Ye S Q, Trieu V N, Stiers D L, McConathy W J
Oklahoma Medical Research Foundation, Oklahoma City 73104.
J Biol Chem. 1988 May 5;263(13):6337-43.
Studies were undertaken to investigate potential interactions among plasma lipoproteins. Techniques used were low density lipoprotein2 (LDL2)-ligand blotting of plasma lipoproteins separated by nondenaturing 2.5-15% gradient gel electrophoresis, ligand binding of plasma lipoproteins by affinity chromatography with either LDL2 or lipoprotein(a) (Lp(a)) as ligands, and agarose lipoprotein electrophoresis. Ligand blotting showed that LDL2 can bind to Lp(a). When apolipoprotein(a) was removed from Lp(a) by reduction and ultracentrifugation, no interaction between LDL2 and reduced Lp(a) was detected by ligand blotting. Ligand binding showed that LDL2-Sepharose 4B columns bound plasma lipoproteins containing apolipoproteins(a), B, and other apolipoproteins. The Lp(a)-Sepharose column bound lipoproteins containing apolipoprotein B and other apolipoproteins. Furthermore, the Lp(a) ligand column bound more lipoprotein lipid than the LDL2 ligand column, with the Lp(a) ligand column having a greater affinity for triglyceride-rich lipoproteins. Lipoprotein electrophoresis of a mixture of LDL2 and Lp(a) demonstrated a single band with a mobility intermediate between that of LDL2 and Lp(a). Chemical modification of the lysine residues of apolipoprotein B (apoB) by either acetylation or acetoacetylation prevented or diminished the interaction of LDL2 with Lp(a), as shown by both agarose electrophoresis and ligand blotting using modified LDL2. Moreover, removal of the acetoacetyl group from the lysine residues of apoB by hydroxylamine reestablished the interaction of LDL2 with Lp(a). On the other hand, blocking of--SH groups of apoB by iodoacetamide failed to show any effect on the interaction between LDL2 and Lp(a). Based on these observations, it was concluded that Lp(a) interacts with LDL2 and other apoB-containing lipoproteins which are enriched in triglyceride; this interaction is due to the presence of apolipoprotein(a) and involves lysine residues of apoB interacting with the plasminogen-like domains (kringle 4) of apolipoprotein(a). Such results suggest that Lp(a) may be involved in triglyceride-rich lipoprotein metabolism, could form transient associations with apoB-containing lipoproteins in the vascular compartment, and alter the intake by the high affinity apoB, E receptor pathway.
开展了多项研究以调查血浆脂蛋白之间的潜在相互作用。所采用的技术包括：对通过非变性2.5 - 15%梯度凝胶电泳分离的血浆脂蛋白进行低密度脂蛋白2（LDL2）配体印迹分析；以LDL2或脂蛋白（a）（Lp（a））作为配体，通过亲和色谱法进行血浆脂蛋白的配体结合分析；以及琼脂糖脂蛋白电泳分析。配体印迹分析表明LDL2可与Lp（a）结合。当通过还原和超速离心从Lp（a）中去除载脂蛋白（a）后，配体印迹分析未检测到LDL2与还原型Lp（a）之间的相互作用。配体结合分析表明，LDL2 - 琼脂糖4B柱可结合含有载脂蛋白（a）、B及其他载脂蛋白的血浆脂蛋白。Lp（a） - 琼脂糖柱可结合含有载脂蛋白B及其他载脂蛋白的脂蛋白。此外，Lp（a）配体柱比LDL2配体柱结合更多的脂蛋白脂质，Lp（a）配体柱对富含甘油三酯的脂蛋白具有更高的亲和力。LDL2和Lp（a）混合物的脂蛋白电泳显示出一条迁移率介于LDL2和Lp（a）之间的单一条带。通过乙酰化或乙酰乙酰化对载脂蛋白B（apoB）的赖氨酸残基进行化学修饰可阻止或减少LDL2与Lp（a）的相互作用，这在使用修饰后的LDL2进行的琼脂糖电泳和配体印迹分析中均得到证实。此外，用羟胺从apoB的赖氨酸残基上去除乙酰乙酰基团可重新建立LDL2与Lp（a）的相互作用。另一方面，用碘乙酰胺封闭apoB的 - SH基团对LDL2与Lp（a）之间的相互作用未显示出任何影响。基于这些观察结果，得出结论：Lp（a）与LDL2及其他富含甘油三酯的含apoB脂蛋白相互作用；这种相互作用归因于载脂蛋白（a）的存在，且涉及apoB的赖氨酸残基与载脂蛋白（a）的纤溶酶原样结构域（kringle 4）相互作用。这些结果表明Lp（a）可能参与富含甘油三酯的脂蛋白代谢，可在血管腔中与含apoB脂蛋白形成瞬时缔合，并改变高亲和力apoB、E受体途径的摄取。
