Merkel Cell Polyomavirus Small T Antigen Promotes Pro-Glycolytic Metabolic Perturbations Required for Transformation

An accurate analytic model describing the microscopic mechanism of high-harmonic generation (HHG) in solids is derived. Extensive first-principles simulations within a time-dependent density-functional framework corroborate the conclusions of the model. Our results reveal that (i) the emitted HHG spectra are highly anisotropic and laser-polarization dependent even for cubic crystals; (ii) the harmonic emission is enhanced by the inhomogeneity of the electron-nuclei potential; the yield is increased for heavier atoms; and (iii) the cutoff photon energy is driver-wavelength independent. Moreover, we show that it is possible to predict the laser polarization for optimal HHG in bulk crystals solely from the knowledge of their electronic band structure. Our results pave the way to better control and optimize HHG in solids by engineering their band structure

Direct evidence for cancer-cell-autonomous extracellular protein catabolism in pancreatic tumors

Mammalian tissues rely on a variety of nutrients to support their physiological functions. It is known that altered metabolism is involved in the pathogenesis of cancer, but which nutrients support the inappropriate growth of intact malignant tumors is incompletely understood. Amino acids are essential nutrients for many cancer cells that can be obtained through the scavenging and catabolism of extracellular protein via macropinocytosis. In particular, macropinocytosis can be a nutrient source for pancreatic cancer cells, but it is not fully understood how the tumor environment influences metabolic phenotypes and whether macropinocytosis supports the maintenance of amino acid levels within pancreatic tumors. Here we utilize miniaturized plasma exchange to deliver labeled albumin to tissues in live mice, and we demonstrate that breakdown of albumin contributes to the supply of free amino acids in pancreatic tumors. We also deliver albumin directly into tumors using an implantable microdevice, which was adapted and modified from ref. 9. Following implantation, we directly observe protein catabolism and macropinocytosis in situ by pancreatic cancer cells, but not by adjacent, non-cancerous pancreatic tissue. In addition, we find that intratumoral inhibition of macropinocytosis decreases amino acid levels. Taken together, these data suggest that pancreatic cancer cells consume extracellular protein, including albumin, and that this consumption serves as an important source of amino acids for pancreatic cancer cells in vivo.National Science Foundation (U.S.) (Grant T32GM007287)National Cancer Institute (U.S.) (Grant F30CA183474)National Institute of General Medical Sciences (U.S.) (Award T32GM007753)National Institutes of Health (U.S.) (Grant P30CA1405141)National Institutes of Health (U.S.) (Grant R01CA168653

Environment Impacts the Metabolic Dependencies of Ras-Driven Non-Small Cell Lung Cancer

Cultured cells convert glucose to lactate, and glutamine is the major source of tricarboxylic acid (TCA)-cycle carbon, but whether the same metabolic phenotype is found in tumors is less studied. We infused mice with lung cancers with isotope-labeled glucose or glutamine and compared the fate of these nutrients in tumor and normal tissue. As expected, lung tumors exhibit increased lactate production from glucose. However, glutamine utilization by both lung tumors and normal lung was minimal, with lung tumors showing increased glucose contribution to the TCA cycle relative to normal lung tissue. Deletion of enzymes involved in glucose oxidation demonstrates that glucose carbon contribution to the TCA cycle is required for tumor formation. These data suggest that understanding nutrient utilization by tumors can predict metabolic dependencies of cancers in vivo. Furthermore, these data argue that the in vivo environment is an important determinant of the metabolic phenotype of cancer cells.National Science Foundation (U.S.) (Grant T32GM007287

Akt regulation of glycolysis mediates bioenergetic stability in epithelial cells

Cells use multiple feedback controls to regulate metabolism in response to nutrient and signaling inputs. However, feedback creates the potential for unstable network responses. We examined how concentrations of key metabolites and signaling pathways interact to maintain homeostasis in proliferating human cells, using fluorescent reporters for AMPK activity, Akt activity, and cytosolic NADH/NAD+ redox. Across various conditions, including glycolytic or mitochondrial inhibition or cell proliferation, we observed distinct patterns of AMPK activity, including both stable adaptation and highly dynamic behaviors such as periodic oscillations and irregular fluctuations that indicate a failure to reach a steady state. Fluctuations in AMPK activity, Akt activity, and cytosolic NADH/NAD+ redox state were temporally linked in individual cells adapting to metabolic perturbations. By monitoring single-cell dynamics in each of these contexts, we identified PI3K/Akt regulation of glycolysis as a multifaceted modulator of single-cell metabolic dynamics that is required to maintain metabolic stability in proliferating cells

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

MCC cell lines exhibit variable ECAR and sensitivity to MCT1 inhibition.

<p><b>A)</b> ECAR (mpH/min) of MKL-1, MKL-2 and WaGa lines (minutes). Cells were treated with oligomycin (1 μM) at the indicated time point (arrow). <b>B-D)</b> XTT proliferation assay of MKL-1, MKL-2 and WaGa cells treated with either DMSO, CHC (5 mM), SR13800 (100 nM), or SR13801 (100 nM) (days).</p

Temporal transcriptome of IMR90 fibroblasts inducibly expressing MCPyV ST.

<p><b>A)</b> IMR90 fibroblasts containing dox-inducible MCPyV ST or GFP vectors were treated with dox and harvested every 8 hours for RNA extraction. Each time point represents three biological replicas. <b>B)</b> Mean ST transcript levels and <b>C)</b> immunoblotting for ST, GFP and vinculin from cells collected every 8 hours for 96 hours following dox treatment. <b>D)</b> Hierarchical clustering and fold change between MCPyV ST and GFP following dox induction for 96 hours. Each bar represents an average of three experiments for each time point. The enrichment of “Cancer Hallmark” gene sets are represented relative to the ST-differentially expressed clusters, including epithelial to mesenchymal transition (EMT), tumor necrosis factor-α (TNFA signaling via NF-κB), hypoxia, mTORC1, oxidative phosphorylation, glycolysis, MYC, and several cell cycle clusters including E2F targets, G2M checkpoint and mitotic spindle. The color bar indicates statistical significance, yellow p < 0.05 and gray p > 0.05.</p

Akt regulation of glycolysis mediates bioenergetic stability in epithelial cells

Cells use multiple feedback controls to regulate metabolism in response to nutrient and signaling inputs. However, feedback creates the potential for unstable network responses. We examined how concentrations of key metabolites and signaling pathways interact to maintain homeostasis in proliferating human cells, using fluorescent reporters for AMPK activity, Akt activity, and cytosolic NADH/NAD+ redox. Across various conditions, including glycolytic or mitochondrial inhibition or cell proliferation, we observed distinct patterns of AMPK activity, including both stable adaptation and highly dynamic behaviors such as periodic oscillations and irregular fluctuations that indicate a failure to reach a steady state. Fluctuations in AMPK activity, Akt activity, and cytosolic NADH/NAD+ redox state were temporally linked in individual cells adapting to metabolic perturbations. By monitoring single-cell dynamics in each of these contexts, we identified PI3K/Akt regulation of glycolysis as a multifaceted modulator of single-cell metabolic dynamics that is required to maintain metabolic stability in proliferating cells

MCPyV ST increases aerobic glycolysis and MCT1 sensitivity.

<p><b>A)</b> Media glucose (Glc) and lactate (Lac) levels (mM) from cultures of IMR90 cells expressing ST or GFP were measured at the indicated day following dox addition. **P < 0.005 calculated using unpaired student’s T test between the marked GFP and ST points. <b>B)</b> ECAR (mpH/min) of IMR90 cells inducibly expressing ST with and without dox addition for 48 hours. ***P < 0.0005 calculated using unpaired student’s T test. <b>C)</b> ECAR of IMR90 cells expressing ST or GFP with CHC (5 mM) or DMSO (minutes) following 48 hours of dox treatment. Cells were treated with oligomycin (1 μM) at the indicated time point. ***P < 0.0005 calculated using unpaired student’s T test between GFP-DMSO and ST-DMSO samples. <b>D)</b> OCR (pmoles/min) of cells (minutes) as in C. <b>E)</b> Growth of IMR90 cells expressing ST or GFP treated with dox and CHC or DMSO was assessed by crystal violet every day for 5 days. ***P < 0.0005 calculated using unpaired, two-tailed student’s T test between ST-DMSO and ST-CHC treatments. Key same as in C.</p

MYC isoforms differentially regulate glycolysis gene expression and ECAR of MCC cells.

<p><b>A)</b> MKL-1 and WaGa cells containing inducible vectors for MYC, MYCN or MYCL were treated with (+) or without (-) dox for 72 hours and lysates were immunoblotted with the indicated antibodies. <b>B)</b> ECAR (mpH/min) of MKL-1 cells inducibly expressing GFP, MYC, MYCN or MYCL after 72 hours of dox addition (minutes). Cells were treated with oligomycin (1 μM) at the indicated time point. *P < 0.05 calculated using unpaired student’s T test between MYC and MYCL samples.</p