Fusion, leakage and surface Hydrophobicity of vesicles containing phosphoinositides:: Influence of steric and electrostatic effects
Fusion, leakage and surface Hydrophobicity of vesicles containing phosphoinositides:: Influence of steric and electrostatic effects
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DOI：
10.1007/s00232-002-1062-0
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发表时间：
2003-03-01
影响因子：
2.4
通讯作者：
Arnold, K
中科院分区：
文献类型：
--
作者：
Müller, M;Zschörnig, O;Arnold, K
通过荧光方法研究了钙和镧离子诱导的含有磷脂酰肌醇（PI）、磷脂酰肌醇-4-单磷酸（PIP）、磷脂酰肌醇-4,5-二磷酸（PIP2）或磷脂酰肌醇-3,4,5-三磷酸（PIP3）的脂质囊泡的融合及其相关的膜特性，例如表面介电常数和囊泡渗漏。脂质囊泡中多磷酸化磷酸肌醇 (PPI) 的存在增强了融合，具体取决于脂质混合测定确定的 PPI 磷酸化水平和 PPI 浓度。即使在囊泡膜中 PPI 的生理相关小浓度下，这种相关性也成立。然而，由于肌醇环的空间效应，非磷酸化 PI 的存在抑制了融合。由磷脂酰丝氨酸（PS）与PI的混合物制成的囊泡的脂质混合的阳离子阈浓度随着PI含量的增加而增加。对于所有研究的囊泡系统，囊泡表面介电常数的降低和囊泡泄漏的增加都伴随着融合。 PI中非磷酸化肌醇环的存在不会干扰融合阳离子引起的表面介电常数的变化。因此，我们推断表面介电常数的降低是膜融合发生的必要条件，但当相互作用的膜被非磷酸化肌醇环阻止紧密接近时，它与膜融合无关。
Calcium and lanthanum ion-induced fusion of lipid vesicles containing phosphatidylinositol (PI), phosphatidylinositol-4-monophosphate (PIP), phosphatidylinositol-4,5-bisphosphate (PIP2) or phosphatidylinositol-3,4,5-trisphosphate (PIP3) and its associated membrane properties, e.g., surface dielectric constant and vesicle leakage, were studied by fluorescence methods. The presence of poly-phosphorylated phosphoinositides (PPI) in lipid vesicles enhanced fusion, depending on the PPI phosphorylation level and the PPI concentration, as determined by the lipid mixing assay. This correlation held even at physiologically relevant small concentrations of PPI in vesicle membranes. However, the presence of nonphosphorylated PI inhibited fusion due to the steric effect of the inositol ring. The cation threshold concentration for the lipid mixing of vesicles made of mixtures of phosphatidylserine (PS) with PI increased with increasing PI contents. For all vesicle systems studied, a decrease in vesicle surface dielectric constant and an increase in vesicle leakage accompanied fusion. The presence of the nonphosphorylated inositol ring in PI did not interfere with the changes in the surface dielectric constant caused by fusogenic cations. Therefore, we deduce that the reduction of the surface dielectric constant is a necessary condition for membrane fusion to occur but it does not correlate with membrane fusion when interacting membranes are blocked for close approach as by the nonphosphorylated inositol ring.