TY - JOUR
T1 - CD95-mediated alteration in Hsp70 levels is dependent on protein stabilization
AU - Concannon, Caoimhín G
AU - FitzGerald, Una
AU - Holmberg, Carina I
AU - Szegezdi, Eva
AU - Sistonen, Lea
AU - Samali, Afshin
PY - 2005
Y1 - 2005
N2 - Engagement of death receptors induces caspase activation and apoptosis. A recent study reported altered protein expression, including increased Hsp70 levels during CD95-mediated apoptosis. Here, we examined the mechanism underlying increased Hsp70 levels in cells challenged with a monoclonal antibody directed against the CD95 receptor. Levels of Hsp70 were found to increase in a dose-dependent manner, occurring independently of either heat shock factor 1 activation or the accumulation of Hsp70 messenger ribonucleic acid (mRNA), suggesting the involvement of posttranslational modifications. Inhibition of translation and de novo protein synthesis by cycloheximide resulted in Hsp70 protein levels diminishing over time in control cells, whereas its level remained constant during CD95 signaling. In addition, death receptor activation through exposure of cells to tumor necrosis factor-related apoptosis-inducing ligand did not alter Hsp70 levels. These findings demonstrate that receptor-specific signaling through the CD95 increases the stability of Hsp70 protein, rather than mRNA, when compared with control cells. The results describe a novel mechanism of heat shock protein accumulation, where increased protein stability and reduced turnover, is the mechanism by which Hsp70 accumulates in cells during CD95-mediated apoptosis.
AB - Engagement of death receptors induces caspase activation and apoptosis. A recent study reported altered protein expression, including increased Hsp70 levels during CD95-mediated apoptosis. Here, we examined the mechanism underlying increased Hsp70 levels in cells challenged with a monoclonal antibody directed against the CD95 receptor. Levels of Hsp70 were found to increase in a dose-dependent manner, occurring independently of either heat shock factor 1 activation or the accumulation of Hsp70 messenger ribonucleic acid (mRNA), suggesting the involvement of posttranslational modifications. Inhibition of translation and de novo protein synthesis by cycloheximide resulted in Hsp70 protein levels diminishing over time in control cells, whereas its level remained constant during CD95 signaling. In addition, death receptor activation through exposure of cells to tumor necrosis factor-related apoptosis-inducing ligand did not alter Hsp70 levels. These findings demonstrate that receptor-specific signaling through the CD95 increases the stability of Hsp70 protein, rather than mRNA, when compared with control cells. The results describe a novel mechanism of heat shock protein accumulation, where increased protein stability and reduced turnover, is the mechanism by which Hsp70 accumulates in cells during CD95-mediated apoptosis.
KW - Apoptosis
KW - Blotting, Western
KW - Caspases/metabolism
KW - Cycloheximide/pharmacology
KW - Dose-Response Relationship, Drug
KW - Electrophoretic Mobility Shift Assay
KW - Enzyme Activation
KW - Flow Cytometry
KW - HSP70 Heat-Shock Proteins/metabolism
KW - Humans
KW - Jurkat Cells
KW - Protein Processing, Post-Translational
KW - Protein Synthesis Inhibitors/pharmacology
KW - Reverse Transcriptase Polymerase Chain Reaction
KW - fas Receptor/metabolism
U2 - 10.1379/csc-69r.1
DO - 10.1379/csc-69r.1
M3 - Article
C2 - 15832948
SN - 1355-8145
VL - 10
SP - 59
EP - 65
JO - Cell Stress and Chaperones
JF - Cell Stress and Chaperones
IS - 1
ER -