Proteasome from cytokine-treated human cells shows stimulated BrAAP activity and depressed PGPH activity

The branched chain amino acid-preferring (BrAAP) activity of multicatalytic proteinase complex isolated from human umbilical vein endothelial cells an d treated with interferon-gamma was increased more than 2-fold, which was a ssociated with a marked increase in LMP7 expression and decreased peptidylg lutamyl peptide-hydrolyzing activity. Increases in BrAAP activity in supern atants from cells treated with interferon-gamma, tumor necrosis factor-alph a, interleukin-1 beta, interleukin-6, or lipopolysaccharide paralleled the increases in LMP7 expression. These findings are consistent with the conclu sion that the increased BrAAP activity of LMP-containing multicatalytic pro teinase complex results from incorporation of LMP7 or other LMP subunits.