Efficient inhibition of macrophage TNF-alpha production upon targeted delivery of K48R ubiquitin

K48R ubiquitin (K48R-Ub) is an analogue of native ubiquitin that does not f orm polyubiquitin chain conjugates. Targeted delivery of this recombinant m utant ubiquitin to human macrophages results in an intracellular increase i n the ubiquitin analogue. IkB alpha polyubiquitination and degradation were significantly inhibited in K48R-Ub targeted macrophages upon stimulation w ith lipopolysaccharide. The ability to reduce IkB alpha degradation was als o associated with a reduced production of TNF-alpha, the gene of which is u nder NF-kB control. At a concentration of 0.1 mu M, dexamethasone was less effective than K48R-Ub in preventing IkB alpha depletion and TNF-alpha rele ase. These data suggest that ubiquitin analogues are potent suppressors of TNF-alpha release in macrophages.