Effect of phosphatidylinositol replacement by diacylglycerol on various physical properties of artificial membranes with respect to the role of phosphatidylinositol response.
Effect of phosphatidylinositol replacement by diacylglycerol on various physical properties of artificial membranes with respect to the role of phosphatidylinositol response.
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就磷脂酰肌醇反应的作用而言，用二酰甘油替代磷脂酰肌醇对人工膜的各种物理性质的影响。
DOI：
10.1016/0005-2736(82)90441-2
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
Y. Nozawa
中科院分区：
文献类型：
--
作者：
K. Ohki;T. Sekiya;T. Yamauchi;Y. Nozawa
为了深入了解细胞外刺激增强磷脂酰肌醇转换的生理作用，采用自旋探针和冷冻断裂电镜对含磷脂酰肌醇或二酰基甘油的人造膜（蛋黄磷脂酰胆碱/牛脑磷脂酰丝氨酸）的物理性质进行了研究。二酰基甘油失去了形成脂质双分子层结构的能力和对钙离子的敏感性。双棕榈酰磷脂酰胆碱脂质体中含有酵母磷脂酰肌醇，降低了双棕榈酰磷脂酰胆碱的相变温度，扩大了相变温度范围。而在相同浓度下，二酰基甘油没有受到磷脂酰肌醇的影响，但相变温度略有升高。在磷脂酰胆碱/磷脂酰丝氨酸/磷脂酰肌醇（摩尔比3:5:2）混合物中，用二酰基甘油代替磷脂酰肌醇，钙离子诱导的磷脂酰肌醇相分离增强。与磷脂酰胆碱/磷脂酰丝氨酸/磷脂酰甘油（摩尔比3:5:2）脂质体相比，磷脂酰胆碱/磷脂酰丝氨酸/磷脂酰肌醇（摩尔比3:5:2）脂质体中磷脂酰胆碱自旋探针的迁移率降低。在40°C时，在磷脂酰胆碱/磷脂酰肌醇（摩尔比为8:2）脂质体中观察到来自质子化硬脂酸自旋探针的额外成分，而在磷脂酰胆碱/二酰基甘油（摩尔比为8:2）脂质体中未观察到该成分。这可能表明由二酰基甘油取代磷脂酰肌醇引起的表面电荷的改变。事实上，在1 mM Ca2+的存在下，在40°C下，磷脂酰胆碱/磷脂酰肌醇脂质体中Ca2+和磷脂酰肌醇分子之间的静电相互作用将额外的成分去除。这些结果支持了磷脂酰肌醇代谢的增强可能通过改变膜的物理状态来触发细胞对外源刺激的各种反应的假设。
In an attempt to gain insight into the physiological role of phosphatidylinositol turnover enhanced by extracellular stimuli, the physical properties of artificial membranes (egg yolk phosphatidylcholine/bovine brain phosphatidylserine) containing phosphatidylinositol or diacylglycerol were studied by ESR using spin probes and freeze-fracture electron microscopy. Diacylglycerol lost both the ability to form lipid bilayer structures and its susceptibility to calcium ions. Yeast phosphatidylinositol included in dipalmitoylphosphatidylcholine liposomes lowered the phase transition temperature of dipalmitoylphosphatidylcholine and expanded the temperature range of phase transition. However, diacylglycerol at the same concentration did not undergo the effects caused by phosphatidylinositol but the phase transition temperature was slightly raised. Phase separation of phosphatidylserine induced by calcium ions was enhanced when the phosphatidylinositol was replaced by diacylglycerol in phosphatidylcholine/ phosphatidylserine/phosphatidylinositol (3:5:2, by molar ratio) mixtures. The mobility of phosphatidylcholine spin probe was decreased in phosphatidylcholine/ phosphatidylserine/diacylglycerol (3:5:2, by molar ratio) liposomes compared with phosphatidylcholine/phosphatidylserine/phosphatidylinositol (3:5:2, by molar ratio) liposomes. An additional component from protonated stearic acid spin probes was observed in phosphatidylcholine/phosphatidylinositol (8:2, by molar ratio) liposomes at 40°C, whereas the component was not seen in phosphatidylcholine/diacylglycerol (8:2, by molar ratio) liposomes. This may indicate the alteration of surface charge induced by the replacement of phosphatidylinositol by diacylglycerol. Indeed, in the presence of 1 mM Ca2+, the additional component was removed by an electrostatic interaction between Ca2+and phosphatidylinositol molecules in phosphatidylcholine/phosphatidylinositol liposomes at 40°C. These results support the hypothesis that the enhanced turnover of phosphatidylinositol may play a triggering role for various cellular responses to exogenous stimuli by altering membrane physical states.