Direct Inhibitor Research Articles

The PI3K-AKT-mTOR axis persists as a therapeutic dependency in KRASG12D-driven non-small cell lung cancer.

KRASG12C and KRASG12D inhibitors represent a major translational breakthrough for non-small cell lung cancer (NSCLC) and cancer in general by directly targeting its most mutated oncoprotein. However, resistance to these small molecules has highlighted the need for rational combination partners necessitating a critical understanding of signaling downstream of KRAS mutant isoforms. We contrasted tumor development between KrasG12C and KrasG12D genetically engineered mouse models (GEMMs). To corroborate findings and determine mutant subtype-specific dependencies, isogenic models of KrasG12C and KrasG12D initiation and adaptation were profiled by RNA sequencing. We also employed cell line models of established KRAS mutant NSCLC and determined therapeutic vulnerabilities through pharmacological inhibition. We analysed differences in survival outcomes for patients affected by advanced KRASG12C or KRASG12D-mutant NSCLC. KRASG12D exhibited higher potency in vivo, manifesting as more rapid lung tumor formation and reduced survival of KRASG12D GEMMs compared to KRASG12C. This increased potency, recapitulated in an isogenic initiation model, was associated with enhanced PI3K-AKT-mTOR signaling. However, KRASG12C oncogenicity and downstream pathway activation were comparable with KRASG12D at later stages of tumorigenesis in vitro and in vivo, consistent with similar clinical outcomes in patients. Despite this, established KRASG12D NSCLC models depended more on the PI3K-AKT-mTOR pathway, while KRASG12C models on the MAPK pathway. Specifically, KRASG12D inhibition was enhanced by AKT inhibition in vitro and in vivo. Our data highlight a unique combination treatment vulnerability and suggest that patient selection strategies for combination approaches using direct KRAS inhibitors should be i) contextualised to individual RAS mutants, and ii) tailored to their downstream signaling.

Chemical inhibition of stomatal differentiation by perturbation of the master-regulatory bHLH heterodimer via an ACT-Like domain

Selective perturbation of protein interactions with chemical compounds enables dissection and control of developmental processes. Differentiation of stomata, cellular valves vital for plant growth and survival, is specified by the basic-helix-loop-helix (bHLH) heterodimers. Harnessing a new amination reaction, we here report a synthesis, derivatization, target identification, and mode of action of an atypical doubly-sulfonylated imidazolone, Stomidazolone, which triggers stomatal stem cell arrest. Our forward chemical genetics followed by biophysical analyses elucidates that Stomidazolone directly binds to the C-terminal ACT-Like (ACTL) domain of MUTE, a master regulator of stomatal differentiation, and perturbs its heterodimerization with a partner bHLH, SCREAM in vitro and in plant cells. On the other hand, Stomidazolone analogs that are biologically inactive do not bind to MUTE or disrupt the SCREAM-MUTE heterodimers. Guided by structural docking modeling, we rationally design MUTE with reduced Stomidazolone binding. These engineered MUTE proteins are fully functional and confer Stomidazolone resistance in vivo. Our study identifies doubly-sulfonylated imidazolone as a direct inhibitor of the stomatal master regulator, further expanding the chemical space for perturbing bHLH-ACTL proteins to manipulate plant development.

Switching from interleukin-6 receptor inhibitors to the direct interleukin-6 inhibitor olokizumab in patients with rheumatoid arthritis: efficacy and safety during one year of therapy

Objective: to investigate the efficacy and safety of olokizumab (OKZ) in patients with rheumatoid arthritis (RA) over a 12-month period after switching from interleukin (IL)-6 receptor inhibitors (iIL6R) for non-medical reasons.Material and methods. A retrospective cohort study conducted in 11 centers in the Russian Federation included 110 patients with confirmed diagnosis of RA according to 2010 ACR/EULAR criteria. In all patients in early 2022 (due to problems with drug supply during the coronavirus pandemic) iIL6R were switched for non-medical reasons to OKZ at a dose of 64 mg once every 2 weeks or once every 4 weeks in accordance with the instructions for the medical use of OKZ.Data on clinical efficacy, safety and changes in the dosing regimen of the drugs over an observation period of one year are presented. We assessed the dynamics of the clinical indicators: number of painful and swollen joints, pain on a visual analogue scale and DAS28-ESR/CRP indices. Routine laboratory tests included assessment of red and white blood cells count, ESR, hemoglobin, CRP, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin and cholesterol. Adverse events (AEs) were recorded in accordance with standard practice.Results and discussion. After 6 months of therapy, the proportion of patients who achieved remission/low disease activity according to DAS28-ESR and DAS28-CRP decreased to 70.1% and 72.9%, respectively, and the proportion of patients with moderate and high activity according to DAS28-ESR increased to 26.1% and 3.7%, respectively, and according to DAS28-CRP to 21.5% and 5.6 %, respectively. After 12 months, remission/low disease activity according to DAS28-ESR and DAS28-CRP was achieved in 81.4% and 83.5% of patients, respectively, and 18.6% and 16.5% of patients had moderate activity.In the OKZ monotherapy group, after 6 months of treatment 22 (71.0%) patients were in remission/low disease activity according to DAS28-ESR and 23 (74.2%) patients according to DAS28-CRP. After one year of observation, remission/low disease activity according to DAS28-ESR and DAS28-CRP had 24 (88.9%) and 23 (85.2%) patients, respectively.In the combined therapy group of OKZ + disease-modifying antirheumatic drugs (DMARDs), remission/low disease activity according to DAS28-ESR was observed in 53 (70.7%) patients and according to DAS28-CRP – in 55 (73.3%) patients by the 6th month of therapy. After 12 months, in this group 55 (78.6%) patients showed remission/low disease activity according to DAS28-ESR and according to DAS28-CRP – 58 (82.9 %) patients.After 6 months, 107 (97.3 %) out of 110 patients included in the study continued treatment. In 1 (0.9%) case OKZ was discontinued due to insufficient effect, in 2 cases contact with the patients was lost. After 12 months, therapy was continued in 97 (88.2%) patients. In 5 (4.5%) cases treatment was discontinued due to insufficient efficacy, in 2 (1.8%) cases – due to increased AST/ALT levels, in another 2 (1.8 %) cases – for non-medical reasons, and in 1 case contact with the patient was lost.Conclusion. OKZ, a direct IL-6 inhibitor, provided effective control over RA symptoms after switching from iIL6R, which allowed to achieve the treatment goal of maintaining remission/low disease activity over 1 year in more than 80% of patients. OKZ has demonstrated a broad spectrum of capabilities in real-world clinical practice, even when used as monotherapy. In terms of safety profile, OKZ was comparable to other IL6 inhibitors.

Primary Prevention of Cancer-Associated Thrombosis: Current Perspectives.

Over the past two decades, the incidence of cancer-associated thrombosis (CAT) has increased. It is nowadays a common and often serious complication among patients with cancer. Although medical thromboprophylaxis is recommended for most surgical and nonsurgical cancer patients, it has been infrequently used in ambulatory patients with cancer because of the burden of treatment and concerns about bleeding. However, various risk assessment scores are now available and randomized placebo-controlled trials have established the efficacy of low-molecular-weight heparin or the direct oral Xa inhibitors rivaroxaban and apixaban in ambulatory patients with cancer at high risk of venous thromboembolism (VTE). This review provides an overview of (1) primary thromboprophylaxis in the setting of hospitalized surgical and medical patients, (2) extended thromboprophylaxis after hospital discharge, (3) performance of risk assessment tools for CAT, and (4) primary thromboprophylaxis in ambulatory patients with cancer. The aim is to provide support to physicians in identifying ambulatory patients with cancer at high VTE risk who benefit most from medical thromboprophylaxis according to current recommendations from international guidelines.

Application of propionate-producing bacterial consortium in ruminal methanogenesis inhibited environment with bromoethanesulfonate as a methanogen direct inhibitor.

Methane production in ruminants is primarily due to the conversion of metabolic hydrogen (H2), produced during anaerobic microbial fermentation, into methane by ruminal methanogens. While this process plays a crucial role in efficiently disposes of H2, it also contributes to environmental pollution and eliminating methane production in the rumen has proven to be challenging. This study investigates the use of probiotics, specifically propionate-producing bacteria, to redirect accumulated H2 in a methane-mitigated environment. For this objective, we supplemented experimental groups with Lactiplantibacillus plantarum and Megasphaera elsdenii for the reinforced acrylate pathway (RA) and Selenomonas ruminantium and Acidipropionibacterium thoenii for the reinforced succinate pathway (RS), as well as a consortium of all four strains (CB), with the total microbial concentration at 1.0 × 1010 cells/mL. To create a methane-mitigated environment, 2-bromoethanesulfonate (BES) was added to all experimental groups at a dose of 15 mg/0.5 g of feed. BES reduced methane production by 85% in vitro, and the addition of propionate-producing bacteria with BES further decreased methane emission by up to 94% compared with the control (CON) group. Although BES did not affect the alpha diversity of the ruminal bacteriome, it reduced total volatile fatty acid production and altered beta diversity of ruminal bacteriota, indicating microbial metabolic adaptations to H2 accumulation. Despite using different bacterial strains targeting divergent metabolic pathways (RA and RS), a decrease in the dominance of the [Eubacterium] ruminantium group suggesting that both approaches may have a similar modulatory effect. An increase in the relative abundance of Succiniclasticum in the CB group suggests that propionate metabolism is enhanced by the addition of a propionate-producing bacterial consortium. These findings recommend using a consortium of propionate-producing bacteria to manage H2 accumulation by altering the rumen bacteriome, thus mitigating the negative effects of methane reduction strategies.

Monitoring the efficiency of reversal on anti-Xa direct oral anticoagulants using point-of-care viscoelastic testing

Bleeding events in patients receiving direct oral anticoagulation (DOAC) can be life-threatening even at therapeutic DOAC plasma concentrations, as anticoagulation impairs hemostasis and should therefore be identified immediately after hospital admission. The anticoagulatory effects of DOAC are typically not measurable in standard coagulation tests, such as PT or aPTT. Specific calibrated anti-FXa-tests allow specific drug monitoring, but they are too time-consuming for critical bleeding events and are commonly not available for 24 h/7 days in routine care. However, recent advances in point-of-care (POC) viscoelastic testing (VET) have shown a promising approach for rapid and quantitative detection of DOAC plasma concentrations using the Russell viper venom factor V activator (RVV for FXa-inhibitors) test or the ecarin clotting time (thrombin inhibitors). In acute bleeding situations, direct FXa inhibitors can be reversed by specific antidote andexanet alfa or hemostasis can be improved by prothrombin complex factor concentrates (PCCs). After reversal, confirmation of reversal efficacy is often requested, but no routine assays are currently available. Thus, the emergency management of bleeding DOAC patients is usually “blinded” with regard to reversal efficacy. POC VET laboratory assays might therefore also be helpful for measuring DOAC effects after reversal. We present a case series demonstrating the usefulness of RVV-clotting time post-DOAC reversal with andexanet alfa.

12509 Identification Of Novel Exercise Training-induced Circulating Proteins: Hemostatic, Apoptotic, And Key Neuronal Factors

Abstract Disclosure: A. Shalit: None. M. Vamvini: None. P. Nigro: None. L.K. Simpson: None. H. Pan: None. J.M. Dreyfuss: None. L.J. Goodyear: Grant Recipient; Self; Daiichi Sankyo. R.J. Middelbeek: None. Exercise training induces a plethora of health benefits including improved glucose homeostasis, decreased cardiovascular disease, and improved cognitive function. An emerging concept is that many of these beneficial effects of exercise are mediated through the secretion of humoral factors into the blood. Identification of these exercise-regulated factors hold promise for novel treatments for disease. Here, we performed proteomic analysis to discover novel circulating factors in response to endurance exercise training in human participants. Given that nutritional status can affect the circulating proteome, another aim was to determine if proteomic adaptations to exercise training have similar effects under both fasted and random-fed conditions. Sedentary normoglycemic participants (3M/5F, age 22-41y) performed a supervised 10-week exercise training program, which by week 4 was 4x60 min exercise at 65-70% V̇O2peak. Fasted and random-sampling morning blood draws were collected pre-training and between 24-72 hours following the final training session. Proteomic detection was by SOMAscan. Exercise training significantly improved V̇O2peak by 17% (p=0.003). Out of 1,310 detected proteins, exercise training significantly changed 293 proteins in the fasted state and 360 proteins in the random-sampling state (p<0.05). Integration showed that 172 proteins were changed under both nutritional conditions (123 upregulated and 49 downregulated). Gene Set Enrichment Analysis (GSEA) of the commonly upregulated proteins showed that training resulted in enrichment in neuronal, hemostatic, and apoptotic pathways, whereas the downregulated proteins were enriched in neuronal and extracellular matrix processes. Since neuronal pathways were identified in both up and downregulated proteins, we focused our analysis there, identifying 31 upregulated and 4 downregulated neuronally-associated proteins. Importantly, exercise training reduced levels of CDK5, a protein that is hyperactivated in neurodegeneration and Alzheimer's disease. Moreover, GSTP1, a direct inhibitor of CDK5, along with downstream proteins inhibited by CDK5 (RAC1, STUB1, 14-3-3ε/YWHAE, HSP90AA1, CFL1), were significantly increased following exercise training.In conclusion, exercise training regulates circulating factors involved in neuronal, hemostatic, apoptotic, and extracellular matrix pathways, with these effects being independent of nutritional status. Our finding of exercise training-induced decreases in multiple proteins of the CDK5 pathway, a pathway whose downregulation is associated with neuroprotection, identify CDK5 as a novel and potentially important mediator of the beneficial effects of exercise training on cognitive function. Presentation: 6/1/2024

Development of Direct AQP2 Water Channel Inhibitors

Development of Direct AQP2 Water Channel Inhibitors

A mechanism of action-reflective, dual cell-based bioassay for determining the bioactivity of sclerostin-neutralizing antibodies

Osteoporosis is a major threat to the elderly worldwide. The Wnt signaling pathway plays a critical role in bone development and homeostasis. Sclerostin, a Wnt ligand inhibitor, competes with Wnt ligands for low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6) on osteoblasts, thereby suppressing bone formation. Sclerostin-neutralizing monoclonal antibodies (mAbs) have emerged as a potential bone-forming therapy for osteoporosis. A cell-based bioassay which determines the relative activity of a product, related to its mechanism of action, is of great importance from drug discovery to quality control and batch release. Currently used cell-based bioassays for sclerostin-neutralizing mAbs usually use Wnt1 or Wnt3a to stimulate the Wnt pathway; sclerostin is a direct inhibitor of Wnt1 but not Wnt3a. Wnt1 is a highly hydrophobic protein that binds to the producing cell membrane and acts in a juxtacrine manner to stimulate the Wnt pathway in neighboring cells. Bioassays for drugs that induce Wnt1 signaling should be performed in a juxtacrine manner. Here, we present a mechanism of action-reflective, dual cell-based reporter gene assay. In this assay, Wnt1 producer cells are co-cultured with cells containing the Wnt reporter genes, Wnt1 on the producer cells activates the Wnt signaling pathway in the reporter cells that are in direct cell-to-cell contact, and sclerostin-neutralizing mAbs specifically and effectively antagonize the sclerostin-mediated Wnt reporter gene suppression. This bioassay demonstrates good specificity, accuracy, linearity, and precision and is suitable for quality control, stability testing, batch release, and biosimilarity assessment of sclerostin-neutralizing mAbs.

Contribution of direct InhA inhibitors to novel drug regimens in a mouse model of tuberculosis.

Isoniazid is an important first-line medicine to treat tuberculosis (TB). Isoniazid resistance increases the risk of poor treatment outcomes and development of multidrug resistance, and is driven primarily by mutations involving katG, encoding the prodrug-activating enzyme, rather than its validated target, InhA. The chemical tractability of InhA has fostered efforts to discover direct inhibitors of InhA (DIIs). In this study, we bridge the gap in understanding the potential contribution of DIIs to novel combination regimens and demonstrate a clear distinction of DIIs, like GSK693 and the newly described GSK138, from isoniazid, based on activity against clinical isolates and contribution to novel drug regimens. The results suggest that DIIs, specifically GSK138 and GSK693, could be promising partners in novel drug regimens, including those used against isoniazid-resistant TB, potentially enhancing their efficacy and/or preventing the selection of resistant mutants and supporting the continued exploration of InhA as a promising target for TB drug development.

Telomerase in Cancer Therapeutics.

While silent in normal differentiated human tissues, telomerase is reactivated in most human cancers. Thus, telomerase is an almost universal oncology target. This update describes preclinical and clinical advancements using a variety of approaches to target telomerase. These include direct telomerase inhibitors, G-quadruplex DNA-interacting ligands, telomerase-based vaccine platforms, telomerase promoter-driven attenuated viruses, and telomerase-mediated telomere targeting approaches. While imetelstat has been recently approved by the Food and Drug Administration (FDA), several other approaches are in late-stage clinical development. The pros and cons of the major approaches will be reviewed.

RARE CASE OF SPONTANEOUS HEMOPERICARDIUM IN A PATIENT RECEIVING APIXABAN: CASE REPORT

Apixaban is a new oral anticoagulant (NOAC) available since 2012, indicated particularly for the prevention of embolic events in patients with non-valvular atrial fibrillation [1]. It is a direct inhibitor of factor Xa, with a half-life of around 12 hours. This new anticoagulant is associated with a lower risk of bleeding than vitamin K antagonists (VKAs) such as warfarin and requires less monitoring [2]. However, several recently published cases have demonstrated a correlation between Apixaban and the occurrence of pericardial effusion. We report the case of a 75-year-old hypertensive man diagnosed with atrial fibrillation 3 months ago, treated with Apixaban 5mg twice daily. He presented to the emergency department with rapidly worsening dyspnea, and echocardiography revealed a large pericardial effusion requiring drainage. A full etiological work-up was carried out, revealing no underlying pathology or triggering event to explain his pericardial effusion. We believe that his recently introduced anticoagulant therapy is the true cause.

Gene deletion of Pregnancy-associated Plasma Protein-A (PAPP-A) improves pathology and cognition in an Alzheimer's disease mouse model

Alzheimer's disease (AD) is a progressive neurodegenerative disease of age with no effective preventative or treatment approaches. Deeper understanding of the mechanisms underlying the accumulation of toxic β-amyloid oligopeptides and the formation of amyloid plaque in AD has the potential to identify new therapeutic targets. Prior research links the insulin-like growth factor (IGF) system to pathologic mechanisms underlying AD. Suppression of local IGF-I receptor (IGFIR) signaling in AD mice has been shown to reduce plaque formation in the brain and delay neurodegeneration and behavioral changes. However, direct inhibitors of IGFIR signaling are not a viable treatment option for AD due to the essentiality of the IGFIR in physiological growth and metabolism. We have previously demonstrated a more selective means to reduce local IGFIR signaling through inhibition of PAPP-A, a novel zinc metalloprotease that regulates local IGF-I bioavailability through cleavage of inhibitory IGF binding proteins. Here we tested if deletion of PAPP-A in a mouse model of AD provides protection against pathology and behavioral changes. We show that compared to AD mice, AD/PAPP-A KO mice had significantly less plaque burden, reduced astrocytic activation, decreased IGF-IR activity, and improved cognition. Human senile AD plaques showed specific immunostaining for PAPP-A. Thus, inhibition of PAPP-A expression or activity may represent a novel treatment strategy for AD.

Evaluation of bleeding risk in patients who received pirtobrutinib in the presence or absence of antithrombotic therapy.

Clinical bleeding events are reported here from 773 patients with B-cell malignancies receiving pirtobrutinib monotherapy from the phase 1/2 BRUIN study (ClinicalTrials.gov identifier: NCT03740529), either in the presence or absence of antithrombotic therapy (antithrombotic exposed [AT-E], n=216; antithrombotic nonexposed [AT-NE], n=557). Among the AT-E cohort, 51.9% received platelet aggregation inhibitors, 36.6% received direct factor Xa inhibitors, 18.5% received heparins, 5.6% received salicylic acid for indications other than platelet aggregation inhibition, and 2.3% received thrombolytics. Warfarin was not permitted. Any-grade bleeding/bruising events occurred in 97 patients (44.9%; 95% confidence interval [CI], 38.3-51.5) in the AT-E cohort and 181 patients (32.5%; 95% CI, 28.6-36.4) in the AT-NE cohort. Most bleeding/bruising events in both cohorts began within the first 6 months of treatment (AT-E: 65.4%; AT-NE: 72.5%). Contusion was the most common bleeding/bruising event in both cohorts (AT-E: 22.7%; AT-NE: 18.1%). Grade ≥3 bleeding/bruising events were reported in six patients (2.8%) in the AT-E cohort and 11 patients (2.0%) in the AT-NE cohort. Bleeding/bruising events requiring or prolonging hospitalization were reported in 2.3% and 1.6% of patients in the AT-E and AT-NE cohorts, respectively. No bleeding/bruising events led to pirtobrutinib dose reduction or permanent discontinuation in the AT-E cohort, and one patient (0.2%) in the AT-NE cohort experienced an event requiring dose reduction. These data support the safety of pirtobrutinib in patients requiring antithrombotic therapies.

Impact of elevated direct factor Xa inhibitor plasma levels on perioperative blood loss in patients undergoing urgent surgery.

Data on the perioperative bleeding risk associated with elevated plasma levels of direct factor Xa inhibitors (FXa inhibitors) are limited. This study examines perioperative red blood cell (RBC) loss in patients undergoing urgent surgery with a residual FXa inhibitor level exceeding 100 mcg/L and without preoperative FXa inhibitor reversal. This retrospective analysis includes data from 32 patients who underwent urgent noncardiac surgery between 2018 and 2022. This study aims to analyze perioperative RBC loss in patients undergoing urgent surgery with a residual FXa inhibitor level exceeding 100 mcg/L and without preoperative FXa inhibitor antidote-based reversal or unspecific treatment with 4-factor prothrombin complex concentrate (PCC). All patients were managed using a watch-and-wait strategy. The last determination of FXa inhibitor plasma concentration prior to surgery showed a median of 245 mcg/L (IQR 144-345), with a median time interval of 3.8 h (IQR 2.4-7.2) before incision. Median RBC loss during surgery was 49 mL (IQR 0-253), 189 mL (IQR 104-217) until POD1 and 254 mL (IQR 58-265) until POD3. Only one patient required intraoperative treatment with 4-factor-PCC and none required reversal with andexanet alfa. Linear regression models found no significant influence of FXa inhibitor plasma levels on intraoperative RBC loss. Rivaroxaban was associated with higher RBC loss until postoperative Day 1 compared with apixaban. No thromboembolic events were observed. Despite markedly elevated plasma concentrations of residual direct FXa inhibitors, perioperative RBC loss was limited in patients undergoing urgent noncardiac surgery. The intraoperative watch-and-wait strategy with selective intraoperative FXa inhibitor reversal or treatment only when required appears to be an appropriate approach.

Solid-Acid Catalyzed Continuous-Flow Aminolysis of Epoxides.

We report a solid-acid catalyzed aminolysis of epoxides under continuous-flow conditions. A titania-zirconia supported molybdenum oxide catalyst demonstrated exceptional substrate compatibility, enabling the synthesis of β-amino alcohols in excellent yields with high catalyst durability. Characterization of the catalyst revealed the crucial role of the titania-zirconia ratio in optimizing its performance. Furthermore, this method was applied to the efficient, sequential-flow synthesis of a rivaroxaban intermediate (an oral anticoagulant and the first direct factor Xa inhibitor), combining a hydrogenation step with the aminolysis reaction without the need for intermediate isolation.

KRASG 12C-inhibitor-based combination therapies for pancreatic cancer: insights from drug screening.

Pancreatic ductal adenocarcinoma (PDAC) has limited treatment options, emphasizing the urgent need for effective therapies. The predominant driver in PDAC is mutated KRAS proto-oncogene, KRA, present in 90% of patients. The emergence of direct KRAS inhibitors presents a promising avenue for treatment, particularly those targeting the KRASG12C mutated allele, which show encouraging results in clinical trials. However, the development of resistance necessitates exploring potent combination therapies. Our objective was to identify effective KRASG12C-inhibitor combination therapies through unbiased drug screening. Results revealed synergistic effects with son of sevenless homolog 1 (SOS1) inhibitors, tyrosine-protein phosphatase non-receptor type 11 (PTPN11)/Src homology region 2 domain-containing phosphatase-2 (SHP2) inhibitors, and broad-spectrum multi-kinase inhibitors. Validation in a novel and unique KRASG12C-mutated patient-derived organoid model confirmed the described hits from the screening experiment. Our findings propose strategies to enhance KRASG12C-inhibitor efficacy, guiding clinical trial design and molecular tumor boards.

Human coronaviruses activate and hijack the host transcription factor HSF1 to enhance viral replication

Organisms respond to proteotoxic-stress by activating the heat-shock response, a cellular defense mechanism regulated by a family of heat-shock factors (HSFs); among six human HSFs, HSF1 acts as a proteostasis guardian regulating severe stress-driven transcriptional responses. Herein we show that human coronaviruses (HCoV), both low-pathogenic seasonal-HCoVs and highly-pathogenic SARS-CoV-2 variants, are potent inducers of HSF1, promoting HSF1 serine-326 phosphorylation and triggering a powerful and distinct HSF1-driven transcriptional-translational response in infected cells. Despite the coronavirus-mediated shut-down of the host translational machinery, selected HSF1-target gene products, including HSP70, HSPA6 and AIRAP, are highly expressed in HCoV-infected cells. Using silencing experiments and a direct HSF1 small-molecule inhibitor we show that, intriguingly, HCoV-mediated activation of the HSF1-pathway, rather than representing a host defense response to infection, is hijacked by the pathogen and is essential for efficient progeny particles production. The results open new scenarios for the search of innovative antiviral strategies against coronavirus infections.

The Shigella flexneri effector IpaH1.4 facilitates RNF213 degradation and protects cytosolic bacteria against interferon-induced ubiquitylation.

A central signal that marshals host defense against many infections is the lymphocyte-derived cytokine interferon-gamma (IFNγ). The IFNγ receptor is expressed on most human cells and its activation leads to the expression of antimicrobial proteins that execute diverse cell-autonomous immune programs. One such immune program consists of the sequential detection, ubiquitylation, and destruction of intracellular pathogens. Recently, the IFNγ-inducible ubiquitin E3 ligase RNF213 was identified as a pivotal mediator of such a defense axis. RNF213 provides host protection against viral, bacterial, and protozoan pathogens. To establish infections, potentially susceptible intracellular pathogens must have evolved mechanisms that subdue RNF213-controlled cell-autonomous immunity. In support of this hypothesis, we demonstrate here that a causative agent of bacillary dysentery, Shigella flexneri, uses the type III secretion system (T3SS) effector IpaH1.4 to induce the degradation of RNF213. S. flexneri mutants lacking IpaH1.4 expression are bound and ubiquitylated by RNF213 in the cytosol of IFNγ-primed host cells. Linear (M1-) and lysine-linked ubiquitin is conjugated to bacteria by RNF213 independent of the linear ubiquitin chain assembly complex (LUBAC). We find that ubiquitylation of S. flexneri is insufficient to kill intracellular bacteria, suggesting that S. flexneri employs additional virulence factors to escape from host defenses that operate downstream from RNF213-driven ubiquitylation. In brief, this study identified the bacterial IpaH1.4 protein as a direct inhibitor of mammalian RNF213 and highlights evasion of RNF213-driven immunity as a characteristic of the human-tropic pathogen Shigella.

Sinensetin interferes with Staphylococcus aureus infections by targeting staphylocoagulase and improves infection survival rates in mouse model of pneumonia.

Coagulase (Coa), a crucial virulence factor of Staphylococcus aureus (S. aureus), is considered a vital target for anti-virulence strategies. The research aimed to discover a natural compound capable of inhibiting S. aureus infection by targeting the virulence factor Coa. The study showed that sinensetin at a concentration of 128 μg mL-1 effectively inhibited both Coa-induced coagulation and biofilm formation in S. aureus. However, western blot results indicated that sinensetin did not impact the expression of Coa protein, suggesting that sinensetin may directly target Coa to counteract the virulence of S. aureus. Thermal shift assay results demonstrated that sinensetin enhanced the thermal stability of Coa, supporting the theory of direct binding. Molecular docking and point mutation experiments identified two key binding sites for sinensetin to Coa as R73A-Coa and R204A-Coa. In vivo studies on mice revealed that sinensetin not only reduced lung tissue damage caused by S. aureus infection, but also decreased inflammatory factors in the lung lavage fluid. Furthermore, combining sinensetin with oxacillin improved the survival rates of the Galleria mellonella and mice. Sinensetin is a promising natural compound that acts as a direct inhibitor of Coa against S. aureus infections.