumor-intrinsic IFN signaling by HDAC inhibition increased tumor cell visibility, promoted long-term antitumor immunity, and blocked cancer growth in bone. Key findings were validated in patients, including loss of tumor-intrinsic IFN signaling and immunogenicity in bone metastases compared to primary tumors. Data herein provide a rationale as to why current immunotherapeutics fail in bone-metastatic prostate cancer, and provide a new therapeutic strategy to overcome the inefficacy of immune-based therapies in solid cancers.