Macrophages act to defend against infection, but can fail to completely prevent bacterial replication and dissemination in an immunocompetent host. Recent studies have shown that activation of a host transcription factor, TFEB, a regulator of lysosomal biogenesis, could restrict intramacrophage replication of the human pathogen Mycobacterium tuberculosis and synergize with suboptimal levels of the antibiotic rifampin to reduce bacterial loads. Currently available small molecule TFEB activators lack selectivity and potency, but could be potentially useful in a variety of pathological conditions with suboptimal lysosomal activity. TFEB nuclear translocation and activation depend on its phosphorylation status which is controlled by multiple cellular pathways. We devised a whole cell, high throughput screening assay to identify small molecules that activate TFEB by establishing a stably transfected HEK293T reporter cell line for ATF4, a basic leucine zipper transcription factor induced by stress response and activated in parallel to TFEB. We optimized its use in vitro using compounds that target endoplasmic reticulum stress and intracellular calcium signaling. We report results from screening the commercially available LOPAC library and the Selleck Chemicals library modified to include only FDA-approved drugs and clinical research compounds. We identified twenty-one compounds across six clinical use categories that activate ATF4, and confirmed that two proteasome inhibitors promote TFEB activation. The results of this study provide an assay that could be used to screen for small molecules that activate ATF4 and TFEB and a potential list of compounds identified as activators of the ATF4 transcription factor in response to cellular stress.

Over half of ovarian clear cell carcinoma (OCCC) cases exhibit deficiencies in the ARID1A gene, a chromatin remodeling complex component. OCCC is resistant to chemotherapy and challenging to treat, necessitating new drug treatment strategies. This study used a publicly available dependency factor database to identify synthetic lethal targets for ARID1A-deficient cancer. The DepMap portal was used to identify genes on which ARID1A-deficient cancer cell lines are highly dependent. Our analysis limited to ovarian cancer cell lines only identified the deubiquitinating enzyme USP8 as a synthetic lethal target in ARID1A-deficient OCCC cancer cell lines and mouse xenograft models. In addition, USP8 inhibitors were more selective for ARID1A-deficient cells than existing candidate drugs used in promising clinical trials for ARID1A-deficient cancers. Suppression of USP8 in ARID1A-deficient cells led to degradation of FGFR2 via the proteasome. Deficiency of ARID1A causes abnormalities in the STAT3 pathway, which is one of the downstream pathways of FGFR2, but suppression of USP8 attenuates phosphorylation of STAT3 pT705 and induces apoptosis. Taken together, our data suggest that USP8 is a novel therapeutic target for ARID1A-deficient OCCC and that USP8 inhibitors suppress FGFR2-STAT3 signaling.
© 2025. The Author(s).

The stability of RNA polymerase II (Pol II) is tightly regulated during transcriptional elongation for proper control of gene expression. Our recent studies revealed that promoter-proximal Pol II is destabilized via the ubiquitin E3 ligase cullin 3 (CUL3) upon loss of transcription elongation factor SPT5. Here, we investigate how CUL3 recognizes chromatin-bound Pol II as a substrate. Using an unbiased proteomic screening approach, we identify armadillo repeat-containing 5 (ARMC5) as a CUL3 adaptor required for VCP/p97-dependent degradation of SPT5-depleted, chromatin-bound Pol II. Genome-wide analyses indicate that ARMC5 targets promoter-proximal Pol II in a BTB domain-dependent manner. Further biochemical analysis demonstrates that interaction between ARMC5 and Pol II requires the transcriptional cyclin-dependent kinase 9 (CDK9), supporting a phospho-dependent degradation model. We propose that defective, promoter-proximal Pol II that lacks SPT5 is rapidly eliminated from chromatin in a noncanonical early termination pathway that requires CDK9-dependent interaction with the CUL3-ARMC5 ubiquitin ligase complex.

Bortezomib (BTZ), a selective 26 S proteasome inhibitor, is clinically useful in treating multiple myeloma and mantle cell lymphoma. BTZ exerts its antitumor effect by suppressing nuclear factor-B in myeloma cells, promoting endothelial cell apoptosis, and inhibiting angiogenesis. Despite its success, pulmonary complications, such as capillary leak syndrome of the vascular hyperpermeability type, were reported prior to its approval. Although the incidence of these complications has decreased with the use of steroids, the underlying mechanism remains unclear. This study aims to investigate how BTZ influences endothelial cell permeability.
We examined the impact of BTZ on vascular endothelial cells, focusing on its effects on RhoA and RhoC proteins. Stress fiber formation, a known indicator of increased permeability, was assessed through the Rho/ROCK pathway.
BTZ was found to elevate the protein levels of RhoA and RhoC in vascular endothelial cells, leading to stress fiber formation via the Rho/ROCK pathway. This process resulted in enhanced vascular permeability in a Rho-dependent manner. Furthermore, the stress fiber formation induced by BTZ had synergistic effects with the inflammatory mediator histamine.
Our findings suggest that BTZ accumulates RhoA and RhoC proteins in endothelial cells, amplifying the inflammatory mediator-induced increase in the active GTP-bound state of Rho, thereby exaggerating vascular permeability during pulmonary inflammation. This study provides novel insights into the molecular mechanism underlying the pulmonary complications of BTZ, suggesting that BTZ may enhance inflammatory responses in pulmonary endothelial cells by increasing RhoA and RhoC protein levels.
© 2024. The Author(s).

Synucleinopathies are a class of neurodegenerative diseases defined by the presence of α-synuclein inclusions. The location and composition of these α-synuclein inclusions directly correlate to the disease pattern. The inclusions in Multiple System Atrophy are located predominantly in oligodendrocytes and are rich in a second protein, p25α. P25α plays a key role in neuronal myelination by oligodendrocytes. In healthy oligodendrocytes, there is little to no α-synuclein present. If aberrant α-synuclein is present, p25α leaves the myelin sheaths and quickly co-aggregates with α-synuclein, resulting in the disruption of the cellular process and ultimately cell death. Herein, we report that p25α is susceptible for 20S proteasome-mediated degradation and that p25α induces α-synuclein aggregation, resulting in proteasome impairment and cell death. In addition, we identified small molecules 20S proteasome enhancers that prevent p25α induced α-synuclein fibrilization, restore proteasome impairment, and enhance cell viability.
© 2024 The Author(s).