Tau protein aggregation and spreading are central features of neurodegenerative diseases such as Alzheimer’s disease and frontotemporal dementia. Here, we investigated the role of phosphatidylinositol 4-kinase type IIIα (PI4KIIIα) in regulating tau propagation. We first used tau biosensor cells to demonstrate that both pharmacological inhibition and genetic reduction in PI4KIIIα effectively reduce the seeding of tau aggregation by extracellular seeds. To extend these findings to a more physiologically relevant system, we generated induced pluripotent stem (iPS) cell-derived cortical neurons carrying pathogenic MAPT mutations. These neurons rapidly acquired tauopathy-associated features, including expression of disease-relevant isoforms such as 4R tau, thereby enabling in vitro modeling of tau pathology. Using this model, we established phenotypic assays to monitor tau propagation and aggregation and applied them to test candidate small molecules. Notably, inhibition of PI4KIIIα consistently reduced seeding of tau assemblies in human neurons, highlighting this kinase as an important player in the seeding of tau pathology. Collectively, our work identifies PI4KIIIα as a regulator of tau pathology and provides new experimental platforms to dissect the molecular mechanisms of tau propagation. These findings open potential avenues for the development of strategies to slow or prevent tau-mediated neurodegeneration in the central nervous system.

Cyclin-dependent kinases (CDKs) play a crucial role in cell cycle (such as CDK1 and CDK4/6) and transcription (such as CDK7, CDK9, and CDK12/13). While CDK inhibitors are clinically effective in cancer therapy, their mechanisms of apoptosis induction remain incompletely understood. Here, we demonstrate that inhibition of CDKs involved in cell cycle control (such as CDK1 or CDK4/6) displays no cytotoxic potential. Surprisingly, inhibition of CDK7, which is involved in the control of cell cycle and transcriptional initiation, also showed no cytotoxicity. Only inhibition of CDK9 (by AZD4573 and atuveciclib) or of CDK12/13 (by SR4835 and THZ531)-which target the transcriptional elongation of RNA polymerase II (RNAPII)-exerted a strong apoptotic potential. Since CDK9 and CDK12/13 target different elongation factors associated with RNAPII (such as SPT6 and NELF for CDK9; CDC73, and LEO1 for CDK12/13), they cannot substitute for each other. Consequently, the combination of AZD4573 with SR4835 resulted in significant, synergistic cytotoxicity. Inhibiting CDK9 or CDK12/13 induced the rapid downregulation of the short-lived, anti-apoptotic Bcl-2 proteins Mcl1 and A1/Bfl1 in Jurkat leukemia cells and SUDHL1 lymphoma cells, whereas the expression of Bcl-2 and Bcl-xL remained unaffected. Since Mcl1 and A1 antagonize the pro-apoptotic Bcl-2 proteins Bak and Bax, apoptosis induction by AZD4573 or SR4835 was blocked in Bak- and Bax/Bak-deficient Jurkat cells and strongly reduced in Bax-deficient cells. Because Bcl-2 only inhibits Bax, but not Bak, AZD4573 and SR4835 were able to induce apoptosis in Jurkat cells overexpressing Bcl-2. As tumor cells frequently upregulate Bcl-2, inhibitors of CDK9 and CDK12/13 represent promising anticancer drugs.

AbstractBackgroundCancer immunotherapy has transformed metastatic cancer treatment, yet challenges persist regarding therapeutic efficacy. RECQL4, a RecQ‐like helicase, plays a central role in DNA replication and repair as part of the DNA damage response, a pathway implicated in enhancing efficacy of immune checkpoint inhibitor (ICI) therapies. However, its role in patient response to ICI remains unclear.MethodsWe analysed whole exome and bulk RNA sequencing data from a pan‐cancer cohort of 25 775 patients and cutaneous melanoma cohorts (untreated: n = 471, anti‐progressive disease [PD]‐1 treated: n = 212). RECQL4 copy number variations and expression levels were assessed for patient outcomes. We performed gene set enrichment analysis to identify RECQL4‐dependent signalling pathways and explored the association between RECQL4 levels and immunoscores. We evaluated the interplay of ICI response and RECQL4 expression in melanoma cohorts of 95 responders and 85 non‐responders prior to and after ICI‐targeted therapy and tested the prognostic power of RECQL4. Finally, we generated genetically engineered RECQL4 variants and conducted comprehensive multi‐omic profiling, employing techniques such as liquid chromatography with tandem mass spectrometry, to elucidate mechanistic insights.ResultsWe identified RECQL4 as a critical negative regulator of poor prognosis and response to ICI therapy, but also demonstrated its suitability as an independent biomarker in melanoma. High tumour purity and limited signatures of tumour immunogenicity associated with response to anti‐PD‐1 correlated with high RECQL4 activity. We found alterations in the secretion profile of immune regulatory factors and immune‐related pathways robustly suppressed in tumours with high RECQL4 levels, underscoring its crucial role in fostering immune evasion. Mechanistically, we identified RECQL4‐mediated regulation of major histocompatibility complex class II molecule expression and uncovered class II major histocompatibility complex transactivator as a mediator bridging this regulation.ConclusionsOur findings unraveled the pivotal role of RECQL4 in immune modulation and its potential as both a predictive biomarker and therapeutic target for optimising immunotherapeutic strategies across various cancer types.Highlights High RECQL4 expression limits survival and can act as an independent prognostic factor in melanoma patients. RECQL4 has the potential to act as a negative feedback mediator of immune checkpoint‐targeted therapy by limiting signatures associated with therapeutic efficacy. RECQL4 favours an immune‐evasive phenotype by downregulating major histocompatibility complex class II molecules.

[This corrects the article DOI: 10.3389/fimmu.2025.1554999.].

Neutrophils are frontline responders against bacterial and fungal pathogens, requiring rapid energy and biosynthetic precursors to mount effective antimicrobial responses. To meet these demands, they primarily rely on aerobic glycolysis, making glucose uptake essential. Murine and human neutrophils express the glucose transporters GLUT1 and GLUT3; however, their specific roles in neutrophil immunobiology have not yet been fully elucidated. Here, we show that neutrophilic immune responses to Candida albicans and Staphylococcus aureus critically depend on GLUT1/3-dependent glucose uptake and glycolysis. Combined deletion of GLUT1 and GLUT3 almost completely abolished glucose uptake and aerobic glycolysis in murine neutrophils, yet did not impair granulopoiesis, indicating that homeostatic neutrophil development is largely independent of extracellular glucose. By contrast, during microbial challenge, loss of GLUT1/3 severely compromised NADPH-dependent ROS production, oxidative burst, and cyclooxygenase-derived lipid mediator (LM) biosynthesis, demonstrating that glucose uptake via GLUT1/3 controls inflammatory effector functions of neutrophils. Moreover, genetic and pharmacologic inhibition of GLUT1/3-mediated glucose utilization reprograms neutrophil metabolism and LM biosynthesis toward an immunomodulatory phenotype. These findings identify a conserved nutrient-sensing metabolic checkpoint that governs neutrophil reprogramming and highlight novel opportunities for therapeutic immunomodulation.

Purpose: Post-traumatic epilepsy (PTE) is one of the most common life-quality reducing consequences of traumatic brain injury (TBI). However, to date there are no pharmacological approaches to predict or to prevent the development of PTE. The P2X7 receptor (P2X7R) is a cationic ATP-dependent membrane channel that is expressed throughout the brain. While increasing evidence suggests a role for the P2X7R during seizures and epilepsy, it is unclear if changes in P2X7R expression can predict TBI-induced epilepsy development, and whether P2X7R antagonism can protect against long-lasting brain hyperexcitability caused by TBI. Methods: TBI was induced in adult male mice using the controlled cortical impact model (CCI). To test the anti-epileptogenic effects of P2X7R antagonism, mice were treated with brain-penetrant P2X7R antagonists JNJ-54175446 (30 mg/kg) or AFC-5128 (30 mg/kg) for 7 days post-CCI. The cell-type specific effects of P2X7Rs on TBI-induced hyperexcitability were analyzed in mice lacking exon 2 of the P2rx7 gene selectively in microglia (P2rx7:Cx3cr1-Cre). Static positron emission tomography (PET) via an intravenous injection of the P2X7R radioligand 18F-JNJ-64413739 and magnetic resonance imaging (MRI) were conducted twice during the first- and third-week post-injury. Results: Following TBI, while there were no obvious changes in P2X7R protein levels in the ipsilateral hippocampus post-injury, there was a delayed increase in P2X7R protein levels in the ipsilateral cortex at 3 months post-injury. Treatment with P2X7R antagonists shortly after TBI reduced long-lasting brain hyperexcitability, reduced cortical contusion volume, and normalized injury-induced hyperactivity to control sham-levels at 3 weeks post-TBI. Notably, mice lacking P2rx7 in microglia had an increased seizure threshold after TBI, suggesting that P2X7R contributed to brain hyperexcitability via its effects on microglia. Finally, P2X7R radioligand uptake after TBI correlated with seizure threshold at 3 weeks post-injury. Conclusions: Our results demonstrate the antiepileptogenic potential of P2X7R antagonism to prevent TBI-induced epilepsy and indicate that P2X7R-based PET imaging may be a useful diagnostic tool to identify people at risk of developing PTE.

Background:Multiple sclerosis (MS) is characterized by chronic inflammation driven by central nervous system (CNS)-resident immune cells such as microglia, especially during the progressive phase of the disease. The P2X7 receptor (P2X7R), a risk protein for MS, is ubiquitously expressed on immune cells. AFC-5128, a CNS-penetrating small molecule inhibitor of P2X7R, is a promising agent for the treatment of autoimmune diseases such as MS. Methods:In vitro, the effects on the calcium influx of primary murine microglia were assessed via Fluo-4 calcium imaging. In vivo, MOG35-55 immunized C57BL/6 mice were treated with AFC-5128, fingolimod (FTY) or vehicle in different treatment paradigms. The mice were scored daily. Microglial marker expression, immune cell phenotyping and serum cytokine analyses were performed via flow cytometry. Immune cell infiltration, demyelination and Iba1+/CD3+ cells were detected in spinal cord cross-sections. The effects of MOG35-55 T-cell restimulation were assessed in vitro. Results:In vitro, treatment of primary microglia with 10 µM AFC-5128 reduced the influx of calcium following ATP stimulation (p<0.0001). In vivo, treatment of mice with AFC-5128 led to a reduction in overall EAE scores in acute and chronic EAE, with the best effects using 200 mg/kg body weight AFC-5128 (p<0.0001). Peripheral immune cell subsets (B cells, T cells and macrophages) and serum cytokine levels of chronic EAE mice treated in a therapeutic paradigm were not affected. While the expression of homeostasis markers of microglia in AFC-5128-treated mice was not affected, there was a trend toward lower expression of phagocytosis-associated markers. Late therapeutic treatment with AFC-5128 had only mild effects on chronic EAE. Conclusion:The treatment of EAE mice with AFC-5128 improved acute and chronic EAE in different treatment paradigms, with positive effects on histological markers and slight modulation of microglial marker expression. Mechanistically, calcium influx of microglia was reduced following AFC-5128 treatment, which implies the ability of AFC-5128 to stabilize calcium homeostasis. Therefore, therapeutic inhibition of P2X7R via AFC-5128 has the potential for translation into a treatment of both relapsing and progressive forms of multiple sclerosis.

Antibody-drug conjugates (ADCs) are a therapeutic modality that combines the targeting precision of monoclonal antibodies with the potent cytotoxicity of small-molecule drugs. Despite recent progress of ADC technology in treatment of cancer, efficacy and safety profile of ADCs is often limited by the characteristics of the payloads, highlighting the need for continued innovation in payload selection strategies. To address the unmet needs, we developed a novel class of ADC payload platform employing a novel payload class that disrupts proteostasis by inhibiting a critical component of the cellular protein degradation machinery. Upon internalization, the proteasome inhibitor (PI) payload can block tumor specific protein degradation pathway such as inhibitor of kappa B (IkB) degradation in hematologic malignancies or can induce the accumulation of misfolded and damaged proteins, leading to apoptotic cell death- particularly effective in tumor cells with high protein turnover. Various antibodies were conjugated with PI payload using different conjugation technologies, generating PI-ADCs for the treatment of solid tumors or hematologic malignancies. The resulting ADCs demonstrated efficient intracellular delivery and payload-dependent activity. Strong in vitro cytotoxicity and robust in vivo anti-tumor efficacy were observed across multiple preclinical tumor models, including those with limited sensitivity to existing ADC therapies. These findings highlight the potential of a new broad spectrum payload class to overcome resistance mechanisms and expand the therapeutic landscape of ADCs across diverse malignancies. Won-Gyun Ahn, Jaehee Jang, Seung-Joo Lee, Yong Soo Kim, Jaeseung Kim, Robert Huber, Uwe Koch, Johannes Bange, Martin Huber, Bert Klebl, Kiyean Nam. Proteasome inhibitor (PI) ADC: A novel broad spectrum payload platform [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A110.

Overcoming drug-resistance and the subsequent relapse that often occurs with monotherapy is crucial in the treatment of acute myeloid leukemia. We here demonstrate that therapy-resistant leukemia initiating cells can be targeted using a novel inhibitor of mitochondrial transcription (IMT). The compound inhibits mitochondrial RNA polymerase activity and sensitizes the resistant population to the induction of apoptosis. In vitro studies on acute myeloid leukemia cells demonstrate that IMT prevents cell proliferation, and together with a selective BCL-2 inhibitor, venetoclax, induces apoptosis and suppress oxidative phosphorylation (OXPHOS) synergistically. AML mouse models treated with IMT in combination with venetoclax show prolonged survival in venetoclax-resistant models. Our findings suggest that certain therapy-resistant leukemia cell populations display a unique dependency on mitochondrial transcription and can be targeted with IMT.

The Hippo pathway plays an important role in organ size control and tissue homeostasis. Dysregulation is involved in many pathologies, including cancer, which has attracted interest in targeting the Hippo pathway. Since the upstream components are bona fide tumor suppressors, it is feasible to target oncogenic downstream targets such as TAZ, a key downstream effector in the Hippo pathway. Its activity is regulated by phosphorylation on multiple sites, with Ser89 playing a critical role in regulation of TAZ activity. Phosphorylation of TAZ at Ser89 promotes binding to 14-3-3 scaffolding proteins, preventing nuclear translocation and abolishing target gene transcription. Here we describe the development of a cell-based assay suitable for high-throughput screening, based on a split NanoLuc luciferase, for monitoring interactions between 14 3-3 and TAZ in living cells. We have validated the assay by screening of a kinase-biased library. The assay can be quickly adapted for higher throughput and thus offers a valuable tool to study new signal inputs involved in regulation of TAZ activity as well as for identification of molecules that modulate the Hippo pathway.

The repertoire of currently available antiviral drugs spans therapeutic applications against a number of important human pathogens distributed worldwide. These include cases of the pandemic severe acute respiratory coronavirus type 2 (SARS-CoV-2 or COVID-19), human immunodeficiency virus type 1 (HIV-1 or AIDS), and the pregnancy- and posttransplant-relevant human cytomegalovirus (HCMV). In almost all cases, approved therapies are based on direct-acting antivirals (DAAs), but their benefit, particularly in long-term applications, is often limited by the induction of viral drug resistance or side effects. These issues might be addressed by the additional use of host-directed antivirals (HDAs). As a strong input from long-term experiences with cancer therapies, host protein kinases may serve as HDA targets of mechanistically new antiviral drugs. The study demonstrates such a novel antiviral strategy by targeting the major virus-supportive host kinase CDK7. Importantly, this strategy focuses on highly selective, 3D structure-derived CDK7 inhibitors carrying a warhead moiety that mediates covalent target binding. In summary, the main experimental findings of this study are as follows: (1) the in vitro verification of CDK7 inhibition and selectivity that confirms the warhead covalent-binding principle (by CDK-specific kinase assays), (2) the highly pronounced antiviral efficacies of the hit compounds (in cultured cell-based infection models) with half-maximal effective concentrations that reach down to picomolar levels, (3) a particularly strong potency of compounds against strains and reporter-expressing recombinants of HCMV (using infection assays in primary human fibroblasts), (4) additional activity against further herpesviruses such as animal CMVs and VZV, (5) unique mechanistic properties that include an immediate block of HCMV replication directed early (determined by Western blot detection of viral marker proteins), (6) a substantial drug synergism in combination with MBV (measured by a Loewe additivity fixed-dose assay), and (7) a strong sensitivity of clinically relevant HCMV mutants carrying MBV or ganciclovir resistance markers. Combined, the data highlight the huge developmental potential of this host-directed antiviral targeting concept utilizing covalently binding CDK7 inhibitors.

ERBB receptor tyrosine kinases are involved in development and diseases like cancer, cardiovascular, neurodevelopmental, and mental disorders. Although existing drugs target ERBB receptors, the next generation of drugs requires enhanced selectivity and understanding of physiological pathway responses to improve efficiency and reduce side effects. To address this, we developed a multilevel barcoded reporter profiling assay, termed 'ERBBprofiler', in living cells to monitor the activity of all ERBB targets and key physiological pathways simultaneously. This assay helps differentiate on-target therapeutic effects from off-target and off-pathway side effects of ERBB antagonists. To challenge the assay, eight established ERBB antagonists were profiled. Known effects were confirmed, and previously uncharacterized properties were discovered, such as pyrotinib's preference for ERBB4 over EGFR. Additionally, two lead compounds selectively targeting ERBB4 were profiled, showing promise for clinical trials. Taken together, this multiparametric profiling approach can guide early-stage drug development and lead to improved future therapeutic interventions.

AbstractHypoglycemia triggers autonomic and endocrine counter-regulatory responses to restore glucose homeostasis, a response that is impaired in patients with diabetes and its long-term complication hypoglycemia-associated autonomic failure (HAAF). We show that insulin-evoked hypoglycemia is severely aggravated in mice lacking the cation channel proteins TRPC1, TRPC4, TRPC5, and TRPC6, which cannot be explained by alterations in glucagon or glucocorticoid action. By using various TRPC compound knockout mouse lines, we pinpointed the failure in sympathetic counter-regulation to the lack of the TRPC5 channel subtype in adrenal chromaffin cells, which prevents proper adrenaline rise in blood plasma. Using electrophysiological analyses, we delineate a previously unknown signaling pathway in which stimulation of PAC1 or muscarinic receptors activates TRPC5 channels in a phospholipase-C-dependent manner to induce sustained adrenaline secretion as a crucial step in the sympathetic counter response to insulin-induced hypoglycemia. By comparing metabolites in the plasma, we identified reduced taurine levels after hypoglycemia induction as a commonality in TRPC5-deficient mice and HAAF patients.

The identification of chemical starting points for the development of molecular glues is challenging. Here, we employed fragment screening and identified an allosteric stabilizer of the complex between 14-3-3 and a TAZ-derived peptide. The fragment binds preferentially to the 14-3-3/TAZ peptide complex and shows moderate stabilization in differential scanning fluorimetry and microscale thermophoresis. The binding site of the fragment was predicted by molecular dynamics calculations to be distant from the 14-3-3/TAZ peptide interface, located between helices 8 and 9 of the 14-3-3 protein. This site was confirmed by nuclear magnetic resonance and X-ray protein crystallography, revealing the first example of an allosteric stabilizer for 14-3-3 protein-protein interactions.

The colony-stimulating factor 1 receptor (CSF1R) is a protein kinase emerging as an attractive target with clinical relevance in cancer, CNS and inflammatory diseases. Molecular docking experiments followed by synthesis and structure-activity relationship have been used to identify low molecular weight structures as promising hits for lead optimization. These molecules are synthesized from a 4-chloro-6-iodo-pyrrolo[2,3-d]pyrimidine building block using Negishi and Suzuki-Miyaura cross-coupling reactions in high yields. Several inhibitors possessed excellent enzymatic potency, and the parent compound preferably binds to the autoinhibited form of CSF1R. Cellular and in vivo profiling indicate that further tuning of drug structure is needed prior to efficacy studies.

Supplementary Methods and Figure from Cellular Targets of Gefitinib