title: Elucidating the role of copper in CHO cell energy metabolism using (13)C metabolic flux analysis.
abstract: (13)C-metabolic flux analysis was used to understand copper deficiency-related restructuring of energy metabolism, which leads to excessive lactate production in recombinant protein-producing CHO cells. Stationary-phase labeling experiments with U-(13)C glucose were conducted on CHO cells grown under high and limiting copper in 3 L fed-batch bioreactors. The resultant labeling patterns of soluble metabolites were measured by GC-MS and used to estimate metabolic fluxes in the central carbon metabolism pathways using OpenFlux. Fluxes were evaluated 300 times from stoichiometrically feasible random guess values and their confidence intervals calculated by Monte Carlo simulations. Results from metabolic flux analysis exhibited significant carbon redistribution throughout the metabolic network in cells under Cu deficiency. Specifically, glycolytic fluxes increased (25%-79% relative to glucose uptake) whereas fluxes through the TCA and pentose phosphate pathway (PPP) were lower (15%-23% and 74%, respectively) compared with the Cu-containing condition. Furthermore, under Cu deficiency, 33% of the flux entering TCA via the pyruvate node was redirected to lactate and malate production. Based on these results, we hypothesize that Cu deficiency disrupts the electron transport chain causing ATP deficiency, redox imbalance, and oxidative stress, which in turn drive copper-deficient CHO cells to produce energy via aerobic glycolysis, which is associated with excessive lactate production, rather than the more efficient route of oxidative phosphorylation.
authors.affiliation: Drug Substance Technologies, Process Development, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA, 91320.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Nargund
authors.affiliation: Attribute Sciences, Process Development, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA, 91320.
authors.forename: Jinshu
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Drug Substance Technologies, Process Development, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA, 91320.
authors.forename: Chetan T
authors.initials: CT
authors.lastname: Goudar
mesh_terms: D000818:Animals; D019149:Bioreactors; D016466:CHO Cells; D002247:Carbon Isotopes / Q000378:metabolism*; D018929:Cell Culture Techniques; D003300:Copper / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004734:Energy Metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006019:Glycolysis; D019344:Lactic Acid / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D064688:Metabolic Flux Analysis / Q000379:methods*; D010427:Pentose Phosphate Pathway; D010766:Phosphorylation; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D008293:Malates; D019344:Lactic Acid; D003300:Copper; C030298:malic acid; D019289:Pyruvic Acid
keywords: 13C-metabolic flux analysis; Chinese hamster ovary; aerobic glycolysis; copper deficiency; lactate production; oxidative phosphorylation