Shakibaei M, Frevert U
Department of Medical and Molecular Parasitology, New York University Medical Center, New York 10010, USA.
J Exp Med. 1996 Nov 1;184(5):1699-711. doi: 10.1084/jem.184.5.1699.
Speed and selectivity of hepatocyte invasion by malaria sporozoites have suggested a receptor-mediated mechanism and the specific interaction of the circumsporozoite (CS) protein with liver-specific heparan sulfate proteoglycans (HSPGs) has been implicated in the targeting to the liver. Here we show that the CS protein interacts not only with cell surface heparan sulfate, but also with the low density lipoprotein receptor-related protein (LRP). Binding of 125I-CS protein to purified LRP occurs with a Kd of 4.9 nM and can be inhibited by the receptor-associated protein (RAP). Blockage of LRP by RAP or anti-LRP antibodies on heparan sulfate-deficient CHO cells results in more than 90% inhibition of binding and endocytosis of recombinant CS protein. Conversely, blockage or enzymatic removal of the cell surface heparan sulfate from LRP-deficient embryonic mouse fibroblasts yields the same degree of inhibition. Heparinase-pretreatment of LRP-deficient fibroblasts or blockage of LRP on heparan sulfate-deficient CHO cells by RAP, lactoferrin, or anti-LRP antibodies reduces Plasmodium berghei invasion by 60-70%. Parasite development in heparinase-pretreated HepG2 cells is inhibited by 65% when RAP is present during sporozoite invasion. These findings suggest that malaria sporozoites utilize the interaction of the CS protein with HSPGs and LRP as the major mechanism for host cell invasion.
疟原虫子孢子侵入肝细胞的速度和选择性提示了一种受体介导的机制，环子孢子（CS）蛋白与肝脏特异性硫酸乙酰肝素蛋白聚糖（HSPG）的特异性相互作用被认为与靶向肝脏有关。在此，我们表明CS蛋白不仅与细胞表面硫酸乙酰肝素相互作用，还与低密度脂蛋白受体相关蛋白（LRP）相互作用。125I-CS蛋白与纯化的LRP结合，解离常数（Kd）为4.9 nM，且可被受体相关蛋白（RAP）抑制。在硫酸乙酰肝素缺陷的中国仓鼠卵巢（CHO）细胞上，RAP或抗LRP抗体阻断LRP会导致重组CS蛋白的结合和内吞作用受到90%以上的抑制。相反，对LRP缺陷的胚胎小鼠成纤维细胞进行细胞表面硫酸乙酰肝素的阻断或酶促去除，也会产生相同程度的抑制。用肝素酶预处理LRP缺陷的成纤维细胞，或在硫酸乙酰肝素缺陷的CHO细胞上用RAP、乳铁蛋白或抗LRP抗体阻断LRP，可使伯氏疟原虫的侵入减少60-70%。当在子孢子侵入期间存在RAP时，肝素酶预处理的HepG2细胞中的寄生虫发育受到65%的抑制。这些发现表明，疟原虫子孢子利用CS蛋白与HSPG和LRP的相互作用作为宿主细胞侵入的主要机制。
