Biology subjects

Andren, A.

Publications and source records attributed to Andren, A..

11 recordsLinked to original sources

bioRxiv2024

Glutaminase deficiency in rod photoreceptors disrupts nonessential amino acid levels to activate the integrated stress response and induce rapid degeneration

Photoreceptor loss results in vision loss in many blinding diseases, and metabolic dysfunction underlies photoreceptor degeneration. So, exploiting photoreceptor metabolism is an attractive strategy to prevent vision loss. Yet, the metabolic pathways that maintain photoreceptor health remain largely unknown. Here, we investigated the dependence of photoreceptors on glutamine (Gln) catabolism. Gln is converted to glutamate via glutaminase (GLS), so mice lacking GLS in rod photoreceptors were generated to inhibit Gln catabolism. Loss of GLS produced rapid rod photoreceptor degeneration. In vivo metabolomic methodologies and metabolic supplementation identified Gln catabolism as critical for glutamate and aspartate biosynthesis. Concordant with this amino acid deprivation, the integrated stress response (ISR) was activated with protein synthesis attenuation, and inhibiting the ISR delayed photoreceptor loss. Furthermore, supplementing asparagine, which is synthesized from aspartate, delayed photoreceptor degeneration. Hence, Gln catabolism is integral to photoreceptor health, and these data reveal a novel metabolic axis in these metabolically-demanding neurons.

cell biology↗

bioRxiv2023

H2S preconditioning induces long-lived perturbations in O2 metabolism

Hydrogen sulfide exposure in moderate doses can induce profound but reversible hypometabolism in mammals. At a cellular level, H2S inhibits the electron transport chain (ETC), augments aerobic glycolysis, and glutamine-dependent carbon utilization via reductive carboxylation; however, the durability of these changes is unknown. We report that despite its volatility, H2S preconditioning increases P50(O2), the O2 pressure for half maximal cellular respiration, and has pleiotropic effects on oxidative metabolism that persist up to 24-48 h later. Notably, cyanide, another complex IV inhibitor, does not induce this type of metabolic memory. Sulfide-mediated prolonged fractional inhibition of complex IV by H2S is modulated by sulfide quinone oxidoreductase, which commits sulfide to oxidative catabolism. Since induced hypometabolism can be beneficial in disease settings that involve insufficient or interrupted blood flow, our study has important implications for attenuating reperfusion-induced ischemic injury, and/or prolonging shelf life of biologics like platelets.

biochemistry↗

bioRxiv2023

Ras-dependent activation of BMAL2 regulates hypoxic metabolism in pancreatic cancer

KRAS is the archetypal oncogenic driver of pancreatic cancer. To identify new modulators of KRAS activity in human pancreatic ductal adenocarcinoma (PDAC), we performed regulatory network analysis on a large collection of expression profiles from laser capture microdissected samples of PDAC and benign controls. We discovered that BMAL2, a member of the PAS family of transcription factors, promotes tumor initiation, progression, and post-resection survival, and is highly correlated with KRAS activity. Functional analysis of BMAL2 target genes suggested a role in regulating the hypoxia response, a hallmark of PDAC. Knockout of BMAL2 in multiple human PDAC cell lines reduced cancer cell viability, invasion, and glycolysis, leading to broad dysregulation of cellular metabolism, particularly under hypoxic conditions. We find that BMAL2 directly regulates hypoxia-responsive target genes and is necessary for the stabilization of HIF1A under low oxygen conditions, while simultaneously destabilizing HIF2A. Notably, in vivo xenograft studies demonstrated that BMAL2 loss significantly impairs tumor growth and reduces tumor volume, underscoring its functional importance in tumor progression. We conclude that BMAL2 is a master transcriptional regulator of hypoxia responses in PDAC that works downstream of KRAS signaling, possibly serving as a long-sought molecular switch that distinguishes HIF1A- and HIF2A-dependent modes of hypoxic metabolism. Statement of SignificanceWe annotate the landscape of KRAS-associated transcriptional drivers of pancreatic cancer initiation, progression, and overall survival, leading to the identification of BMAL2 as a novel regulator of hypoxic metabolism. BMAL2 helps execute the oncogenic transcriptional programs of KRAS and serves as a long-sought switch between HIF1A- and HIF2A-dependent modes of hypoxic metabolism.

cancer biology↗

bioRxiv2023

Sulfide oxidation promotes hypoxic angiogenesis and neovascularization

Angiogenic programming in the vascular endothelium is a tightly regulated process to maintain tissue homeostasis and is activated in tissue injury and the tumor microenvironment. The metabolic basis of how gas signaling molecules regulate angiogenesis is elusive. Herein, we report that hypoxic upregulation of NO synthesis in endothelial cells reprograms the transsulfuration pathway and increases H2S biogenesis. Furthermore, H2S oxidation by mitochondrial sulfide quinone oxidoreductase (SQOR) rather than downstream persulfides, synergizes with hypoxia to induce a reductive shift, limiting endothelial cell proliferation that is attenuated by dissipation of the mitochondrial NADH pool. Tumor xenografts in whole-body WBCreSQORfl/fl knockout mice exhibit lower mass and reduced angiogenesis compared to SQORfl/fl controls. WBCreSQORfl/fl mice also exhibit reduced muscle angiogenesis following femoral artery ligation, compared to controls. Collectively, our data reveal the molecular intersections between H2S, O2 and NO metabolism and identify SQOR inhibition as a metabolic vulnerability for endothelial cell proliferation and neovascularization. HighlightsO_LIHypoxic induction of *NO in endothelial cells inhibits CBS and switches CTH reaction specificity C_LIO_LIHypoxic interruption of the canonical transsulfuration pathway promotes H2S synthesis C_LIO_LISynergizing with hypoxia, SQOR deficiency induces a reductive shift in the ETC and restricts proliferation C_LIO_LISQOR KO mice exhibit lower neovascularization in tumor xenograft and hind limb ischemia models C_LI

biochemistry↗

bioRxiv2022

PINK1 supports colorectal cancer growth by regulating the labile iron pool.

Mitophagy is a cargo-specific autophagic process that recycles damaged mitochondria to promote mitochondrial turnover. PTEN-induced putative kinase 1 (PINK1) mediates the canonical mitophagic pathway. We show that PINK1 expression is positively correlated with decreased colon cancer survival, and mitophagy is required for colon cancer growth following nutrient stress. However, the mechanism by which PINK1 maintains colon cancer growth remains equivocal. Inducible knockdown (KD) of PINK1 in a panel of colon cancer cell lines inhibited colon cancer cell proliferation, whereas disruption of other mitophagy receptors did not similarly impact cellular proliferation. Mechanistically, we observed a decrease in mitochondrial respiration, membrane hyperpolarization, accumulation of mitochondrial DNA, and depletion of antioxidant glutathione following PINK1 KD. Mitochondria are important hubs for storing iron and synthesizing iron-dependent cofactors such as heme and iron sulfur clusters. An increase iron storage protein ferritin and a decrease labile iron pool was observed in PINK1 KD cells. However, neither total cellular iron nor markers of iron starvation/overload were affected. Cellular iron storage and the labile iron pool are maintained via autophagic degradation of ferritin (ferritinophagy). Overexpressing nuclear receptor coactivator 4 (NCOA4), a key adaptor for ferritinophagy, rescued cell growth and the labile iron pool in PINK1 KD cells. We demonstrate that PINK1 regulates intracellular iron availability by integrating mitophagy to ferritinophagy. In conclusion, these results indicate that PINK1 is essential for maintaining intracellular iron homeostasis to support survival and growth in colorectal cancer cells.

cancer biology↗

bioRxiv2021

OXPHOS Promotes Apoptotic Resistance and Persistence in TH17 cells

Apoptotic cell death is a cell-intrinsic, immune tolerance mechanism that regulates the magnitude and resolution of T cell-mediated responses. Evasion of apoptosis is critical for the generation of memory T cells, as well as autoimmune T cells, and knowledge of the mechanisms that enable resistance to apoptosis will provide insight into ways to modulate their activity during protective and pathogenic responses. IL-17-producing CD4 T cells (TH17s) are long-lived, memory cells. These features enable their role in host defense, chronic inflammatory disorders, and anti-tumor immunity. A growing number of reports now indicate that TH17s in vivo require mitochondrial oxidative phosphorylation (OXPHOS), a metabolic phenotype that is poorly induced in vitro. To elucidate the role of OXPHOS in TH17 processes, we developed a system to polarize TH17s that metabolically resembled their in vivo counterparts. We discovered that directing TH17s to use OXPHOS promotes mitochondrial fitness, glutamine anaplerosis, and an anti-apoptotic phenotype marked by high BCL-XL and low BIM. Through competitive co-transfer experiments and tumor studies, we further revealed how OXPHOS protects TH17s from cell death while enhancing their persistence in the periphery and tumor microenvironment. Together, our work demonstrates a non-classical role of metabolism in regulating TH17 cell fate and highlights the potential for therapies that target OXPHOS in TH17-driven diseases.

immunology↗

bioRxiv2021

Multi-omic Characterization of Pancreatic Cancer-Associated Macrophage Polarization Reveals Deregulated Metabolic Programs Driven by the GMCSF-PI3K Pathway

The pancreatic ductal adenocarcinoma (PDA) microenvironment is composed of a variety of cell types and marked by extensive fibrosis and inflammation. Tumor-associated macrophages (TAM) are abundant, and they are important mediators of disease progression and invasion. TAMs are polarized in situ to a tumor promoting and immunosuppressive phenotype via cytokine signaling and metabolic crosstalk from malignant epithelial cells and other components of the tumor microenvironment (TME). However, the specific distinguishing features and functions of TAMs remain poorly defined. Here, we generated tumor-educated macrophages (TEM) in vitro and performed detailed, multi-omic characterization (i.e. transcriptomics, proteomics, metabolomics). Our results reveal unique genetic and metabolic signatures of TEMs, the veracity of which were queried against our in-house single cell RNA sequencing (scRNA-seq) dataset of human pancreatic tumors. This analysis identified expression of novel, metabolic TEM markers in human pancreatic TAMs, including ARG1, ACLY, and TXNIP. We then utilized our TEM model system to study the role of mutant Kras signaling in cancer cells on TEM polarization. This revealed an important role for GM-CSF and lactate on TEM polarization, molecules released from cancer cells in a mutant Kras-dependent manner. Lastly, we demonstrate that GM-CSF dysregulates TEM gene expression and metabolism through PI3K-AKT pathway signaling. Collectively, our results define new markers and programs to classify pancreatic TAMs, how these are engaged by cancer cells, and the precise signaling pathways mediating polarization.

cancer biology↗

bioRxiv2021

Sirtuin 5 levels are limiting in preserving cardiac function and suppressing fibrosis in response to pressure overload

Heart failure (HF) is defined as an inability of the heart to pump blood adequately to meet the bodys metabolic demands. HF with reduced systolic function is characterized by cardiac hypertrophy, ventricular fibrosis and remodeling, and decreased cardiac contractility, leading to cardiac functional impairment and death. Transverse aortic constriction (TAC) is a well-established model for inducing hypertrophy and HF in rodents. Mice globally deficient in sirtuin 5 (SIRT5), a NAD+-dependent deacylase, are hypersensitive to cardiac stress and display increased mortality after TAC. Prior studies assessing SIRT5 functions in the heart have all employed loss-of-function approaches. In this study, we generated SIRT5 overexpressing (SIRT5OE) mice, and evaluated their response to chronic pressure overload induced by TAC. Compared to littermate controls, SIRT5OE mice were protected from left ventricular dilation and impaired ejection fraction, adverse functional consequences of TAC. Transcriptomic analyses revealed that SIRT5 suppresses key HF sequelae, including the metabolic switch from fatty acid oxidation to glycolysis, immune activation, and increased fibrotic signaling. We conclude that SIRT5 is a limiting factor in the preservation of cardiac function in response to experimental pressure overload.

pathology↗

bioRxiv2021

Nutrient profiling reveals extracellular uridine as a fuel for pancreatic cancer through uridine phosphorylase 1

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease characterized by high invasiveness, therapeutic resistance, and metabolic aberrations. Although altered metabolism drives PDA growth and survival, the complete spectrum of metabolites used as nutrients by PDA remains largely unknown. Here, we aimed to determine novel nutrients utilized by PDA. We assessed how >175 metabolites impacted metabolic activity in 19 PDA cell lines under nutrient-restricted conditions. This analysis identified uridine as a novel metabolite driver of PDA survival in glucose-deprived conditions. Uridine utilization strongly correlated with expression of the enzyme uridine phosphorylase 1 (UPP1). Metabolomics profiling, notably 13C-stable isotope tracing, revealed that uridine-derived ribose is the relevant component supporting redox balance, survival, and proliferation in glucose-deprived PDA cells. We demonstrate that UPP1 catabolizes uridine, shunting its ribose component into central carbon metabolism to support glycolysis, the tricarboxylic acid (TCA) cycle and nucleotide biosynthesis. Compared to non-tumoral tissues, we show that PDA tumors express high UPP1, which correlated with poor overall survival in multiple patient cohorts. Further, uridine is enriched in the pancreatic tumor microenvironment, and we demonstrate that this may be provided in part by tumor associated macrophages. Finally, we found that inhibition of UPP1 restricted the ability of PDA cells to use uridine, and that UPP1 knockout impairs tumor growth in vivo. Our data identifies uridine catabolism as a critical aspect of compensatory metabolism in nutrient-deprived PDA cells, suggesting a novel metabolic axis for PDA therapy.

cancer biology↗

bioRxiv2020

The Pancreatic Tumor Microenvironment Buffers Redox Imbalance Imposed by Disrupted Mitochondrial Metabolism

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDA) restricts vascularization and, consequently, access to blood-derived nutrients and oxygen, which impacts tumor growth. Intracellular redox imbalance is another restraint on cellular proliferation, yet it is unknown if the TME contributes to the maintenance of redox homeostasis in PDA cells. Here, we demonstrate that the loss of mitochondrial glutamate-oxaloacetate transaminase 2 (GOT2), a component in the malate-aspartate shuttle, disturbs redox homeostasis and halts proliferation of PDA cells in vitro. In contrast, GOT2 inhibition has no effect on in vivo tumor growth or tumorigenesis in an autochthonous model. We propose that this discrepancy is explained by heterocellular pyruvate exchange from the TME, including from cancer associated fibroblasts. More broadly, pyruvate similarly confers resistance to inhibitors of mitochondrial respiration. Genetic or pharmacologic inhibition of pyruvate uptake or metabolism abrogated pyruvate-mediated alleviation of reductive stress from NADH buildup. In sum, this work describes a potential resistance mechanism mediated by metabolic crosstalk within the pancreatic TME. These findings have important implications for metabolic treatment strategies since several mitochondrial inhibitors are currently in clinical trials for PDA and other cancers.

cancer biology↗

bioRxiv2020

GOT1 Inhibition Primes Pancreatic Cancer for Ferroptosis through the Autophagic Release of Labile Iron

Pancreatic ductal adenocarcinoma (PDA) is one of the deadliest solid malignancies, with a 5-year survival rate at ten percent. PDA have unique metabolic adaptations in response to cell-intrinsic and environmental stressors, and identifying new strategies to target these adaptions is an area of active research. We previously described a dependency on a cytosolic aspartate aminotransaminase (GOT1)-dependent pathway for NADPH generation. Here, we sought to identify metabolic dependencies induced by GOT1 inhibition that could be exploited to selectively kill PDA. Using pharmacological methods, we identified cysteine, glutathione, and lipid antioxidant function as metabolic vulnerabilities following GOT1 withdrawal. Targeting any of these pathways was synthetic lethal in GOT1 knockdown cells and triggered ferroptosis, an oxidative, non-apoptotic, iron-dependent form of cell death. Mechanistically, GOT1 inhibition promoted the activation of autophagy in response to metabolic stress. This enhanced the availability of labile iron through ferritinophagy, the autolysosome-mediated degradation of ferritin. In sum, our study identifies a novel biochemical connection between GOT1, iron regulation, and ferroptosis, and suggests the rewired malate-aspartate shuttle plays a role in protecting PDA from severe oxidative challenge. HighlightsO_LIPDA exhibit varying dependence on GOT1 for in vitro and in vivo growth. C_LIO_LIExogenous cystine, glutathione synthesis, and lipid antioxidant fidelity are essential under GOT1 suppression. C_LIO_LIGOT1 inhibition sensitizes pancreatic cancer cell lines to ferroptosis. C_LIO_LIGOT1 inhibition represses anabolic metabolism and promotes the release of iron through autophagy. C_LI

cancer biology↗