TU Wien, Institute of Applied Physics, Vienna, 1040, Austria; Upper Austria University of Applied Sciences, Campus Linz, Garnisonstrasse 21, 4020, Linz, Austria.
Medical University of Vienna, Center for Pathobiochemistry and Genetics, Institute of Medical Chemistry, Vienna, 1090, Austria.
Atherosclerosis. 2018 Oct;277:53-59. doi: 10.1016/j.atherosclerosis.2018.08.032. Epub 2018 Aug 27.
Exchange of cholesterol between high-density lipoprotein (HDL) particles and cells is a key process for maintaining cellular cholesterol homeostasis. Recently, we have shown that amphiphilic cargo derived from HDL can be transferred directly to lipid bilayers. Here we pursued this work using a fluorescence-based method to directly follow cargo transfer from HDL particles to the cell membrane.
HDL was either immobilized on surfaces or added directly to cells, while transfer of fluorescent cargo was visualized via fluorescence imaging.
In Chinese hamster ovary (CHO) cells expressing the scavenger receptor class B type 1 (SR-B1), transfer of amphiphilic cargo from HDL particles to the plasma membrane was observed immediately after contact, whereas hydrophobic cargo remained associated with the particles; about 60% of the amphiphilic cargo of surface-bound HDL was transferred to the plasma membrane. Essentially no cargo transfer was observed in cells with low endogenous SR-B1 expression. Interestingly, transfer of fluorescently-labeled cholesterol was also facilitated by using an artificial linker to bind HDL to the cell surface.
Our data hence indicate that the tethering function of SR-B1 is sufficient for efficient transfer of free cholesterol to the plasma membrane.
高密度脂蛋白（HDL）颗粒与细胞之间胆固醇的交换是维持细胞胆固醇稳态的关键过程。最近，我们已经证明，源自 HDL 的两亲性货物可以直接转移到脂质双层中。在这里，我们使用基于荧光的方法来直接跟踪货物从 HDL 颗粒向细胞膜的转移，进一步研究了这一过程。
HDL 要么固定在表面上，要么直接添加到细胞中，同时通过荧光成像可视化荧光货物的转移。
在表达清道夫受体 B 型 1（SR-B1）的中国仓鼠卵巢（CHO）细胞中，在与细胞膜接触后立即观察到亲脂性货物从 HDL 颗粒向质膜的转移，而疏水性货物仍与颗粒结合；约 60%表面结合的 HDL 的亲脂性货物被转移到质膜上。在内源性 SR-B1 表达水平低的细胞中，几乎没有观察到货物转移。有趣的是，使用人工连接子将 HDL 结合到细胞表面也促进了荧光标记胆固醇的转移。
因此，我们的数据表明，SR-B1 的连接功能足以将游离胆固醇有效地转移到质膜上。
