Inhibition of ubiquitin-proteasome pathway–mediated IκBα degradation by a naturally occurring antibacterial peptide
Youhe Gao, … , Alfred L. Goldberg, Michael Simons
Youhe Gao, … , Alfred L. Goldberg, Michael Simons
Published August 1, 2000
Citation Information: J Clin Invest. 2000;106(3):439-448. https://doi.org/10.1172/JCI9826.
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Inhibition of ubiquitin-proteasome pathway–mediated IκBα degradation by a naturally occurring antibacterial peptide

Abstract

Induction of NF-κB–dependent gene expression plays an important role in a number of biological processes including inflammation and ischemia-reperfusion injury. However, few attempts aimed at selective regulation of this transcription factor have been successful. We report here that a naturally occurring antibacterial peptide PR39 reversibly binds to the α7 subunit of the 26S proteasome and blocks degradation of NF-κB inhibitor IκBα by the ubiquitin-proteasome pathway without affecting overall proteasome activity. IκBα phosphorylation and ubiquitination occur normally after PR39 treatment, and binding of valosin-containing proteins is not impaired. The inhibition of IκBα degradation abolishes induction of NF-κB–dependent gene expression in cell culture and in mouse models of acute pancreatitis and myocardial infarction, including upregulation of endothelial adhesion proteins VCAM-1 and ICAM-1. In the latter model, sustained infusion of PR39 peptide resulted in significant reduction of myocardial infarct size. PR39 and related peptides may provide novel means to regulate cellular function and to control of NF-κB–dependent gene expression for therapeutic purposes.

Authors

Youhe Gao, Stewart Lecker, Mark J. Post, Antti J. Hietaranta, Jian Li, Rudiger Volk, Min Li, Kaori Sato, Ashok K. Saluja, Michael L. Steer, Alfred L. Goldberg, Michael Simons

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PR39 inhibits NF-κB–dependent gene expression in cell culture and in mic...
PR39 inhibits NF-κB–dependent gene expression in cell culture and in mice. (a and b) PR39 administration blocks NF-κB–dependent gene expression in cell culture. (a) Luciferase activity (fold increase), after exposure to 1 ng/mL TNF-α of ECV cells transfected with (NF-κB)4-TK-Luc construct, was measured in the absence (control) or presence of 100 nM PR39 or 10 μM MG132. Note significant inhibition of induction of NF-κB activity by TNF-α in PR39-treated cells. AP < 0.01 versus control. (b) Luciferase activity in ECV cells expressing CMV-Luc construct in the absence (control) or presence of 100 nM of PR39 or 10 μM of MG132. Note the lack of any effect of PR39 on CMV-driven luciferase activity. (c and d) PR39 blocks IκBα degradation and NF-κB–dependent transcription in the mouse pancreas after induction of acute pancreatitis. (c) Western blot analysis of IκBα in the mouse pancreas after exposure to caerulein in the absence (–) or presence (+) of pretreatment with 10 mg/kg intravenously injected PR39. (d) NF-κB activation in mouse pancreatic tissues in the setting of caerulein-induced pancreatitis examined using electromobility-shift assay. Note almost complete disappearance of NF-κB gel shift in PR39-treated animals. Excess of oligonucleotide competitor of NF-κB binding site (100×) was used to demonstrate band specificity (κB oligo).