Berlin E, Hannah J S, Yamane K, Peters R C, Howard B V
Metabolism and Nutrient Interactions Laboratory, Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, MD 20705, USA.
Int J Biochem Cell Biol. 1996 Oct;28(10):1131-9. doi: 10.1016/1357-2725(96)00063-5.
Dietary saturated fatty acids, especially lauric (12:0), myristic (14:0) and palmitic (16:0) acids, which are hypercholesterolemic, influence cell membrane fatty acid composition and affect LDL receptor function. When membrane phospholipid fatty acids in Chinese hamster ovary cells, containing the human LDL receptor, were modified (Hannah J. S. et al., 1995 Metabolism 44, 1428-1434), LDL receptor function was affected, but correlations with DPH-determined membrane fluidity were weak. The role of fluidity in various membrane domains with respect to the LDL receptor is examined here. Membrane fluidity was assessed by measuring steady-state fluorescence polarization of diphenylhexatriene (DPH) and its polar propionic acid (DPH-PA) and trimethylammonium (TMA-DPH) derivatives from 38 to 4 degrees C in fatty acid modified Chinese hamster ovary cells. Fatty acid changes modulated mid-bilayer fluidity as determined with DPH, but fluidity in phospholipid headgroup domains, assessed with DPH-PA and TMA-DPH, was independent of fatty acyl composition. The DPH fluidity was related to membrane unsaturation (P < 0.02), oleate contents (P < 0.009) in particular, but inversely related (P < 0.0002) to the longer chain (> or = 20 C atoms) unsaturated fatty acids with from four to six double bonds. The LDL binding was independent of fluidity, but there were weak relations between LDL internalization and DPH-PA anisotropy and between LDL degradation and TMA-DPH anisotropy. It was concluded that LDL binding was not related to mid-bilayer fluidity, but the results with the polar probes suggest a role of fluidity in modulating vertical displacement of the LDL/LDL receptor complex across the plasma membrane.
膳食饱和脂肪酸，尤其是具有高胆固醇血症作用的月桂酸（12:0）、肉豆蔻酸（14:0）和棕榈酸（16:0），会影响细胞膜脂肪酸组成并影响低密度脂蛋白（LDL）受体功能。当含有人类LDL受体的中国仓鼠卵巢细胞中的膜磷脂脂肪酸被修饰时（汉娜·J.S.等人，1995年，《新陈代谢》44卷，1428 - 1434页），LDL受体功能受到影响，但与用二苯基己三烯（DPH）测定的膜流动性的相关性较弱。本文研究了流动性在不同膜结构域中对LDL受体的作用。通过在脂肪酸修饰的中国仓鼠卵巢细胞中测量二苯基己三烯（DPH）及其极性丙酸（DPH - PA）和三甲基铵（TMA - DPH）衍生物在38至4摄氏度之间的稳态荧光偏振来评估膜流动性。脂肪酸变化调节了用DPH测定的双层中部流动性，但用DPH - PA和TMA - DPH评估的磷脂头部结构域的流动性与脂肪酰基组成无关。DPH流动性与膜不饱和度相关（P < 0.02），尤其与油酸含量相关（P < 0.009），但与具有四至六个双键的较长链（≥20个碳原子）不饱和脂肪酸呈负相关（P < 0.0002）。LDL结合与流动性无关，但LDL内化与DPH - PA各向异性之间以及LDL降解与TMA - DPH各向异性之间存在较弱的关系。得出的结论是，LDL结合与双层中部流动性无关，但极性探针的结果表明流动性在调节LDL/LDL受体复合物跨质膜的垂直位移中起作用。
