Methionine oxidation impairs reverse cholesterol transport by apolipoprotein A-1
Methionine oxidation impairs reverse cholesterol transport by apolipoprotein A-1
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DOI：
10.1073/pnas.0802025105
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发表时间：
2008-08-26
影响因子：
11.1
通讯作者：
Heinecke, Jay W.
中科院分区：
文献类型：
--
作者：
Shao, Baohai;Cavigiolio, Giorgio;Heinecke, Jay W.
HDL通过接受来自动脉壁巨噬细胞泡沫细胞的游离胆固醇来预防血管疾病。这一途径严重依赖于卵磷脂：胆固醇酰基转移酶（LCAT），它能迅速将胆固醇转化为胆固醇酯。LCAT的生理激活因子是载脂蛋白A-1 (apoA-1)，主要的HDL蛋白。然而，如果apoa - 1暴露于活性中间体，则胆固醇的去除会受到损害。在患有心血管疾病的人群中，髓过氧化物酶（MPO）会氧化HDL， MPO的氧化会损害apoA-I在体外激活LCAT的能力。由于apoA-1中单个蛋氨酸残基Met-148位于该蛋白LCAT活化结构域的中心附近，我们确定其被MPO氧化是否可以解释LCAT活性的丧失。质谱分析表明，Met-148氧化为蛋氨酸亚砜与盘状HDL和HDL3（酶的生理底物）中LCAT活性的丧失有关。用蛋氨酸亚砜还原酶逆转氧化恢复HDL激活LCAT的能力。含有Met-148 -> Leu突变的apoA-I制备的盘状HDL对MPO的失活具有显著的抗性。基于文献中的结构数据，我们提出Met-148的氧化破坏了apoA-I的中心环，该环与LCAT激活域重叠。这些观察结果暗示apoA-I中单个Met的氧化在LCAT激活受损中，这是逆转胆固醇运输的关键早期步骤。
HDL protects against vascular disease by accepting free cholesterol from macrophage foam cells in the artery wall. This pathway is critically dependent on lecithin:cholesterol acyltransferase (LCAT), which rapidly converts cholesterol to cholesteryl ester. The physiological activator of LCAT is apolipoprotein A-1 (apoA-1), the major HDL protein. However, cholesterol removal is compromised if apoA-I is exposed to reactive intermediates. In humans with established cardiovascular disease, myeloperoxidase (MPO) oxidizes HDL, and oxidation by MPO impairs apoA-I's ability to activate LCAT in vitro. Because a single methionine residue in apoA-1, Met-148, resides near the center of the protein's LCAT activation domain, we determined whether its oxidation by MPO could account for the loss of LCAT activity. Mass spectrometric analysis demonstrated that oxidation of Met-148 to methionine sulfoxide associated quantitatively with loss of LCAT activity in both discoidal HDL and HDL3, the enzyme's physiological substrates. Reversing oxidation with methionine sulfoxide reductase restored HDL's ability to activate LCAT. Discoidal HDL prepared with apoA-I containing a Met-148 -> Leu mutation was significantly resistant to inactivation by MPO. Based on structural data in the literature, we propose that oxidation of Met-148 disrupts apoA-I's central loop, which overlaps the LCAT activation domain. These observations implicate oxidation of a single Met in apoA-I in impaired LCAT activation, a critical early step in reverse cholesterol transport.