Fig. 7

Deficiency of parkin promotes IL-1β-induced OC resorptive capacity. A OCPs of WT or Parkin^−/− mice were treated with IL-1β for 48 h in the presence of RANKL. OC cells were starved for 4 h, retreated with IL-1β, and analyzed for pERK, ERK, acetylated α-tubulin, or HDAC6 expression by western blot. B BMMs from WT or Parkin^−/− mice were plated onto a bone slice and further incubated in the presence of the IL-1β. C OCPs of WT or Parkin^−/− mice were treated with IL-1β in the presence of RANKL and then analyzed for acetylated α-tubulin, cathepsin K, or β-actin expression by western blot. D OCPs of WT or Parkin^−/− mice were cultured with IL-1β. Afterward, anti-HDAC6 immunoprecipitation was performed, followed by western blotting with acetylated α-tubulin or parkin antibodies. The input of acetylated α-tubulin, pERK, ERK, parkin, or β-actin is shown. E, F RANKL-primed OCPs of Parkin^−/− were treated with IL-1β with PD98059. E Cells were harvested and analyzed by western blot using acetylated α-tubulin, cathepsin K, or β-actin antibody. F The culture media from OCs of WT or Parkin^−/− mice were treated with PD98059 (PD) or IL-1β was collected and the Cathepsin K activity was measured. G BMMs from Parkin^−/− mice were transduced with Mock or parkin (parkin O/E) retrovirus and cultured IL-1β. Transduced Parkin^−/− BMMs were analyzed for acetylated α-tubulin, parkin, and cathepsin K expression by western blot. H, I Transduced Parkin^−/− BMMs were cultured on bone slices and incubated with IL-1β. H Cathepsin K activity was measured, and I the number of resorption pits was estimated. *P < 0.05, **P < 0.005, and ***P < 0.001 between the indicated groups. Data are represented as means ± SD from three independent experiments; P-values were calculated by Kruskal–Wallis or Tukey post hoc comparison tests. J Schematic diagram of the proposed mechanism by which parkin regulates bone homeostasis