Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, 467-8601, Japan.
Department of Rehabilitation Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
BMC Musculoskelet Disord. 2022 May 26;23(1):495. doi: 10.1186/s12891-022-05419-1.
Heat shock protein (HSP) 90 functions as a molecular chaperone and is constitutively expressed and induced in response to stress in many cell types. We have previously demonstrated that transforming growth factor-β (TGF-β), the most abundant cytokine in bone cells, induces the expression of HSP27 through Smad2, p44/p42 mitogen-activated protein kinase (MAPK), p38 MAPK, and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in mouse osteoblastic MC3T3-E1 cells. This study investigated the effects of HSP90 on the TGF-β-induced HSP27 expression and the underlying mechanism in mouse osteoblastic MC3T3-E1 cells.
Clonal osteoblastic MC3T3-E1 cells were treated with the HSP90 inhibitors and then stimulated with TGF-β. HSP27 expression and the phosphorylation of Smad2, p44/p42 MAPK, p38 MAPK, and SAPK/JNK were evaluated by western blot analysis.
HSP90 inhibitors 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG) and onalespib significantly enhanced the TGF-β-induced HSP27 expression. TGF-β inhibitor SB431542 reduced the enhancement by 17-DMAG or onalespib of the TGF-β-induced HSP27 expression levels. HSP90 inhibitors, geldanamycin, onalespib, and 17-DMAG did not affect the TGF-β-stimulated phosphorylation of Smad2. Geldanamycin did not affect the TGF-β-stimulated phosphorylation of p44/p42 MAPK or p38 MAPK but significantly enhanced the TGF-β-stimulated phosphorylation of SAPK/JNK. Onalespib also increased the TGF-β-stimulated phosphorylation of SAPK/JNK. Furthermore, SP600125, a specific inhibitor for SAPK/JNK, significantly suppressed onalespib or geldanamycin's enhancing effect of the TGF-β-induced HSP27 expression levels.
Our results strongly suggest that HSP90 inhibitors upregulated the TGF-β-induced HSP27 expression and that these effects of HSP90 inhibitors were mediated through SAPK/JNK pathway in osteoblasts.
热休克蛋白（HSP）90 作为分子伴侣发挥作用，在许多细胞类型中，它在受到应激时组成性表达并被诱导。我们之前已经证明，转化生长因子-β（TGF-β）是骨细胞中最丰富的细胞因子，通过 Smad2、p44/p42 丝裂原活化蛋白激酶（MAPK）、p38 MAPK 和应激激活蛋白激酶/c-Jun N 端激酶（SAPK/JNK）诱导小鼠成骨细胞 MC3T3-E1 细胞中 HSP27 的表达。本研究探讨了 HSP90 对 TGF-β诱导的 HSP27 表达的影响及其在小鼠成骨细胞 MC3T3-E1 细胞中的潜在机制。
用 HSP90 抑制剂处理克隆成骨细胞 MC3T3-E1 细胞，然后用 TGF-β 刺激。通过 Western blot 分析评估 HSP27 表达和 Smad2、p44/p42 MAPK、p38 MAPK 和 SAPK/JNK 的磷酸化。
HSP90 抑制剂 17-二甲基氨基乙基氨基-17-去甲氧基格尔德霉素（17-DMAG）和 onalespib 显著增强了 TGF-β 诱导的 HSP27 表达。TGF-β 抑制剂 SB431542 降低了 17-DMAG 或 onalespib 对 TGF-β 诱导的 HSP27 表达水平的增强作用。HSP90 抑制剂格尔德霉素、onalespib 和 17-DMAG 不影响 TGF-β 刺激的 Smad2 磷酸化。格尔德霉素不影响 TGF-β 刺激的 p44/p42 MAPK 或 p38 MAPK 的磷酸化，但显著增强了 TGF-β 刺激的 SAPK/JNK 的磷酸化。Onalespib 也增加了 TGF-β 刺激的 SAPK/JNK 的磷酸化。此外，SAPK/JNK 的特异性抑制剂 SP600125 显著抑制了 onalespib 或格尔德霉素对 TGF-β 诱导的 HSP27 表达水平的增强作用。
我们的结果强烈表明，HSP90 抑制剂上调了 TGF-β 诱导的 HSP27 表达，HSP90 抑制剂的这些作用是通过成骨细胞中的 SAPK/JNK 途径介导的。
