Expression of IκBα in the nucleus of human peripheral blood T lymphocytes

Publisher Website
Google Scholar
Abstract
According to current models the inhibitory capacity of IκBα would be mediated through the retention of Rel/NF-κB proteins in the cytosol. However, IκBα has also been detected in the nucleus of cell lines and when overexpressed by transient transfection. To gain better insight into the potential role of nuclear IκBα in a physiological context we have analysed its presence in the nucleus of human peripheral blood T lymphocytes (PBL). We demonstrate the nuclear localization of IκBα in PBL by different techniques: Western blot, indirect immunofluorescence and electron microscopy. Low levels of nuclear IκBα were detected in resting cells whereas a superinduction was obtained after PMA activation. The nuclear pool of IκBα showed a higher stability than cytosolic IκBα and was partially independent of the resynthesis of the protein. Unexpectedly, the presence of nuclear IκBα did not inhibit NF-κB binding to DNA and this phenomenon was not due to the presence of IκBβ at the nuclear level. Immunoprecipitation experiments failed to demonstrate an association between nuclear IκBα and NF-κB proteins. Our results demonstrate that in resting and PMA-activated human PBL, IκBα is present in the nucleus in an apparently inactive form unable to disrupt NF-κB binding from DNA.