VAMP-associated Proteins (VAP) as Receptors That Couple Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Proteostasis with Lipid Homeostasis
VAMP-associated Proteins (VAP) as Receptors That Couple Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Proteostasis with Lipid Homeostasis
复制标题
DOI：
10.1074/jbc.m115.692749
复制
发表时间：
2016-03-04
影响因子：
4.8
通讯作者：
Aridor, Meir
中科院分区：
文献类型：
--
作者：
Ernst, Wayne L.;Shome, Kuntala;Aridor, Meir
未酯化的胆固醇在表达错误折叠的囊性纤维化跨膜传导调节因子（CFTR）的细胞中的晚期内体中积累。CFTR在内质网（ER）中的错误折叠或ER应激的一般激活导致动力蛋白介导的胆固醇负载的晚期内体在高尔基体区域的聚集，这是由ER定位的VAMP相关蛋白（VAP）调节的过程。我们假设VAP作为细胞内受体，通过与酸性轨道（FFAT）结合信号（发现于脂质分选和传感蛋白，LSS）中的两种苯丙氨酸相互作用，将脂质稳态与蛋白稳态调节偶联。VAPB抑制F508-CFTR的降解。该活性被映射到配体结合主要精子蛋白（MSP）结构域，这足以调节CFTR生物合成。我们确定了MSP内非结构化环中的突变，该突变将VAPB调节的CFTR生物发生与FFAT的基本相互作用解偶联。利用这些信息，我们定义了VAPB和蛋白质稳态调节剂（配体）之间的功能和物理相互作用，包括未折叠的蛋白质反应传感器ATF 6和ER降解簇，包括FAF 1，VCP，BAP 31和Derlin-1。VAPB通过与RMA 1-Derlin-BAP 31-VCP通路相互作用抑制ER中F508-CFTR的降解。含有串联FFAT信号的假配体的分析支持VAP相互作用的竞争模型，指导CFTR生物发生。结果表明，VAP-配体结合夫妇蛋白质稳态和脂质稳态导致观察到的表型的脂质异常蛋白质折叠疾病的模型。
Unesterified cholesterol accumulates in late endosomes in cells expressing the misfolded cystic fibrosis transmembrane conductance regulator (CFTR). CFTR misfolding in the endoplasmic reticulum (ER) or general activation of ER stress led to dynein-mediated clustering of cholesterol-loaded late endosomes at the Golgi region, a process regulated by ER-localized VAMP-associated proteins (VAPs). We hypothesized that VAPs serve as intracellular receptors that couple lipid homeostasis through interactions with two phenylalanines in an acidic track (FFAT) binding signals (found in lipid sorting and sensing proteins, LSS) with proteostasis regulation. VAPB inhibited the degradation of F508-CFTR. The activity was mapped to the ligand-binding major sperm protein (MSP) domain, which was sufficient in regulating CFTR biogenesis. We identified mutations in an unstructured loop within the MSP that uncoupled VAPB-regulated CFTR biogenesis from basic interactions with FFAT. Using this information, we defined functional and physical interactions between VAPB and proteostasis regulators (ligands), including the unfolded protein response sensor ATF6 and the ER degradation cluster that included FAF1, VCP, BAP31, and Derlin-1. VAPB inhibited the degradation of F508-CFTR in the ER through interactions with the RMA1-Derlin-BAP31-VCP pathway. Analysis of pseudoligands containing tandem FFAT signals supports a competitive model for VAP interactions that direct CFTR biogenesis. The results suggest a model in which VAP-ligand binding couples proteostasis and lipid homeostasis leading to observed phenotypes of lipid abnormalities in protein folding diseases.