Autophagy provides metabolic substrates to maintain energy charge and nucleotide pools in Ras-driven lung cancer cells

Jessie Yanxiang Guo, Xin Teng, Saurabh V. Laddha, Sirui Ma, Stephen C. Van Nostrand, Yang Yang, Sinan Khor, Chang S. Chan, Joshua D. Rabinowitz, Eileen White

Research output: Contribution to journalArticlepeer-review

122 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)1704-1717
Number of pages14
JournalGenes and Development
Volume30
Issue number15
DOIs
StatePublished - Aug 1 2016

All Science Journal Classification (ASJC) codes

  • Genetics
  • Developmental Biology

Keywords

  • Amino acid
  • Autophagy
  • Energy charge
  • Mitochondrial metabolism
  • Nucleotide
  • ROS
  • Ras-driven cancer

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