Expression and biological activity of ABCA1 in alveolar epithelial cells
Expression and biological activity of ABCA1 in alveolar epithelial cells
复制标题
DOI：
10.1165/rcmb.2007-0020oc
复制
发表时间：
2008-03-01
影响因子：
6.4
通讯作者：
Rothblat, George H.
中科院分区：
文献类型：
--
作者：
Bates, Sandra R.;Tao, Jian-Qin;Rothblat, George H.
肺泡I型肺泡上皮细胞维持这些大型鳞状细胞所必需的脂质稳态的机制尚不清楚。这些过程可能涉及ATP结合盒转运蛋白A1（ABCA 1），这是一种在载脂蛋白A-I（apoA-I）介导的细胞胆固醇和磷脂动员中至关重要的转运蛋白。免疫组化数据表明ABCA 1存在于肺I型和II型细胞和培养的肺细胞中。从大鼠肺中分离的II型细胞在10%血清中培养5天，向具有I型样表型的细胞转分化，所述细胞与I型细胞特异性单克隆抗体VIIIB 2反应。在将I型样肺细胞与上调ABCA 1基因的试剂（9-顺式-视黄酸[9 cRA]和22-羟基胆固醇[22-OH，9 cRA/22-OH]）孵育后，ABCA 1蛋白水平在8至16小时后提高至最大水平，并保持升高24小时。在apoA-I和9 cRA/22-OH的存在下，放射性磷脂和胆固醇从肺细胞的流出分别比对照组刺激3- 20倍。普罗布考可抑制脂质流出。从与apoA-I孵育的刺激细胞的培养基的蔗糖密度梯度分析鉴定了以1.063和1.210 g/ml之间的密度分离的具有低或高apoA-I含量的异质脂质颗粒。因此，具有I型表型标记的肺细胞含有功能性ABCA 1蛋白，释放脂质至apoA-I蛋白，并且能够产生类似于新生高密度脂蛋白的颗粒，表明ABCA 1在维持肺脂质稳态中的重要作用。
The mechanisms used by alveolar type I pneumocytes for maintenance of the lipid homeostasis necessary to sustain these large squamous cells are unknown. The processes may involve the ATP-binding cassette transporter A1 (ABCA1), a transport protein shown to be crucial in apolipoprotein A-I (apoA-I)-mediated mobilization of cellular cholesterol and phospholipid. Immunohistochemical data demonstrated the presence of ABCA1 in lung type I and type II cells and in cultured pneumocytes. Type II cells isolated from rat lungs and cultured for 5 days in 10% serum trans-differentiated toward cells with a type I-like phenotype which reacted with the type I cell-specific monoclonal antibody VIIIB2. Upon incubation of the type I-like pneumocytes with agents that up-regulate the ABCA1 gene (9-cis-retinoic acid [9cRA] and 22-hydroxycholesterol [22-OH, 9cRA/22-OH]), ABCA1 protein levels were enhanced to maximum levels after 8 to 16 hours and remained elevated for 24 hours. In the presence of apoA-I and 9cRA/22-OH, efflux of radioactive phospholipid and cholesterol from pneumocytes was stimulated 3-to20-fold, respectively, over controls. Lipid efflux was inhibited by Probucol. Sucrose density gradient analysis of the media from stimulated cells incubated with apoA-I identified heterogeneous lipid particles that isolated at a density between 1.063 and 1.210 g/ml, with low or high apoA-I content. Thus, pneumocytes with markers for the type I phenotype contained functional ABCA1 protein, released lipid to apoA-I protein, and were capable of producing particles resembling nascent high-density lipoprotein, indicating an important role for ABCA1 in the maintenance of lung lipid homeostasis.