Protein tyrosine kinase p56lck-deficiency confers hypersusceptibility to rho-fluorophenylalanine (pFPhe)-induced apoptosis by augmenting mitochondrial apoptotic pathway in human Jurkat T cells.
Phenylalanine analog, rho-fluorophenylalanine (pFPhe)-mediated cytotoxicity and several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9, -3, and -8, Bid cleavage, degradation of PARP and PLCgamma-1, and DNA fragmentation were more significant in p56(lck)-deficient Jurkat T cells (JCaM1.6) than in wild-type Jurkat T cells (E6.1). The susceptibility of JCaM1.6 toward apoptogenic activity of pFPhe decreased after acquisition of p56(lck) by transfection. The p56(lck) kinase activity increased 1.6-fold at 15-30 min after pFPhe treatment. The pan-caspase inhibitor (z-VAD-fmk) completely blocked the pFPhe-mediated apoptotic changes except caspase-9 activation. The caspase-8 inhibitor (z-IETD-fmk), which failed to influence pFPhe-induced caspase-9 activation, completely blocked caspase-8 activation and PLCgamma-1 degradation with a marked reduction in caspase-3 activation and PARP degradation, indicating pFPhe-induced caspase-8 activation as a downstream event of mitochondria-dependent activation of caspase-9. These results indicate that the deficiency of p56(lck) augments pFPhe-induced mitochondrial cytochrome c release and resultant apoptotic cell death in Jurkat T cells.
Laboratory of Immunobiology, School of Life Sciences and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu, Republic of Korea.
Hae Sun
HS
Park
Do Youn
DY
Jun
Cho Rong
CR
Han
Young Ho
YH
Kim
D017209:Apoptosis / Q000235:genetics*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism*; D004351:Drug Resistance / Q000235:genetics*; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics*; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology; D009842:Oligopeptides / Q000494:pharmacology; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D010135:p-Fluorophenylalanine / Q000494:pharmacology*
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; D010135:p-Fluorophenylalanine; D045304:Cytochromes c; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051966:Phospholipase C gamma; D020169:Caspases