Oxysterol Binding Protein-related Protein 9 (ORP9) Is a Cholesterol Transfer Protein That Regulates Golgi Structure and Function
Oxysterol Binding Protein-related Protein 9 (ORP9) Is a Cholesterol Transfer Protein That Regulates Golgi Structure and Function
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DOI：
10.1091/mbc.e08-09-0905
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发表时间：
2009-03-01
影响因子：
3.3
通讯作者：
Ridgway, Neale D.
中科院分区：
文献类型：
--
作者：
Ngo, Mike;Ridgway, Neale D.
氧固醇结合蛋白（OSBP）和OSBP相关蛋白（ORP）组成了一个大的基因家族，差异定位于细胞器膜，反映了在固醇信号传导和/或运输的功能作用。OSBP在内质网（ER）和高尔基体之间分配，在高尔基体中它赋予神经酰胺转运和鞘磷脂合成的固醇依赖性调节。ORP 9 L也定位于ER-高尔基体，但其在分泌和脂质转运中的作用尚不清楚。在这里，我们证明了ORP 9 L之间的trans-Golgi/trans-Golgi网络（TGN），和ER的分区是由磷脂酰肌醇4-磷酸（PI-4P）特异性PH结构域和VAMP相关蛋白（VAP），分别介导的。在体外，OSBP和ORP 9 L介导的PI-4P依赖的脂质体之间的胆固醇运输，这表明它们的主要体内功能是高尔基体和ER之间的固醇转移。通过RNAi消耗ORP 9 L导致高尔基体断裂，抑制囊泡体病毒糖蛋白从ER转运，并在核内体/溶酶体中积累胆固醇。蛋白质转运和细胞生长抑制的完全停止是通过诱导型过表达的ORP 9 S实现的，ORP 9 S是一种缺乏PH结构域的显性负性变体。我们的结论是，ORP 9保持早期分泌途径的完整性，通过介导的ER和trans-Golgi/TGN之间的固醇运输。
Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a large gene family that differentially localize to organellar membranes, reflecting a functional role in sterol signaling and/or transport. OSBP partitions between the endoplasmic reticulum (ER) and Golgi apparatus where it imparts sterol-dependent regulation of ceramide transport and sphingomyelin synthesis. ORP9L also is localized to the ER-Golgi, but its role in secretion and lipid transport is unknown. Here we demonstrate that ORP9L partitioning between the trans-Golgi/trans-Golgi network (TGN), and the ER is mediated by a phosphatidylinositol 4-phosphate (PI-4P)-specific PH domain and VAMP-associated protein (VAP), respectively. In vitro, both OSBP and ORP9L mediated PI-4P-dependent cholesterol transport between liposomes, suggesting their primary in vivo function is sterol transfer between the Golgi and ER. Depletion of ORP9L by RNAi caused Golgi fragmentation, inhibition of vesicular somatitus virus glycoprotein transport from the ER and accumulation of cholesterol in endosomes/lysosomes. Complete cessation of protein transport and cell growth inhibition was achieved by inducible overexpression of ORP9S, a dominant negative variant lacking the PH domain. We conclude that ORP9 maintains the integrity of the early secretory pathway by mediating transport of sterols between the ER and trans-Golgi/TGN.