Biology subjects

Potts, P. R.

Publications and source records attributed to Potts, P. R..

9 recordsLinked to original sources

bioRxiv2026

Testis-Specific MAGEA3/6 Regulate Glycolysis to Promote Metabolic Flexibility and Reveal Therapeutic Vulnerabilities in Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor characterized by metabolic plasticity that enables cancer cells to survive nutrient deprivation and therapeutic stress. Melanoma-associated antigens A3 and A6 (MAGEA3/6), members of the cancer-testis antigen family with a previously identified protective role in spermatogenesis during nutritional stress, have been implicated in cancer progression and metabolic regulation. However, their contribution to metabolic adaptation in pancreatic cancer remains poorly understood. Here, we investigated the molecular mechanisms underlying MAGEA3/6-mediated resistance to glycolytic inhibition using complementary gain- and loss-of-function models, pharmacological inhibition of metabolic pathways, cellular metabolic assays, and integrated transcriptomic, proteomic, metabolomic, and lipidomic analyses. MAGEA3/6 expression enhanced resistance to 2-deoxy-D-glucose (2-DG), with MAGEA6-expressing MIA PaCa-2 cells exhibiting a greater than 2.5-fold increase in the half-maximal inhibitory concentration (IC50). Conversely, MAGEA3/6 depletion reduced clonogenic growth and migration and increased sensitivity to 2-DG. Resistance persisted despite pharmacological inhibition of mTORC1, the pentose phosphate pathway, or glutaminase, suggesting metabolic adaptations beyond these pathways. Unexpectedly, MAGEA6 expression was associated with increased rather than decreased AMPK1 protein abundance, contrasting with previously reported MAGEA3/6-mediated AMPK degradation and suggesting context-dependent regulation of this master regulator of cellular metabolism. MAGEA6 also reduced hexokinase HK1 and HK2 abundance while increasing several downstream glycolytic enzymes, revealing discordant regulation of glycolysis. Seahorse analyses and integrated multi-omics profiling identified extensive remodeling of mitochondrial metabolism, glutamine-aspartate metabolism, phospholipid composition, lipid storage, and redox homeostasis. Interestingly, despite enhanced resistance to glycolytic inhibition, MAGEA6-expressing cells exhibited increased sensitivity to hydrogen peroxide-induced oxidative stress, revealing a potential metabolic vulnerability. Given that MAGEA3/6 are physiologically expressed primarily in the male germline during early spermatogenesis, a process highly sensitive to metabolic and oxidative stress, these findings also raise important questions about their physiological roles in protecting developing germ cells and maintaining metabolic and redox homeostasis. Together, our findings recognize MAGEA3/6 as regulators of metabolic plasticity in PDAC and highlight how understanding their molecular functions in both spermatogenesis and cancer may uncover previously unrecognized metabolic vulnerabilities and potential therapeutic opportunities.

cancer biology↗

bioRxiv2026

Reprogramming VHL with molecular glues enables selective degradation of caspase-2

Molecular glue degraders (MGDs) reprogram E3 ligases to eliminate neosubstrates, yet their application has largely been confined to CRBN. Here, we identify caspase-2 as a new neosubstrate for von Hippel-Lindau (VHL), expanding the scope of VHL-based MGDs. Guided by a focused VHL ligand library design, we employed TurboID-based proximity labeling to discover stereoisomeric compounds (dCASP2-1 and dCASP2-2) that selectively recruit caspase-2 to VHL and promote its ubiquitin-proteasome system-dependent degradation. Further structure-activity relationship (SAR) studies yielded dCASP2-3 and dCASP2-4, which enhanced degradation potency (by 622-fold relative to dCASP2-1) and abolished enantioselectivity. Mechanistic mapping localized the degrader-induced interface to a two-helix region of the caspase-2 CARD domain, with residues H33, P34, and D100 essential for VHL engagement. Degron-guided computational modeling of the VHL/MGD/caspase-2 ternary complex provided structural insight into neosubstrate recognition. Together, we report the development of VHL molecular glues that selectively and potently degrade caspase-2, offering chemical probes to interrogate its functions in apoptosis and stress responses, while broadening the substrate landscape of VHL-based MGDs.

biochemistry↗

bioRxiv2025

Discovery of a VHL molecular glue degrader of GEMIN3 by Picowell RNA-seq

Targeted protein degradation (TPD) is an emerging therapeutic modality in which small molecules are used to recruit targets to the natural protein degradation machinery of the cell. Molecular glue degraders (MGD) are monovalent small molecules that accomplish this by redirecting E3 ubiquitin ligases to target proteins, offering the potential to degrade previously unliganded and "undruggable" proteins in cancer, neurodegenerative, and other diseases. While attractive due to their drug-like properties, MGDs are exceptionally hard to discover and have largely been identified serendipitously. The Von Hippel-Lindau (VHL) E3 ligase is the second most widely used effector for TPD, though current VHL-based degraders are primarily large heterobifunctional PROTACs (proteolysis-targeting chimeras) designed using target-based ligands. Here, we have instead pursued target-agnostic discovery of VHL MGDs leveraging proprietary ultra-miniaturized microfluidics devices (Picowells) to facilitate unbiased RNA-seq screening of a biased E3-focused library. This resulted in dGEM3, a novel VHL molecular glue that targets the survival of motor neuron (SMN) complex member GEMIN3 for degradation. Through a combination of cellular, biochemical, and biophysical assays, we have characterized the GEMIN3 degron within its helicase ATP-binding domain, and how the kinetics of ternary complex formation impact degradation. These findings provide insights on the re-programmability of VHL for novel targets using drug-like molecular glues.

biochemistry↗

bioRxiv2025

A Cancer-Specific Antigen Drives Histone Acetylation by Stabilizing the Acetyltransferases

Histone acetylation is a critical epigenetic modification that regulates gene expression by modulating chromatin structure and function. Histone acetyltransferases are essential for maintaining acetylation homeostasis and the disruption of this balance can lead to aberrant gene expression and cancer development. Here, we describe that the cancer-specific protein MAGE-A10 increases cellular histone acetylation by stabilizing essential histone acetyltransferases KAT2A and KAT2B. The aberrant expression of MAGE-A10 in tumors prevents the degradation of KAT2A/2B through p62-mediated autophagy. Mechanistically, MAGE-A10 antagonizes the binding of KAT2A/2B with the E3 ubiquitin ligase complex CUL4A-DDB1, thereby decreasing the formation of their K63-linked ubiquitination. Furthermore, KAT2A enhances the transcription of the MAGE-A10 gene, forming a positive feedback loop that contributes to tumorigenesis. These findings provide insights into the molecular mechanisms hijacked in cancer that drive perturbed histone acetylation and suggest potential therapeutic strategies.

cancer biology↗

bioRxiv2025

Covalent Destabilizing Degrader of AR and AR-V7 in Androgen-Independent Prostate Cancer Cells

Androgen-independent prostate cancers, correlated with heightened aggressiveness and poor prognosis, are caused by mutations or deletions in the androgen receptor (AR) or expression of truncated variants of AR that are constitutively activated. Currently, drugs and drug candidates against AR target the steroid-binding domain to antagonize or degrade AR. However, these compounds cannot therapeutically access largely intrinsically disordered truncated splice variants of AR, such as AR-V7, that only possess the DNA binding domain and are missing the ligand binding domain. Targeting intrinsically disordered regions within transcription factors has remained challenging and is considered "undruggable". Herein, we leveraged a cysteine-reactive covalent ligand library in a cellular screen to identify degraders of AR and AR-V7 in androgen-independent prostate cancer cells. We identified a covalent compound EN1441 that selectively degrades AR and AR-V7 in a proteasome-dependent manner through direct covalent targeting of an intrinsically disordered cysteine C125 in AR and AR-V7. EN1441 causes significant and selective destabilization of AR and AR-V7, leading to aggregation of AR/AR-V7 and subsequent proteasome-mediated degradation. Consistent with targeting both AR and AR-V7, we find that EN1441 completely inhibits total AR transcriptional activity in androgen-independent prostate cancer cells expressing both AR and AR-V7 compared to AR antagonists or degraders that only target the ligand binding domain of full-length AR, such as enzalutamide and ARV-110. Our results put forth a pathfinder molecule EN1441 that targets an intrinsically disordered cysteine within AR to destabilize, degrade, and inhibit both AR and AR-V7 in androgen-independent prostate cancer cells and highlights the utility of covalent ligand discovery approaches in directly targeting, destabilizing, inhibiting, and degrading classically undruggable transcription factor targets.

cancer biology↗

bioRxiv2024

LYMTACs: Chimeric Small Molecules Repurpose Lysosomal Membrane Proteins for Target Protein Relocalization and Degradation

Proximity-inducing modalities that co-opt cellular pathways offer new opportunities to regulate oncogenic drivers. Inspired by the success of proximity-based chimeras in both intracellular and extracellular target space, here we describe the development of LYsosome Membrane TArgeting Chimeras (LYMTACs) as a novel small molecule-based platform that functions intracellularly to modulate the membrane proteome. Conceptually, LYMTACs are heterobifunctional small molecules that co-opt short-lived lysosomal membrane proteins (LMPs) as effectors to deliver targets for lysosomal degradation. We demonstrate that a promiscuous kinase inhibitor-based LYMTAC selectively targets membrane proteins for lysosomal degradation via RNF152, a short-lived LMP. To extend these findings, we show that oncogenic, membrane-associated KRASG12D protein can be tethered to RNF152, inducing KRAS relocalization to the lysosomal membrane, inhibiting downstream phospho-ERK signaling, and leading to lysosomal degradation of KRASG12D in a LYMTAC-dependent manner. Notably, potent cell killing could be attributed to the multi-pharmacology displayed by LYMTACs, which differentiates the LYMTAC technology from existing modalities. Thus, LYMTACs represent a proximity-based therapeutic approach that promises to expand the target space for challenging membrane proteins through targeted protein relocalization and degradation.

cancer biology↗

bioRxiv2024

VIPER-TACs leverage viral E3 ligases for disease-specific targeted protein degradation

In targeted protein degradation (TPD) a protein of interest is degraded by chemically induced proximity to an E3 ubiquitin ligase. One limitation of using TPD therapeutically is that most E3 ligases have broad tissue expression, which can contribute to toxicity via target degradation in healthy cells. Many pathogenic and oncogenic viruses encode E3 ligases (vE3s), which de facto have strictly limited expression to diseased cells. Here, we provide proof-of-concept for Viral E3 Pan-Essential Removing Targeting Chimeras (VIPER-TACs) that are bi-functional molecules that utilize viral E3 ubiquitin ligases to selectively degrade pan-essential proteins and eliminate diseased cells. We find that the human papillomavirus (HPV) ligase E6 can degrade the SARS1 pan-essential target protein in a model of HPV-positive cervical cancer to selectively kill E6 expressing cancer cells. Thus, VIPER-TACs have the capacity to dramatically increase the therapeutic window, alleviate toxicity concerns, and ultimately expand the potential target space for TPD.

cancer biology↗

bioRxiv2024

Melanoma antigens in pediatric medulloblastoma contribute to tumor heterogeneity and species-specificity of group 3 tumors

BackgroundMedulloblastoma (MB) is the most malignant childhood brain cancer. Group 3 MB subtype accounts for about 25% of MB diagnoses and is associated with the most unfavorable outcomes. Herein, we report that more than half of group 3 MB tumors express melanoma antigens (MAGEs), which are potential prognostic and therapeutic markers. MAGEs are tumor antigens, expressed in several types of adult cancers and associated with poorer prognosis and therapy resistance; however, their expression in pediatric cancers is mostly unknown. The aim of this study was to determine whether MAGEs are activated in pediatric MB. MethodsTo determine MAGE frequency in pediatric MB, we obtained formalin-fixed paraffin-embedded tissue (FFPE) samples of 34 patients, collected between 2008 - 2015, from the Childrens Medical Center Dallas pathology archives and applied our validated reverse transcription quantitative PCR (RT-qPCR) assay to measure the relative expression of 23 MAGE cancer-testis antigen genes. To validate our data, we analyzed several published datasets from pediatric MB patients and patient-derived orthotopic xenografts, totaling 860 patients. We then examined how MAGE expression affects the growth and oncogenic potential of medulloblastoma cells by CRISPR-Cas9- and siRNA-mediated gene depletion. ResultsOur RT-qPCR analysis suggested that MAGEs were expressed in group 3/4 medulloblastoma. Further mining of bulk and single-cell RNA-sequencing datasets confirmed that 50-75% of group 3 tumors activate a subset of MAGE genes. Depletion of MAGEAs, B2, and Cs alter MB cell survival, viability, and clonogenic growth due to decreased proliferation and increased apoptosis. ConclusionsThese results indicate that targeting MAGEs in medulloblastoma may be a potential therapeutic option for group 3 medulloblastomas. Key PointsO_LISeveral Type I MAGE CTAs are expressed in >60% of group 3 MBs. C_LIO_LIType I MAGEs affect MB cell proliferation and apoptosis. C_LIO_LIMAGEs are potential biomarkers and therapeutic targets for group 3 MBs. C_LI Importance of the StudyThis study is the first comprehensive analysis of all Type I MAGE CTAs (MAGEA, -B, and -C subfamily members) in pediatric MBs. Our results show that more than 60% of group 3 MBs express MAGE genes, which are required for the viability and growth of cells in which they are expressed. Collectively, these data provide novel insights into the antigen landscape of pediatric MBs. The activation of MAGE genes in group 3 MBs presents potential stratifying and therapeutic options. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=175 SRC="FIGDIR/small/594201v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1ac274aorg.highwire.dtl.DTLVardef@1479944org.highwire.dtl.DTLVardef@19f5aaforg.highwire.dtl.DTLVardef@fad069_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Enhanced stress tolerance through reduction of G3BP and suppression of stress granules

Stress granules (SG) are membrane-less ribonucleoprotein condensates that form in response to various stress stimuli via phase separation. SG act as a protective mechanism to cope with acute stress, but persistent SG have cytotoxic effects that are associated with several age-related diseases. Here, we demonstrate that the testis-specific protein, MAGE-B2, increases cellular stress tolerance by suppressing SG formation through translational inhibition of the key SG nucleator G3BP. MAGE-B2 reduces G3BP protein levels below the critical concentration for phase separation and suppresses SG initiation. Importantly, knockout of the MAGE-B2 mouse ortholog confers hypersensitivity of the male germline to heat stress in vivo. Thus, MAGE-B2 provides cytoprotection to maintain mammalian spermatogenesis, a highly thermo-sensitive process that must be preserved throughout reproductive life. These results demonstrate a mechanism that allows for tissue-specific resistance against stress through fine-tuning phase separation and could aid in the development of male fertility therapies.

cell biology↗