title: Differential Glutamate Metabolism in Proliferating and Quiescent Mammary Epithelial Cells.
abstract: Mammary epithelial cells transition between periods of proliferation and quiescence during development, menstrual cycles, and pregnancy, and as a result of oncogenic transformation. Utilizing an organotypic 3D tissue culture model coupled with quantitative metabolomics and proteomics, we identified significant differences in glutamate utilization between proliferating and quiescent cells. Relative to quiescent cells, proliferating cells catabolized more glutamate via transaminases to couple non-essential amino acid (NEAA) synthesis to α-ketoglutarate generation and tricarboxylic acid (TCA) cycle anaplerosis. As cells transitioned to quiescence, glutamine consumption and transaminase expression were reduced, while glutamate dehydrogenase (GLUD) was induced, leading to decreased NEAA synthesis. Highly proliferative human tumors display high transaminase and low GLUD expression, suggesting that proliferating cancer cells couple glutamine consumption to NEAA synthesis to promote biosynthesis. These findings describe a competitive and partially redundant relationship between transaminases and GLUD, and they reveal how coupling of glutamate-derived carbon and nitrogen metabolism can be regulated to support cell proliferation.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Coloff
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: J Patrick
authors.initials: JP
authors.lastname: Murphy
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Braun
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Isaac S
authors.initials: IS
authors.lastname: Harris
authors.affiliation: Human Metabolome Technologies America, Boston, MA 02134, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Shelton
authors.affiliation: Human Metabolome Technologies, Tsuruoka, 997-0052 Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Kami
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gygi
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Selfors
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address: joan_brugge@hms.harvard.edu.
authors.forename: Joan S
authors.initials: JS
authors.lastname: Brugge
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism*; D005260:Female; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology*; D055432:Metabolomics; D008954:Models, Biological; D009587:Nitrogen Isotopes; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D040901:Proteomics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D000637:Transaminases / Q000378:metabolism
chemical_list: D005969:Glutamate Dehydrogenase; D018698:Glutamic Acid; D009587:Nitrogen Isotopes; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D000637:Transaminases