Selective up-regulation of caspase-3 gene expression following TCR engagement.
Activation-induced cell death (AICD) in T lymphocytes depends on the expression of Fas-ligand, which triggers the apoptotic process after binding to its receptor Fas. This leads to the activation of cysteine proteases of the caspase family and especially of caspase-3, a critical effector protein during AICD. We have previously observed the up-regulation of caspase-3 expression in effector but not memory T cells stimulated in vivo. In this study, we further characterized the regulation of caspase expression following T cell receptor (TCR) signaling and demonstrate that a three-fold increase in caspase-3 mRNA levels was observed by semi-quantitative and real-time RT-PCR analysis. Caspase-3 expression was selectively increased among five different caspases following TCR stimulation, as assessed by RNase protection assay. Real-time RT-PCR analysis demonstrated that a three-fold up-regulation in caspase-3 mRNA levels was observed following TCR triggering, whereas caspase-8 mRNA levels remained unchanged. The increase in caspase-3 mRNA levels occurred before cleavage and activation of caspase-3 and in the absence of apoptosis. TCR-mediated induction in caspase-3 expression was not dependent on STAT1 activation, since following stimulation of KOX-14 cells the transcription factor was not phosphorylated. Together, these results show that TCR activation triggers the selective increase in caspase-3 mRNA levels, independently of caspase activity and the induction of apoptosis.
Sabbagh
Laurent
L
Laboratoire d'Immunologie, Centre de Recherche du CHUM, Campus St. Luc, Pavillon Edouard-Asselin, 264 Boul. Rene Levesque Est #1307D, Montreal, Que., Canada H2X 1P1.
Bourbonnière
Martin
M
Sékaly
Rafick-Pierre
RP
Cohen
Luchino Y
LY
D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D053148:Caspase 3; D020169:Caspases / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D053222:Fas Ligand Protein; D015971:Gene Expression Regulation, Enzymologic; D006825:Hybridomas / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D050794:STAT1 Transcription Factor; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D015534:Trans-Activators / Q000378:metabolism; D015854:Up-Regulation
D004268:DNA-Binding Proteins; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D004247:DNA; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases