Vogt Anna M, Barragan Antonio, Chen Qijun, Kironde Fred, Spillmann Dorothe, Wahlgren Mats
Microbiology and Tumor Biology Center (MTC), Karolinska Institutet, Stockholm, Sweden.
Blood. 2003 Mar 15;101(6):2405-11. doi: 10.1182/blood-2002-07-2016. Epub 2002 Nov 14.
Plasmodium falciparum may cause severe forms of malaria when excessive sequestration of infected and uninfected erythrocytes occurs in vital organs. The capacity of wild-type isolates of P falciparum-infected erythrocytes (parasitized red blood cells [pRBCs]) to bind glycosaminoglycans (GAGs) such as heparin has been identified as a marker for severe disease. Here we report that pRBCs of the parasite FCR3S1.2 and wild-type clinical isolates from Uganda adhere to heparan sulfate (HS) on endothelial cells. Binding to human umbilical vein endothelial cells (HUVECs) and to human lung endothelial cells (HLECs) was found to be inhibited by HS/heparin or enzymes that remove HS from cell surfaces. (35)S-labeled HS extracted from HUVECs bound directly to the pRBCs' membrane. Using recombinant proteins corresponding to the different domains of P falciparum erythrocyte membrane protein 1 (PfEMP1), we identified Duffy-binding-like domain-1alpha (DBL1alpha) as the ligand for HS. DBL1alpha bound in an HS-dependent way to endothelial cells and blocked the adherence of pRBCs in a dose-dependent manner. (35)S-labeled HS bound to DBL1alpha-columns and eluted as a distinct peak at 0.4 mM NaCl. (35)S-labeled chondroitin sulfate (CS) of HUVECs did not bind to PfEMP1 or to the pRBCs' membrane. Adhesion of pRBCs of FCR3S1.2 to platelet endothelial cell adhesion molecule-1 (PECAM-1)/CD31, mediated by the cysteine-rich interdomain region 1alpha (CIDR1alpha), was found be operative with, but independent of, the binding to HS. HS and the previously identified HS-like GAG on uninfected erythrocytes may act as coreceptors in endothelial and erythrocyte binding of rosetting parasites, causing excessive sequestration of both pRBCs and RBCs.
当重要器官中出现感染和未感染红细胞的过度滞留时，恶性疟原虫可能会引发严重形式的疟疾。恶性疟原虫感染的红细胞（寄生红细胞[pRBC]）与诸如肝素等糖胺聚糖（GAG）结合的能力已被确定为严重疾病的一个标志物。在此我们报告，寄生虫FCR3S1.2的pRBC以及来自乌干达的野生型临床分离株会黏附在内皮细胞上的硫酸乙酰肝素（HS）上。发现与人类脐静脉内皮细胞（HUVEC）和人类肺内皮细胞（HLEC）的结合会被HS/肝素或从细胞表面去除HS的酶所抑制。从HUVEC中提取的(35)S标记的HS直接结合到pRBC的膜上。使用对应于恶性疟原虫红细胞膜蛋白1（PfEMP1）不同结构域的重组蛋白，我们确定达菲结合样结构域1α（DBL1α）为HS的配体。DBL1α以HS依赖的方式结合到内皮细胞上，并以剂量依赖的方式阻断pRBC的黏附。(35)S标记的HS结合到DBL1α柱上，并在0.4 mM NaCl浓度下作为一个独特的峰洗脱下来。HUVEC的(35)S标记的硫酸软骨素（CS）不与PfEMP1或pRBC的膜结合。发现FCR3S1.2的pRBC与血小板内皮细胞黏附分子1（PECAM-1）/CD31的黏附，由富含半胱氨酸的结构域间区域1α（CIDR1α）介导，在与HS结合时起作用，但与之无关。HS以及先前在未感染红细胞上鉴定出的类似HS的GAG可能在内皮细胞和红细胞结合形成花环状寄生虫的过程中充当共受体，导致pRBC和RBC的过度滞留。
