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.
View: Text | PDF
Article

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

×

Figure 4

Options: View larger image (or click on image) Download as PowerPoint
Selective nature of PR39 effect. (a) PR39 does not substantially affect ...
Selective nature of PR39 effect. (a) PR39 does not substantially affect proteasome-dependent degradation of total cellular protein. Pulse-chase analysis of total cellular protein degradation in the U937 cells in the absence (control) or presence of 1 μM PR39 or 1 μM MG132. Note significantly lower inhibition of total cell protein degradation by PR39 than by MG132 (mean ± SD). (b) Lack of induction of HSP-70 expression in PR39-treated cells. Western blotting of cell extract from untreated (control) and PR39-treated (1 μM), or MG132-treated (1 μM) U937 cells demonstrated the appearance of HSP-70 expression after 3 hours of exposure to MG132 but not PR39. (c) Effect of PR39 administration on proteasome-dependent protein levels in cells. The level of proteasome-regulated cell-cycle repressor p21, and c-Fos transcription factor were determined by Western blotting in HUVEC cells pretreated with 100 nM of PR39 or 10 μM of MG132. Note the lack of the effect of PR39 treatment on the expression level of these proteins whereas the treatment with MG132 increased expression of both by inhibiting their degradation by the proteasome. (d) PR39 does not affect cell growth in culture. The effect of PR39 or proteasome inhibitors MG132 (MG) and lactacystin (LC) on cell growth in culture was tested using ECV304 cells. Cell counts 48 hours after stimulation of synchronized ECV304 cells with 10% serum in the presence of buffer (control) or 1 μM of PR39, lactacystin, or MG132, demonstrated significant inhibition of cell growth by both proteasome inhibitors, but not by PR39 (mean ± SD). AP < 0.01 versus control. Con, control.