Structural Mechanism for GSDMD Targeting by Autoprocessed Caspases in Pyroptosis.

The pyroptosis execution protein GSDMD is cleaved by inflammasome-activated caspase-1 and LPS-activated caspase-11/4/5. The cleavage unmasks the pore-forming domain from GSDMD-C-terminal domain. How the caspases recognize GSDMD and its connection with caspase activation are unknown. Here, we show site-specific caspase-4/11 autoprocessing, generating a p10 product, is required and sufficient for cleaving GSDMD and inducing pyroptosis. The p10-form autoprocessed caspase-4/11 binds the GSDMD-C domain with a high affinity. Structural comparison of autoprocessed and unprocessed capase-11 identifies a ß sheet induced by the autoprocessing. In caspase-4/11-GSDMD-C complex crystal structures, the ß sheet organizes a hydrophobic GSDMD-binding interface that is only possible for p10-form caspase-4/11. The binding promotes dimerization-mediated caspase activation, rendering a cleavage independently of the cleavage-site tetrapeptide sequence. Crystal structure of caspase-1-GSDMD-C complex shows a similar GSDMD-recognition mode. Our study reveals an unprecedented substrate-targeting mechanism for caspases. The hydrophobic interface suggests an additional space for developing inhibitors specific for pyroptotic caspases.

Crystal Structure of the Human Cannabinoid Receptor CB1.

Cannabinoid receptor 1 (CB1) is the principal target of Δ9-tetrahydrocannabinol (THC), a psychoactive chemical from Cannabis sativa with a wide range of therapeutic applications and a long history of recreational use. CB1 is activated by endocannabinoids and is a promising therapeutic target for pain management, inflammation, obesity, and substance abuse disorders. Here, we present the 2.8 Å crystal structure of human CB1 in complex with AM6538, a stabilizing antagonist, synthesized and characterized for this structural study. The structure of the CB1-AM6538 complex reveals key features of the receptor and critical interactions for antagonist binding. In combination with functional studies and molecular modeling, the structure provides insight into the binding mode of naturally occurring CB1 ligands, such as THC, and synthetic cannabinoids. This enhances our understanding of the molecular basis for the physiological functions of CB1 and provides new opportunities for the design of next-generation CB1-targeting pharmaceuticals.

Tail engagement of arrestin at the glucagon receptor.

Arrestins have pivotal roles in regulating G protein-coupled receptor (GPCR) signalling by desensitizing G protein activation and mediating receptor internalization1,2. It has been proposed that the arrestin binds to the receptor in two different conformations, 'tail' and 'core', which were suggested to govern distinct processes of receptor signalling and trafficking3,4. However, little structural information is available for the tail engagement of the arrestins. Here we report two structures of the glucagon receptor (GCGR) bound to ß-arrestin 1 (ßarr1) in glucagon-bound and ligand-free states. These structures reveal a receptor tail-engaged binding mode of ßarr1 with many unique features, to our knowledge, not previously observed. Helix VIII, instead of the receptor core, has a major role in accommodating ßarr1 by forming extensive interactions with the central crest of ßarr1. The tail-binding pose is further defined by a close proximity between the ßarr1 C-edge and the receptor helical bundle, and stabilized by a phosphoinositide derivative that bridges ßarr1 with helices I and VIII of GCGR. Lacking any contact with the arrestin, the receptor core is in an inactive state and loosely binds to glucagon. Further functional studies suggest that the tail conformation of GCGR-ßarr governs ßarr recruitment at the plasma membrane and endocytosis of GCGR, and provides a molecular basis for the receptor forming a super-complex simultaneously with G protein and ßarr to promote sustained signalling within endosomes. These findings extend our knowledge about the arrestin-mediated modulation of GPCR functionalities.

Structural basis of tethered agonism of the adhesion GPCRs ADGRD1 and ADGRF1.

Adhesion G protein-coupled receptors (aGPCRs) are essential for a variety of physiological processes such as immune responses, organ development, cellular communication, proliferation and homeostasis1-7. An intrinsic manner of activation that involves a tethered agonist in the N-terminal region of the receptor has been proposed for the aGPCRs8,9, but its molecular mechanism remains elusive. Here we report the G protein-bound structures of ADGRD1 and ADGRF1, which exhibit many unique features with regard to the tethered agonism. The stalk region that proceeds the first transmembrane helix acts as the tethered agonist by forming extensive interactions with the transmembrane domain; these interactions are mostly conserved in ADGRD1 and ADGRF1, suggesting that a common stalk-transmembrane domain interaction pattern is shared by members of the aGPCR family. A similar stalk binding mode is observed in the structure of autoproteolysis-deficient ADGRF1, supporting a cleavage-independent manner of receptor activation. The stalk-induced activation is facilitated by a cascade of inter-helix interaction cores that are conserved in positions but show sequence variability in these two aGPCRs. Furthermore, the intracellular region of ADGRF1 contains a specific lipid-binding site, which proves to be functionally important and may serve as the recognition site for the previously discovered endogenous ADGRF1 ligand synaptamide. These findings highlight the diversity and complexity of the signal transduction mechanisms of the aGPCRs.

Structures of human mGlu2 and mGlu7 homo- and heterodimers.

The metabotropic glutamate receptors (mGlus) are involved in the modulation of synaptic transmission and neuronal excitability in the central nervous system1. These receptors probably exist as both homo- and heterodimers that have unique pharmacological and functional properties2-4. Here we report four cryo-electron microscopy structures of the human mGlu subtypes mGlu2 and mGlu7, including inactive mGlu2 and mGlu7 homodimers; mGlu2 homodimer bound to an agonist and a positive allosteric modulator; and inactive mGlu2-mGlu7 heterodimer. We observed a subtype-dependent dimerization mode for these mGlus, as a unique dimer interface that is mediated by helix IV (and that is important for limiting receptor activity) exists only in the inactive mGlu2 structure. The structures provide molecular details of the inter- and intra-subunit conformational changes that are required for receptor activation, which distinguish class C G-protein-coupled receptors from those in classes A and B. Furthermore, our structure and functional studies of the mGlu2-mGlu7 heterodimer suggest that the mGlu7 subunit has a dominant role in controlling dimeric association and G-protein activation in the heterodimer. These insights into mGlu homo- and heterodimers highlight the complex landscape of mGlu dimerization and activation.

Structures of Gi-bound metabotropic glutamate receptors mGlu2 and mGlu4.

The metabotropic glutamate receptors (mGlus) have key roles in modulating cell excitability and synaptic transmission in response to glutamate (the main excitatory neurotransmitter in the central nervous system)1. It has previously been suggested that only one receptor subunit within an mGlu homodimer is responsible for coupling to G protein during receptor activation2. However, the molecular mechanism that underlies the asymmetric signalling of mGlus remains unknown. Here we report two cryo-electron microscopy structures of human mGlu2 and mGlu4 bound to heterotrimeric Gi protein. The structures reveal a G-protein-binding site formed by three intracellular loops and helices III and IV that is distinct from the corresponding binding site in all of the other G-protein-coupled receptor (GPCR) structures. Furthermore, we observed an asymmetric dimer interface of the transmembrane domain of the receptor in the two mGlu-Gi structures. We confirmed that the asymmetric dimerization is crucial for receptor activation, which was supported by functional data; this dimerization may provide a molecular basis for the asymmetric signal transduction of mGlus. These findings offer insights into receptor signalling of class C GPCRs.

Topical Versus Intravenous Tranexamic Acid in Patients Undergoing Cardiac Surgery: The DEPOSITION Randomized Controlled Trial.

BACKGROUND: Although intravenous tranexamic acid is used in cardiac surgery to reduce bleeding and transfusion, topical tranexamic acid results in lower plasma concentrations compared to intravenous tranexamic acid, which may lower the risk of seizures. We aimed to determine whether topical tranexamic acid reduces the risk of in-hospital seizure without increasing the risk of transfusion among cardiac surgery patients. METHODS: We conducted a multicenter, double dummy, blinded, randomized controlled trial of patients recruited by convenience sampling in academic hospitals undergoing cardiac surgery with cardiopulmonary bypass. Between September 17, 2019, and November 28, 2023, a total of 3242 patients from 16 hospitals in 6 countries were randomly assigned (1:1 ratio) to receive either intravenous tranexamic acid (control) through surgery or topical tranexamic acid (treatment) at the end of surgery. The primary outcome was seizure, and the secondary outcome was red blood cell transfusion. After the last planned interim analysis-when 75% of anticipated participants had completed follow up-the Data and Safety Monitoring Board recommended to terminate the trial, and upon unblinding, the Operations Committee stopped the trial for safety. RESULTS: Among 3242 randomized patients (mean age, 66.0 years; 77.7% male), in-hospital seizure occurred in 4 of 1624 patients (0.2%) in the topical group and in 11 of 1628 patients (0.7%) in the intravenous group (absolute risk difference, -0.5%; 95% CI, -0.9 to 0.03; P = .07). Red blood cell transfusion occurred in 570 patients (35.1%) in the topical group and in 433 (26.8%) in the intravenous group (absolute risk difference, 8.3%; 95% CI, 5.2 to 11.5; P = .007). The absolute risk difference in transfusion of ≥4 units of red blood cells in the topical group compared to the intravenous group was 8.2% (95% CI, 3.4 to 12.9). CONCLUSIONS: Among patients having cardiac surgery, topical administration of tranexamic acid resulted in an 8.3% absolute increase in transfusion without reducing the incidence of seizure, compared to intravenous tranexamic acid.

NK-cell-elicited gasdermin-D-dependent hepatocyte pyroptosis induces neutrophil extracellular traps that facilitate HBV-related acute-on-chronic liver failure.

BACKGROUND AND AIMS: HBV infection is a major etiology of acute-on-chronic liver failure (ACLF). At present, the pattern and regulation of hepatocyte death during HBV-ACLF progression are still undefined. Evaluating the mode of cell death and its inducers will provide new insights for developing therapeutic strategies targeting cell death. In this study, we aimed to elucidate whether and how immune landscapes trigger hepatocyte death and lead to the progression of HBV-related ACLF. APPROACH AND RESULTS: We identified that pyroptosis represented the main cell death pattern in the liver of patients with HBV-related ACLF. Deficiency of MHC-I in HBV-reactivated hepatocytes activated cytotoxic NK cells, which in turn operated in a perforin/granzyme-dependent manner to trigger GSDMD/caspase-8-dependent pyroptosis of hepatocytes. Neutrophils selectively accumulated in the pyroptotic liver, and HMGB1 derived from the pyroptotic liver constituted an important factor triggering the generation of pathogenic extracellular traps in neutrophils (NETs). Clinically, elevated plasma levels of myeloperoxidase-DNA complexes were a promising prognostic biomarker for HBV-related ACLF. More importantly, targeting GSDMD pyroptosis-HMGB1 release in the liver abrogates NETs that intercept the development of HBV-related ACLF. CONCLUSIONS: Studying the mechanisms that selectively modulate GSDMD-dependent pyroptosis, as well as its immune landscapes, will provide a novel strategy for restoring the liver function of patients with HBV-related ACLF.

The 14-3-3 protein GRF8 modulates salt stress tolerance in apple via the WRKY18-SOS pathway.

Salinity is a severe abiotic stress that limits plant survival, growth, and development. 14-3-3 proteins are phosphopeptide-binding proteins that are involved in numerous signaling pathways, such as metabolism, development, and stress responses. However, their roles in salt tolerance are unclear in woody plants. Here, we characterized an apple (Malus domestica) 14-3-3 gene, GENERAL REGULATORY FACTOR 8 (MdGRF8), the product of which promotes salinity tolerance. MdGRF8 overexpression improved salt tolerance in apple plants, whereas MdGRF8-RNA interference (RNAi) weakened it. Yeast 2-hybrid, bimolecular fluorescence complementation, pull-down, and coimmunoprecipitation assays revealed that MdGRF8 interacts with the transcription factor MdWRKY18. As with MdGRF8, overexpressing MdWRKY18 enhanced salt tolerance in apple plants, whereas silencing MdWRKY18 had the opposite effect. We also determined that MdWRKY18 binds to the promoters of the salt-related genes SALT OVERLY SENSITIVE 2 (MdSOS2) and MdSOS3. Moreover, we showed that the 14-3-3 protein MdGRF8 binds to the phosphorylated form of MdWRKY18, enhancing its stability and transcriptional activation activity. Our findings reveal a regulatory mechanism by the MdGRF8-MdWRKY18 module for promoting the salinity stress response in apple.

Flanking strand separation activity of RecA nucleoprotein filaments in DNA strand exchange reactions.

The recombinase RecA/Rad51 ATPase family proteins catalyze paramount DNA strand exchange reactions that are critically involved in maintaining genome integrity. However, it remains unclear how DNA strand exchange proceeds when encountering RecA-free defects in recombinase nucleoprotein filaments. Herein, by designing a series of unique substrates (e.g. truncated or conjugated incoming single-stranded DNA, and extended donor double-stranded DNA) and developing a two-color alternating excitation-modified single-molecule real-time fluorescence imaging assay, we resolve the two key steps (donor strand separation and new base-pair formation) that are usually inseparable during the reaction, revealing a novel long-range flanking strand separation activity of synaptic RecA nucleoprotein filaments. We further evaluate the kinetics and free energetics of strand exchange reactions mediated by various substrates, and elucidate the mechanism of flanking strand separation. Based on these findings, we propose a potential fundamental molecular model involved in flanking strand separation, which provides new insights into strand exchange mechanism and homologous recombination.

Structural basis for high-affinity recognition of aflatoxin B1 by a DNA aptamer.

The 26-mer DNA aptamer (AF26) that specifically binds aflatoxin B1 (AFB1) with nM-level high affinity is rare among hundreds of aptamers for small molecules. Despite its predicted stem-loop structure, the molecular basis of its high-affinity recognition of AFB1 remains unknown. Here, we present the first high-resolution nuclear magnetic resonance structure of AFB1-AF26 aptamer complex in solution. AFB1 binds to the 16-residue loop region of the aptamer, inducing it to fold into a compact structure through the assembly of two bulges and one hairpin structure. AFB1 is tightly enclosed within a cavity formed by the bulges and hairpin, held in a place between the G·C base pair, G·G·C triple and multiple T bases, mainly through strong π-π stacking, hydrophobic and donor atom-π interactions, respectively. We further revealed the mechanism of the aptamer in recognizing AFB1 and its analogue AFG1 with only one-atom difference and introduced a single base mutation at the binding site of the aptamer to increase the discrimination between AFB1 and AFG1 based on the structural insights. This research provides an important structural basis for understanding high-affinity recognition of the aptamer, and for further aptamer engineering, modification and applications.

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering.

Herein, we present a synthetic approach to fabricate Au nanoheptamers composed of six individual Au nanospheres interconnected through thin metal bridges arranged in an octahedral configuration. The resulting structures envelop central Au nanospheres, producing Au nanosphere heptamers with an open architectural arrangement. Importantly, the initial Pt coating of the Au nanospheres is a crucial step for protecting the inner Au nanospheres during multiple reactions. As-synthesized Au nanoheptamers exhibit multiple hot spots formed by nanogaps between nanospheres, resulting in strong electromagnetic near-fields. Additionally, we conducted surface-enhanced Raman-scattering-based detection of a chemical warfare agent simulant in the gas phase and achieved a limit of detection of 100 ppb, which is 3 orders lower than that achieved using Au nanospheres and Au nanohexamers. This pseudocore-shell nanostructure represents a significant advancement in the realm of complex nanoparticle synthesis, moving the field one step closer to sophisticated nanoparticle engineering.

Van der Waals Magnetic Electrode Transfer for Two-Dimensional Spintronic Devices.

Two-dimensional (2D) materials are promising candidates for spintronic applications. Maintaining their atomically smooth interfaces during integration of ferromagnetic (FM) electrodes is crucial since conventional metal deposition tends to induce defects at the interfaces. Meanwhile, the difficulties in picking up FM metals with strong adhesion and in achieving conductance match between FM electrodes and spin transport channels make it challenging to fabricate high-quality 2D spintronic devices using metal transfer techniques. Here, we report a solvent-free magnetic electrode transfer technique that employs a graphene layer to assist in the transfer of FM metals. It also serves as part of the FM electrode after transfer for optimizing spin injection, which enables the realization of spin valves with excellent performance based on various 2D materials. In addition to two-terminal devices, we demonstrate that the technique is applicable for four-terminal spin valves with nonlocal geometry. Our results provide a promising future of realizing 2D spintronic applications using the developed magnetic electrode transfer technique.

Mitochondria-derived Vesicle Packaging as a Novel Therapeutic Mechanism in Pulmonary Hypertension.

Increasing evidence suggests that mitochondrial dysfunction in pulmonary endothelial cells (ECs) plays a causative role in the initiation and progression of pulmonary hypertension (PH); how mitochondria become dysfunctional in PH remains elusive. Mitochondria-derived vesicles (MDVs) are small subcellular vesicles that excise from mitochondria. Whether MDV deregulation causes mitochondrial dysfunction in PH is unknown. The aim of this study was to determine MDV regulation in ECs and to elucidate how MDV deregulation in ECs leads to PH. MDV formation and mitochondrial morphology/dynamics were examined in ECs of EC-specific liver kinase B1 (LKB1) knockout mice (LKB1ec-/-), in monocrotaline-induced PH rats, and in lungs of patients with PH. Pulmonary ECs of patients with PH and hypoxia-treated pulmonary ECs exhibited increased mitochondrial fragmentation and disorganized mitochondrial ultrastructure characterized by electron lucent-swelling matrix compartments and concentric layering of the cristae network, together with defective MDV shedding. MDVs actively regulated mitochondrial membrane dynamics and mitochondrial ultrastructure via removing mitofission-related cargoes. The shedding of MDVs from parental mitochondria required LKB1-mediated mitochondrial recruitment of Rab9 GTPase. LKB1ec-/- mice spontaneously developed PH with decreased mitochondrial pools of Rab9 GTPase, defective MDV shedding, and disequilibrium of the mitochondrial fusion-fission cycle in pulmonary ECs. Aerosol intratracheal delivery of adeno-associated virus LKB1 reversed PH, together with improved MDV shedding and mitochondrial function in rats in vivo. We conclude that LKB1 regulates MDV shedding and mitochondrial dynamics in pulmonary ECs by enhancing mitochondrial recruitment of Rab9 GTPase. Defects of LKB1-mediated MDV shedding from parental mitochondria instigate EC dysfunction and PH.

Graft Failure After Coronary Artery Bypass Grafting and Its Association With Patient Characteristics and Clinical Events: A Pooled Individual Patient Data Analysis of Clinical Trials With Imaging Follow-Up.

BACKGROUND: Graft patency is the postulated mechanism for the benefits of coronary artery bypass grafting (CABG). However, systematic graft imaging assessment after CABG is rare, and there is a lack of contemporary data on the factors associated with graft failure and on the association between graft failure and clinical events after CABG. METHODS: We pooled individual patient data from randomized clinical trials with systematic CABG graft imaging to assess the incidence of graft failure and its association with clinical risk factors. The primary outcome was the composite of myocardial infarction or repeat revascularization occurring after CABG and before imaging. A 2-stage meta-analytic approach was used to evaluate the association between graft failure and the primary outcome. We also assessed the association between graft failure and myocardial infarction, repeat revascularization, or all-cause death occurring after imaging. RESULTS: Seven trials were included comprising 4413 patients (mean age, 64.4±9.1 years; 777 [17.6%] women; 3636 [82.4%] men) and 13 163 grafts (8740 saphenous vein grafts and 4423 arterial grafts). The median time to imaging was 1.02 years (interquartile range [IQR], 1.00-1.03). Graft failure occurred in 1487 (33.7%) patients and in 2190 (16.6%) grafts. Age (adjusted odds ratio [aOR], 1.08 [per 10-year increment] [95% CI, 1.01-1.15]; P=0.03), female sex (aOR, 1.27 [95% CI, 1.08-1.50]; P=0.004), and smoking (aOR, 1.20 [95% CI, 1.04-1.38]; P=0.01) were independently associated with graft failure, whereas statins were associated with a protective effect (aOR, 0.74 [95% CI, 0.63-0.88]; P<0.001). Graft failure was associated with an increased risk of myocardial infarction or repeat revascularization occurring between CABG and imaging assessment (8.0% in patients with graft failure versus 1.7% in patients without graft failure; aOR, 3.98 [95% CI, 3.54-4.47]; P<0.001). Graft failure was also associated with an increased risk of myocardial infarction or repeat revascularization occurring after imaging (7.8% versus 2.0%; aOR, 2.59 [95% CI, 1.86-3.62]; P<0.001). All-cause death after imaging occurred more frequently in patients with graft failure compared with patients without graft failure (11.0% versus 2.1%; aOR, 2.79 [95% CI, 2.01-3.89]; P<0.001). CONCLUSIONS: In contemporary practice, graft failure remains common among patients undergoing CABG and is strongly associated with adverse cardiac events.

Coacervate Phase Evolution and Membrane Formation in Natural Seawater.

Marine organisms produce biological materials through the complex self-assembly of protein condensates in seawater, but our understanding of the mechanisms of microstructure evolution and maturation remains incomplete. Here, we show that critical processing attributes of mussel holdfast proteins can be captured by the design of an amphiphilic, fluorescent polymer (PECHIA) consisting of a polyepichlorohydrin backbone grafted with 1-imidazolium acetonitrile. Aqueous solutions of PECHIA were extruded into seawater, wherein the charge repulsion of PECHIA is screened by high salinity, facilitating interfacial condensation via enhanced "cation-dipole" interactions. Diffusion of seawater into the PECHIA solution caused droplets to form immiscibly within the PECHIA phase (i.e., inverse coacervation). Simultaneously, weakly alkaline seawater catalyzes nitrile cyclization and time-dependent solidification of the PECHIA phase, leading to hierarchically porous membranes analogous to porous architectures in mussel plaques. In contrast to conventional polymer processing technologies, processing of this biomimetic polymer required neither organic solvents nor heating and enabled the template-free production of hollow spheres and fibers over a wide range of salinities.

Role of a novel circRNA-CGNL1 in regulating pancreatic cancer progression via NUDT4-HDAC4-RUNX2-GAMT-mediated apoptosis.

BACKGROUND: Pancreatic cancer (PC) is an extremely malignant tumor with low survival rate. Effective biomarkers and therapeutic targets for PC are lacking. The roles of circular RNAs (circRNAs) in cancers have been explored in various studies, however more work is needed to understand the functional roles of specific circRNAs. In this study, we explore the specific role and mechanism of circ_0035435 (termed circCGNL1) in PC. METHODS: qRT-PCR analysis was performed to detect circCGNL1 expression, indicating circCGNL1 had low expression in PC cells and tissues. The function of circCGNL1 in PC progression was examined both in vitro and in vivo. circCGNL1-interacting proteins were identified by performing RNA pulldown, co-immunoprecipitation, GST-pulldown, and dual-luciferase reporter assays. RESULTS: Overexpressing circCGNL1 inhibited PC proliferation via promoting apoptosis. CircCGNL1 interacted with phosphatase nudix hydrolase 4 (NUDT4) to promote histone deacetylase 4 (HDAC4) dephosphorylation and subsequent HDAC4 nuclear translocation. Intranuclear HDAC4 mediated RUNX Family Transcription Factor 2 (RUNX2) deacetylation and thereby accelerating RUNX2 degradation. The transcription factor, RUNX2, inhibited guanidinoacetate N-methyltransferase (GAMT) expression. GAMT was further verified to induce PC cell apoptosis via AMPK-AKT-Bad signaling pathway. CONCLUSIONS: We discovered that circCGNL1 can interact with NUDT4 to enhance NUDT4-dependent HDAC4 dephosphorylation, subsequently activating HDAC4-RUNX2-GAMT-mediated apoptosis to suppress PC cell growth. These findings suggest new therapeutic targets for PC.

Activation of farnesoid X receptor enhances the efficacy of normothermic machine perfusion in ameliorating liver ischemia-reperfusion injury.

The shortage of transplant organs remains a severe global issue. Normothermic machine perfusion (NMP) has the potential to increase organ availability, yet its efficacy is hampered by the inflammatory response during machine perfusion. Mouse liver ischemia-reperfusion injury (IRI) models, discarded human liver models, and porcine marginal liver transplantation models were utilized to investigate whether farnesoid X receptor (FXR) activation could mitigate inflammation-induced liver damage. FXR expression levels before and after reperfusion were measured. Gene editing and coimmunoprecipitation techniques were employed to explore the regulatory mechanism of FXR in inflammation inhibition. The expression of FXR correlates with the extent of liver damage after reperfusion. Activation of FXR significantly suppressed the inflammatory response triggered by IRI, diminished the release of proinflammatory cytokines, and improved liver function recovery during NMP, assisting discarded human livers to reach transplant standards. Mechanistically, FXR disrupts the interaction between p65 and p300, thus inhibiting modulating the nuclear factor kappa-B signaling pathway, a key instigator of inflammation. Our research across multiple species confirms that activating FXR can optimize NMP by attenuating IRI-related liver damage, thereby improving the utilization of marginal livers for transplantation.

Antibody-Bridged DNAzyme Walker for Sensitive Detection of Small Molecules.

Sensitive detection of small molecules with biological and environmental interests is important for many applications, such as food safety, disease diagnosis, and environmental monitoring. Herein, we propose a highly selective antibody-bridged DNAzyme walker to sensitively detect small molecules. The antibody-bridged DNAzyme walker consists of a track, small-molecule-labeled DNAzyme walking strand, and antibody against small molecules. The track is built by co-modifying fluorophore-labeled substrates and small-molecule-labeled DNA linkers onto a gold nanoparticle (AuNP). In the absence of the target molecule, the antibody binds small molecule labels at the DNAzyme walking strand and the DNA linker, driving the DNAzyme walking strand on the surface of the AuNP. The attached DNAzyme walking strand moves along the track and cleaves substrates to generate high fluorescence signals to achieve signal amplification. As target molecules exist, they competitively bind with antibody to displace the small-molecule-labeled linker and DNAzyme walking strand, rendering the DNAzyme walker inactive in substrate cleavage and causing weak fluorescence. By using this antibody-bridged DNAzyme walker, we achieved sensitive detection of two biologically important small molecules, digoxin and folic acid. This work provides a new paradigm by combining the signal amplification strategy of a DNA walker and immunorecognition for sensitive and selective detection of small molecules.

CRISPR/Cas12a-Amplified Aptamer Switch Microplate Assay for Small Molecules.

The presence of small molecule contaminants such as mycotoxins and heavy metals in foods and the environment causes a serious threat to human health and huge economic losses. The development of simple, rapid, sensitive, and on-site methods for small molecule pollutant detection is highly demanded. Here, combining the advantages of structure-switchable aptamer-mediated signal conversion and CRISPR/Cas12a-based signal amplification, we developed a CRISPR/Cas12a-amplified aptamer switch assay on a microplate for sensitive small molecule detection. In this assay, a short DNA strand complementary to the aptamer (cDNA) is immobilized on a microplate, which can capture the aptamer-linked active DNA probe (Apt-acDNA) in the sample solution when the target is absent. With the addition of the Cas12a reporter system, the captured Apt-acDNA probes activate Cas12a to indiscriminately cleave fluorescent DNA substrates, producing a high fluorescence signal. When the target is present, the Apt-acDNA probe specifically binds to the target rather than hybridizing with cDNA on the microplate, and the fluorescence signal is reduced. The analytical performance of our method was demonstrated by the detection of two highly toxic pollutants, aflatoxin B1 (AFB1) and cadmium ion (Cd2+), as examples. The assay exhibited good selectivity and high sensitivity, with detection limits of 31 pM AFB1 and 3.9 nM Cd2+. It also allowed the detection of targets in the actual sample matrix. With the general signal conversion strategy, this method can be used to detect other targets by simply changing the aptamer and cDNA, showing potential practical applications in broad fields.