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A small molecule ubiquitination inhibitor blocks NF-kappa B-dependent cytokine expression in cells and rats

Abstract

A small molecule inhibitor of NF-kappaB-dependent cytokine expression was discovered that blocked TNFalpha-induced IkappaBalpha degradation in MM6 cells but not the degradation of beta-catenin in Jurkat cells. Ro106-9920 blocked LPS-dependent expression of TNFalpha, IL-1betaand IL-6 in fresh human peripheral blood mononuclear cells with IC(50) values below 1 {micro)M. Ro106-9920 also blocked TNFalpha production in a dose-dependent manner following oral administration in two acute models of inflammation (air pouch and LPS challenge). Ro106-9920 was observed to inhibit an ubiquitination activity that does not require betaTRCP, but associates with IkappaBalpha and will ubiquitinate IkappaBalphaS32/36E (IkappaBalphaee) specifically at lysine 21 or 22. Ro106-9920 was identified in a cell free system as a time-dependent inhibitor of IkappaBalphaee ubiquitination with an IC(50) value of 2.3 0.09 {micro}M. The E3 ligase activity is inhibited by cysteine alkylating reagents, supported by E2UBCH7 and requires cIAP2 or a cIAP2 associated protein for activity. These activities are inconsistent to what has been reported for SCF(superbetaTRCP}, the putative E3 for IkappaBalpha ubiquitination. Ro106-9920 was observed to be selective for IkappaBalphaee ubiquitination over E1, E2UBCH7, nonspecific ubiquitination of cellular proteins and 97 other molecular targets. We propose that Ro106-9920 selectively inhibits an uncharacterized, but essential, ubiquitination activity associated with LPS and TNFalpha induced IkappaBalpha degradation and NF-kappaB activation.

Authors: Swinney DC, Xu YZ, Scarafia LE, Lee I, Mak AY, Gan QF, Ramesha CS, Mulkins MA, Dunn J, So OY, Biegel T, Dinh M, Volkel P, Barnett J, Dalrymple SA, Lee S, Huber M
Journal: J Biol Chem 277: 23573-23581
Year: 2002
PubMed: Find in PubMed