Cytokine-inducible expression in endothelial cells of an I kappa B alpha-like gene is regulated by NF kappa B.

Abstract

The transient expression of many different genes is mediated by the inducible transcription factor p50‐p65 NF kappa B, which in turn is regulated by complex formation with its inhibitor I kappa B alpha. We describe here that in porcine aortic endothelial cells, either IL‐1 alpha, TNF alpha or LPS upregulates an inhibitor of NF kappa B which we refer to as ECI‐6. ECI‐6 is by structural and functional criteria an I kappa B alpha protein, the porcine homologue of MAD‐3, pp40 and RL/IF‐1. We have studied the promoter of the ECI‐6/I kappa B alpha gene and provide three lines of evidence that its expression is directly regulated by NF kappa B. First, the 5′ regulatory region of ECI‐6/I kappa B alpha contains two sites that bind NF kappa B in electrophoretic mobility shift assays. Second, expression following transfection of an ECI‐6/I kappa B alpha promoter‐luciferase reporter construct is dependent on a co‐transfected NF kappa B‐p65 subunit. Third, pretreatment of endothelial cells with antioxidants, agents that inhibit activation of NF kappa B, inhibit the expression of ECI‐6/I kappa B alpha. We conclude that the regulated expression of ECI‐6/I kappa B alpha could represent a novel feedback mechanism by which NF kappa B downregulates its own activity after transient activation of target genes has been achieved.

Two distinct mechanisms contribute to the constitutive activation of RelB in lymphoid cells.

“…In the case of c-Rel and v-Rel proteins, it has been shown that a potential protein kinase A (PK-A) phosphorylation site localized close to the nuclear localization sequence (NLS) in the RHD is involved in regulating nuclear/cytoplasmic distribution (Mosialos et al, 1991 Our finding that the constitutive activation, at least to some extent, is due to a loss of regulation by IKB-a, also suggests a way of explaining how to escape the autoregulatory feedback loop. As the gene coding for IKB-a contains KB-motifs in its own promoter, a consequence of high constitutive levels of KB binding proteins should result in overexpression of IKB (de Martin et al, 1993;Le Bail et al, 1993;Scott et al, 1993;Sun et al, 1993). This in turn would down-regulate KB activity, unless a mechanism such as the one described here is implemented.…”

“…Released NF-cKB/Rel complexes translocate to the nucleus and transactivate their respective target genes. One of the target genes encodes the IKB-a protein and this autoregulatory feedback loop is most probably responsible for the transient nature of the induction of this pathway (de Martin et al, 1993;Le Bail et al, 1993;Scott et al, 1993;Sun et al, 1993). The current theory for the constitutive lymphoid activity of the KB-motif invokes a constitutive activation of this pathway, i.e.…”

Differential regulation of TSG-14 expression in murine fibroblasts and peritoneal macrophages

“…It is interesting that treatments with IFN-␥ also did not appreciably alter the kinetics or degree of I B-␣ resynthesis. Because I B-␣ resynthesis is known to be positively regulated by NF-B activity [36,37], failure to affect this event suggested that the entire process of NF-B activation is not impeded by IFN-␥. Other experiments indicated that IL-4 and IL-10 also failed to affect LPS-induced I B-␣ degradation or I B-␣ resynthesis (data not shown).…”

Increased NF-κB DNA binding but not transcriptional activity during apoptosis induced by the COX-2-selective inhibitor NS-398 in colorectal carcinoma cells

“…Porcine IkBa is strongly homologous to human IkBa (de Martin et al, 1993) and this adenoviral vector has previously been shown to inhibit activation of NF-kB in human cells (Liu et al, 2001). rAd.IkBa was a kind gift from Dr Ranier de Martin (Department of Vascular Biology and Thrombosis Research, University of Vienna, Austria).…”