Epand R M
Department of Biochemistry, McMaster University, Hamilton, Ont., Canada.
Biochem Cell Biol. 1990 Jan;68(1):17-23. doi: 10.1139/o90-003.
Phospholipid bilayers can undergo morphological rearrangements to other phases. The formation of one of these nonbilayer phases, the hexagonal phase, is preceded by an increase in the hydrophobicity of the bilayer surface and a destabilization of the bilayer structure. Certain membrane additives promote, while others inhibit, the formation of the hexagonal phase. Many of the molecular features that determine this phase preference are understood. Some of the properties of membranes are modulated by agents that affect the relative stability of the bilayer and hexagonal phases. Addition of bilayer stabilizers to a membrane decreases its fusogenic behaviour. One such bilayer stabilizer is cholesterol sulfate, which may function physiologically to inhibit the fusion of sperm cells. Several antiviral agents are also found to be bilayer stabilizers and some have been shown to inhibit membrane fusion phenomena. Another biological property that is modulated in a predictable manner by agents which affect the bilayer-hexagonal phase equilibrium is insulin-promoted glucose uptake in adipocytes. Bilayer stabilizers inhibit this process showing that the effects of insulin can be modulated by the bulk biophysical properties of the membrane. The activity of a number of membrane-bound enzymes is also lowered by bilayer stabilizers. Neutral and zwitterionic bilayer stabilizers are inhibitors of protein kinase C. Thus, the alteration of the bilayer-hexagonal phase transition by drugs may provide a useful parameter for predicting their effects on biological membranes.
磷脂双层可经历形态重排转变为其他相态。这些非双层相态之一即六方相的形成，之前会出现双层表面疏水性增加以及双层结构不稳定的情况。某些膜添加剂会促进六方相的形成，而其他一些则会抑制其形成。许多决定这种相态偏好的分子特征已为人所知。膜的一些特性会受到影响双层相和六方相相对稳定性的试剂的调节。向膜中添加双层稳定剂会降低其融合行为。一种这样的双层稳定剂是硫酸胆固醇，它可能在生理上起到抑制精子细胞融合的作用。还发现几种抗病毒剂也是双层稳定剂，并且一些已被证明能抑制膜融合现象。另一种可被影响双层 - 六方相平衡的试剂以可预测方式调节的生物学特性是胰岛素促进脂肪细胞对葡萄糖的摄取。双层稳定剂会抑制这一过程，表明胰岛素的作用可被膜的整体生物物理特性所调节。许多膜结合酶的活性也会被双层稳定剂降低。中性和两性离子双层稳定剂是蛋白激酶C的抑制剂。因此，药物对双层 - 六方相转变的改变可能为预测其对生物膜的影响提供一个有用的参数。
