ABCA1 mediates unfolding of apolipoprotein AI N terminus on the cell surface before lipidation and release of nascent high-density lipoprotein.
ABCA1 mediates unfolding of apolipoprotein AI N terminus on the cell surface before lipidation and release of nascent high-density lipoprotein.
复制标题
DOI：
10.1161/atvbaha.112.301195
复制
发表时间：
2013-06
期刊：
影响因子：
--
通讯作者：
Smith JD
中科院分区：
文献类型：
--
作者：
Wang S;Gulshan K;Brubaker G;Hazen SL;Smith JD
To gain insight into the mechanism by which ABCA1 generates nascent HDL. HEK293 cells were stably transfected with ABCA1 vectors encoding wild type (WT) and the W590S and C1477R Tangier disease mutation isoforms, along with the K939M ATP binding domain mutant. ApoAI binding, plasma membrane remodeling, cholesterol efflux, apoAI cell surface unfolding, and apoAI cell surface lipidation were determined, the latter two measured using novel fluorescent apoAI indicators. The W590S isoform had decreased plasma membrane remodeling and lipid efflux activities, the C1477R isoform had decreased apoAI binding, and lipid efflux activities, while the K939M isoform did not bind apoAI, remodel the membrane, or efflux cholesterol. However, all ABCA1 isoforms led to apoAI unfolding at the cell surface, which was higher for the isoforms that increased apoAI binding. ApoAI lipidation was not detected on ABCA1 expressing cells, only in the conditioned medium, consistent with rapid release of nascent HDL from ABCA1 expressing cells. We identified a third activity of ABCA1, the ability to unfold the N-terminus of apoAI on the cell surface. Our results support a model in which unfolded apoAI on the cell surface is an intermediate in its lipidation, and that once apoAI is lipidated, it forms an unstable structure that is rapidly released from the cells to generate HDL.
