Zilkha Neurogenetic Institute and Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
J Biol Chem. 2013 May 24;288(21):15154-66. doi: 10.1074/jbc.M112.439570. Epub 2013 Apr 11.
Soluble low density lipoprotein receptor-related protein-1 (sLRP1) binds ~70% of amyloid β-peptide (Aβ) in human plasma. In Alzheimer disease (AD) and individuals with mild cognitive impairment converting to AD, plasma sLRP1 levels are reduced and sLRP1 is oxidized, which results in diminished Aβ peripheral binding and higher levels of free Aβ in plasma. Experimental studies have shown that free circulating Aβ re-enters the brain and that sLRP1 and/or its recombinant wild type cluster IV (WT-LRPIV) prevent Aβ from entering the brain. Treatment of Alzheimer APPsw(+/0) mice with WT-LRPIV has been shown to reduce brain Aβ pathology. In addition to Aβ, LRPIV binds multiple ligands. To enhance LRPIV binding for Aβ relative to other LRP1 ligands, we generated a library of LRPIV-derived fragments and full-length LRPIV variants with glycine replacing aspartic acid residues 3394, 3556, and 3674 in the calcium binding sites. Compared with WT-LRPIV, a lead LRPIV-D3674G mutant had 1.6- and 2.7-fold higher binding affinity for Aβ40 and Aβ42 in vitro, respectively, and a lower binding affinity for other LRP1 ligands (e.g. apolipoprotein E2, E3, and E4 (1.3-1.8-fold), tissue plasminogen activator (2.7-fold), matrix metalloproteinase-9 (4.1-fold), and Factor Xa (3.8-fold)). LRPIV-D3674G cleared mouse endogenous brain Aβ40 and Aβ42 25-27% better than WT-LRPIV. A 3-month subcutaneous treatment of APPsw(+/0) mice with LRPIV-D3674G (40 μg/kg/day) reduced Aβ40 and Αβ42 levels in the hippocampus, cortex, and cerebrospinal fluid by 60-80% and improved cerebral blood flow responses and hippocampal function at 9 months of age. Thus, LRPIV-D3674G is an efficient new Aβ clearance therapy.
可溶性低密度脂蛋白受体相关蛋白-1（sLRP1）与人血浆中的 ~70%的淀粉样β肽（Aβ）结合。在阿尔茨海默病（AD）和转化为 AD 的轻度认知障碍个体中，血浆 sLRP1 水平降低，sLRP1 被氧化，导致外周 Aβ 结合减少，血浆中游离 Aβ 水平升高。实验研究表明，游离循环中的 Aβ重新进入大脑，sLRP1 和/或其重组野生型 IV 型（WT-LRPIV）可防止 Aβ进入大脑。用 WT-LRPIV 治疗阿尔茨海默氏病 APPsw（+/0）小鼠已被证明可减少大脑中的 Aβ 病理学。除 Aβ外，LRPIV 还结合多种配体。为了增强 LRPIV 与 Aβ的结合相对于其他 LRP1 配体的结合，我们生成了一个 LRPIV 衍生片段文库和全长 LRPIV 变体文库，其中在钙结合位点中的天冬氨酸残基 3394、3556 和 3674 被甘氨酸取代。与 WT-LRPIV 相比，一个先导 LRPIV-D3674G 突变体对 Aβ40 和 Aβ42 的体外结合亲和力分别提高了 1.6 倍和 2.7 倍，而对其他 LRP1 配体（例如载脂蛋白 E2、E3 和 E4（1.3-1.8 倍）、组织型纤溶酶原激活物（2.7 倍）、基质金属蛋白酶-9（4.1 倍）和因子 Xa（3.8 倍）的结合亲和力较低。LRPIV-D3674G 比 WT-LRPIV 更好地清除了小鼠内源性脑 Aβ40 和 Aβ42 的 25-27%。用 LRPIV-D3674G（40 μg/kg/天）对 APPsw（+/0）小鼠进行 3 个月的皮下治疗，可使海马体、皮层和脑脊液中的 Aβ40 和 Αβ42 水平降低 60-80%，并改善 9 个月时的大脑血流反应和海马体功能。因此，LRPIV-D3674G 是一种有效的新型 Aβ 清除疗法。
