title: Autophagy provides metabolic substrates to maintain energy charge and nucleotide pools in Ras-driven lung cancer cells.
abstract: Autophagy degrades and is thought to recycle proteins, other macromolecules, and organelles. In genetically engineered mouse models (GEMMs) for Kras-driven lung cancer, autophagy prevents the accumulation of defective mitochondria and promotes malignancy. Autophagy-deficient tumor-derived cell lines are respiration-impaired and starvation-sensitive. However, to what extent their sensitivity to starvation arises from defective mitochondria or an impaired supply of metabolic substrates remains unclear. Here, we sequenced the mitochondrial genomes of wild-type or autophagy-deficient (Atg7(-/-)) Kras-driven lung tumors. Although Atg7 deletion resulted in increased mitochondrial mutations, there were too few nonsynonymous mutations to cause generalized mitochondrial dysfunction. In contrast, pulse-chase studies with isotope-labeled nutrients revealed impaired mitochondrial substrate supply during starvation of the autophagy-deficient cells. This was associated with increased reactive oxygen species (ROS), lower energy charge, and a dramatic drop in total nucleotide pools. While starvation survival of the autophagy-deficient cells was not rescued by the general antioxidant N-acetyl-cysteine, it was fully rescued by glutamine or glutamate (both amino acids that feed the TCA cycle and nucleotide synthesis) or nucleosides. Thus, maintenance of nucleotide pools is a critical challenge for starving Kras-driven tumor cells. By providing bioenergetic and biosynthetic substrates, autophagy supports nucleotide pools and thereby starvation survival.
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA; Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey 08901, USA; Department of Chemical Biology, Rutgers Ernest Mario School of Pharmacy, Piscataway, New Jersey 08854, USA;
authors: Jessie Yanxiang
authors: JY
authors: Guo
authors: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA;
authors: Xin
authors: X
authors: Teng
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
authors: Saurabh V
authors: SV
authors: Laddha
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
authors: Sirui
authors: S
authors: Ma
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
authors: Stephen C
authors: SC
authors: Van Nostrand
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
authors: Yang
authors: Y
authors: Yang
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
authors: Sinan
authors: S
authors: Khor
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA; Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey 08901, USA;
authors: Chang S
authors: CS
authors: Chan
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA; Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA;
authors: Joshua D
authors: JD
authors: Rabinowitz
authors: Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA; Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA.
authors: Eileen
authors: E
authors: White
mesh_terms: D000818:Animals; D001343:Autophagy; D000071193:Autophagy-Related Protein 7 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D017353:Gene Deletion; D014644:Genetic Variation; D054629:Genome, Mitochondrial / Q000235:genetics; D005973:Glutamine / Q000494:pharmacology; D008175:Lung Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009705:Nucleosides / Q000494:pharmacology; D009711:Nucleotides / Q000378:metabolism*; D010084:Oxidation-Reduction; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D009705:Nucleosides; D009711:Nucleotides; D005973:Glutamine; D018631:ras Proteins; D000071193:Autophagy-Related Protein 7
keywords: ROS; Ras-driven cancer; amino acid; autophagy; energy charge; mitochondrial metabolism; nucleotide