POLYHISTIDINE MEDIATES AN ACID-DEPENDENT FUSION OF NEGATIVELY CHARGED LIPOSOMES
POLYHISTIDINE MEDIATES AN ACID-DEPENDENT FUSION OF NEGATIVELY CHARGED LIPOSOMES
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DOI：
10.1021/bi00314a026
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
HUANG, L
中科院分区：
文献类型：
--
作者：
WANG, CY;HUANG, L
聚组氨酸促进通过超声处理制备的带负电荷的脂质体的融合。通过负染EM、凝胶过滤和荧光磷脂的共振能量转移证明脂质体融合。脂质体融合需要多聚组氨酸的存在，而同等浓度的组氨酸没有影响。在pH 7.4下可检测到很少或没有脂质体融合，但当培养基的pH降低至低于6.5时，脂质体融合大大增强。虽然酸性磷脂是必要的融合，脂质体制成的酸性脂质单独显示只有低水平的融合活性。由带负电荷的磷脂和中性磷脂（如磷脂酰胆碱和磷脂酰乙醇胺（PE），但不是鞘磷脂）的混合物（1：1）组成的脂质体显示出高水平（约80%）的融合能力。对于由PE/磷脂酰丝氨酸（PS）（1：1）制成的脂质体，在pH5.2和2.5 μ g/ml聚组氨酸的融合导致平均脂质体直径从296增加到2400埃，表明发生了多轮融合。脂质体融合不是非常泄漏，如缺乏释放包封的钙黄绿素所揭示的。对于PE/PS（1：1）脂质体，对于高达约30%的脂质体融合，观察到约10%的染料泄漏，并且在80%的脂质体融合时观察到约45%的泄漏。由于聚组氨酸在酸性pH下成为强聚阳离子，脂质体融合可能是由聚组氨酸与带负电荷的磷脂结合诱导的双层相分离的直接结果。因此，这种现象是类似的脂质体融合诱导的其他聚阳离子，如聚赖氨酸在中性pH值。该系统可以作为一个模型，用于研究病毒包膜与靶细胞膜的酸依赖性融合，如在流感，水泡性口炎，和Semliki森林病毒的情况下。
Polyhistidine facilitates the fusion of negatively charged liposomes prepared by sonication. Liposome fusion was demonstrated by negative-stain EM, gel filtration, and resonance energy transfer of the fluorescent phospholipids. Liposome fusion required the presence of polyhistidine, whereas histidine at equivalent concentrations had no effect. Little or no liposome fusion was detectable at pH 7.4, but it was greatly enhanced when the pH of the medium was reduced below 6.5. Although acidic phospholipid is necessary for fusion, liposomes made of acidic lipids alone showed only low levels of fusion activity. Liposomes composed of mixtures (1:1) of a negatively charged phospholipid and a neutral phospholipid such as phosphatidylcholine and phosphatidylethanolamine (PE), but not spingomyelin, showed high levels (about 80%) of fusion competency. For liposomes made of PE/phosphatidylserine (PS) (1:1), fusion at pH 5.2 and 2.5 .mu.g/ml polyhistidine resulted in an increase in the average liposome diameter from 296 to 2400 .ANG., indicating multiple rounds of fusion had occurred. Liposome fusion was not very leaky as revealed by the lack of release of encapsulated calcein. For PE/PS (1:1) liposomes, about 10% of dye leakage was observed for up to about 30% liposome fusion and about 45% leakage at 80% liposome fusion. Since polyhistidine becomes a strong polycation at acidic pH, liposome fusion may be a direct result of the bilayer phase separation induced by the binding of polyhistidine with the negatively charged phospholipids. Therefore, this phenomenon is similar to the liposome fusion induced by other polycations such as polylysine at neutral pH. This system may serve as a model for studies on the acid-dependent fusion of viral envelopes with target cell membranes, such as in the case of the influenza, vesicular stomatitis, and Semliki Forest viruses.