title: Proteasome inhibitors and immunosuppressive drugs promote the cleavage of eIF4GI and eIF4GII by caspase-8-independent mechanisms in Jurkat T cell lines.
abstract: Previously, we have shown that translation eukaryotic initiation factor (eIF) 4GI is cleaved during anti-Fas-mediated apoptosis. Here, we have investigated the effects of the proteasome inhibitors, MG132 and lactacystin, and the immunosuppressants, 2-amino-2[2-(4-octylphenyl)ethyl]-1,3,propane diol (FTY720) and cyclosporin A, on the integrity of eIF4GI and eIF4GII in T cells. Using wild-type Jurkat T cells, we show that the proteasome inhibitors MG132 and lactacystin promote the cleavage of eIF4G, activate caspase-8 and caspase-3-like activities and decrease cell viability. Furthermore, MG132 also promotes the cleavage of eIF4G and the activation of caspase-3-like activity in a caspase-8-deficient Jurkat cell line which is resistant to anti-Fas-mediated apoptosis. Using specific anti-peptide antisera, we show that both eIF4GI and eIF4GII are cleaved in either cell line in response to MG132 and lactacystin. In response to such treatments, we demonstrate that the fragments of eIF4GI generated include those previously observed with anti-Fas antiserum together with a novel product which lacks the ability to interact with eIF4E. In contrast, cells treated with the immunosuppressants FTY720 and cyclosporin A appear to contain only the novel cleavage fragment of eIF4GI and to lack those characteristic of cells treated with anti-Fas antiserum. These data suggest that caspase-8 activation is not required for apoptosis and eIF4G cleavage mediated by proteasome inhibitors and immunosuppressants in human T cells.
authors.affiliation: Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK. s.j.morley@sussex.ac.uk
authors.forename: S J
authors.initials: SJ
authors.lastname: Morley
authors.forename: V M
authors.initials: VM
authors.lastname: Pain
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002154:Calpain / Q000037:antagonists & inhibitors; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D039603:Eukaryotic Initiation Factor-4G; D000068876:Fingolimod Hydrochloride; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D019169:Jurkat Cells; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D010446:Peptide Fragments / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011409:Propylene Glycols / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D013110:Sphingosine / Q000031:analogs & derivatives; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C113920:EIF4G1 protein, human; C491300:EIF4G2 protein, human; D039603:Eukaryotic Initiation Factor-4G; D007166:Immunosuppressive Agents; D007976:Leupeptins; D009097:Multienzyme Complexes; D010446:Peptide Fragments; D010448:Peptide Initiation Factors; D011409:Propylene Glycols; D019014:fas Receptor; C067713:lactacystin; D016572:Cyclosporine; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D002154:Calpain; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine