胆固醇是如何被磷脂酰乙醇胺吸引到质膜的细胞质叶的。
How cholesterol could be drawn to the cytoplasmic leaf of the plasma membrane by phosphatidylethanolamine.
作者信息
Giang Ha, Schick M
机构信息
Department of Physics, University of Washington, Seattle, Washington.
Department of Physics, University of Washington, Seattle, Washington.
出版信息
Biophys J. 2014 Nov 18;107(10):2337-44. doi: 10.1016/j.bpj.2014.10.012.
In the mammalian plasma membrane, cholesterol can translocate rapidly between the exoplasmic and cytoplasmic leaves, so that its distribution between them should be given by the equality of its chemical potential in the leaves. Due to its favorable interaction with sphingomyelin, which is almost entirely in the outer leaf, one expects the great majority of cholesterol to be there also. Experimental results do not support this, implying that there is some mechanism attracting cholesterol to the inner leaf. We hypothesize that it is drawn there to reduce the bending free energy of the membrane caused by the presence of PE (phosphatidylethanolamine). It does this in two ways: first by simply diluting the amount of PE in the inner leaf, and second by ordering the tails of the PE to reduce its spontaneous curvature. Incorporating this mechanism into a model free energy for the bilayer, we find that between 50 and 60% of the total cholesterol should be in the inner leaf of human erythrocytes.
在哺乳动物的质膜中，胆固醇能够在外质叶和细胞质叶之间快速转运，因此其在这两层之间的分布应由其在这两层中的化学势相等来决定。由于胆固醇与几乎完全位于外叶的鞘磷脂具有良好的相互作用，人们预期绝大多数胆固醇也会在外叶。然而实验结果并不支持这一点，这意味着存在某种机制将胆固醇吸引到内叶。我们推测，胆固醇被吸引到内叶是为了降低由磷脂酰乙醇胺（PE）的存在而导致的膜弯曲自由能。它通过两种方式实现这一点：一是简单地稀释内叶中PE的量，二是使PE的尾部有序排列以降低其自发曲率。将这一机制纳入双层膜的自由能模型中，我们发现，在人类红细胞中，总胆固醇的50%至60%应位于内叶。
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