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Jiang L.,Childrens Medical Center Dallas | Shestov A.A.,University of Pennsylvania | Swain P.,Seahorse Bioscience, Inc. | Yang C.,Childrens Medical Center Dallas | And 13 more authors.
Nature | Year: 2016

Cells receive growth and survival stimuli through their attachment to an extracellular matrix (ECM). Overcoming the addiction to ECM-induced signals is required for anchorage-independent growth, a property of most malignant cells. Detachment from ECM is associated with enhanced production of reactive oxygen species (ROS) owing to altered glucose metabolism. Here we identify an unconventional pathway that supports redox homeostasis and growth during adaptation to anchorage independence. We observed that detachment from monolayer culture and growth as anchorage-independent tumour spheroids was accompanied by changes in both glucose and glutamine metabolism. Specifically, oxidation of both nutrients was suppressed in spheroids, whereas reductive formation of citrate from glutamine was enhanced. Reductive glutamine metabolism was highly dependent on cytosolic isocitrate dehydrogenase-1 (IDH1), because the activity was suppressed in cells homozygous null for IDH1 or treated with an IDH1 inhibitor. This activity occurred in absence of hypoxia, a well-known inducer of reductive metabolism. Rather, IDH1 mitigated mitochondrial ROS in spheroids, and suppressing IDH1 reduced spheroid growth through a mechanism requiring mitochondrial ROS. Isotope tracing revealed that in spheroids, isocitrate/citrate produced reductively in the cytosol could enter the mitochondria and participate in oxidative metabolism, including oxidation by IDH2. This generates NADPH in the mitochondria, enabling cells to mitigate mitochondrial ROS and maximize growth. Neither IDH1 nor IDH2 was necessary for monolayer growth, but deleting either one enhanced mitochondrial ROS and reduced spheroid size, as did deletion of the mitochondrial citrate transporter protein. Together, the data indicate that adaptation to anchorage independence requires a fundamental change in citrate metabolism, initiated by IDH1-dependent reductive carboxylation and culminating in suppression of mitochondrial ROS. © 2016 Macmillan Publishers Limited. All rights reserved. Source

Noguez J.H.,University of South Florida | Diyabalanage T.K.K.,University of South Florida | Miyata Y.,University of South Florida | Xie X.-S.,rmott Center for Human Growth and Development | And 4 more authors.
Bioorganic and Medicinal Chemistry | Year: 2011

Palmerolides D-G are new bioactive macrolides isolated from the Antarctic tunicate Synoicum adareanum and are related to the melanoma-selective cytotoxin palmerolide A. Most of these palmerolides are potent V-ATPase inhibitors and have sub-micromolar activity against melanoma. Though palmerolide A remains the most potent of this series of natural products against mammalian V-ATPase, recent data suggests that palmerolide D is the most potent against melanoma. A comparison of the bioactivity data obtained for these natural product palmerolides has provided insight into the substructures necessary to retain V-ATPase inhibition and cytotoxic activity. © 2011 Elsevier Ltd. All rights reserved. Source

Shi Y.,Qingdao University of Science and Technology | Sha G.,Qingdao Agricultural Academy | Sun X.,rmott Center for Human Growth and Development
Planta | Year: 2014

NAGNAG alternative splicing is one type of alternative splicing in mammals and plants. There are two opposite arguments regarding the mechanism of this NAGNAG event, i.e. whether splice variation is controllable by the cell or is just biological noise. In this paper, we systematically investigated NAGNAG acceptors in Arabidopsis thaliana using both cDNA/EST and RNA-Seq data. We identified 9,473 NAGNAG motifs, including 529 cDNA/EST-confirmed NAGNAG acceptors. A nomenclature tree for this type of alternative splicing was defined based on the cDNA/EST validation, location in the exon, sequence and expression level. Low expression of some NAGNAG motifs was observed in various tissues or pathogen-infected samples, indicating the existence of background splicing. Tissue-specific or treatment-specific differences in the dynamic profiles suggest that some NAGNAG acceptors are highly regulated. © 2013 Springer-Verlag Berlin Heidelberg. Source

Mashimo T.,Southwestern Medical Center | Mashimo T.,Simmons Comprehensive Cancer Center | Mashimo T.,Annette rauss Center For Neuro Oncology | Pichumani K.,Advanced Imaging Research Center | And 34 more authors.
Cell | Year: 2014

Glioblastomas and brain metastases are highly proliferative brain tumors with short survival times. Previously, using 13C-NMR analysis of brain tumors resected from patients during infusion of 13C-glucose, we demonstrated that there is robust oxidation of glucose in the citric acid cycle, yet glucose contributes less than 50% of the carbons to the acetyl-CoA pool. Here, we show that primary and metastatic mouse orthotopic brain tumors have the capacity to oxidize [1,2-13C]acetate and can do so while simultaneously oxidizing [1,6-13C]glucose. The tumors do not oxidize [U-13C]glutamine. In vivo oxidation of [1,2-13C]acetate was validated in brain tumor patients and was correlated with expression of acetyl-CoA synthetase enzyme 2, ACSS2. Together, the data demonstrate a strikingly common metabolic phenotype in diverse brain tumors that includes the ability to oxidize acetate in the citric acid cycle. This adaptation may be important for meeting the high biosynthetic and bioenergetic demands of malignant growth. © 2014 Elsevier Inc. All rights reserved. Source

Nam Y.-J.,Southwestern Medical Center | Nam Y.-J.,Vanderbilt University | Lubczyk C.,Southwestern Medical Center | Bhakta M.,Southwestern Medical Center | And 8 more authors.
Development (Cambridge) | Year: 2014

Various combinations of cardiogenic transcription factors, including Gata4 (G), Hand2 (H), Mef2c (M) and Tbx5 (T), can reprogram fibroblasts into induced cardiac-like myocytes (iCLMs) in vitro and in vivo. Given that optimal cardiac function relies on distinct yet functionally interconnected atrial, ventricular and pacemaker (PM) cardiomyocytes (CMs), it remains to be seen which subtypes are generated by direct reprogramming and whether this process can be harnessed to produce a specific CM of interest. Here, we employ a PM-specificHcn4-GFPreportermouse and a spectrumofCMsubtypespecific markers to investigate the range of cellular phenotypes generated by reprogramming of primary fibroblasts. Unexpectedly, we find that a combination of four transcription factors (4F) optimized for Hcn4-GFP expression does not generate beating PM cells due to inadequate sarcomeric protein expression and organization. However, applying strict single-cell criteria to GHMT-reprogrammed cells, we observe induction of diverse cellular phenotypes, including those resembling immature forms of all three major cardiac subtypes (i.e. atrial, ventricular and pacemaker). In addition, we demonstrate that cells induced by GHMT are directly reprogrammed and do not arise from an Nxk2.5+ progenitor cell intermediate. Taken together, our results suggest a remarkable degree of plasticity inherent to GHMT reprogramming and provide a starting point for optimization of CM subtype-specific reprogramming protocols. © 2014, Published by The Company of Biologists Ltd. Source

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