Biology subjects

Sohl, C. D.

Publications and source records attributed to Sohl, C. D..

5 recordsLinked to original sources

bioRxiv2026

Mutant Isocitrate Dehydrogenase 1 Alters Extracellular Vesicle Secretion and Cargo Composition in Cellular Models

Somatic mutations in isocitrate dehydrogenase 1 (IDH1) define major subtypes of adult diffuse gliomas and occur across a broad spectrum of cancers. These mutations ablate the conventional turnover of isocitrate to alpha-ketoglutarate and confer the neomorphic production of D-2-hydroxyglutarate (D2HG), which drives epigenetic remodeling. Growing evidence suggests this neomorphic activity may also affect how tumor cells communicate; small extracellular vesicles (sEVs) are elevated in gliomas, though how mutant IDH1 shapes sEV production and cargo remains poorly understood. Using glioblastoma and chondrosarcoma cell models, we show expression of mutant IDH1 correlates with a trend of increased sEV secretion, and that D2HG is packaged into sEVs that are taken up by cells. Cell-permeable D2HG treatment dose-dependently increased sEV release from IDH1 wild type cells. Untargeted proteomics showed that mutant IDH1 expression remodeled sEV cargo in a cell type-specific fashion, with mutant chondrosarcoma sEVs enriched in one-carbon metabolism enzymes, and mutant glioma sEVs in lysosomal luminal proteins and endoplasmic reticulum (ER) chaperones. Mutant IDH1 glioma cell transcriptomics suggested expanded ER folding capacity and reduced ribosomal pathways, and sEVs from these cells decreased nascent protein synthesis in IDH1 wild type recipient cells. Together, this suggests sEVs can serve as carriers of mutant IDH1 phenotypes.

cancer biology↗

bioRxiv2024

Catalytically distinct IDH1 mutants tune phenotype severity in tumor models

Mutations in isocitrate dehydrogenase 1 (IDH1) impart a neomorphic reaction that produces D-2-hydroxyglutarate (D2HG), which can inhibit DNA demethylases to drive tumorigenesis. Mutations affect residue R132 and display distinct catalytic profiles for D2HG production. We show that catalytic efficiency of D2HG production is greater in IDH1 R132Q than R132H mutants, and expression of R132Q in cellular and xenograft models leads to higher D2HG concentrations in cells, tumors, and sera compared to R132H. Though expression of IDH1 R132Q leads to hypermethylation in DNA damage pathways, DNA hypomethylation is more notable when compared to R132H expression. Transcriptome analysis shows increased expression of many pro-tumor pathways upon expression of IDH1 R132Q versus R132H, including transcripts of EGFR and PI3K signaling pathways. Thus, IDH1 mutants appear to modulate D2HG levels via altered catalysis, resulting in distinct epigenetic and transcriptomic consequences where higher D2HG levels appear to be associated with more aggressive tumors.

genomics↗

bioRxiv2024

Active site remodeling in IDH1 mutants drives distinct kinetic and potential resistance mechanisms

Mutations in human isocitrate dehydrogenase 1 (IDH1) drive tumor formation in a variety of cancers by replacing its conventional activity with a neomorphic activity that generates an oncometabolite. Little is understood of the mechanistic differences among tumor-driving IDH1 mutants. We previously reported that the R132Q mutant uniquely preserves conventional activity while catalyzing robust oncometabolite production, allowing an opportunity to compare these reaction mechanisms within a single active site. Here, we employed static and dynamic structural methods and found that, compared to R132H, the R132Q active site adopted a conformation primed for catalysis with optimized substrate binding and hydride transfer to drive improved conventional and neomorphic activity over R132H. This active site remodeling revealed a possible mechanism of resistance to selective mutant IDH1 therapeutic inhibitors. This work enhances our understanding of fundamental IDH1 mechanisms while pinpointing regions for improving inhibitor selectivity.

biochemistry↗

bioRxiv2020

An acidic residue buried in the dimer interface of isocitrate dehydrogenase 1 (IDH1) helps regulate catalysis and pH sensitivity

Isocitrate dehydrogenase 1 (IDH1) catalyzes the reversible NADP+-dependent conversion of isocitrate to -ketoglutarate (-KG) to provide critical cytosolic substrates and drive NADPH-dependent reactions like lipid biosynthesis and glutathione regeneration. In biochemical studies, the forward reaction is studied at neutral pH, while the reverse reaction is typically characterized in more acidic buffers. This led us to question whether IDH1 catalysis is pH-regulated, which would have functional implications under conditions that alter cellular pH, like apoptosis, hypoxia, cancer, and neurodegenerative diseases. Here, we show evidence of catalytic regulation of IDH1 by pH, identifying a trend of increasing kcat values for -KG production upon increasing pH in the buffers we tested. To understand the molecular determinants of IDH1 pH sensitivity, we used the pHinder algorithm to identify buried ionizable residues predicted to have shifted pKa values. Such residues can serve as pH sensors, with changes in protonation states leading to conformational changes that regulate catalysis. We identified an acidic residue buried at the IDH1 dimer interface, D273, with a predicted pKa value upshifted into the physiological range. D273 point mutations had decreased catalytic efficiency and, importantly, loss of pH-regulated catalysis. Based on these findings, we conclude that IDH1 activity is regulated, at least in part, by pH. We show this regulation is mediated by at least one buried acidic residue [~]12 [A] from the IDH1 active site. By establishing mechanisms of regulation of this well-conserved enzyme, we highlight catalytic features that may be susceptible to pH changes caused by cell stress and disease.

biochemistry↗

bioRxiv2019

Activity of Selected Nucleoside Analogue ProTides against Zika Virus in Human Neural Stem Cells

Zika virus (ZIKV), an emerging flavivirus which causes neurodevelopmental impairment to fetuses and has been linked to Guillain-Barre syndrome, continues to threaten global health due to the absence of targeted prophylaxis or treatment. Nucleoside analogues are good examples of efficient anti-viral inhibitors, and prodrug strategies using phosphate masking groups (ProTides) have been employed to improve the bioavailability of ribonucleoside analogues. Here, we synthesized and tested a library of 13 ProTides against ZIKV in human neural stem cells. Strong activity was observed for 2'-C-methyluridine and 2'-C-ethynyluridine ProTides with an aryloxyl phosphoramidate masking group. Conversion of the aryloxyl phosphoramidate ProTide group of 2'-C-methyluridine to a 2-(methylthio)ethyl phosphoramidate completely abolished antiviral activity of the compound. The aryloxyl phosphoramidate ProTide of 2'-C-methyluridine outperformed the hepatitis C virus (HCV) drug sofosbuvir in suppression of viral titers and protection from cytopathic effect, while the former compounds triphosphate active metabolite was better incorporated by purified ZIKV NS5 polymerase over time. Molecular superpositioning revealed different orientations of residues opposite the 2'-fluoro group of sofosbuvir. These findings suggest both a nucleobase and ProTide group bias for the anti-ZIKV activity of nucleoside analogue ProTides in a disease-relevant cell model.

microbiology↗