Kim Hyoin, Kei Kyungmin, Sonn Jong Kyung
Department of Biology, College of Natural Sciences, Kyungpook National University, 80 Daehakoro, Daegu, 41566, Korea.
In Vitro Cell Dev Biol Anim. 2016 Jan;52(1):120-9. doi: 10.1007/s11626-015-9954-3. Epub 2015 Oct 1.
Staurosporine has been known to induce chondrogenesis in monolayer cultures of mesenchymal cells by dissolving actin stress fibers. The aim of this study was to further elucidate how the alteration of actin filaments by staurosporine induces chondrogenesis. Specifically, we examined whether the transforming growth factor (TGF)-β pathway is implicated. SB505124 strongly suppressed staurosporine-induced chondrogenesis without affecting the drug's action on the actin cytoskeleton. Staurosporine increased the phosphorylation of TGF-β receptor I (TβRI) but had no significant effect on the expression levels of TGF-β1, TGF-β2, TGF-β3, TβRI, TβRII, and TβRIII. Phosphorylation of Smad2 and Smad3 was not increased by staurosporine. However, SB505124 almost completely suppressed the phosphorylation of Smad2 and Smad3. In addition, inhibition of Smad3 blocked staurosporine-induced chondrogenesis. Inhibition of Akt, p38 mitogen-activated protein kinase (MAPK), and c-jun N-terminal kinase (JNK) suppressed chondrogenesis induced by staurosporine. Phosphorylation of Akt, p38 MAPK, and JNK was increased by staurosporine. SB505124 reduced the phosphorylation of Akt and p38 MAPK, while it had no effect on the phosphorylation of JNK. The phosphorylation level of extracellular signal-regulated kinase (ERK) was not significantly affected by staurosporine. In addition, inhibition of ERK with PD98059 alone did not induce chondrogenesis. Taken together, these results suggest that staurosporine induces chondrogenesis through TGF-β pathways including canonical Smads and non-canonical Akt and p38 MAPK signaling.
已知星形孢菌素可通过溶解肌动蛋白应激纤维在间充质细胞的单层培养中诱导软骨形成。本研究的目的是进一步阐明星形孢菌素引起的肌动蛋白丝改变如何诱导软骨形成。具体而言，我们研究了转化生长因子（TGF）-β途径是否参与其中。SB505124强烈抑制星形孢菌素诱导的软骨形成，而不影响该药物对肌动蛋白细胞骨架的作用。星形孢菌素增加了TGF-β受体I（TβRI）的磷酸化，但对TGF-β1、TGF-β2、TGF-β3、TβRI、TβRII和TβRIII的表达水平没有显著影响。星形孢菌素未增加Smad2和Smad3的磷酸化。然而，SB505124几乎完全抑制了Smad2和Smad3的磷酸化。此外，抑制Smad3可阻断星形孢菌素诱导的软骨形成。抑制Akt、p38丝裂原活化蛋白激酶（MAPK）和c-jun氨基末端激酶（JNK）可抑制星形孢菌素诱导的软骨形成。星形孢菌素增加了Akt、p38 MAPK和JNK的磷酸化。SB505124降低了Akt和p38 MAPK的磷酸化，而对JNK的磷酸化没有影响。细胞外信号调节激酶（ERK）的磷酸化水平未受到星形孢菌素的显著影响。此外，单独用PD98059抑制ERK不会诱导软骨形成。综上所述，这些结果表明星形孢菌素通过包括经典Smads和非经典Akt及p38 MAPK信号传导的TGF-β途径诱导软骨形成。
