Overexpression of the heat shock protein 70 enhances the TCR/CD3- and Fas/Apo-1/CD95-mediated apoptotic cell death in Jurkat T cells.
To investigate whether the protective effects of the 70-kDa heat shock protein (hsp70) extend to the apoptotic mode of cell death, we transfected Jurkat T cells with the gene for the human hsp70 and challenged the cells with an anti-Fas mAb or with two different murine anti-CD3 mAbs. The anti-Fas mAb-triggered apoptotic cell death and the anti-CD3 mAb-mediated activation-induced cell death were significantly enhanced in the gene-transfected Jurkat cells overexpressing hsp70 compared with the unmanipulated and the vector-transfected cells. On the other hand, the well-established protective effect that this protein offers to the cells was unaffected, as determined by enhanced viability of gene-transfected cells exposed to a lethal heat shock. To investigate the mechanisms that are responsible for the increased susceptibility of the gene-transfected cells to apoptotic death, we studied the TCR/CD3-initiated events that showed a significant down-regulation of the protein tyrosine phosphorylation levels and the cytoplasmic free Ca2+ responses. As for the Fas/Apo-1/CD95-mediated early events, the activity of protein serine/threonine phosphatases was markedly increased in the cells overexpressing hsp70. Our study demonstrates that hsp70 overexpression offers thermoprotection but enhances TCR/CD3- and the Fas-induced apoptotic cell death. This phenomenon is associated with a down-regulation of the Ag receptor-initiated early signal transduction pathways and with an up-regulation of Fas-mediated early metabolic events.
Liossis
S N
SN
Department of Clinical Physiology, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100, USA.
Ding
X Z
XZ
Kiang
J G
JG
Tsokos
G C
GC
D017209:Apoptosis / Q000502:physiology*; D017252:CD3 Complex / Q000276:immunology*; D002118:Calcium / Q000502:physiology; D005434:Flow Cytometry; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D019014:fas Receptor / Q000276:immunology*
D017252:CD3 Complex; D018840:HSP70 Heat-Shock Proteins; D011948:Receptors, Antigen, T-Cell; D019014:fas Receptor; D014443:Tyrosine; D002118:Calcium