cGAS phase separation inhibits TREX1-mediated DNA degradation and enhances cytosolic DNA sensing

Phase separation in mitochondrial fate and mitochondrial diseases

Mitochondria are central metabolic organelles that control cell fate and the development of mitochondrial diseases. Traditionally, phase separation directly regulates cell functions by driving RNA, proteins, or other molecules to concentrate into lipid droplets. Recent studies show that phase separation regulates cell functions and diseases through the regulation of subcellular organelles, particularly mitochondria. In fact, phase separation is involved in various mitochondrial activities including nucleoid assembly, autophagy, and mitochondria-related inflammation. Here, we outline the key mechanisms through which phase separation influences mitochondrial activities and the development of mitochondrial diseases. Insights into how phase separation regulates mitochondrial activities and diseases will help us develop interventions for related diseases.

Enhancing nano-immunotherapy of cancer through cGAS-STING pathway modulation

Activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a critical role in cancer immunotherapy due to the secretion of multiple pro-inflammatory cytokines and chemokines. Numerous cGAS-STING agonists have been developed for preclinical and clinical trials in tumor immunity. However, several obstacles, such as agonist molecules requiring multiple doses, rapid degradation and poor targeting, weaken STING activation at the tumor site. The advancement of nanotechnology provides an optimized platform for the clinical application of STING agonists. In this review, we summarize events of cGAS-STING pathway activation, the dilemma of delivering STING agonists, and recent advances in the nano-delivery of cGAS-STING agonist formulations for enhancing tumor immunity. Furthermore, we address the future challenges associated with STING-based therapies and offer insights to guide subsequent clinical applications.

LncRNA RMG controls liquid-liquid phase separation of MEIS2 to regulate myogenesis

Long non-coding RNAs (lncRNAs) regulate liquid-liquid phase separation (LLPS), driving the formation of biomolecular condensates essential for cellular function. However, this regulatory mechanism is yet to be reported in skeletal muscles. In this study, we comprehensively analyzed lncRNAs in skeletal muscle across multiple pig breeds, developmental stages, and tissues. Our analysis identified over 10,000 novel lncRNAs. We found that the lnc-regulator of muscle growth (lnc-RMG) regulates myogenesis by modulating the LLPS of Meis homeobox 2 (MEIS2). Lnc-RMG was specifically expressed in the skeletal muscle, with significantly higher expression in the fetal stage than in the embryonic stage. Notably, lnc-RMG was highly conserved between pigs and humans and exhibits similar biological functions in myogenesis. Furthermore, lnc-RMG knockdown promoted skeletal muscle regeneration. Mechanistically, lnc-RMG produces mature microRNA (miR)-133a-3p, which targets and inhibits MEIS2 expression, thereby inhibiting MEIS2 LLPS. This inhibition promoted the transcription of transforming growth factor-β receptor II (TGFβR2), ultimately regulating myogenesis. Overall, our findings revealed a novel lnc-RMG/miR-133a-3p/MEIS2/TGFβR2 axis that regulated myogenesis through LLPS and provided new insights into the molecular mechanisms that drive muscle development and regeneration. These findings highlight potential therapeutic targets for muscle-related diseases and novel strategies for livestock improvement.

Rational design of chemical- and light-inducible cGAS activation based on mechanistic insights

Cyclic GMP-AMP synthase (cGAS) plays a pivotal role in the cGAS-STING pathway as a DNA sensor that binds to double-stranded DNA (dsDNA) and subsequently induces type I interferon expression, thereby contributing significantly to the innate immune response. Several human and viral proteins have been identified to enhance or inhibit cGAS activity. The underlying molecular basis that underpins these regulatory effects remain elusive. In this study, we employ the highly sensitive dcFCCS method to systematically examine phase separation and binding affinities among cGAS, dsDNA, and several accessory proteins. We reveal that the binding strength between cGAS and accessory proteins is the key factor to affect cGAS phase separation and enzymatic activity, which guide us to develop a chemical-inducible strategy and a light-inducible strategy to manipulate cGAS phase separation and immune signaling in test tubes and in living cells. Thus, our mechanistic insights offer guidance for manipulating multi-component phase separation systems.

ATM and IRAK1 orchestrate two distinct mechanisms of NF-κB activation in response to DNA damage

DNA damage in cells induces the expression of inflammatory genes. However, the mechanism by which cells initiate an innate immune response in the presence of DNA lesions blocking transcription remains unknown. Here we find that genotoxic stresses lead to an acute activation of the transcription factor NF-κB through two distinct pathways, each triggered by different types of DNA lesions and coordinated by either ataxia-telangiectasia mutated (ATM) or IRAK1 kinases. ATM stimulates NF-κB in cells with DNA double-strand breaks. By contrast, IRAK1-induced NF-κB signaling occurs in neighboring cells through IL-1α secretion from transcriptionally stressed cells caused by DNA lesions blocking RNA polymerases. Subsequently, both pathways stimulate TRAF6 and the IKK complex to promote NF-κB-mediated inflammatory gene expression. These findings provide an alternative mechanism for damaged cells with impaired transcription to initiate an inflammatory response without relying on their own gene expression, a necessary step that injured cells depend on during canonical innate immune responses.

Regulation of the cGAS-STING Pathway

The cGAS-cGAMP-STING pathway is essential for immune defense against pathogens. Upon binding DNA, cGAS synthesizes cGAMP, which activates STING, leading to potent innate immune effector responses. However, lacking specific features to distinguish between self and nonself DNA, cGAS-STING immunity requires precise regulation to prevent aberrant activation. Several safeguard mechanisms acting on different levels have evolved to maintain tolerance to self DNA and ensure immune homeostasis under normal conditions. Disruption of these safeguards can lead to erroneous activation by self DNA, resulting in inflammatory conditions but also favorable antitumor immunity. Insights into structural and cellular checkpoints that control and terminate cGAS-STING signaling are essential for comprehending and manipulating DNA-triggered innate immunity in health and disease.

Liquid-liquid phase separation-related genes associated with prognosis, tumor microenvironment characteristics, and tumor cell features in bladder cancer

OBJECTIVE

This study aimed to explore the Liquid-liquid phase separation (LLPS)-related genes associated with the prognosis of bladder cancer (BCa) and assess the potential application of LLPS-related prognostic signature for predicting prognosis in BCa patients.

METHODS

Clinical information and transcriptome data of BCa patients were extracted from the Cancer Genome Atlas-BLCA (TCGA-BLCA) database and the GSE13507 database. Furthermore, 108 BCa patients who received treatment at our institution were subjected to a retrospective analysis. The least absolute shrinkage and selection operator (LASSO) analysis was performed to develop an LLPS-related prognostic signature for BCa. The CCK8, wound healing and Transwell assays were performed.

RESULTS

Based on 62 differentially expressed LLPS-related genes (DELRGs), three DELRGs were screened by LASSO analysis including kallikrein-related peptidase 5 (KLK5), monoacylglycerol O-acyltransferase 2 (MOGAT2) and S100 calcium-binding protein A7 (S100A7). Based on three DELRGs, a novel LLPS-related prognostic signature was constructed for individualized prognosis assessment. Kaplan-Meier curve analyses showed that LLPS-related prognostic signature was significantly correlated with overall survival (OS) of BCa. ROC analyses demonstrated the LLPS-related prognostic signature performed well in predicting the prognosis of BCa patients in the training group (the area under the curve (AUC) = 0.733), which was externally verified in the validation cohort 1 (AUC = 0.794) and validation cohort 2 (AUC = 0.766). Further experiments demonstrated that inhibiting KLK5 could affect the proliferation, migration, and invasion of BCa cells.

CONCLUSIONS

In this study, a novel LLPS-related prognostic signature was successfully developed and validated, demonstrating strong performance in predicting the prognosis of BCa patients.

An Overview of Liquid-Liquid Phase Separation and Its Mechanisms in Sepsis

Sepsis is a systemic inflammatory response syndrome triggered by the invasion of bacteria or pathogenic microorganisms into the human body, which may lead to a variety of serious complications and pose a serious threat to the patient's life and health. Liquid-liquid phase separation (LLPS) is a biomolecular process in which different biomolecules, such as proteins and nucleic acids, form liquid condensates through interactions, and these condensates play key roles in cellular physiological processes. LLPS may affect the development of sepsis through several pathways, such as modulation of inflammatory factors, immune responses, and cell death, by altering the function or activity of biomolecules, which, in turn, affect the cellular response to infection and inflammation. In this paper, we first discuss the mechanism of phase separation, then summarize the studies of LLPS in sepsis, and finally propose the potential application of LLPS in sepsis treatment strategies, while pointing out the limitations of the existing studies and the directions for future research.

Nucleic-acid-induced ZCCHC3 condensation promotes broad innate immune responses

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) and cyclic GMP-AMP synthase (cGAS) recognize aberrant nucleic acids and initiate antiviral responses. Host factor zinc finger CCHC domain-containing protein 3 (ZCCHC3) positively regulates both RLRs- and cGAS-mediated signaling through unknown mechanisms. Here, we show that ZCCHC3 employs a broad and unified strategy to promote these pathways in human cell lines. Rather than developing strong protein-protein interactions, ZCCHC3 harbors multiple nucleic-acid-binding modules and undergoes robust liquid phase condensation with nucleic acids. RNA-induced ZCCHC3 condensates enrich and activate RLRs, which then facilitate the interaction of RLRs with the downstream adaptor mitochondrial antiviral-signaling (MAVS). Direct and high-resolution structure determination of liquid condensates confirms the assembly of active-form MAVS filaments. Furthermore, ZCCHC3 efficiently promotes the condensation and enrichment of DNA, cGAS, ATP, and GTP, thereby enhancing cGAS signaling. ZCCHC3 mutants defective in RNA/DNA-induced condensation lost their regulatory efficiency in both pathways. These results highlight unexpectedly broad connections between biomolecular condensation and innate immunity.

To cleave or not and how? The DNA exonucleases and endonucleases in immunity

DNA exonucleases and endonucleases are key executors of the genome during many physiological processes. They generate double-stranded DNA by cleaving damaged endogenous or exogenous DNA, triggering the activation of the innate immune pathways such as cGAS-STING-IFN, and enabling the body to produce anti-viral or anti-tumor immune responses. This is of great significance for maintaining the stability of the genome and improving the therapeutic efficacy of tumors. In addition, genomic instability caused by exonuclease mutations contributes to the development of various autoimmune diseases. This review summarizes the DNA exonucleases and endonucleases which have critical functions in immunity and associated diseases.

Biomolecular Condensates in Telomere Maintenance of ALT Cancer Cells

Alternative Lengthening of Telomeres (ALT) pathway is a telomerase-independent mechanism that utilizes homology-directed repair (HDR) to sustain telomere length in specific cancers. Biomolecular condensates, such as ALT-associated promyelocytic leukemia nuclear bodies (APBs), have emerged as critical players in the ALT pathway, supporting telomere maintenance in ALT-positive cells. These condensates bring together DNA repair proteins, telomeric repeats, and other regulatory elements. By regulating replication stress and promoting DNA synthesis, ALT condensates create an environment conducive to HDR-based telomere extension. This review explores recent advancements in ALT, focusing on understanding the role of biomolecular condensates in ALT and how they impact telomere dynamics and stability.

The role of cGAS-STING pathway ubiquitination in innate immunity and multiple diseases

The cGAS-STING pathway is essential in innate immunity, especially in antiviral responses and cellular stress management. cGAS acts as a cytoplasmic DNA sensor by initiating the synthesis of the second messenger cyclic GMP-AMP synthase (cGAMP), which subsequently activates the STING pathway, leading to the production of type I interferons and other cytokines, as well as the activation of inflammatory mediators. Recent studies have demonstrated that ubiquitination changes closely regulate the function of the cGAS-STING pathway. Ubiquitination modifications influence the stability and activity of cGAS and STING, while also influencing the accuracy of the immune response by adjusting their degradation and signal intensity. E3 ubiquitin ligase specifically facilitates the degradation or modulates the signaling of cGAS-STING-associated proteins via ubiquitination alterations. Furthermore, the ubiquitination of the cGAS-STING pathway serves distinct functions in various cell types and engages with NF-κB, IRF3/7, autophagy, and endoplasmic reticulum stress. This ubiquitin-mediated regulation is crucial for sustaining the balance of innate immunity, while excessive or inadequate ubiquitination can result in autoimmune disorders, cancers, and viral infections. An extensive examination of the ubiquitination process within the cGAS-STING pathway elucidates its specific regulatory mechanisms in innate immunity and identifies novel targets for the intervention of associated diseases.

Crucial role of the cGAS N terminus in mediating flowable and functional cGAS-DNA condensate formation via DNA interactions

The DNA-sensing protein cGAS plays a pivotal role in the innate immune response and pathogenesis of various diseases. DNA triggers liquid-liquid phase separation (LLPS) and enhances the enzymatic activity of cGAS. However, the regulatory mechanisms of the disordered N terminus remain unclear. Here, we showed that cGASNterm, the N-terminal intrinsic disordered region (IDR) of cGAS, modulates the material properties, specifically the flowability, of the condensed phase of cGAS and is required for full enzymatic activity. Full-length cGAS and cGASNterm form liquid droplets in the presence of DNA, while the cGAS catalytic domain forms gel-like solid aggregates with compromised enzymatic activity. Multiple key amino acids responsible for the cGASNterm-DNA interaction were identified by NMR spectroscopy as well as other biophysical methods and proven to be critical for the functional LLPS of cGAS both in vitro and in vivo. Interestingly, cGASNterm acts in trans to transform the solid aggregates of the cGAS catalytic domain into liquid droplets, subsequently restoring its enzymatic activity. Together, our findings highlight the importance of the IDR of cGAS in LLPS upon DNA stimulation and, more importantly, in modulating the fluidity and permeability of the droplets formed by full-length cGAS, which is crucial for its intact enzymatic activity.

In situ self-reassembling nanosystem enhances PD-L1 blockade for cancer immunotherapy

Although immune checkpoint inhibitors (ICIs) have made great progress in cancer treatment, their off-tumor distribution, low affinity of traditional ICIs and insufficient T cells infiltration at tumor site limit immunotherapeutic efficacy. Herein, we engineer a highly specific and effective PD-L1 inhibitor (PEC) that modulates the level of binding sites with PD-L1. Specifically, PEC is a hybrid system composed of E. coli membrane expressing PD-L1 binding protein and cancer cell membrane. Notably, PEC can target the tumor site, produce oxygen in response to H2O2, rupture into membrane fragments, and reassemble to form vesicles retaining the PD-L1 binding protein. Through in situ fracture and reassembly, PEC transforms from a hybrid membrane to a single E. coli membrane, leading to the increased density of PD-L1 binding protein. Consequently, the reassembled vesicles can bind to more PD-L1 on tumor cells and induce its degradation in lysosomes. Furthermore, the cGAS-STING signaling activators HZD is encapsulated into PEC to promote T cells infiltration. We demonstrate that PEC@HZD achieves sequential T cells recruitment and functional enhancement, thus stimulating a powerful antitumor immune response. This work provides a new perspective on tailoring ICIs to improve cancer immunotherapy.

Regulation of cGAS-STING signalling and its diversity of cellular outcomes

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling pathway, which recognizes both pathogen DNA and host-derived DNA, has emerged as a crucial component of the innate immune system, having important roles in antimicrobial defence, inflammatory disease, ageing, autoimmunity and cancer. Recent work suggests that the regulation of cGAS-STING signalling is complex and sophisticated. In this Review, we describe recent insights from structural studies that have helped to elucidate the molecular mechanisms of the cGAS-STING signalling cascade and we discuss how the cGAS-STING pathway is regulated by both activating and inhibitory factors. Furthermore, we summarize the newly emerging understanding of crosstalk between cGAS-STING signalling and other signalling pathways and provide examples to highlight the wide variety of cellular processes in which cGAS-STING signalling is involved, including autophagy, metabolism, ageing, inflammation and tumorigenesis.

Emerging regulatory mechanisms and functions of biomolecular condensates: implications for therapeutic targets

Cells orchestrate their processes through complex interactions, precisely organizing biomolecules in space and time. Recent discoveries have highlighted the crucial role of biomolecular condensates-membrane-less assemblies formed through the condensation of proteins, nucleic acids, and other molecules-in driving efficient and dynamic cellular processes. These condensates are integral to various physiological functions, such as gene expression and intracellular signal transduction, enabling rapid and finely tuned cellular responses. Their ability to regulate cellular signaling pathways is particularly significant, as it requires a careful balance between flexibility and precision. Disruption of this balance can lead to pathological conditions, including neurodegenerative diseases, cancer, and viral infections. Consequently, biomolecular condensates have emerged as promising therapeutic targets, with the potential to offer novel approaches to disease treatment. In this review, we present the recent insights into the regulatory mechanisms by which biomolecular condensates influence intracellular signaling pathways, their roles in health and disease, and potential strategies for modulating condensate dynamics as a therapeutic approach. Understanding these emerging principles may provide valuable directions for developing effective treatments targeting the aberrant behavior of biomolecular condensates in various diseases.

Chromosomal instability as a driver of cancer progression

Chromosomal instability (CIN) refers to an increased propensity of cells to acquire structural and numerical chromosomal abnormalities during cell division, which contributes to tumour genetic heterogeneity. CIN has long been recognized as a hallmark of cancer, and evidence over the past decade has strongly linked CIN to tumour evolution, metastasis, immune evasion and treatment resistance. Until recently, the mechanisms by which CIN propels cancer progression have remained elusive. Beyond the generation of genomic copy number heterogeneity, recent work has unveiled additional tumour-promoting consequences of abnormal chromosome segregation. These mechanisms include complex chromosomal rearrangements, epigenetic reprogramming and the induction of cancer cell-intrinsic inflammation, emphasizing the multifaceted role of CIN in cancer.

Biomolecular condensates: phasing in regulated host-pathogen interactions

Biomolecular condensates are membraneless organelles formed through liquid-liquid phase separation. Innate immunity is essential to host defense against infections, but pathogens also harbor sophisticated mechanisms to evade host defense. The formation of biomolecular condensates emerges as a key biophysical mechanism in host-pathogen interactions, playing pivotal roles in regulating immune responses and pathogen life cycles within the host. In this review we summarize recent advances in our understanding of how biomolecular condensates remodel membrane-bound organelles, influence infection-induced cell death, and are hijacked by pathogens for survival, as well as how they modulate mammalian innate immunity. We discuss the implications of dysregulated formation of biomolecular condensates during host-pathogen interactions and infectious diseases and propose future directions for developing potential treatments against such infections.

The emerging roles of liquid-liquid phase separation in tumor immunity

Recent advancements in tumor immunotherapy, particularly PD-1 targeted therapy, have shown significant promise, marking major progress in tumor treatment approaches. Despite this, the development of resistance to therapy and mechanisms of immune evasion by tumors pose considerable obstacles to the broad application of immunotherapy. This necessitates a deeper exploration of complex immune signaling pathways integral to tumor immunity. This review aims to critically analyze the role of liquid-liquid phase separation (LLPS) within tumor immunity, specifically its impact on immune signaling pathways and its potential to foster the development of novel cancer therapies. LLPS, a biophysical process newly recognized for its ability to spontaneously segregate and organize biomacromolecules into liquid-like condensates through weak multivalent interactions, offers a novel perspective on the formation of signaling clusters and the functionality of immune molecules. The review delves into the micromolecular mechanisms behind the creation of signaling condensates via LLPS and reviews recent progress in adjusting signaling pathways pertinent to tumor immunity, including the T cell receptor (TCR), B cell receptor (BCR), immune checkpoints, and innate immune pathways such as the cGAS-STING pathway, stress granules, and the ADP-heptose-ALPK1 signaling axis. Furthermore, it considers the prospects of utilizing LLPS to generate groundbreaking cancer therapies capable of navigating past current treatment barriers. Through an extensive examination of LLPS's impact on tumor immunity, the review seeks to highlight novel therapeutic strategies and address the challenges and future directions in this rapidly evolving field.

The cGAS-STING pathway in ischemia-reperfusion injury in acute cerebral infarction: a new therapeutic opportunities?

The innate immune response is the body's first line of defense against external pathogens and endogenous damage signals. The cGAS-STING pathway is a crucial component of the innate immune response, playing a key role in initiating antiviral and anti-infective immune responses by recognizing cytosolic DNA. Acute cerebral infarction is one of the leading causes of death and disability worldwide, with the primary treatment approach being the restoration of blood flow to ischemic brain tissue. However, reperfusion injury remains a significant challenge during treatment. The overactivation of the cGAS-STING pathway and its association with ischemia-reperfusion injury have been confirmed in numerous studies. This article will systematically elucidate the mechanisms of the cGAS-STING pathway, its role in ischemia-reperfusion injury in acute cerebral infarction, the current research status of cGAS-STING inhibitors, and the application of nanomaterials in this context, evaluating the therapeutic potential of this pathway.

Viral N protein hijacks deaminase-containing RNA granules to enhance SARS-CoV-2 mutagenesis

Host cell-encoded deaminases act as antiviral restriction factors to impair viral replication and production through introducing mutations in the viral genome. We sought to understand whether deaminases are involved in SARS-CoV-2 mutation and replication, and how the viral factors interact with deaminases to trigger these processes. Here, we show that APOBEC and ADAR deaminases act as the driving forces for SARS-CoV-2 mutagenesis, thereby blocking viral infection and production. Mechanistically, SARS-CoV-2 nucleocapsid (N) protein, which is responsible for packaging viral genomic RNA, interacts with host deaminases and co-localizes with them at stress granules to facilitate viral RNA mutagenesis. N proteins from several coronaviruses interact with host deaminases at RNA granules in a manner dependent on its F17 residue, suggesting a conserved role in modulation of viral mutagenesis in other coronaviruses. Furthermore, mutant N protein bearing a F17A substitution cannot localize to deaminase-containing RNA granules and leads to reduced mutagenesis of viral RNA, providing support for its function in enhancing deaminase-dependent viral RNA editing. Our study thus provides further insight into virus-host cell interactions mediating SARS-CoV-2 evolution.

[Latest Findings on the Role of Liquid-Liquid Phase Separation in the Regulation of Immune Cell Activation and Key Signaling]

Liquid-liquid phase separation (LLPS) is a process in which certain proteins or protein-RNA complexes form phase-separated droplets with different components and properties through multivalent interactions within a cell. In recent years, the role of LLPS in immunomodulation has received extensive attention. Compared with phase separation-related studies in other fields, limited research has been done on LLPS and the immune system. In this review, we first introduced the basic characteristics of LLPS associated with the immune system, and then explored the functions of LLPS in innate immune-related signaling pathways and adaptive immune cells. LLPS plays a crucial role in immune signal transduction, immune cell activation, and antigen presentation. It is involved in facilitating the aggregation of signaling molecules, regulating the intensity and duration of signal transduction, and influencing the functional state of immune cells. The discovery of LLPS provides a new theoretical basis for elucidating the activation mechanism of the immune system and is expected to bring new perspectives for understanding the cellular defense mechanisms. In-depth investigation of the role of LLPS in the immune system not only helps us gain a more comprehensive understanding of the immune response process, but also provides potential targets and strategies for the development of new immunotherapies and the treatment of autoimmune diseases.

The crosstalk between DNA-damage responses and innate immunity

DNA damage is typically caused during cell growth by DNA replication stress or exposure to endogenous or external toxins. The accumulation of damaged DNA causes genomic instability, which is the root cause of many serious disorders. Multiple cellular organisms utilize sophisticated signaling pathways against DNA damage, collectively known as DNA damage response (DDR) networks. Innate immune responses are activated following cellular abnormalities, including DNA damage. Interestingly, recent studies have indicated that there is an intimate relationship between the DDR network and innate immune responses. Diverse kinds of cytosolic DNA sensors, such as cGAS and STING, recognize damaged DNA and induce signals related to innate immune responses, which link defective DDR to innate immunity. Moreover, DDR components operate in immune signaling pathways to induce IFNs and/or a cascade of inflammatory cytokines via direct interactions with innate immune modulators. Consistently, defective DDR factors exacerbate the innate immune imbalance, resulting in severe diseases, including autoimmune disorders and tumorigenesis. Here, the latest progress in understanding crosstalk between the DDR network and innate immune responses is reviewed. Notably, the dual function of innate immune modulators in the DDR network may provide novel insights into understanding and developing targeted immunotherapies for DNA damage-related diseases, even carcinomas.

Emerging roles of liquid-liquid phase separation in liver innate immunity

Biomolecular condensates formed by liquid-liquid phase separation (LLPS) have become an extensive mechanism of macromolecular metabolism and biochemical reactions in cells. Large molecules like proteins and nucleic acids will spontaneously aggregate and assemble into droplet-like structures driven by LLPS when the physical and chemical properties of cells are altered. LLPS provides a mature molecular platform for innate immune response, which tightly regulates key signaling in liver immune response spatially and physically, including DNA and RNA sensing pathways, inflammasome activation, and autophagy. Take this, LLPS plays a promoting or protecting role in a range of liver diseases, such as viral hepatitis, non-alcoholic fatty liver disease, liver fibrosis, hepatic ischemia-reperfusion injury, autoimmune liver disease, and liver cancer. This review systematically describes the whole landscape of LLPS in liver innate immunity. It will help us to guide a better-personalized approach to LLPS-targeted immunotherapy for liver diseases.

Mutations in the non-catalytic polyproline motif destabilize TREX1 and amplify cGAS-STING signaling

The cGAS-STING pathway detects cytosolic DNA and activates a signaling cascade that results in a type I interferon (IFN) response. The endoplasmic reticulum (ER)-associated exonuclease TREX1 suppresses cGAS-STING by eliminating DNA from the cytosol. Mutations that compromise TREX1 function are linked to autoinflammatory disorders, including systemic lupus erythematosus (SLE) and Aicardi-Goutières syndrome (AGS). Despite key roles in regulating cGAS-STING and suppressing excessive inflammation, the impact of many disease-associated TREX1 mutations-particularly those outside of the core catalytic domains-remains poorly understood. Here, we characterize a recessive AGS-linked TREX1 P61Q mutation occurring within the poorly characterized polyproline helix (PPII) motif. In keeping with its position outside of the catalytic core or ER targeting motifs, neither the P61Q mutation, nor aggregate proline-to-alanine PPII mutation, disrupts TREX1 exonuclease activity, subcellular localization, or cGAS-STING regulation in overexpression systems. Introducing targeted mutations into the endogenous TREX1 locus revealed that PPII mutations destabilize the protein, resulting in impaired exonuclease activity and unrestrained cGAS-STING activation. Overall, these results demonstrate that TREX1 PPII mutations, including P61Q, impair proper immune regulation and lead to autoimmune disease through TREX1 destabilization.

Targeting protein condensation in cGAS-STING signaling pathway

The cGAS-STING signaling pathway plays a pivotal role in sensing cytosolic DNA and initiating innate immune responses against various threats, with disruptions in this pathway being associated with numerous immune-related disorders. Therefore, precise regulation of the cGAS-STING signaling is crucial to ensure appropriate immune responses. Recent research, including ours, underscores the importance of protein condensation in driving the activation and maintenance of innate immune signaling within the cGAS-STING pathway. Consequently, targeting condensation processes in this pathway presents a promising approach for modulating the cGAS-STING signaling and potentially managing associated disorders. In this review, we provide an overview of recent studies elucidating the role and regulatory mechanism of protein condensation in the cGAS-STING signaling pathway while emphasizing its pathological implications. Additionally, we explore the potential of understanding and manipulating condensation dynamics to develop novel strategies for mitigating cGAS-STING-related disorders in the future.

Biomolecular condensates and disease pathogenesis

Biomolecular condensates or membraneless organelles (MLOs) formed by liquid-liquid phase separation (LLPS) divide intracellular spaces into discrete compartments for specific functions. Dysregulation of LLPS or aberrant phase transition that disturbs the formation or material states of MLOs is closely correlated with neurodegeneration, tumorigenesis, and many other pathological processes. Herein, we summarize the recent progress in development of methods to monitor phase separation and we discuss the biogenesis and function of MLOs formed through phase separation. We then present emerging proof-of-concept examples regarding the disruption of phase separation homeostasis in a diverse array of clinical conditions including neurodegenerative disorders, hearing loss, cancers, and immunological diseases. Finally, we describe the emerging discovery of chemical modulators of phase separation.

A novel TREX1 inhibitor, VB-85680, upregulates cellular interferon responses

Activation of the cGAS-STING pathway plays a key role in the innate immune response to cancer through Type-1 Interferon (IFN) production and T cell priming. Accumulation of cytosolic double-stranded DNA (dsDNA) within tumor cells and dying cells is recognized by the DNA sensor cyclic GMP-AMP synthase (cGAS) to create the secondary messenger cGAMP, which in turn activates STING (STimulator of INterferon Genes), resulting in the subsequent expression of IFN-related genes. This process is regulated by Three-prime Repair EXonuclease 1 (TREX1), a 3' → 5' exonuclease that degrades cytosolic dsDNA, thereby dampening activation of the cGAS-STING pathway, which in turn diminishes immunostimulatory IFN secretion. Here, we characterize the activity of VB-85680, a potent small-molecule inhibitor of TREX1. We first demonstrate that VB-85680 inhibits TREX1 exonuclease activity in vitro in lysates from both human and mouse cell lines. We then show that treatment of intact cells with VB-85680 results in activation of downstream STING signaling, and activation of IFN-stimulated genes (ISGs). THP1-Dual™ cells cultured under low-serum conditions exhibited an enhanced ISG response when treated with VB-85680 in combination with exogenous DNA. Collectively, these findings suggest the potential of a TREX1 exonuclease inhibitor to work in combination with agents that generate cytosolic DNA to enhance the acquisition of the anti-tumor immunity widely associated with STING pathway activation.

Nucleic Acid Materials-Mediated Innate Immune Activation for Cancer Immunotherapy

Abnormally localized nucleic acids (NAs) are considered as pathogen associated molecular patterns (PAMPs) in innate immunity. They are recognized by NAs-specific pattern recognition receptors (PRRs), leading to the activation of associated signaling pathways and subsequent production of type I interferons (IFNs) and pro-inflammatory cytokines, which further trigger the adaptive immunity. Notably, NAs-mediated innate immune activation is highly dependent on the conformation changes, especially the aggregation of PRRs. Evidence indicates that the characteristics of NAs including their length, concentration and even spatial structure play essential roles in inducing the aggregation of PRRs. Therefore, nucleic acid materials (NAMs) with high valency of NAs and high-order structures hold great potential for activating innate and adaptive immunity, making them promising candidates for cancer immunotherapy. In recent years, a variety of NAMs have been developed and have demonstrated significant efficacy in achieving satisfactory anti-tumor immunity in multiple mouse models, exhibiting huge potential for clinical application in cancer treatment. This review aims to discuss the mechanisms of NAMs-mediated innate immune response, and summarize their applications in cancer immunotherapy.

Phase separation as a new form of regulation in innate immunity

Innate immunity is essential for the host against pathogens, cancer, and autoimmunity. The innate immune system encodes many sensor, adaptor, and effector proteins and relies on the assembly of higher-order signaling complexes to activate immune defense. Recent evidence demonstrates that many of the core complexes involved in innate immunity are organized as liquid-like condensates through a mechanism known as phase separation. Here, we discuss phase-separated condensates and their diverse functions. We compare the biochemical, structural, and mechanistic details of solid and liquid-like assemblies to explore the role of phase separation in innate immunity. We summarize the emerging evidence for the hypothesis that phase separation is a conserved mechanism that controls immune responses across the tree of life. The discovery of phase separation in innate immunity provides a new foundation to explain the rules that govern immune system activation and will enable the development of therapeutics to treat immune-related diseases properly.

Engineered droplet-forming peptide as photocontrollable phase modulator for fused in sarcoma protein

The assembly and disassembly of biomolecular condensates are crucial for the subcellular compartmentalization of biomolecules in the control of cellular reactions. Recently, a correlation has been discovered between the phase transition of condensates and their maturation (aggregation) process in diseases. Therefore, modulating the phase of condensates to unravel the roles of condensation has become a matter of interest. Here, we create a peptide-based phase modulator, JSF1, which forms droplets in the dark and transforms into amyloid-like fibrils upon photoinitiation, as evidenced by their distinctive nanomechanical and dynamic properties. JSF1 is found to effectively enhance the condensation of purified fused in sarcoma (FUS) protein and, upon light exposure, induce its fibrilization. We also use JSF1 to modulate the biophysical states of FUS condensates in live cells and elucidate the relationship between FUS phase transition and FUS proteinopathy, thereby shedding light on the effect of protein phase transition on cellular function and malfunction.

Liquid-liquid phase separation in innate immunity

Intrinsic and innate immune responses are essential lines of defense in the body's constant surveillance of pathogens. The discovery of liquid-liquid phase separation (LLPS) as a key regulator of this primal response to infection brings an updated perspective to our understanding of cellular defense mechanisms. Here, we review the emerging multifaceted role of LLPS in diverse aspects of mammalian innate immunity, including DNA and RNA sensing and inflammasome activity. We discuss the intricate regulation of LLPS by post-translational modifications (PTMs), and the subversive tactics used by viruses to antagonize LLPS. This Review, therefore, underscores the significance of LLPS as a regulatory node that offers rapid and plastic control over host immune signaling, representing a promising target for future therapeutic strategies.

The regulation of liquid-liquid phase separated condensates containing nucleic acids

Liquid-liquid phase separation (LLPS) has been recognized as a universal biological phenomenon. It plays an important role in life activities. LLPS is induced by weak interactions between intrinsically disordered regions or low complex domains. Nucleic acids are widely present in cells, and shown to be closely related to LLPS. Their structure and electronegativity provide the excellent platforms for the formation of phase-separated condensates. In this review, we summarize the interconnected regulation between nucleic acids and LLPS demonstrated in in vivo and in vitro studies. Beside homogeneous and single-phase condensates, complicated and multicompartment LLPS induced by nucleic acids is discussed as well. Recent advances about nucleic-acid-induced LLPS as a new pathogenic mechanism and drug design direction are highlighted, especially virus-mediated disease treatment and prevention.

The multiple faces of cGAS-STING in antitumor immunity: prospects and challenges

As a key sensor of double-stranded DNA (dsDNA), cyclic GMP-AMP synthase (cGAS) detects cytosolic dsDNA and initiates the synthesis of 2'3' cyclic GMP-AMP (cGAMP) that activates the stimulator of interferon genes (STING). This finally promotes the production of type I interferons (IFN-I) that is crucial for bridging innate and adaptive immunity. Recent evidence show that several antitumor therapies, including radiotherapy (RT), chemotherapy, targeted therapies and immunotherapies, activate the cGAS-STING pathway to provoke the antitumor immunity. In the last decade, the development of STING agonists has been a major focus in both basic research and the pharmaceutical industry. However, up to now, none of STING agonists have been approved for clinical use. Considering the broad expression of STING in whole body and the direct lethal effect of STING agonists on immune cells in the draining lymph node (dLN), research on the optimal way to activate STING in tumor microenvironment (TME) appears to be a promising direction. Moreover, besides enhancing IFN-I signaling, the cGAS-STING pathway also plays roles in senescence, autophagy, apoptosis, mitotic arrest, and DNA repair, contributing to tumor development and metastasis. In this review, we summarize the recent advances on cGAS-STING pathway's response to antitumor therapies and the strategies involving this pathway for tumor treatment.

The structural basis for 2'-5'/3'-5'-cGAMP synthesis by cGAS

cGAS activates innate immune responses against cytosolic double-stranded DNA. Here, by determining crystal structures of cGAS at various reaction stages, we report a unifying catalytic mechanism. apo-cGAS assumes an array of inactive conformations and binds NTPs nonproductively. Dimerization-coupled double-stranded DNA-binding then affixes the active site into a rigid lock for productive metal•substrate binding. A web-like network of protein•NTP, intra-NTP, and inter-NTP interactions ensures the stepwise synthesis of 2'-5'/3'-5'-linked cGAMP while discriminating against noncognate NTPs and off-pathway intermediates. One divalent metal is sufficient for productive substrate binding, and capturing the second divalent metal is tightly coupled to nucleotide and linkage specificities, a process which manganese is preferred over magnesium by 100-fold. Additionally, we elucidate how mouse cGAS achieves more stringent NTP and linkage specificities than human cGAS. Together, our results reveal that an adaptable, yet precise lock-and-key-like mechanism underpins cGAS catalysis.

Mining phase separation-related diagnostic biomarkers for endometriosis through WGCNA and multiple machine learning techniques: a retrospective and nomogram study

OBJECTIVE

The objective of this study was to investigate the role of phase separation-related genes in the development of endometriosis (EMs) and to identify potential characteristic genes associated with the condition.

METHODS

We used GEO database data, including 74 non-endometriosis and 74 varying-degree EMs patients. Our approach involved identifying significant gene modules, exploring gene intersections, identifying core genes, and screening for potential EMs biomarkers using weighted gene co-expression network analysis (WGCNA) and various machine learning approaches. We also performed gene set enrichment analysis (GSEA) to understand relevant pathways. This comprehensive approach helps investigate EMs genetics and potential biomarkers.

RESULTS

Nine genes were identified at the intersection, suggesting their involvement in EMs. GSEA linked DEGs to pathways like complement and coagulation cascades, DNA replication, chemokines, apical plasma membrane processes, and diseases such as Hepatitis B, Human T-cell leukemia virus 1 infection, and COVID-19. Five feature genes (FOS, CFD, CCNA1, CA4, CST1) were selected by machine learning for an effective EMs diagnostic nomogram. GSEA indicated their roles in mismatch repair, cell cycle regulation, complement and coagulation cascades, and IL-17 inflammation. Notable differences in immune cell proportions (CD4 T cells, CD8 T cells, DCs, macrophages) were observed between normal and disease groups, suggesting immune involvement.

CONCLUSIONS

This study suggests the potential involvement of phase separation-related genes in the pathogenesis of endometriosis (EMs) and identifies promising biomarkers for diagnosis. These findings have implications for further research and the development of new therapeutic strategies for EMs.

Biomolecular Condensates Decipher Molecular Codes of Cell Fate: From Biophysical Fundamentals to Therapeutic Practices

Cell fate is precisely modulated by complex but well-tuned molecular signaling networks, whose spatial and temporal dysregulation commonly leads to hazardous diseases. Biomolecular condensates (BCs), as a newly emerging type of biophysical assemblies, decipher the molecular codes bridging molecular behaviors, signaling axes, and clinical prognosis. Particularly, physical traits of BCs play an important role; however, a panoramic view from this perspective toward clinical practices remains lacking. In this review, we describe the most typical five physical traits of BCs, and comprehensively summarize their roles in molecular signaling axes and corresponding major determinants. Moreover, establishing the recent observed contribution of condensate physics on clinical therapeutics, we illustrate next-generation medical strategies by targeting condensate physics. Finally, the challenges and opportunities for future medical development along with the rapid scientific and technological advances are highlighted.

How enzyme-centered approaches are advancing research on cyclic oligo-nucleotides

Cyclic nucleotides are the most diversified category of second messengers and are found in all organisms modulating diverse pathways. While cAMP and cGMP have been studied over 50 years, cyclic di-nucleotide signaling in eukaryotes emerged only recently with the anti-viral molecule 2´3´cGAMP. Recent breakthrough discoveries have revealed not only the astonishing chemical diversity of cyclic nucleotides but also surprisingly deep-rooted evolutionary origins of cyclic oligo-nucleotide signaling pathways and structural conservation of the proteins involved in their synthesis and signaling. Here we discuss how enzyme-centered approaches have paved the way for the identification of several cyclic nucleotide signals, focusing on the advantages and challenges associated with deciphering the activation mechanisms of such enzymes.

Technologies for studying phase-separated biomolecular condensates

Biomolecular condensates, also referred to as membrane-less organelles, function as fundamental organizational units within cells. These structures primarily form through liquid-liquid phase separation, a process in which proteins and nucleic acids segregate from the surrounding milieu to assemble into micron-scale structures. By concentrating functionally related proteins and nucleic acids, these biomolecular condensates regulate a myriad of essential cellular processes. To study these significant and intricate organelles, a range of technologies have been either adapted or developed. In this review, we provide an overview of the most utilized technologies in this rapidly evolving field. These include methods used to identify new condensates, explore their components, investigate their properties and spatiotemporal regulation, and understand the organizational principles governing these condensates. We also discuss potential challenges and review current advancements in applying the principles of biomolecular condensates to the development of new technologies, such as those in synthetic biology.

DNA-PK-Mediated Cytoplasmic DNA Sensing Stimulates Glycolysis to Promote Lung Squamous Cell Carcinoma Malignancy and Chemoresistance

Detection of cytoplasmic DNA is an essential biological mechanism that elicits IFN-dependent and immune-related responses. A better understanding of the mechanisms regulating cytoplasmic DNA sensing in tumor cells could help identify immunotherapeutic strategies to improve cancer treatment. Here we identified abundant cytoplasmic DNA accumulated in lung squamous cell carcinoma (LUSC) cells. DNA-PK, but not cGAS, functioned as a specific cytoplasmic DNA sensor to activate downstream ZAK/AKT/mTOR signaling, thereby enhancing the viability, motility, and chemoresistance of LUSC cells. DNA-PK-mediated cytoplasmic DNA sensing boosted glycolysis in LUSC cells, and blocking glycolysis abolished the tumor-promoting activity of cytoplasmic DNA. Elevated DNA-PK-mediated cytoplasmic DNA sensing was positively correlated with poor prognosis of human patients with LUSC. Targeting signaling activated by cytoplasmic DNA sensing with the ZAK inhibitor iZAK2 alone or in combination with STING agonist or anti-PD-1 antibody suppressed the tumor growth and improved the survival of mouse lung cancer models and human LUSC patient-derived xenografts model. Overall, these findings established DNA-PK-mediated cytoplasmic DNA sensing as a mechanism that supports LUSC malignancy and highlight the potential of targeting this pathway for treating LUSC.

SIGNIFICANCE

DNA-PK is a cytoplasmic DNA sensor that activates ZAK/AKT/mTOR signaling and boosts glycolysis to enhance malignancy and chemoresistance of lung squamous cell carcinoma.

Intrinsic factors behind long COVID: IV. Hypothetical roles of the SARS-CoV-2 nucleocapsid protein and its liquid-liquid phase separation

When the SARS-CoV-2 virus infects humans, it leads to a condition called COVID-19 that has a wide spectrum of clinical manifestations, from no symptoms to acute respiratory distress syndrome. The virus initiates damage by attaching to the ACE-2 protein on the surface of endothelial cells that line the blood vessels and using these cells as hosts for replication. Reactive oxygen species levels are increased during viral replication, which leads to oxidative stress. About three-fifths (~60%) of the people who get infected with the virus eradicate it from their body after 28 days and recover their normal activity. However, a large fraction (~40%) of the people who are infected with the virus suffer from various symptoms (anosmia and/or ageusia, fatigue, cough, myalgia, cognitive impairment, insomnia, dyspnea, and tachycardia) beyond 12 weeks and are diagnosed with a syndrome called long COVID. Long-term clinical studies in a group of people who contracted SARS-CoV-2 have been contrasted with a noninfected matched group of people. A subset of infected people can be distinguished by a set of cytokine markers to have persistent, low-grade inflammation and often self-report two or more bothersome symptoms. No medication can alleviate their symptoms efficiently. Coronavirus nucleocapsid proteins have been investigated extensively as potential drug targets due to their key roles in virus replication, among which is their ability to bind their respective genomic RNAs for incorporation into emerging virions. This review highlights basic studies of the nucleocapsid protein and its ability to undergo liquid-liquid phase separation. We hypothesize that this ability of the nucleocapsid protein for phase separation may contribute to long COVID. This hypothesis unlocks new investigation angles and could potentially open novel avenues for a better understanding of long COVID and treating this condition.

Biomolecular Condensates as Novel Antiviral Targets

Viral infections pose a significant health risk worldwide. There is a pressing need for more effective antiviral drugs to combat emerging novel viruses and the reemergence of previously controlled viruses. Biomolecular condensates are crucial for viral replication and are promising targets for novel antiviral therapies. Herein, we review the role of biomolecular condensates in the viral replication cycle and discuss novel strategies to leverage condensate biology for antiviral drug discovery. Biomolecular condensates may also provide an opportunity to develop antivirals that are broad-spectrum or less prone to acquired drug resistance.

Micronuclei and Cancer

Chromosome-containing micronuclei are a feature of human cancer. Micronuclei arise from chromosome mis-segregation and characterize tumors with elevated rates of chromosomal instability. Although their association with cancer has been long recognized, only recently have we broadened our understanding of the mechanisms that govern micronuclei formation and their role in tumor progression. In this review, we provide a brief historical account of micronuclei, depict the mechanisms underpinning their creation, and illuminate their capacity to propel tumor evolution through genetic, epigenetic, and transcriptional transformations. We also posit the prospect of leveraging micronuclei as biomarkers and therapeutic targets in chromosomally unstable cancers.

SIGNIFICANCE

Micronuclei in chromosomally unstable cancer cells serve as pivotal catalysts for cancer progression, instigating transformative genomic, epigenetic, and transcriptional alterations. This comprehensive review not only synthesizes our present comprehension but also outlines a framework for translating this knowledge into pioneering biomarkers and therapeutics, thereby illuminating novel paths for personalized cancer management.

LINE-1: an emerging initiator of cGAS-STING signalling and inflammation that is dysregulated in disease

The cGAS-STING (cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)) axis integrates DNA damage and cellular stress with type I interferon (IFN) signalling to facilitate transcriptional changes underlying inflammatory stress responses. The cGAS-STING pathway responds to cytosolic DNA in the form of double-stranded DNA, micronuclei, and long interspersed nuclear element 1 (L1) retroelements. L1 retroelements are a class of self-propagating non-long terminal repeat transposons that have remained highly active in mammalian genomes. L1 retroelements are emerging as important inducers of cGAS-STING and IFN signalling, which are often dysregulated in several diseases, including cancer. A key repressor of cGAS-STING and L1 activity is the exonuclease three prime repair exonuclease 1 (TREX1), and loss of TREX1 promotes the accumulation of L1. In addition, L1 dysregulation is a common theme among diseases with chronic induction of type I IFN signalling through cGAS-STING, such as Aicardi-Goutières syndrome, Fanconi anemia, and dermatomyositis. Although TREX1 is highly conserved in tetrapod species, other suppressor proteins exist that inhibit L1 retrotransposition. These suppressor genes when mutated are often associated with diseases characterized by unchecked inflammation that is associated with high cGAS-STING activity and elevated levels of L1 expression. In this review, we discuss these interconnected pathways of L1 suppression and their role in the regulation of cGAS-STING and inflammation in disease.

Innate immune responses to RNA: sensing and signaling

Nucleic acids are among the most essential PAMPs (pathogen-associated molecular patterns). Animals have evolved numerous sensors to recognize nucleic acids and trigger immune signaling against pathogen replication, cellular stress and cancer. Many sensor proteins (e.g., cGAS, AIM2, and TLR9) recognize the molecular signature of infection or stress and are responsible for the innate immune response to DNA. Remarkably, recent evidence demonstrates that cGAS-like receptors acquire the ability to sense RNA in some forms of life. Compared with the nucleic-acid sensing by cGAS, innate immune responses to RNA are based on various RNA sensors, including RIG-I, MDA5, ADAR1, TLR3/7/8, OAS1, PKR, NLRP1/6, and ZBP1, via a broad-spectrum signaling axis. Importantly, new advances have brought to light the potential clinical application of targeting these signaling pathways. Here, we highlight the latest discoveries in the field. We also summarize the activation and regulatory mechanisms of RNA-sensing signaling. In addition, we discuss how RNA sensing is tightly controlled in cells and why the disruption of immune homeostasis is linked to disease.

Potential cGAS-STING pathway functions in DNA damage responses, DNA replication and DNA repair

The major innate immune responder to the DNA of pathogens is the cyclic GMP-AMP (cGAMP) synthase (cGAS) - stimulator of interferon genes (STING) pathway. Most prominently, the outcome of cGAS signalling is the activation of inflammatory transcription through interferon regulatory factor 3 (IRF3) and nuclear factor kappa B (NF-kB). In addition, the cGAS-STING pathway can lead to the direct modulation of cellular processes independently of transcription, such as activation of autophagy. Under unperturbed conditions, several mechanisms are in place to prevent the activation of cGAS by self-DNA, chiefly its sequestration on chromatin, which interferes with binding to stimulatory DNA. However, under conditions of genotoxic stress and chromosomal instability, this inhibition breaks down, resulting in the activation of cGAS, which drives sterile inflammation, as well as cell fate and immune responses in cancer. Recently, several studies have suggested that cGAS, STING, or downstream pathway components can also regulate the DNA damage response, DNA damage checkpoint signalling, DNA repair and DNA replication. Here, I review these proposed mechanisms, and discuss some unanswered questions relating to them.

Programmed initiation and enhancement of cGAS/STING pathway for tumour immunotherapy via tailor-designed ZnFe2O4-based nanosystem

The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of interferon genes (STING) signalling pathway has been a promising target for anticancer immunity, but rationally activating and enhancing this pathway in tumour cells is critical. Herein, a glutathione sensitive ZnFe2O4-based nanosystem is developed to programmatically initiate and enhance the STING signalling pathway in tumour cells. The prepared ZnFe2O4 nanoparticles were coated with cancer cell membrane (CCM), which enabled the nanosystem target tumour cells. In tumour cells, ZnFe2O4 nanoparticles could be disintegrated by responding to high level glutathione, and the released Fe3+ generated reactive oxygen species to induce the DNA leakage into the cytoplasm to stimulate cGAS. Then Zn2+ promoted cGAS-DNA phase separation to intensify the cGAS enzymatic activity. In addition, the low dose encapsulation of paclitaxel (PTX) acting as an antimitotic agent (ZnFe2O4-PTX@CCM) ensured the sustained activation of cGAS/STING pathway. The in vitro and in vivo results confirmed that ZnFe2O4-PTX@CCM elevated the cGAS/STING activity, promoted dendritic cell maturation, increased cytotoxic T lymphocyte and natural killer cells infiltration, eventually inhibiting the tumour progress and postoperative recurrence. This study provided feasible references on constructing STING activation nanosystem for tumour immunotherapy.

Biomolecular condensates in kidney physiology and disease

The regulation and preservation of distinct intracellular and extracellular solute microenvironments is crucial for the maintenance of cellular homeostasis. In mammals, the kidneys control bodily salt and water homeostasis. Specifically, the urine-concentrating mechanism within the renal medulla causes fluctuations in extracellular osmolarity, which enables cells of the kidney to either conserve or eliminate water and electrolytes, depending on the balance between intake and loss. However, relatively little is known about the subcellular and molecular changes caused by such osmotic stresses. Advances have shown that many cells, including those of the kidney, rapidly (within seconds) and reversibly (within minutes) assemble membraneless, nano-to-microscale subcellular assemblies termed biomolecular condensates via the biophysical process of hyperosmotic phase separation (HOPS). Mechanistically, osmotic cell compression mediates changes in intracellular hydration, concentration and molecular crowding, rendering HOPS one of many related phase-separation phenomena. Osmotic stress causes numerous homo-multimeric proteins to condense, thereby affecting gene expression and cell survival. HOPS rapidly regulates specific cellular biochemical processes before appropriate protective or corrective action by broader stress response mechanisms can be initiated. Here, we broadly survey emerging evidence for, and the impact of, biomolecular condensates in nephrology, where initial concentration buffering by HOPS and its subsequent cellular escalation mechanisms are expected to have important implications for kidney physiology and disease.

Understanding nucleic acid sensing and its therapeutic applications

Nucleic acid sensing is involved in viral infections, immune response-related diseases, and therapeutics. Based on the composition of nucleic acids, nucleic acid sensors are defined as DNA or RNA sensors. Pathogen-associated nucleic acids are recognized by membrane-bound and intracellular receptors, known as pattern recognition receptors (PRRs), which induce innate immune-mediated antiviral responses. PRR activation is tightly regulated to eliminate infections and prevent abnormal or excessive immune responses. Nucleic acid sensing is an essential mechanism in tumor immunotherapy and gene therapies that target cancer and infectious diseases through genetically engineered immune cells or therapeutic nucleic acids. Nucleic acid sensing supports immune cells in priming desirable immune responses during tumor treatment. Recent studies have shown that nucleic acid sensing affects the efficiency of gene therapy by inhibiting translation. Suppression of innate immunity induced by nucleic acid sensing through small-molecule inhibitors, virus-derived proteins, and chemical modifications offers a potential therapeutic strategy. Herein, we review the mechanisms and regulation of nucleic acid sensing, specifically covering recent advances. Furthermore, we summarize and discuss recent research progress regarding the different effects of nucleic acid sensing on therapeutic efficacy. This study provides insights for the application of nucleic acid sensing in therapy.

Discovery of novel cGAS inhibitors based on natural flavonoids

Cyclic GMP-AMP synthase (cGAS) plays an important role in the inflammatory response. It has been reported that aberrant activation of cGAS is associated with a variety of immune-mediated inflammatory disorders. The development of small molecule inhibitors of cGAS has been considered as a promising therapeutic strategy for the diseases. Flavonoids, a typical class of natural products, are known for their anti-inflammatory activities. Although cGAS is closely associated with inflammation, the potential effects of natural flavonoid compounds on cGAS have been rarely studied. Therefore, we screened an in-house natural flavonoid library by pyrophosphatase (PPiase) coupling assay and identified novel cGAS inhibitors baicalein and baicalin. Subsequently, crystal structures of the two natural flavonoids in complex with human cGAS were determined, which provide mechanistic insight into the anti-inflammatory activities of baicalein and baicalin at the molecular level. After that, a virtual screening based on the crystal structures of baicalein and baicalin in complex with human cGAS was performed. As a result, compound C20 was identified to inhibit both human and mouse cGAS with IC50 values of 2.28 and 1.44 μM, respectively, and its detailed interactions with human cGAS were further revealed by the X-ray crystal structure determination. These results demonstrate the potential of natural products used as hits in drug discovery and provide valuable hints for further development of cGAS inhibitors.