GCN2 Protein Kinase Is Required to Activate Amino Acid Deprivation Responses in Mice Treated with the Anti-cancer Agent l-Asparaginase

Abstract

Asparaginase depletes circulating asparagine and glutamine, activating amino acid deprivation responses (AADR) such as phosphorylation of eukaryotic initiation factor 2 (p-eIF2) leading to increased mRNA levels of asparagine synthetase and CCAAT/enhancer-binding protein ␤ homologous protein (CHOP) and decreased mammalian target of rapamycin complex 1 (mTORC1) signaling. The objectives of this study were to assess the role of the eIF2 kinases and protein kinase R-like endoplasmic reticulum resident kinase (PERK) in controlling AADR to asparaginase and to compare the effects of asparaginase on mTORC1 to that of rapamycin. In experiment 1, asparaginase increased hepatic p-eIF2 in wild-type mice and mice with a liver-specific PERK deletion but not in GCN2 null mice nor in GCN2-PERK double null livers. In experiment 2, wild-type and GCN2 null mice were treated with asparaginase (3 IU per g of body weight), rapamycin (2 mg per kg of body weight), or both. In wild-type mice, asparaginase but not rapamycin increased p-eIF2, p-ERK1/2, p-Akt, and mRNA levels of asparagine synthetase and CHOP in liver. Asparaginase and rapamycin each inhibited mTORC1 signaling in liver and pancreas but maximally together. In GCN2 null livers, all responses to asparaginase were precluded except CHOP mRNA expression, which remained partially elevated. Interestingly, rapamycin blocked CHOP induction by asparaginase in both wild-type and GCN2 null livers. These results indicate that GCN2 is required for activation of AADR to asparaginase in liver. Rapamycin modifies the hepatic AADR to asparaginase by preventing CHOP induction while maximizing inhibition of mTORC1.

General Control Nonderepressible 2 (GCN2) Kinase Protects Oligodendrocytes and White Matter during Branched-chain Amino Acid Deficiency in Mice

“…Immunoblot Analysis-Tissues were processed for SDS-PAGE and immunoblotting as described previously (6,16). Primary antibody for eIF2␣ phosphorylated at serine 51 was purchased from Cell Signaling Technology (Beverly, MA).…”

Erratum: From Krebs to clinic: glutamine metabolism to cancer therapy

“…Suppression of the ISR by glutamine input has been shown to be critical for survival of several cancer cell and tumor types including neuroblastoma and breast cancer 65,97,98 . It was also observed that GCN2 is activated in mice in response to treatment with asparaginase 99 , which is approved by the US Food and Drug Administration (FDA) for the treatment of acute lymphoblastic leukemia (ALL) and may deplete serum asparagine and glutamine [100][101][102] .…”

“…GCN2, a serine-threonine kinase with a regulatory domain that is structurally similar to histidine-tRNA synthetase, is allosterically activated by uncharged tRNAs with amino acid deprivation (including glutamine deprivation) and in turn activates the integrated stress response (ISR) 96,214,215 . Glutamine can suppress GCN2 activation through its contribution to amino acid pools by aminotransferases 65,[97][98][99] . To control endoplasmic reticulum (ER) homeostasis, glutamine supports protein folding and trafficking through its contribution to uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) as part of the hexosamine biosynthesis pathway.…”

ATF4-dependent Regulation of the JMJD3 Gene during Amino Acid Deprivation Can Be Rescued in Atf4-deficient Cells by Inhibition of Deacetylation

“…1B). To establish whether or not the JMJD3 gene is responsive to AA deprivation in vivo, mice were treated with the drug asparaginase, which depletes circulating asparagine and glutamine levels and activates the AAR (33). Analysis of mouse liver tissue showed that asparaginase treatment resulted in about a 2-fold increase in Jmjd3 mRNA (Fig.…”