The most common mutation in surfactant protein C gene (SFTPC), SFTPC^I73T, causes interstitial lung disease with few therapeutic options. We previously demonstrated that EMC3, an important component of the multiprotein endoplasmic reticulum membrane complex (EMC), is required for surfactant homeostasis in alveolar type 2 epithelial (AT2) cells at birth. In the present study, we investigated the role of EMC3 in the control of SFTPC^I73T metabolism and its associated alveolar dysfunction. Using a knock-in mouse model phenocopying the I73T mutation, we demonstrated that conditional deletion of Emc3 in AT2 cells rescued alveolar remodeling/simplification defects in neonatal and adult mice. Proteomic analysis revealed that Emc3 depletion reversed the disruption of vesicle trafficking pathways and rescued the mitochondrial dysfunction associated with I73T mutation. Affinity purification-mass spectrometry analysis identified potential EMC3 interacting proteins in lung AT2 cells, including valosin containing protein (VCP) and its interactors. Treatment of Sftpc^I73T knock-in mice and SFTPC^I73T-expressing iAT2 cells derived from SFTPC^I73T patient-specific iPSCs with the VCP inhibitor CB5083 restored alveolar structure and SFTPC^I73T trafficking, respectively. Taken together, the present work identifies the EMC complex and VCP in the metabolism of the disease-associated SFTPC^I73T mutant, providing therapeutical targets for SFTPC^I73T-associated interstitial lung disease.

中文翻译：

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EMC3 调节与间质性肺病相关的 SFTPCI73T 突变的运输和肺毒性


表面活性剂蛋白 C 基因 （SFTPC） 中最常见的突变 SFTPC^I73T 会导致间质性肺病，几乎没有治疗选择。我们之前证明 EMC3 是多蛋白内质网膜复合物 （EMC） 的重要组成部分，是出生时肺泡 2 型上皮 （AT2） 细胞表面活性剂稳态所必需的。在本研究中，我们研究了 EMC3 在控制 SFTPC^I73T 代谢及其相关肺泡功能障碍中的作用。使用敲入小鼠模型表型复制 I73T 突变，我们证明 AT2 细胞中 Emc3 的条件性缺失挽救了新生和成年小鼠的肺泡重塑/简化缺陷。蛋白质组学分析显示，Emc3 耗竭逆转了囊泡运输途径的破坏，并挽救了与 I73T 突变相关的线粒体功能障碍。亲和纯化-质谱分析确定了肺 AT2 细胞中潜在的 EMC3 相互作用蛋白，包括含缬氨酸的蛋白质 （VCP） 及其相互作用物。用 VCP 抑制剂 CB5083 处理 Sftpc^I73T 敲入小鼠和源自 SFTPC^I73T 患者特异性 iPSC 的 SFTPC^I73T 表达 iAT2 细胞，分别恢复了肺泡结构和 SFTPC^I73T 运输。综上所述，本研究确定了疾病相关 SFTPC^I73T 突变体代谢中的 EMC 复合物和 VCP，为 SFTPC^I73T 相关间质性肺病提供了治疗靶点。