Inhibition of NF-κB Activity by a Membrane-Transducing Mutant of IκBα

Abstract

The transcription factor NF-κB is regulated by the IκB family of proteins. The nonphosphorylatable, nondegradable superrepressor IκBα (srIκBα) mutant is a potent inhibitor of NF-κB activity when expressed in cells. We generated a form of srIκBα in which its N terminus is fused to the protein transduction domain of HIV TAT (TAT-srIκBα). Purified TAT-srIκBα protein rapidly and efficiently entered HeLa or Jurkat T cells. TAT-srIκBα, when exogenously added to HeLa cells, inhibited in a dose-dependent manner TNF-α- or IL-1β-induced NF-κB activation and binding of NF-κB to its consensus DNA sequence. TAT-srIκBα was coimmunoprecipitated with the p65 subunit of NF-κB, and this interaction was resistant to stimulation with IL-1β. Therefore, TAT-srIκBα-mediated inhibition could result from its nonreversible binding and sequestration of endogenous NF-κB. In contrast, exogenously added TAT-srIκBα did not inhibit IL-1β-induced activation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, or p38 mitogen-activated protein kinases or the phosphorylation and degradation of endogenous IκBα. These results identify a novel way for direct regulation of NF-κB activity in diverse cell types that may be useful for therapeutic purposes.

l-Arginine Decreases Inflammation and Modulates the Nuclear Factor-κB/Matrix Metalloproteinase Cascade in Mdx Muscle Fibers

“…Our results showed that L-arginine treatment has an inhibitory effect on the total NF-B level in mdx diaphragm and concomitant inhibition of IB-␣ degradation ( Figure 3). In line with previous reports, 30 we suggest that the decreased level of inflammatory cytokines (TNF-␣, IL-1␤, and IL-6) after L-arginine treatment could directly affect the expression level and the activity of NF-B in dystrophic muscle myofibers. Moreover, one of the mechanisms by which NF-B signaling appears to contribute to dystrophy is by promoting chronic inflammation.…”

Cell Membrane Lipid Rafts Mediate Caveolar Endocytosis of HIV-1 Tat Fusion Proteins

“…In the case of Tat, it has been demonstrated that the intraperitoneal injection of a 120-kDa ␤-galactosidase/Tat fusion protein results in the transcellular transduction into virtually all tissues in mice, including the passage of the blood-brain barrier (12). Based on these observations, the translocating activity of the Tat basic domain is now being extensively utilized for several therapeutic applications, including protection from apoptosis in the brain (13,14) and in the heart (15), extension of the cytotoxic activity of herpes simplex virus-1 thymidine kinase for cancer gene therapy (16), improvement of the IB␣ activity (17), enhancement of antigen presentation by dendritic cells (18,19), quenching of the tumor phenotype (20), and enhancement of viral-mediated gene delivery (21), to name but a few of the current applications. In addition, the Tat transduction domain has also been shown to mediate cell internalization of large molecules or particles, including magnetic nanoparticles (22), phage vectors (23), liposomes (24), and plasmid DNA (25).…”

Identification of a p65 Peptide That Selectively Inhibits NF-κ B Activation Induced by Various Inflammatory Stimuli and Its Role in Down-regulation of NF-κB-mediated Gene Expression and Up-regulation of Apoptosis

“…These include Grb2-binding peptide (16), mitogen-activated protein kinase (17), STAT3 (18), NEMO-IKK-interacting peptide (19), and peptides carrying nuclear localization sequences (20 -23). Besides peptides, PTD have also been used to deliver larger full-length polypeptides, including IB␣ (24), cyclin-dependent kinase inhibitory protein p27 (25), antiapoptotic protein Bcl-x L (26), and proapoptotic proteins (27).…”