Cell membrane lipid composition and distribution: implications for cell function and lessons learned from photoreceptors and platelets.
Cell membrane lipid composition and distribution: implications for cell function and lessons learned from photoreceptors and platelets.
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发表时间：
1997-12
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通讯作者：
K. Boesze-Battaglia;R. Schimmel
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作者：
K. Boesze-Battaglia;R. Schimmel
光感受器杆细胞和血小板是显著不同的，但都说明了一个类似的现象。两者都受到膜胆固醇的强烈影响，并且胆固醇在两种细胞类型的膜中的分布由膜内的脂质组成决定。在视杆细胞中，胆固醇强烈抑制视紫红质活性。质膜中相对较高水平的胆固醇用于抑制并由此保存视紫红质的活性，视紫红质在这些相同细胞的盘膜的低胆固醇环境中变得完全活跃。胆固醇在盘膜和质膜之间的这种生理上重要的分配发生是因为盘膜富含磷脂酰乙醇胺，从而为甾醇提供了一个有害的环境。血小板的胆固醇富集使这些细胞对聚集刺激更敏感。刺激血小板聚集引起胆固醇从外层单层快速跨双层移动。胆固醇的这种刺激依赖性再分配似乎是由于磷脂酰乙醇胺进入外单层的伴随运动。有吸引力的，但仍然未经证实的假设是，胆固醇易位在整个血小板反应中起着重要作用，并与胆固醇对这些细胞的致敏作用密切相关。
Photoreceptor rod cells and blood platelets are remarkably different, yet both illustrate a similar phenomenon. Both are strongly affected by membrane cholesterol, and the distribution of cholesterol in the membranes of both cell types is determined by the lipid composition within the membranes. In rod cells, cholesterol strongly inhibits rhodopsin activity. The relatively higher level of cholesterol in the plasma membrane serves to inhibit, and thereby conserve, the activity of rhodopsin, which becomes fully active in the low-cholesterol environment of the disk membranes of these same cells. This physiologically important partitioning of cholesterol between disk membranes and plasma membranes occurs because the disk membranes are enriched with phosphatidylethanolamine, thus providing a thermodynamically unfavorable environment for the sterol. Cholesterol enrichment of platelets renders these cells more responsive to stimuli of aggregation. Stimuli for platelet aggregation cause a rapid transbilayer movement of cholesterol from the outer monolayer. This stimulus-dependent redistribution of cholesterol appears to result from the concomitant movement of phosphatidylethanolamine into the outer monolayer. The attractive, yet still unproven, hypothesis is that cholesterol translocation plays an important role in the overall platelet response and is intimately related to the sensitizing actions of cholesterol on these cells.