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首页> 外文期刊>Biochemistry >Sterol Carrier Protein-2-Facilitated Intermembrane Transfer of Cholesterol- and Phospholipid-Derived Hydroperoxides
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Sterol Carrier Protein-2-Facilitated Intermembrane Transfer of Cholesterol- and Phospholipid-Derived Hydroperoxides

机译：胆固醇和磷脂衍生的氢过氧化物的甾醇载体蛋白2促进膜间转移

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Sterol carrier protein-2 (SCP-2) facilitates cholesterol (Ch) and phospholipid (PL) transfer/ exchange between membranes and appears to play a key role in intracellular lipid trafficking.Whether SCP-2 can also facilitate lipid hydroperoxide (LOOH) transfer between membranes and thereby potentially enhance dissemination of peroxidative damage was examined in this study.Transfer kinetics of photochemically generated cholesterol hydroperoxide (ChOOH) species (5alpha-OOH,6alpha/6beta-OOH,7alpha/7beta-OOH) and phospholipid hydroperoxide (PLOOH) families (PCOOH,PEOOH,PSOOH) were determined,using HPLC with electrochemical detection for peroxide analysis.LOOH donor/acceptor pairs employed in transfer experiments included (i) all liposomes (e.g.,agglutinable SUVs/ nonagglutinable LUVs);(ii) photoperoxidized erythrocyte ghosts/SUV s or vice versa;and (iii) SUVs/mitochondria.In a SUV/ghost system at 37degC,the rate constant for total ChOOH spontaneous transfer was ~8 times greater than that for unoxidized Ch.Purified bovine liver and human recombinant SCP-2 exhibited an identical ability to stimulate overall ChOOH transfer,0.5 unit/mL (based on [~(14)C]Ch transfer) increasing the first-order rate constant (kappa) approx7-fold.SCP-2-enhanced translocation of individual ChOOHs increased with increasing hydrophilicity in the following order:6beta-OOH<6alpha-OOH<5alpha-OOH<7alpha/7beta-OOH.Likewise,SCP-2 stimulated PCOOH,PEOOH,or PSOOH transfer approx6-fold,but the net kappa was 1/5 that of 5alpha-OOH and 1/10 that of 7alpha/7beta-OOH.Donor membrane properties favoring SCP-2-enhanced LOOH transfer included (i) increasing PL unsaturation and (ii) increasing net negative charge imposed by phosphatidylserine.Cytotoxic relevance was demonstrated by showing that SCP-2 accelerates 7alpha-OOH transfer from SUVs to isolated mitochondria and that this enhances peroxide-induced loss of the mitochondrial membrane potential.On the basis of these findings,we postulate that SCP-2,by trafficking ChOOHs and PLOOHs in addition to parent lipids,might exacerbate cell injury under oxidative stress conditions.
机译：甾醇载体蛋白2（SCP-2）促进膜之间的胆固醇（Ch）和磷脂（PL）转移/交换，似乎在细胞内脂质运输中起关键作用.SCP-2是否也可以促进脂质氢过氧化物（LOOH）转移在这项研究中研究了膜之间的相互作用，从而潜在地增强了过氧化损伤的传播。光化学生成的胆固醇氢过氧化物（ChOOH）物种（5alpha-OOH，6alpha / 6beta-OOH，7alpha / 7beta-OOH）和磷脂氢过氧化物（PLOOH）的转移动力学家族（PCOOH，PEOOH，PSOOH），通过HPLC电化学检测进行过氧化物分析。转移实验中使用的LOOH供体/受体对包括（i）所有脂质体（例如，可凝集的SUV /不可凝集的LUV）;（ii）光过氧化的红血球（iii）SUV /线粒体。在SUV /鬼魂系统中，在37℃下，总ChOOH自发转移的速率常数约为u的8倍。未氧化的Ch。纯化的牛肝和人类重组SCP-2表现出相同的刺激总体ChOOH转移的能力，0.5单位/ mL（基于[〜（14）C] Ch转移），可提高一级速率常数（kappa）约7单个ChOOH的SCP-2-增强易位性随亲水性的增加按以下顺序增加：6beta-OOH <6alpha-OOH <5alpha-OOH <7alpha / 7beta-OOH。同样地，SCP-2刺激了PCOOH，PEOOH或PSOOH转移约为6倍，但净kappa为5alpha-OOH的1/5和7alpha / 7beta-OOH的1/10。有利于SCP-2增强LOOH转移的施主膜特性包括（i）增加PL不饱和度和（ii）磷脂酰丝氨酸施加的净负电荷增加，显示出SCP-2加速了7alpha-OOH从SUV转移至孤立的线粒体的细胞毒性相关性，并增强了过氧化物引起的线粒体膜电位的损失。调查结果，我们推测是通过贩运SCP-2除母体脂质外，ChOOH和PLOOH还可能在氧化应激条件下加剧细胞损伤。

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