Biology subjects

Gad, M.

Publications and source records attributed to Gad, M..

4 recordsLinked to original sources

bioRxiv2026

SLC33A1 exports oxidized glutathione to maintain endoplasmic reticulum redox homeostasis

The endoplasmic reticulum (ER) requires an oxidative environment to support the efficient maturation of secretory and membrane proteins. This is in part established by glutathione, a redox-active metabolite present in reduced (GSH) and oxidized (GSSG) forms. The ER maintains a higher GSSG:GSH ratio than the cytosol; however, the mechanisms controlling ER redox balance remain poorly understood. To address this, we developed a method for the rapid immunopurification of the ER, enabling comprehensive profiling of its proteome and metabolome. Combining this approach with CRISPR screening, we identified SLC33A1 as the major ER GSSG exporter in mammalian cells. Loss of SLC33A1 leads to GSSG accumulation in the ER and a liposome-based assay demonstrates that SLC33A1 directly transports GSSG. Cryo-EM structures and molecular dynamics simulations reveal how SLC33A1 binds GSSG and identify residues critical for its transport. Finally, an imbalance in GSSG:GSH ratio induces ER stress and dependency on the ER-associated degradation (ERAD) pathway, driven by a shift in protein disulfide isomerases (PDIs) toward their oxidized forms. Altogether, our work establishes SLC33A1-mediated GSSG export as a key mechanism for ER redox homeostasis and protein maturation.

cell biology↗

bioRxiv2025

Inhibition of 3-mercaptopyruvate sulfurtransferase enhances CD8⁺ T-cell antitumor immunity

Hydrogen sulfide (H2S) is a redox-active gasotransmitter implicated in tumor progression and immune regulation. The enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) is a key contributor to endogenous H2S and polysulfide production, but its role in tumor-immune interactions remains poorly defined. Here, we show that 3-MST is the most abundantly expressed H2S-synthesizing enzyme in human renal cell carcinoma cells (RCC) and that high 3-MST expression correlates with reduced patient survival. Pharmacological inhibition of 3-MST lowered intracellular H2S levels in Renca renal carcinoma cells, suppressed proliferation, induced apoptosis, and increased surface expression of the immunogenic markers CD70, CD86, and PD-L1. In immune cells, partial inhibition of 3-MST promoted T cell activation, as evidenced by increased CD69 expression on both CD4 helper and CD8 cytotoxic T cells. In contrast, complete inhibition of 3-MST, achieved by high concentrations of the inhibitor, modestly reduced CD8 T cell proliferation. Functionally, 3-MST inhibition potentiated antigen-specific CD8 T cell-mediated killing of tumor cells, an effect further amplified by PD-L1 blockade. These results establish 3-MST as a redox-sensitive metabolic driver of tumor growth and immune evasion in RCC and demonstrate that its inhibition can boost antitumor immune responses, offering a potential avenue for combination immunotherapy.

pharmacology and toxicology↗

bioRxiv2023

Mass-immigration shapes the antibiotic resistome of wastewater treatment plants

Wastewater treatment plants (WWTPs) are the hotspots for the spread of antibiotic resistance genes (ARGs) into the environment. Nevertheless, a comprehensive assessment of the city-level and short-term daily variations of ARG surveillance is still lacking in WWTPs. Here, 285 ARGs and ten mobile gene elements (MGEs) were monitored in seven WWTPs in Xiamen via high-throughput qPCR (HT-qPCR) for seven days. The average daily load of ARGs to WWTPs was about 1.21 x 1020 copies/d, and a total of 1.44 x 1018 copies/d was discharged to the environment across the entire city. Interestingly, no daily variations were observed in ARG richness, abundance, and community composition. Stochastic processes were the main force determining the assembly of ARG communities, with their relative importance ranked in the order of influent (INF) > effluent (EFF) > activated sludge (AS). Further analyses indicated that bacteria and ARGs from upstream treatment units played an increasingly dominant role in shaping ARG communities in AS and EFF, respectively, suggesting the importance of mass-immigration of bacteria and ARGs from the source on ARG transport in wastewater treatment units. This emphasizes the need to revise the way we mitigate ARG contamination but focus on the source of ARGs in urban wastewater.

microbiology↗

bioRxiv2021

Molecular competition can shape enhancer activity in the Drosophila embryo

Transgenic reporters allow the measurement of regulatory DNA activity in vivo and consequently have long been useful tools in the study of enhancers. Despite the utility of transgenic reporters, few studies have investigated the potential effects these reporters have on the expression of other transgenic reporters or endogenous genes. A full understanding of the impacts transgenic reporters have on expression is required for accurate interpretation of transgenic reporter data and characterization of gene regulatory mechanisms. Here, we investigate the impact transgenic reporters have on the expression of other transgenic reporters and endogenous genes. By measuring the expression of Kruppel (Kr) enhancer reporters in live Drosophila embryos that contain either one or two copies of identical reporters, we find reporters have an inhibitory effect on one anothers expression. Further, expression of a nearby endogenous gene is decreased in the presence of a Kr enhancer reporter. Through the use of competitor binding site arrays, we present evidence that reporters, and potentially endogenous genes, are competing for transcription factors (TFs). Increasing the number of competitor Bcd binding sites decreases the peak levels and spatial extent of Bcd-regulated enhancer reporters expression. To understand how small numbers of added TF binding sites could impact gene expression to the extent we observe, we develop a simple thermodynamic model of our system. Our model predicts competition of the measured magnitude specifically if TF binding is restricted to distinct nuclear subregions, underlining the importance of the non-homogenous nature of the nucleus in regulating gene expression.

systems biology↗