Figure 2

The effects of celastrol carboxyl group modification on HSP70 induction. (A) Structure of celastrol and its modifications. The circled point indicates the modification location. R1 represents one of the structures that used by Klaić et al. to create celastrol analogues, while R2 is tri-peptide of glycine, the analogue used in this paper. (B) Identifications of (a) tri-peptide of glycine and (b) the celastrol analogue were `performed by mass spectrum analysis. (C) Effects of the celastrol analogue on HSP70 expression and HSF1 phosphorylation. U937 cells were treated with 600 nM of celastrol, GGG, Cel-GGG, 17-AAG, or NB for 24 h. For phosphorylation assay, cells were incubated with drugs for 10 min. WB detected HSP70 and p-HSF1 (s303 and s326). (D) The histogram shows western blot band density statistics for part C. * represents P < 0.05 vs. control. (E) Effect of the celastrol analogue on proliferation inhibition. Cells were treated with 600 nM of celastrol or its analogue for 24 h, and cellular survival was analyzed by FCM according to our previous report. GGG: tri-peptide of glycine; Cel-GGG: celastrol joined with tri-peptide of glycine through peptide formation.