Diffusion coefficient of fluorescent phosphatidylinositol 4,5-bisphosphate in the plasma membrane of cells
Diffusion coefficient of fluorescent phosphatidylinositol 4,5-bisphosphate in the plasma membrane of cells
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DOI：
10.1091/mbc.e07-12-1208
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发表时间：
2008-04-01
影响因子：
3.3
通讯作者：
McLaughlin, Stuart
中科院分区：
文献类型：
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作者：
Golebiewska, Urszula;Nyako, Marian;McLaughlin, Stuart
磷脂酰肌醇 4,5-二磷酸 (PIP2) 控制着细胞中数量惊人的过程。因此，许多研究人员认为质膜内层可能存在不同的 PIP2 库。如果 PIP2 的很大一部分通过静电方式结合到膜蛋白上碱性残基的非结构化簇上，则 PIP2 扩散常数 D 应该减小。我们将 Bodipy TMR-PIP2 的胶束显微注射到细胞中，并使用荧光相关光谱测量了成纤维细胞和上皮细胞内叶的 D。所有细胞类型的平均 +/- SD 值为 D = 0.8 +/- 0.2 mu m(2)/s（n = 218；25 摄氏度）。这比 Rat1 细胞上形成的气泡 D 低三倍，D = 2.5 +/- 0.8 μ m(2)/s (n = 26)。它还显着低于外叶或巨型单层囊泡中的 D 以及这些细胞膜内叶上其他脂质的扩散系数。最简单的解释是这些质膜内叶上大约三分之二的 PIP2 是可逆结合的。
Phosphatidylinositol 4,5-bisphosphate (PIP2) controls a surprisingly large number of processes in cells. Thus, many investigators have suggested that there might be different pools of PIP2 on the inner leaflet of the plasma membrane. If a significant fraction of PIP2 is bound electrostatically to unstructured clusters of basic residues on membrane proteins, the PIP2 diffusion constant, D, should be reduced. We microinjected micelles of Bodipy TMR-PIP2 into cells, and we measured D on the inner leaflet of fibroblasts and epithelial cells by using fluorescence correlation spectroscopy. The average +/- SD value from all cell types was D = 0.8 +/- 0.2 mu m(2)/s (n = 218; 25 degrees C). This is threefold lower than the D in blebs formed on Rat1 cells, D = 2.5 +/- 0.8 mu m(2)/s (n = 26). It is also significantly lower than the D in the outer leaflet or in giant unilamellar vesicles and the diffusion coefficient for other lipids on the inner leaflet of these cell membranes. The simplest interpretation is that approximately two thirds of the PIP2 on inner leaflet of these plasma membranes is bound reversibly.