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Physiological responses of Saccharopolyspora erythraea towards perturbation of intracellular ATP

ABSTRACT: Saccharopolyspora erythraea is used for industrial-scale production of erythromycin. To explore the physiological role of co-factors in regulation of primary and secondary metabolism of S. erythraea, we initially overexpressed the endogenous F1-ATPase in an erythromycin high-producing strain, E3. The engineered strain is named EA. The F1-ATPase expression resulted in a lower [ATP]/[ADP] ratio, which was accompanied by a dramatic increased production of a reddish pigment and a decreased erythromycin production. Transcriptional analysis revealed that the intracellular [ATP]/[ADP] ratio appeared to exert a global regulation on the metabolism of S.erythraea, and the lower [ATP]/[ADP] ratio induced physiological changes to restore the energy balance, mainly via pathways that tend to produce ATP or NADH. The results also indicated a state of redox stress in the engineered strain, which was correlated to the alteration of electron transport at the branch of the terminal oxidases.

ORGANISM(S): Saccharopolyspora erythraea

PROVIDER: GSE134767 | GEO | 2020/02/26

REPOSITORIES: GEO

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Project description:This a model from the article: Glucose sensing in the pancreatic beta cell: a computational systems analysis. Fridlyand LE, Philipson LH.Theor Biol Med Model.2010 May 24;7:15. 20497556, Abstract: BACKGROUND: Pancreatic beta-cells respond to rising blood glucose by increasing oxidative metabolism, leading to an increased ATP/ADP ratio in the cytoplasm. This leads to a closure of KATP channels, depolarization of the plasma membrane, influx of calcium and the eventual secretion of insulin. Such mechanism suggests that beta-cell metabolism should have a functional regulation specific to secretion, as opposed to coupling to contraction. The goal of this work is to uncover contributions of the cytoplasmic and mitochondrial processes in this secretory coupling mechanism using mathematical modeling in a systems biology approach. METHODS: We describe a mathematical model of beta-cell sensitivity to glucose. The cytoplasmic part of the model includes equations describing glucokinase, glycolysis, pyruvate reduction, NADH and ATP production and consumption. The mitochondrial part begins with production of NADH, which is regulated by pyruvate dehydrogenase. NADH is used in the electron transport chain to establish a proton motive force, driving the F1F0 ATPase. Redox shuttles and mitochondrial Ca2+ handling were also modeled. RESULTS: The model correctly predicts changes in the ATP/ADP ratio, Ca2+ and other metabolic parameters in response to changes in substrate delivery at steady-state and during cytoplasmic Ca2+ oscillations. Our analysis of the model simulations suggests that the mitochondrial membrane potential should be relatively lower in beta cells compared with other cell types to permit precise mitochondrial regulation of the cytoplasmic ATP/ADP ratio. This key difference may follow from a relative reduction in respiratory activity. The model demonstrates how activity of lactate dehydrogenase, uncoupling proteins and the redox shuttles can regulate beta-cell function in concert; that independent oscillations of cytoplasmic Ca2+ can lead to slow coupled metabolic oscillations; and that the relatively low production rate of reactive oxygen species in beta-cells under physiological conditions is a consequence of the relatively decreased mitochondrial membrane potential. CONCLUSION: This comprehensive model predicts a special role for mitochondrial control mechanisms in insulin secretion and ROS generation in the beta cell. The model can be used for testing and generating control hypotheses and will help to provide a more complete understanding of beta-cell glucose-sensing central to the physiology and pathology of pancreatic beta-cells. This model was taken from the Vcell MathModel directory and was converted to SBML This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team. For more information see the terms of use. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

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Physiological responses of Saccharopolyspora erythraea towards perturbation of intracellular ATP

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