普罗布考在载脂蛋白和高密度脂蛋白合成的

介导方面及蛋白水解方面灭活血膜内ABCA1

Wu CA etal. J Biol Chem. 2004; 279(29):30168-74. Epub 2004 May 12

已表明普罗布考通过螺旋状载脂蛋白抑制细胞脂质释放，从而降低血高密度脂蛋白。我们试图探索人成纤维细胞WI-38内这一作用的根本机制。普罗布考剂量依赖性地抑制apoA-I介导的细胞脂质释放和apoA-I与细胞的结合。它不影响低密度脂蛋白的细胞摄入，即不影响转运胆固醇到细胞表面以重新合成或提供为低密度脂蛋白，也不影响细胞总胆固醇含量，尽管从乙酸生物合成脂有点增加。普罗布考不影响ABCA1的mRNA水平，且尽管普罗布考存在，ABCA1仍与标记蛋白一起移至血膜。可是，在普罗布考处理的细胞内，ABCA1的蛋白水平增加，在放线菌素酮存在下，其衰减速率减慢。ABCA1可被钙蛋白酶消化但不被胰蛋白酶消化，普罗布考处理细胞内的ABCA1消化受抑制。结论：普罗布考灭活血膜内的ABCA1作用包括，ABCA1介导的载脂蛋白结合及其脂质释放、蛋白水解。

J Biol Chem. 2004 Jul 16;279(29):30168-74. Epub 2004 May 12.
 
Probucol inactivates ABCA1 in the plasma membrane with respect to its mediation of apolipoprotein binding and high density lipoprotein assembly and to its proteolytic degradation.

Wu CA, Tsujita M, Hayashi M, Yokoyama S.

Biochemistry, Cell Biology, and Metabolism, Nagoya City University Graduate School of Medical Sciences, Kawasumi 1, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.

Probucol has been shown to inhibit the release of cellular lipid by helical apolipoprotein and thereby to reduce plasma high density lipoprotein. We attempted to explore the underlying mechanism for this effect in human fibroblast WI-38. Probucol inhibited the apoA-I-mediated cellular lipid release and binding of apoA-I to the cells in a dose-dependent manner. It did not influence cellular uptake of low density lipoprotein, transport of cholesterol to the cell surface whether de novo synthesized or delivered as low density lipoprotein, and overall cellular content of cholesterol, although biosynthesis of lipids from acetate was somewhat increased. Probucol did not affect the mRNA level of ABCA1, and ABCA1 was recovered along with marker proteins for plasma membrane regardless of the presence of probucol. However, the protein level of ABCA1 increased, and the rate of its decay in the presence of cycloheximide was slower in the probucol-treated cells. ABCA1 in the probucol-treated cells was resistant to digestion by calpain but not by trypsin. We concluded that probucol inactivates ABCA1 in the plasma membrane with respect to its function in mediating binding of and lipid release by apolipoprotein and with respect to proteolytic degradation by calpain.