Biology subjects

Tsai, P.-Y.

Publications and source records attributed to Tsai, P.-Y..

9 recordsLinked to original sources

bioRxiv2026

SIRT5 acts in the tumor microenvironment via endothelial cell metabolism to support breast cancer growth

Triple-negative breast cancer (TNBC) is characterized by aggressive progression and poor prognosis, partly due to abnormal angiogenesis. While the metabolic reprogramming of tumor cells is well characterized, the metabolic regulation of tumor-associated endothelial cells (ECs) remains unclear. Here, we identified the mitochondrial deacylase SIRT5, which has established tumor-promoting roles in TNBC cells, as a key regulator of endothelial metabolic homeostasis and tumor angiogenesis. SIRT5-deficient host mice showed significant defects in supporting the growth of orthotopic SIRT5-proficient mammary tumor transplants, and the resulting neoplasms showed defects in tumor vascularization. In a 3D microfluidic vessel-on-chip model, SIRT5 loss compromised vascular barrier integrity and EC sprouting. Mechanistically, SIRT5-deficient ECs exhibited diminished mitochondrial respiratory capacity but apparently normal glycolysis. SIRT5 loss also caused increased mitochondrial reactive oxygen species levels, and a mitochondrial antioxidant rescued the endothelial cell defects following SIRT5 loss, indicating that SIRT5-mediated mitochondrial redox homeostasis in the tumor microenvironment is necessary to maintain vascular function. Orthotopic co-transplantation of TNBC and EC cells with or without SIRT5 knockdown demonstrated that endothelial SIRT5 promotes increased tumor growth in vivo. These results suggest that targeting SIRT5 offers a potential therapeutic strategy to disrupt tumor angiogenesis and suppress TNBC progression by targeting the metabolic vulnerabilities of the tumor endothelium.

cancer biology↗

bioRxiv2024

The Mitochondrial Brown Adipose Tissue Maintenance Factor Nipsnap1 Interfaces Directly with the Beta-Oxidation Protein Machinery.

BackgroundThe activation of brown adipose tissue (BAT) is associated with improved metabolic health in humans. We previously identified the mitochondrial protein 4-Nitrophenylphosphatase Domain and Non-Neuronal SNAP25-Like 1 (Nipsnap1) as a novel regulatory factor that integrates with lipid metabolism and is critical to sustain the long-term activation of BAT, but the precise mechanism and function of Nipsnap1 is unknown. ObjectivesDefine how the regulatory factor Nipsnap1 integrates with lipid metabolism. MethodsWe generated adeno-associated viral (AAV) constructs that overexpress Nipsnap1 in the thermogenic fat of mice. We then measured both whole-body and cellular mitochondrial metabolism and mapped the first Nipsnap1 interacting protein-protein network. ResultsHerein, we show that adipose-specific overexpression of Nipsnap1 in mice increases energy expenditure through the utilization of lipids as an energy substrate. The increase in energy expenditure results in reduced weight gain. Additionally, we show that Nipsnap1 overexpression in primary adipocytes increases lipid beta-oxidation. Moreover, we mapped the first protein- protein network of Nipsnap1 in brown adipocytes and show that Nipsnap1 interacts with proteins that regulate both peroxisomal and mitochondrial fatty acid beta-oxidation. ConclusionThis study elucidates a mechanistic function of Nipsnap1 in thermogenic fat where Nipsnap1 facilitates a functional connection between peroxisomal and mitochondrial beta-oxidation pathways. By enhancing lipid utilization as energy substrates, Nipsnap1 plays a pivotal role in sustaining thermogenic fat activation to increase energy expenditure. These findings underscore the potential of Nipsnap1 as a therapeutic target for metabolic health.

cell biology↗

bioRxiv2024

Small molecule oxybutynin rescues proliferative capacity of complex III-defective MPCs

Mitochondrial disease encompasses a group of genetically inherited disorders hallmarked by an inability of the respiratory chain to produce sufficient ATP. These disorders present with multisystemic pathologies that predominantly impact highly energetic tissues such as skeletal muscle. There is no cure or effective treatment for mitochondrial disease. We have discovered a small molecule known as oxybutynin that can bypass Complex III mitochondrial dysfunction in primary murine and human skeletal muscle progenitor cells (MPCs). Oxybutynin administration improves MPC proliferative capacity, enhances cellular glycolytic function, and improves myotube formation. Mechanistically, results from our isothermal shift assay indicates that oxybutynin interacts with a suite of proteins involved in mRNA processing which then trigger the upregulation biological pathways to circumvent CIII mitochondrial dysfunction. Taken together, we provide evidence for the small molecule oxybutynin as a potential therapeutic candidate for the future treatment of CIII mitochondrial dysfunction.

cell biology↗

bioRxiv2024

AQP1- A regulatory factor associated with brown adipose tissue silencing

The activation of non-shivering thermogenesis (NST) in brown adipose tissue (BAT) by environmental cold challenge yields strong metabolic benefit in the face of diet-induced obesity (DIO). Yet, a critical barrier to leveraging brown fat NST for therapeutic use against metabolic disease is that BAT is silenced and inactive at physiological ambient temperature conditions in humans. The mechanisms that govern this silencing process remain poorly understood. Here, we identified a putative BAT-silencing factor, aquaporin-1 (AQP1), in brown fat from wild-type (WT) mice via proteomics analysis. We generated the first BAT-specific AQP1 knockout mice (AQP1-KO) and revealed that AQP1-KO could activate NST under BAT silencing environmental conditions and that the AQP1-KO mice were significantly protected against DIO and metabolic dysfunction compared to Flox controls. We found that AQP1-KO mice on high fat diet (HFD) had reduced weight gain through reductions in fat mass, improved glucose tolerance, and increased whole body energy expenditure compared to Flox control mice. Mechanistically, we show that AQP1 ablation in mice had upregulated gene expression related to the electron transport chain (ETC) and mitochondrial translation contributing to the activation of NST under BAT environmental silenced conditions. Significance StatementNovel strategies to combat obesity-associated metabolic dysfunction are urgently needed to curb the growing obesity epidemic. Investigation of brown adipose tissue (BAT) silencing mechanisms may reveal novel therapeutic targets that when ablated, can activate BAT to increase energy expenditure and protect subjects against the metabolic dysfunction associated with obesity. We have identified Aquaporin 1 (AQP1) as a putative BAT silencer regulatory factor and show through the generation of the first BAT-specific aquaporin-1 knockout (AQP1-KO) mouse that BAT can be activated under environmental silencing conditions. We further show that these mice are protected against diet-induced obesity, with improved glucose tolerance, and increased energy expenditure. These findings highlight AQP1 as a promising therapeutic target in the emerging research field of BAT silencers.

molecular biology↗

bioRxiv2023

DNAJB1-PRKACA fusion protein-regulated LINC00473 promotes tumor growth and alters mitochondrial fitness in fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is a rare liver cancer that disproportionately affects adolescents and young adults. Currently, no standard of care is available and there remains a dire need for new therapeutics. Most patients harbor the fusion oncogene DNAJB1-PRKACA (DP fusion), but clinical inhibitors are not yet developed and it is critical to identify downstream mediators of FLC pathogenesis. Here, we identify long non-coding RNA LINC00473 among the most highly upregulated genes in FLC tumors and determine that it is strongly suppressed by RNAi-mediated inhibition of the DP fusion in FLC tumor epithelial cells. We show by loss- and gain-of-function studies that LINC00473 suppresses apoptosis, increases the expression of FLC marker genes, and promotes FLC growth in cell-based and in vivo models of disease. Mechanistically, LINC00473 plays an important role in promoting glycolysis and altering mitochondrial activity. Specifically, LINC00473 knockdown leads to increased spare respiratory capacity, an indicator of mitochondrial fitness. Overall, we propose that LINC00473 could be a viable target for this devastating disease. HighlightsFibrolamellar carcinoma (FLC) is a lethal liver cancer lacking effective therapeutic options. Ma et al. demonstrate that primate-specific RNA LINC00473 is enriched in tumor epithelial cells and functions to promote FLC growth and dysregulate cellular energetics, unveiling an important mechanism downstream of the fusion oncogene, DNAJB1-PRKACA, in FLC pathogenesis. In BriefO_LILINC00473 is consistently elevated in primary FLC tumor tissue from different patient cohorts and in multiple disease models. C_LIO_LIDP fusion, the signature oncoprotein of FLC, drives LINC00473 expression. C_LIO_LILINC00473 promotes FLC growth via anti-apoptotic function. C_LIO_LILINC00473 modulates FLC energetics by promoting glycolysis and altering mitochondrial fitness. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/543290v2_ufig1.gif" ALT="Figure 1"> View larger version (56K): org.highwire.dtl.DTLVardef@20e0f2org.highwire.dtl.DTLVardef@904fbborg.highwire.dtl.DTLVardef@62af84org.highwire.dtl.DTLVardef@f114be_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

ADO-MEDIATED SYNTHESIS OF TAURINE ALTERS THE CHROMATIN LANDSCAPE OF INGUINAL ADIPOSE TISSUE TO ENHANCE NON-SHIVERING THERMOGENESIS

Non-shivering thermogenesis (NST) has strong potential to combat obesity, however, a safe molecular approach to activate this process has not yet been identified. The sulfur amino acid taurine has the ability to safely activate NST and confer protection against obesity and metabolic disease in both mice and humans, but the mechanism of action is unknown. In this study, we discover that a suite of taurine biosynthetic enzymes, especially that of cysteamine dioxygenase (ADO), significantly increases in response to {beta}3 adrenergic signaling in inguinal tissues (IWAT) in order increase intracellular concentrations of taurine. We further show that ADO is critical for thermogenic mitochondrial function as its ablation in thermogenic adipocytes significantly reduces taurine levels which lead to declines in mitochondrial oxygen consumption rates. Finally, we demonstrate via assay for transposase-accessible chromatin with sequencing (ATAC-Seq) that taurine supplementation has the ability to remodel the chromatin landscape to increase the chromatin accessibility and transcription of genes, such as glucose-6-phosphate isomerase 1 (Gpi1), that are critical for NST. Taken together, our studies highlight a potential mechanism for taurine in the activation of NST that can be leveraged toward the treatment of obesity and metabolic disease.

cell biology↗

bioRxiv2022

Nipsnap1- A Regulatory Factor Required for Long-Term Maintenance of Non-Shivering Thermogenesis

The molecular activation of non-shivering thermogenesis (NST) has strong potential to combat obesity and metabolic disease. However, the mechanisms surrounding the maintenance of NST once it is fully activated, remain unexplored. Here, we present 4-Nitrophenylphosphatase Domain and Non-Neuronal SNAP25-Like 1 (Nipsnap1) as a critical regulator of long-term thermogenic maintenance in brown adipose tissue (BAT). Nipsnap1 localizes to the mitochondrial matrix and increases its transcript and protein levels in response to both chronic cold and {beta}3 adrenergic signaling. Through the generation of BAT-specific Nipsnap1 knockout mice (N1-KO), we show that these mice are unable to sustain activated energy expenditure and fail to protect their body temperature in the face of an extended cold challenge. Mechanistically, we demonstrate that Nipsnap1 integrates with lipid metabolism and BAT-specific ablation of Nipsnap1 leads to severe defects in {beta}-oxidation capacity. Our findings identify Nipsnap1 as a potent regulator of long-term NST maintenance.

molecular biology↗

bioRxiv2022

Equilibrative Nucleoside Transporter 3 is an IFN-stimulated Gene that Facilitates Viral Genome Release

An increasing body of evidence emphasizes the role of metabolic reprogramming in immune cells to fight off infections. However, little is known about the regulation of metabolite transporters that facilitate and support metabolic demands. In this study, we found that equilibrative nucleoside transporter 3 (ENT3) expression is part of the innate immune response, and is rapidly upregulated upon bacterial and viral infection. The transcription of ENT3 is directly under the regulation of IFN-induced signaling, positioning this metabolite transporter as an Interferon-stimulated gene (ISG). Moreover, we unveil that several viruses, including SARS-CoV2, require ENT3 to facilitate their entry into the cytoplasm. The removal or suppression of ENT3 expression is sufficient to significantly decrease viral replication in vitro and in vivo.

immunology↗

bioRxiv2020

Adaptation of pancreatic cancer cells to nutrient deprivation is reversible and requires glutamine synthetase stabilization by mTORC1

Pancreatic ductal adenocarcinoma (PDA) is a lethal, therapy-resistant cancer that thrives in a highly desmoplastic, nutrient-deprived microenvironment. Several studies investigated the effects of depriving PDA of either glucose or glutamine alone. However, the consequences on PDA growth and metabolism of limiting both preferred nutrients have remained largely unknown. Here, we report the selection for clonal human PDA cells that survive and adapt to limiting levels of both glucose and glutamine. We find that adapted clones exhibit increased growth in vitro and enhanced tumor-forming capacity in vivo. Mechanistically, adapted clones share common transcriptional and metabolic programs, including amino acid use for de novo glutamine and nucleotide synthesis. They also display enhanced mTORC1 activity that prevents the proteasomal degradation of glutamine synthetase (GS), the rate-limiting enzyme for glutamine synthesis. This phenotype is notably reversible, with PDA cells acquiring alterations in open chromatin upon adaptation. Silencing of GS suppresses the enhanced growth of adapted cells and mitigates tumor growth. These findings identify non-genetic adaptations to nutrient deprivation in PDA and highlight GS as a dependency that could be targeted therapeutically in pancreatic cancer patients. SignificancePancreatic ductal adenocarcinoma (PDA) is a highly lethal malignancy with no effective therapies. PDA aggressiveness partly stems from its ability to grow within a uniquely dense stroma restricting nutrient access. This study demonstrates that PDA clones that survive chronic nutrient deprivation acquire reversible non-genetic adaptations allowing them to switch between metabolic states optimal for growth under nutrient-replete or nutrient-deprived conditions. One contributing factor to this adaptation mTORC1 activation, which stabilizes glutamine synthetase (GS) necessary for glutamine generation in nutrient-deprived cancer cells. Our findings imply that although total GS levels may not be a prognostic marker for aggressive disease, GS inhibition is of high therapeutic value, as it targets specific cell clusters adapted to nutrient starvation, thus mitigating tumor growth.

cancer biology↗