Role of glutamine depletion in directing tissue-specific nutrient stress responses to L-asparaginase.
L-asparaginase is important in the induction regimen for treating acute lymphoblastic leukemia. Cytotoxic complications are clinically significant problems lacking mechanistic insight. To reveal tissue-specific molecular responses to this drug, mice were administered asparaginase from either Escherichia coli (clinically used) or Wolinella succinogenes (novel, glutaminase-free form). Both enzymes abolished serum asparagine, but only the E. coli form reduced circulating glutamine. E. coli asparaginase reduced protein synthesis in liver and spleen but not pancreas via increased phosphorylation of the translation factor eIF2. In contrast, treatment with Wolinella caused no untoward changes in protein synthesis in any tissue examined. Treating mice deleted for the eIF2 kinase, GCN2, with the E. coli enzyme showed eIF2 phosphorylation to be GCN2-dependent, but only initially. Furthermore, although eIF2 phosphorylation was not increased in the pancreas or by Wolinella asparaginase, expression of the amino acid stress response genes, asparagine synthetase and CHOP/GADD153, increased as a result of both enzymes, even in tissues demonstrating no change in eIF2 phosphorylation. Finally, signaling downstream of the mammalian target of rapamycin kinase was repressed in liver and pancreas by E. coli but not Wolinella asparaginase. These data demonstrate that the nutrient stress response to asparaginase is tissue-specific and exacerbated by glutamine depletion. Importantly, increased expression of asparagine synthetase and CHOP does not require eIF2 phosphorylation, signifying alternate or auxiliary means of inducing gene expression under conditions of amino acid depletion in the whole animal.
Reinert
Rachel B
RB
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Evansville, Indiana 47712, USA.
Oberle
L Morgan
LM
Wek
Sheree A
SA
Bunpo
Piyawan
P
Wang
Xue Ping
XP
Mileva
Izolda
I
Goodwin
Leslie O
LO
Aldrich
Carla J
CJ
Durden
Donald L
DL
McNurlan
Margaret A
MA
Wek
Ronald C
RC
Anthony
Tracy G
TG
D000818:Animals; D001215:Asparaginase / Q000494:pharmacology*; D001216:Asparagine / Q000097:blood; D004926:Escherichia coli / Q000201:enzymology; D005260:Female; D005973:Glutamine / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000628:therapy*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016968:Wolinella / Q000201:enzymology
D005973:Glutamine; D001216:Asparagine; C070634:Eif2ak4 protein, mouse; D017346:Protein Serine-Threonine Kinases; D001215:Asparaginase