FIGURE 9.

rHSP90α induces the NF-κB signaling pathway through the CD91 receptor. A, immunoblot analyses of the phosphorylation status of IKKα/β and NF-κB in HCT-115 and SW480 cells treated for 24 h with 15 μg/ml rHSP90α in the presence of the antagonizing antibody against CD91. Representative results from three independent experiments indicate that rHSP90α-induced IKKα/β and NF-κB phosphorylation could be prevented by anti-CD91 antibody, suggesting that rHSP90α induces IKK signaling through CD91. B, rHSP90α induces a physical association of CD91 with IKKα and IKKβ. HCT-115 and SW480 cells were treated for 24 h with 15 μg/ml rHSP90α and then double-stained with anti-CD91 and anti-IKKα antibodies, with anti-CD91 and anti-IKKβ antibodies, or with anti-IKKα and anti-IKKβ antibodies, followed by the proximity ligation assay. After nuclei were counterstained with DAPI, red fluorescent dots, resulting from the direct contacts of CD91 with IKKα/β and of IKKα with IKKβ, were observed by confocal microscopy.