Inhibition of Cdk6 expression through p38 MAP kinase is involved in differentiation of mouse prechondrocyte ATDC5
Inhibition of Cdk6 expression through p38 MAP kinase is involved in differentiation of mouse prechondrocyte ATDC5
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DOI：
10.1002/jcp.20350
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发表时间：
2005-09-01
影响因子：
5.6
通讯作者：
Kawaguchi, H
中科院分区：
文献类型：
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作者：
Moro, T;Ogasawara, T;Kawaguchi, H
由于在G1期的细胞周期的时间逮捕是细胞分化的先决条件，本研究调查的参与细胞周期因子在培养的小鼠前软骨细胞系ATDC 5的分化。在G1期细胞周期因子检查，蛋白质和mRNA水平的细胞周期蛋白依赖性激酶（Cdk 6）在分化培养基中的培养过程中下调。Cdk 6的蛋白质降解不参与这种下调，因为蛋白酶体抑制剂不逆转蛋白质水平。当向培养物中加入p38 MAPK、ERK-1/2和PI 3 K/Akt的抑制剂时，只有p38 MAPK抑制剂SB 203580阻断了分化培养基引起的Cdk 6蛋白水平的降低，表明Cdk 6抑制是由p38 MAPK途径介导的。事实上，p38 MAPK被证实在ATDC 5细胞分化期间被磷酸化。Cdk 6在ATDC 5细胞中的强表达阻断了软骨细胞的分化，并抑制了Sox 5和Sox 6的表达。然而，Cdk 6过表达并不影响细胞增殖或细胞周期进程，这表明Cdk 6对分化的抑制作用是通过在很大程度上独立于其细胞周期调控的机制来实现的。这些结果表明，Cdk 6可能是软骨细胞分化的调节剂，其p38介导的下调参与了有效的分化。
Because a temporal arrest in the G1-phase of the cell cycle is a prerequisite for cell differentiation, this study investigated the involvement of cell cycle factors in the differentiation of cultured mouse prechondrocyte cell line ATDC5. Among the G1 cell cycle factors examined, both protein and mRNA levels of cyclin-dependent kinase (Cdk6) were downregulated during the culture in a differentiation medium. The protein degradation of Cdk6 was not involved in this downregulation because proteasome inhibitors did not reverse the protein level. When inhibitors of p38 MAPK, ERK-1/2, and PI3K/Akt were added to the culture, only a p38 MAPK inhibitor SB203580 blocked the decrease in the Cdk6 protein level by the differentiation medium, indicating that the Cdk6 inhibition was mediated by p38 MAPK pathway. In fact, p38 MAPK was confirmed to be phosphorylated during differentiation of ATDC5 cells. Enforced expression of Cdk6 in ATDC5 cells blocked the chondrocyte differentiation and inhibited Sox5 and Sox6 expressions. However, the Cdk6 overexpression did not affect the proliferation or the cell cycle progression, suggesting that the inhibitory effect of Cdk6 on the differentiation was exerted by a mechanism largely independent of its cell cycle regulation. These results indicate that Cdk6 may be a regulator of chondrocyte differentiation and that its p38-mediated downregulation is involved in the efficient differentiation.