Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.1.1 (asparaginase)
 2,695 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 beta 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.
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PMID:GCN2 protein kinase is required to activate amino acid deprivation responses in mice treated with the anti-cancer agent L-asparaginase. 1978 59

mTOR exists in two distinct complexes. mTOR complex 1 (mTORC1) is potently inhibited by the immunosupressive macrolide rapamycin; whereas, mTORC2 is insensitive to this durg. These mTOR complexes play an integral role in the regulation of many cellular processes including protein synthesis, autophagy, lipid synthesis, mitochondrial metabolism/biogenesis, and cell cycle. Both mTOR complexes are important for maintaining cellular homeostasis and the growth of many types of cancer. Rapamycin and rapalogs have been effective in treating only a small number of these cancers, and other methods are being developed in order to address the short-comings of these drugs. The most direct of these approaches include ATP-competitive inhibitors of the mTOR kinase or dual inhibitors of both mTOR and PI3 kinase. However, other methods of inhibiting mTORC1 may prove clinically useful as well. These include amino acid depletion using asparaginase and inhibition of the Rheb GTPases with farnesyl transferase inhibitors or statins. Most excitingly, mTORC1 activation has been shown to cause and sensitize cells to DNA damage and ER stress. Many of the drugs currently used in the clinic for the treatment of cancer cause these types of stress, and existing drugs may be tailored to treat tumors with high mTORC1 activity.
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PMID:Rheb/mTOR activation and regulation in cancer: novel treatment strategies beyond rapamycin. 2156 13