DDIT3/CHOP promotes autophagy in chondrocytes via SIRT1-AKT pathway
DDIT3/CHOP promotes autophagy in chondrocytes via SIRT1-AKT pathway
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DDIT3/CHOP 通过 SIRT1-AKT 途径促进软骨细胞自噬
DOI：
10.1016/j.bbamcr.2021.119074
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发表时间：
2021-06-08
影响因子：
5.1
通讯作者：
Wang, Jiawei
中科院分区：
文献类型：
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作者：
Yang, Chang;Xu, Xiaoxiao;Wang, Jiawei
内质网应激可通过未折叠蛋白反应（unfolded protein response，UPR）启动自噬。DDIT 3/CHOP作为UPR的关键下游基因，在软骨细胞中表达。然而，DDIT 3/CHOP对软骨细胞自噬的调控机制尚不清楚。在这项研究中，自噬标记Beclin 1和LC 3B的表达水平被发现减少，而p62在DDIT 3/CHOP KO小鼠的胫骨生长板和肋原代软骨细胞中增加。在体外，过表达DDIT 3/CHOP诱导ATDC 5软骨细胞的自噬，表现出升高的LC 3B免疫荧光信号和升高的自噬体和自溶酶体数量。对获得和丧失功能的分析表明，Beclin 1的蛋白水平和LC 3BII/I的比率在DDIT 3/CHOP过表达的细胞中增加，而在DDIT 3/CHOP敲低的细胞中降低。氯喹（CQ）引起的p62水平的降低和LC 3BII的额外积累进一步表明DDIT 3/CHOP增强自噬通量。通过CHIP、qRT-PCR和Western blot分析，我们发现DDIT 3/CHOP直接结合SIRT 1的启动子以促进其表达。此外，SIRT 1增强ATDC 5细胞的自噬活性，抑制或激活SIRT 1可部分逆转过表达或下调DDIT 3/CHOP对自噬的影响。此外，发现AKT信号传导负责ATDC 5细胞中DDIT 3/CHOP调节的自噬。SIRT 1敲低逆转了DDIT 3/CHOP过表达对AKT信号传导的影响。总之，我们的数据阐明了DDIT 3/CHOP通过SIRT 1-AKT途径促进ATDC 5软骨细胞的自噬。这些结果也在原代软骨细胞中得到证实。
Endoplasmic reticulum (ER) stress can initiate autophagy via unfolded protein response (UPR). As a key downstream gene of UPR, DDIT3/CHOP is expressed in chondrocytes. However, the regulation mechanism of DDIT3/CHOP on autophagy in chondrocytes remains unclear. In this study, the expression levels of autophagic markers Beclin1 and LC3B were found to decrease while p62 increase in the tibial growth plate and costal primary chondrocytes from DDIT3/CHOP KO mice. In vitro, overexpressing DDIT3/CHOP induced autophagy in ATDC5 chondrocytes, displaying an elevated immunofluorescence signal of LC3B and elevated numbers of autophagosomes and autolysosomes. Analysis of the gain- and loss-of-function indicated that the protein level of Beclin1 and the ratio of LC3BII/I increased in DDIT3/CHOP overexpression cells, whereas decreased in DDIT3/CHOP knockdown cells. The decreased level of p62 and additional accumulation of LC3BII caused by chloroquine (CQ) further indicated that DDIT3/CHOP enhanced autophagic flux. Mechanistically, we found that DDIT3/CHOP binds directly to the promoter of SIRT1 to promote its expression by CHIP, qRT-PCR, and Western blot analysis. In addition, SIRT1 enhanced autophagic activity in ATDC5 cells, and inhibition or activation of SIRT1 partially reversed the effect of overexpressing or downregulating DDIT3/CHOP on autophagy. Furthermore, AKT signaling was found to be responsible for DDIT3/CHOP-regulated autophagy in ATDC5 cells. SIRT1 knockdown reversed the effect of DDIT3/CHOP overexpression on AKT signaling. In conclusion, our data clarifies that DDIT3/CHOP promotes autophagy in ATDC5 chondrocytes through the SIRT1-AKT pathway. These results were also confirmed in the primary chondrocytes.