Project description:Glioblastoma, the most frequent primary malignant brain tumor in adults, is characterized by profound yet dynamic hypoxia and nutrient depletion. To sustain survival and proliferation, tumor cells are compelled to acquire metabolic plasticity with the induction of adaptive metabolic programs. We have previously shown that the peroxisome proliferator–activated receptor γ coactivator (PGC)-1α is a key regulator of cellular respiration, proliferation and invasion in glioblastoma. Here, we interrogated the pathways necessary to enable processing of nutrients other than glucose. We employed genetic approaches (PGC-1α stable/inducible overexpression, CRISPR/Cas9 knockout), pharmacological interventions with a novel inhibitor of adenosine monophosphate kinase (AMPK) in glioblastoma cell culture systems and a proteomic approach to investigate mechanisms of metabolic plasticity towards non-glucose nutrients including galactose, fatty acids and ketone bodies. Moreover, spatially resolved multi-omic analysis integrating transcriptomics and matrix-assisted laser desorption/ionization (MALDI) was used to correlate the gene expression pattern of PGC-1α with local metabolic and genetic architecture in human glioblastoma tissue sections. A nutrient switch from glucose to galactose, ketone bodies or fatty acids triggered an initial activation of AMPK, which in turn activated PGC-1α-dependent adaptive programs towards mitochondrial metabolism. This sensor-effector mechanism was essential for metabolic plasticity with both functional AMPK and PGC-1α necessary for survival and growth of cells under non-glucose nutrient sources. In human glioblastoma tissue specimens, PGC-1α-expression correlated with non-hypoxic tumor niches defining a specific metabolic compartment. Our findings reveal a cell-intrinsic nutrient sensing and switching mechanism. The exposure to alternative fuels triggers a starvation signal that subsequently is passed on via AMPK and PGC-1α to induce adaptive programs which result in upregulation of the enzymatic machinery necessary for broader spectrum nutrient metabolism. The integration of spatially resolved transcriptomic data from human glioblastoma samples confirms the relevance of PGC-1α especially in non-hypoxic tumor regions. Thus, the AMPK-PGC-1α axis is a candidate for therapeutic inhibition in glioblastoma.
Project description:The mechanistic underpinnings of the fasting response in skeletal muscle is still poorly understood. We therefore investigated the role of the transcriptional coactivator PGC-1beta (peroxisome proliferator-activated receptor gamma coactivator 1beta) in this context. To do so, the fasting response in quadriceps muscle was assessed in fed and 24 hours fasted mice and compared between wildtype and PGC-1beta muscle-specific knockout mice (both on a C57Bl6/J background). Morphological, functional and transcriptional parameters were determined. The results indicate that PGC-1beta significantly contributes to the metabolic remodelling of skeletal muscle to fasting by promoting catabolic pathways that help to improve energy production and sequester substrates for gluconeogenesis. Accordingly, muscle-specific knockouts for PGC-1beta exhibit mitigated protein degradation and muscle fiber atrophy. These findings contribute to our understanding of muscle plasticity in different metabolic contexts.
Project description:LKB1 encodes a Ser/Thr kinase and acts as an evolutionarily conserved sensor of cellular energy status in eukaryotic cells. LKB1 functions as the major upstream kinase to phosphorylate AMPK and 12 other AMPK-related kinases, which is required for their activation in many cellular contexts. Once activated, AMPK and AMPK-related kinases phosphorylate a diverse array of downstream effectors to switch on ATP-generating catabolic processes and switch off ATP-consuming anabolic processes, thus restoring energy balance during periods of energetic stress. To study the role and mechanisms of Lkb1 in the regulation of hematopoietic stem cell (HSC) biology, we performed transcriptome analysis of sorted LSK (Lin-, Sca-1+, c-Kit+) cells from Lkb1 WT and KO bone marrows at 1 day post-completing tamoxifen injection (DPI). To identify more proximal molecular effects, we chose 1 DPI due to the modest phenotypes in Lkb1 KO mice, yet documentation of efficient Lkb1 deletion in LSK cells at this very early time point.
Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of primary hepatocytes and intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the transcriptional response to metformin. Transcriptionally, AMPK and mTORC1 were both important for regulation of anabolic metabolism and inflammatory programs triggered by metformin treatment.
Project description:A healthy metabolism relies on the precise regulation of anabolic and catabolic pathways. Insulin and AMPK serve as key regulators of anabolism and catabolism, respectively. While insulin deficiency markedly impairs anabolism, insulin resistance in obesity leads to metabolic dysfunction especially via altered brain insulin receptor activity. Density-enhanced phosphatase-1 (DEP-1), a ubiquitously expressed receptor-like tyrosine phosphatase, has been described as an insulin receptor phosphatase in peripheral tissues. Strikingly, diet-induced obese mice exhibit elevated DEP-1 expression in the brain. This study uncovers DEP-1's role in brain insulin signaling and its impact on ana- and catabolic pathways. Neurons lacking DEP-1 exhibit heightened insulin receptor phosphorylation and downstream signaling upon acute insulin stimulation. Surprisingly, this is accompanied by simultaneous activation of the AMPK cascade due to increased phospholipase C gamma 1 signaling. These opposing pathways in male DEP-1 forebrain/hippocampus-specific knockout mice result in heightened lipolysis in white adipose tissue, and enhanced fat oxidation in brown adipose tissue due to elevated sympathetic activation and enhanced beta-adrenergic receptor expression.
Project description:LKB1 encodes a Ser/Thr kinase and acts as an evolutionarily conserved sensor of cellular energy status in eukaryotic cells. LKB1 functions as the major upstream kinase to phosphorylate AMPK and 12 other AMPK-related kinases, which is required for their activation in many cellular contexts. Once activated, AMPK and AMPK-related kinases phosphorylate a diverse array of downstream effectors to switch on ATP-generating catabolic processes and switch off ATP-consuming anabolic processes, thus restoring energy balance during periods of energetic stress. To study the role and mechanisms of Lkb1 in the regulation of hematopoietic stem cell (HSC) biology, we performed transcriptome analysis of sorted LSK (Lin-, Sca-1+, c-Kit+) cells from Lkb1 WT and KO bone marrows at 1 day post-completing tamoxifen injection (DPI). To identify more proximal molecular effects, we chose 1 DPI due to the modest phenotypes in Lkb1 KO mice, yet documentation of efficient Lkb1 deletion in LSK cells at this very early time point. We treated Lkb1 L/L rosa26CreERT2 and Lkb1 L/L mice (C57BL/Ka-CD45.2:Thy-1.1 background) with Tamoxifen for 5 days to somatically delete Lkb1 in adult mice, and generated Lkb1 WT and KO mice. At 1 DPI, we prepared single-cell suspensions from bone marrow (from femoral and tibial bones), and stained and sorted LSK populations using FACSAria (Becton Dickinson, Mountain View, CA). The RNA was extracted from sorted LSK cells, amplified and subjected to gene profiling. The samples include 3 Lkb1 WT (Lkb1 WT 5-7) and 4 Lkb1 KO (Lkb1 KO 4-7) replicates.
Project description:Skeletal muscle tissue shows an extraordinary cellular plasticity, but the underlying molecular mechanisms are still poorly understood. Here we use a combination of experimental and computational approaches to unravel the complex transcriptional network of muscle cell plasticity centered on the peroxisome proliferator-activated receptor M-NM-3 coactivator 1M-NM-1 (PGC-1M-NM-1), a regulatory nexus in endurance training adaptation. By integrating data on genome-wide binding of PGC-1M-NM-1 and gene expression upon PGC-1M-NM-1 over-expression with comprehensive computational prediction of transcription factor binding sites (TFBSs), we uncover a hitherto underestimated number of transcription factor partners involved in mediating PGC-1M-NM-1 action. In particular, principal component analysis of TFBSs at PGC-1M-NM-1 binding regions predicts that, besides the well-known role of the estrogen-related receptor M-NM-1 (ERRM-NM-1), the activator protein-1 complex (AP-1) plays a major role in regulating the PGC-1M-NM-1-controlled gene program of hypoxia response. Our findings thus reveal the complex transcriptional network of muscle cell plasticity controlled by PGC-1M-NM-1. We used microarrays to detect changes in gene expression in C2C12 cells following PGC-1alpha over-expression or GFP (control) over-expression. We used 3 biological replicates for each condition.
Project description:Reprogramming of cellular metabolism plays a central role in fuelling malignant transformation, and AMPK as well as the PGC-1α/ERRα axis are key regulators of this process. Intersection of gene expression and binding event datasets in breast cancer cells shows that activation of AMPK significantly increases the expression of PGC-1α/ERRα and promotes the binding of ERRα to its cognate sites. Unexpectedly, the data also reveal that ERRα, in concert with PGC-1α, negatively regulates the expression of several one-carbon metabolism genes resulting in substantial perturbations in purine biosynthesis. This PGC-1α/ERRα-mediated repression of one-carbon metabolism promotes the sensitivity of breast cancer cells and tumors to the anti-folate drug methotrexate. These data implicate the PGC-1α/ERRα axis as a core regulatory node of folate cycle metabolism and further suggest that activators of AMPK could be used to modulate this pathway in cancer. We used microarrays to detail the global programme of gene expression following AMPK activation by AICAR in BT474 breast cancer cells.
Project description:Reprogramming of cellular metabolism plays a central role in fuelling malignant transformation, and AMPK as well as the PGC-1α/ERRα axis are key regulators of this process. Intersection of gene expression and binding event datasets in breast cancer cells shows that activation of AMPK significantly increases the expression of PGC-1α/ERRα and promotes the binding of ERRα to its cognate sites. Unexpectedly, the data also reveal that ERRα, in concert with PGC-1α, negatively regulates the expression of several one-carbon metabolism genes resulting in substantial perturbations in purine biosynthesis. This PGC-1α/ERRα-mediated repression of one-carbon metabolism promotes the sensitivity of breast cancer cells and tumors to the anti-folate drug methotrexate. These data implicate the PGC-1α/ERRα axis as a core regulatory node of folate cycle metabolism and further suggest that activators of AMPK could be used to modulate this pathway in cancer. We used microarrays to detail the global program of gene expression following AMPK activation by AICAR in BT474 breast cancer cells.
Project description:Background: The AMP-activated protein kinase (AMPK) is an intracellular fuel sensor for lipid and glucose metabolism. In addition to the short-term regulation of metabolic enzymes by phosphorylation, AMPK may also exert long-term effects on the transcription of downstream genes through the regulation of transcription factors and coactivators. In this study, RNA interference (RNAi) was conducted to investigate the effects of knockdown of TcAMPKα on lipid and carbohydrate metabolism in the red flour beetle, Tribolium castaneum, and the transcriptome profiles of dsTcAMPKα-injected and dsEGFP-injected beetles under normal conditions were compared by RNA-sequencing. Results: RNAi-mediated suppression of TcAMPKα increased whole-body triglyceride (TG) level and the ratio between glucose and trehalose, as was confirmed by in vivo treatment with the AMPK-activating compound, 5-Aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR). A total of 1184 differentially expressed genes (DEGs) were identified between dsTcAMPKα-injected and dsEGFP-injected beetles. These include genes involved in lipid and carbohydrate metabolism as well as insulin/insulin-like growth factor signaling (IIS). Real-time quantitative polymerase chain reaction analysis confirmed the differential expression of selected genes. Interestingly, metabolism-related transcription factors such as sterol regulatory element-binding protein 1 (SREBP1) and carbohydrate response element-binding protein (ChREBP) were also significantly upregulated in dsTcAMPKα-injected beetles. Conclusions: AMPK plays a critical role in the regulation of beetle metabolism. The findings of DEGs involved in lipid and carbohydrate metabolism provide valuable insight into the role of AMPK signaling in the transcriptional regulation of insect metabolism.