Free cholesterol alters lipid raft structure and function regulating neutrophil Ca2+ entry and respiratory burst:: Correlations with calcium channel raft trafficking
Free cholesterol alters lipid raft structure and function regulating neutrophil Ca2+ entry and respiratory burst:: Correlations with calcium channel raft trafficking
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DOI：
10.4049/jimmunol.178.8.5253
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发表时间：
2007-04-15
影响因子：
4.4
通讯作者：
Hauser, Carl J.
中科院分区：
文献类型：
--
作者：
Kannan, Kolenkode B.;Barlos, Dimitrios;Hauser, Carl J.
最近的研究将胆固醇过多和动脉粥样硬化与炎症联系起来。链接。这些过程之间的关系尚不清楚，但胆固醇是脂筏的重要组成部分。筏被认为集中膜信号分子，从而通过G蛋白偶联途径调节细胞信号。我们使用甲基β-环糊精消耗胆固醇从多形核中性粒细胞（PMN）筏，从而研究筏破坏G蛋白偶联的Ca 2+动员的影响。甲基β-环糊精对G蛋白偶联激动剂血小板活化因子或fMLP引起的Ca 2+储存耗竭没有影响，但消除了激动剂刺激的Ca 2+内流。游离胆固醇在非常低的浓度下调节Ca 2+进入PMN通过非特异性Ca 2+通道以双相方式。使用毒胡萝卜素研究证实了胆固醇调节Ca 2+进入的特异性。对胆固醇的反应似乎是生理性的，因为它们以成比例的双相方式调节呼吸爆发。进一步研究发现，游离胆固醇在PMN脂筏组分中积累，促进膜筏的形成和极化。最后，瞬时受体电位钙通道蛋白TRPC 1重新分配到筏馏分响应胆固醇。胆固醇利用率、Ca 2+信号传导和呼吸爆发之间的一致双相关系表明，Ca 2+内流和中性粒细胞活化受到胆固醇和其他环境脂筏成分之间的定量关系的调节。因此，症状性胆固醇过量和炎症之间的关联可能部分反映了调节免疫细胞Ca 2+进入的脂筏结构中的游离胆固醇依赖性变化。其他细胞类型中的Ca 2+进入依赖性反应也可能反映胆固醇生物利用度和脂质掺入筏。
Recent studies associate cholesterol excess and atherosclerosis with inflammation. The link. between these processes is not understood, but cholesterol is an important component of lipid rafts. Rafts are thought to concentrate membrane signaling molecules and thus regulate cell signaling through G protein-coupled pathways. We used methyl beta-cyclodextrin to deplete cholesterol from polymorphonuclear neutrophil (PMN) rafts and thus study the effects of raft disruption on G protein-coupled Ca2+ mobilization. Methyl beta-cyclodextrin had no effect on Ca2+ store depletion by the G protein-coupled agonists platelet-activating factor or fMLP, but abolished agonist-stimulated Ca2+ entry. Free cholesterol at very low concentrations regulated Ca2+ entry into PMN via nonspecific Ca2+ channels in a biphasic fashion. The specificity of cholesterol regulation for Ca2+ entry was confirmed using thapsigargin studies. Responses to cholesterol appear physiologic because they regulate respiratory burst in a proportional biphasic fashion. Investigating further, we found that free cholesterol accumulated in PMN lipid raft fractions, promoting formation and polarization of membrane rafts. Finally, the transient receptor potential calcium channel protein TRPC1 redistributed to raft fractions in response to cholesterol. The uniformly biphasic relationships between cholesterol availability, Ca2+ signaling and respiratory burst suggest that Ca2+ influx and PMN activation are regulated by the quantitative relationships between cholesterol and other environmental lipid raft components. The association between symptomatic cholesterol excess and inflammation may therefore in part reflect free cholesterol-dependent changes in lipid raft structure that regulate immune cell Ca2+ entry. Ca2+ entry-dependent responses in other cell types may also reflect cholesterol bioavailability and lipid incorporation into rafts.