A critical role of cavin (polymerase I and transcript release factor) in caveolae formation and organization
A critical role of cavin (polymerase I and transcript release factor) in caveolae formation and organization
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DOI：
10.1074/jbc.m707890200
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发表时间：
2008-02-15
影响因子：
4.8
通讯作者：
Pilch, Paul F.
中科院分区：
文献类型：
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作者：
Liu, Libin;Pilch, Paul F.
窖蛋白相关蛋白（PTRF，即窖蛋白）已被证明是窖蛋白小窝中一种高度丰富的蛋白质成分，但其在其中的功能作用尚不清楚。在此，我们通过共聚焦显微镜证实窖蛋白在脂肪细胞中与窖蛋白 -1共定位，并通过蔗糖梯度浮选在脂筏组分中与窖蛋白 -1共同分布。然而，窖蛋白并不直接与窖蛋白 -1结合，因为窖蛋白小窝的溶解会破坏它们之间的相互作用。用β - 环糊精消耗胆固醇会导致窖蛋白在质膜脂筏组分中的显著下调。在HEK293 - Cav -1细胞中过表达窖蛋白以及在3T3 - L1脂肪细胞中敲低窖蛋白分别会提高和降低窖蛋白 -1的水平，这表明窖蛋白在维持窖蛋白 -1的水平方面具有重要作用。一种窖蛋白的截短形式，即eGFP - 窖蛋白 -1 - 322，其从C末端缺失了74个氨基酸，通过共聚焦显微镜显示出微管网络定位。用拉春库林B或诺考达唑破坏细胞骨架成分会降低窖蛋白的表达，但不影响窖蛋白 -1的量。我们提出，窖蛋白在窖蛋白小窝内表面的存在可能通过与细胞骨架的相互作用稳定了这些结构，因此窖蛋白在窖蛋白小窝的形成和组织中起着重要作用。
Cavin (PTRF) has been shown to be a highly abundant protein component of caveolae, but its functional role there is unknown. Here, we confirm that cavin co-localizes with caveolin-1 in adipocytes by confocal microscopy and co-distributes with caveolin-1 in lipid raft fractions by sucrose gradient flotation. However, cavin does not directly associate with caveolin-1 as solubilization of caveolae disrupts their interaction. Cholesterol depletion with beta-cyclodextrin causes a significant down-regulation of cavin from plasma membrane lipid raft fractions. Overexpression of cavin in HEK293-Cav-1 cells and knockdown of cavin in 3T3-L1 adipocytes enhances and diminishes caveolin-1 levels, respectively, indicating an important role for cavin in maintaining the level of caveolin-1. A truncated form of cavin, eGFP-cavin-1-322, which lacks 74 amino acids from the C-terminal, reveals a microtubular network localization by confocal microscopy. Disruption of cytoskeletal elements with latrunculin B or nocodazole diminishes cavin expression without affecting the caveolin-1 amount. We propose that the presence of cavin on the inside surface of caveolae stabilizes these structures, probably through interaction with the cytoskeleton, and cavin therefore plays an important role in caveolae formation and organization.