Selective inhibitors of the osteoblast proteasome stimulate bone formation in vivo and in vitro
J. Clin. Invest. I.R. Garrett, et al. 111:1771 doi:10.1172/JCI16198 [Go to this article.]

Figure 4
Effect of proteasome inhibition on BMP-2 protein expression and bone formation. (a) Luciferase activity of cell lysates of 2T3 cells transfected with murine BMP-2 promoter (–2712/+165) operatively linked to firefly luciferase cDNA and treated with either simvastatin (dashed line), PS1 (dotted line), or epoxomicin (solid line). (b) Effects of PS1 (50 and 100 nM) on mRNA expression of BMP-2, BMP-4, and BMP-6 in FRC cells. FRC cells were treated with PS1 (50 and 100 nM) for 6 hours and cultured for 48 hours. The mRNA expression of BMP-2, BMP-4, and BMP-6 was detected by Northern blot analysis and quantitated by the PhosphoImager analysis method. PS1 increased BMP-2 mRNA expression 2.4-fold and 3.5-fold at concentrations of 50 and 100 nM, but had no significant effect on BMP-4 and BMP-6 mRNA expression. (c) Correlation of BMP-2 protein production from Hu09 human osteoblastic cells and inhibitory activity on the proteasome among proteasome inhibitors of different types. (d) Correlation of BMP-2 protein production from Hu09 human osteoblastic cells and bone formation activity (as assessed by effects on calvarial bone organ cultures).