Naturally occurring point mutations in apolipoprotein A-I (apoA-I), the major protein component of high-density lipoprotein (HDL), may affect plasma HDL-cholesterol levels and cardiovascular risk. Here, we evaluated the effect of human apoA-I mutations L144R (associated with low HDL-cholesterol), L178P (associated with low HDL-cholesterol and increased cardiovascular risk) and A164S (associated with increased cardiovascular risk and mortality without low HDL-cholesterol) on the structural integrity and functions of lipid-free and lipoprotein-associated apoA-I in an effort to explain the phenotypes of subjects carrying these mutations. All three mutants, in lipid-free form, presented structural and thermodynamic aberrations, with apoA-I[L178P] presenting the greatest thermodynamic destabilization. Additionally, apoA-I[L178P] displayed reduced ABCA1-mediated cholesterol efflux capacity. When in reconstituted HDL (rHDL), apoA-I[L144R] and apoA-I[L178P] were more thermodynamically destabilized compared to wild-type apoA-I, both displayed reduced SR-BI-mediated cholesterol efflux capacity and apoA-I[L144R] showed severe LCAT activation defect. ApoA-I[A164S] was thermodynamically unaffected when in rHDL, but exhibited a series of functional defects. Specifically, it had reduced ABCG1-mediated cholesterol and 7-ketocholesterol efflux capacity, failed to reduce ROS formation in endothelial cells and had reduced capacity to induce endothelial cell migration. Mechanistically, the latter was due to decreased capacity of rHDL-apoA-I[A164S] to activate Akt kinase possibly by interacting with endothelial LOX-1 receptor. The impaired capacity of rHDL-apoA-I[A164S] to preserve endothelial function may be related to the increased cardiovascular risk for this mutation. Overall, our structure–function analysis of L144R, A164S and L178P apoA-I mutants provides insights on how HDL-cholesterol levels and/or atheroprotective properties of apoA-I/HDL are impaired in carriers of these mutations.

载脂蛋白 AI (apoA-I) 是高密度脂蛋白 (HDL) 的主要蛋白质成分，自然发生的点突变可能会影响血浆 HDL 胆固醇水平和心血管风险。在此，我们评估了人类 apoA-I 突变 L144R（与低 HDL 胆固醇相关）、L178P（与低 HDL 胆固醇和心血管风险增加相关）和 A164S（与不存在低 HDL 胆固醇的情况下心血管风险和死亡率增加相关）的影响）研究无脂和脂蛋白相关 apoA-I 的结构完整性和功能，以努力解释携带这些突变的受试者的表型。所有三种突变体在无脂形式下均表现出结构和热力学畸变，其中 apoA-I[L178P] 表现出最大的热力学不稳定。此外，apoA-I[L178P] 显示出 ABCA1 介导的胆固醇流出能力降低。当在重组 HDL (rHDL) 中时，与野生型 apoA-I 相比，apoA-I[L144R] 和 apoA-I[L178P] 在热力学上更加不稳定，两者都表现出 SR-BI 介导的胆固醇流出能力和 apoA-I 降低。 L144R]显示出严重的LCAT激活缺陷。 ApoA-I[A164S] 在 rHDL 中时热力学不受影响，但表现出一系列功能缺陷。具体来说，它降低了 ABCG1 介导的胆固醇和 7-酮胆固醇外流能力，未能减少内皮细胞中 ROS 的形成，并降低了诱导内皮细胞迁移的能力。从机制上讲，后者是由于 rHDL-apoA-I[A164S] 可能通过与内皮 LOX-1 受体相互作用而激活 Akt 激酶的能力下降所致。 rHDL-apoA-I[A164S] 保护内皮功能的能力受损可能与该突变增加的心血管风险有关。 总体而言，我们对 L144R、A164S 和 L178P apoA-I 突变体的结构功能分析提供了有关这些突变携带者中 HDL 胆固醇水平和/或 apoA-I/HDL 的动脉粥样硬化特性如何受损的见解。