Celastrol inhibits the proteasome-dependent degradation of proteins.

(A) RAW264.7 cells were treated with 3 µM celastrol or 10 µM MG132 (or DMSO vehicle) for 30 min, followed by a 10 min treatment with 1 µg/mL LPS. Cellular lysates were prepared and probed for IκB-α or α-tubulin by Western blotting. A representative result of three independent experiments is shown. (B) RAW264.7 cells were treated with indicated concentrations of celastrol or MG132 for 1 h. Cellular lysates were prepared and probed with anti-ubiquitin or anti-α-tubulin. A representative result of three independent experiments is shown. (C) RAW264.7 cells were treated with 10 µM celastrol, 10 µM MG132 and/or 10 µM geldanamycin for 1 h. Cellular lysates were prepared and probed with anti-ubiquitin or anti-α-tubulin. A representative result of three independent experiments is shown. (D) RAW264.7 cells were treated with various concentrations of celastrol or MG132 in the presence (black bars) or absence (white bars) of LeTx for 4 h. Cell viability was assessed using the MTS assay. The means of three experiments±SEM are reported.