To determine the influence of ubiquitin-proteasome in regulating the TRAIL-mediated apoptosis.
RASF cells and SCID mice were divided into 4 groups treated with PBS,anti-DR5, lactacystin, and anti-DR5 plus lactacystin. The apoptosis of cells was detected with Hoechst 33342 and TUNEL. The effect of caspase inhibitor on cell apoptosis was analysed with Hoechst 33342 and Luminescent ATP Lite.
Block ubiquitin-proteasome with lactacystin, a highly specific and irreversible proteasome inhibitor, induced 95% cell apoptosis both in vitro and in vivo. In contrast, there was no apoptosis of cells after the treatment with anti-DR5 antibody or lactacystin alone.
The inhibition of ubiquitin-proteasome pathway can sensitize rheumatoid arthritis synovial fibroblast cells to TRAIL- induced apoptosis, and the activation of caspase 8 and caspase 4 is necessary in this process.