The 78-kD Glucose-Regulated Protein Regulates Endoplasmic Reticulum Homeostasis and Distal Epithelial Cell Survival during Lung Development
The 78-kD Glucose-Regulated Protein Regulates Endoplasmic Reticulum Homeostasis and Distal Epithelial Cell Survival during Lung Development
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78千道尔顿葡萄糖调节蛋白在肺发育过程中调控内质网稳态及远端上皮细胞存活
DOI：
10.1165/rcmb.2015-0327oc
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发表时间：
2016-07-01
影响因子：
6.4
通讯作者：
Zhou, Beiyun
中科院分区：
文献类型：
--
作者：
Flodby, Per;Li, Changgong;Zhou, Beiyun
支气管肺发育不良（BPD）是一种早产儿慢性肺部疾病，与内质网（ER）应激有关。为了研究 ER 应激在 BPD 发病机制中的因果作用，我们生成了肺上皮细胞特异性 KO Grp78 的条件敲除 (KO) 小鼠 (cGrp78(f/f))，Grp78 是编码 ER 伴侣 78-kD 葡萄糖调节蛋白 (GRP78) 的基因，GRP78 是 ER 稳态和未折叠蛋白反应 (UPR) 的主要调节因子。肺上皮特异性 Grp78 KO 破坏了肺形态发生，导致发育停滞，增加了肺泡上皮 II 型细胞凋亡，并减少了围产期肺中表面活性蛋白和 I 型细胞标志物的表达。 cGrp78(f/f) 幼崽出生后立即死亡，可能是由于呼吸困难。重要的是，Grp78 KO 触发 UPR 激活，并显着诱导促凋亡转录因子 CCAAT/增强子结合蛋白 (C/EBP) 同源蛋白 (CHOP)。参与氧化应激和细胞死亡的基因表达增加以及编码抗氧化酶的基因表达减少表明氧化应激在肺泡上皮细胞（AEC）凋亡中发挥作用。 Smad3 磷酸化和转化生长因子-β/Smad3 靶标 Cdkn1a（编码 p21）和 Gadd45a 的表达增加表明 UPR 凋亡臂、氧化应激和转化生长因子-β/Smad 信号通路之间的相互作用有助于 Grp78 KO 诱导的 AEC 凋亡和发育停滞。化学伴侣牛磺熊去氧胆酸减少了离体培养的 cGrp78(f/f) 肺中的 UPR 激活和细胞凋亡，证实了 ER 应激在观察到的 AEC 异常中的作用。这些结果证明，GRP78 通过调节 ER 应激，在肺发育过程中 AEC 存活和基因表达中发挥关键作用，并表明 UPR 作为 BPD 的潜在治疗靶点。
Bronchopulmonary dysplasia (BPD), a chronic lung disease of prematurity, has been linked to endoplasmic reticulum (ER) stress. To investigate a causal role for ER stress in BPD pathogenesis, we generated conditional knockout (KO) mice (cGrp78(f/f)) with lung epithelial cell-specific KO of Grp78, a gene encoding the ER chaperone 78-kD glucose-regulated protein (GRP78), a master regulator of ER homeostasis and the unfolded protein response (UPR). Lung epithelial-specific Grp78 KO disrupted lung morphogenesis, causing developmental arrest, increased alveolar epithelial type II cell apoptosis, and decreased surfactant protein and type I cell marker expression in perinatal lungs. cGrp78(f/f) pups died immediately after birth, likely owing to respiratory distress. Importantly, Grp78 KO triggered UPR activation with marked induction of the proapoptotic transcription factor CCAAT/enhancer-binding proteins (C/EBP) homologous protein (CHOP). Increased expression of genes involved in oxidative stress and cell death and decreased expression of genes encoding antioxidant enzymes suggest a role for oxidative stress in alveolar epithelial cell (AEC) apoptosis. Increased Smad3 phosphorylation and expression of transforming growth factor-beta/Smad3 targets Cdkn1a (encoding p21) and Gadd45a suggest that interactions among the apoptotic arm of the UPR, oxidative stress, and transforming growth factor-beta/Smad signaling pathways contribute to Grp78 KO-induced AEC apoptosis and developmental arrest. Chemical chaperone Tauroursodeoxycholic acid reduced UPR activation and apoptosis in cGrp78(f/f) lungs cultured ex vivo, confirming a role for ER stress in observed AEC abnormalities. These results demonstrate a key role for GRP78 in AEC survival and gene expression during lung development through modulation of ER stress, and suggest the UPR as a potential therapeutic target in BPD.