Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States.
Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, United States.
Elife. 2019 Sep 5;8:e50231. doi: 10.7554/eLife.50231.
Cultured mouse peritoneal macrophages release large numbers of ~30-nm cholesterol-rich particles. Here, we show that those particles represent fragments of the plasma membrane that are pulled away and left behind during the projection and retraction of filopodia and lamellipodia. Consistent with this finding, the particles are enriched in proteins found in focal adhesions, which attach macrophages to the substrate. The release of particles is abolished by blocking cell movement (either by depolymerizing actin with latrunculin A or by inhibiting myosin II with blebbistatin). Confocal microscopy and NanoSIMS imaging studies revealed that the plasma membrane-derived particles are enriched in 'accessible cholesterol' (a mobile pool of cholesterol detectable with the modified cytolysin ALO-D4) but not in sphingolipid-sequestered cholesterol [a pool detectable with ostreolysin A (OlyA)]. The discovery that macrophages release cholesterol-rich particles during cellular locomotion is likely relevant to cholesterol efflux and could contribute to extracellular cholesterol deposition in atherosclerotic plaques.
培养的小鼠腹腔巨噬细胞释放大量~30nm 的富含胆固醇的颗粒。在这里，我们表明这些颗粒代表质膜的碎片，在丝状伪足和片状伪足的伸出和缩回过程中被拉离并留下。与这一发现一致的是，这些颗粒富含在黏着斑中发现的蛋白质，这些蛋白质将巨噬细胞附着在基质上。通过阻止细胞运动（用 latrunculin A 解聚肌动蛋白或用 blebbistatin 抑制肌球蛋白 II）可以消除颗粒的释放。共聚焦显微镜和 NanoSIMS 成像研究表明，质膜衍生的颗粒富含“可及胆固醇”（一种用改良细胞毒素 ALO-D4 检测到的胆固醇的流动池），而不是鞘脂隔离的胆固醇[一种用 ostreolysin A (OlyA) 检测到的池]。巨噬细胞在细胞运动过程中释放富含胆固醇的颗粒的发现可能与胆固醇外排有关，并可能导致动脉粥样硬化斑块中细胞外胆固醇的沉积。
