Domain III of Plasmodium falciparum apical membrane antigen 1 binds to the erythrocyte membrane protein Kx
Domain III of Plasmodium falciparum apical membrane antigen 1 binds to the erythrocyte membrane protein Kx
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DOI：
10.1073/pnas.0501594102
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发表时间：
2005-04-12
影响因子：
11.1
通讯作者：
Miller, LH
中科院分区：
文献类型：
--
作者：
Kato, K;Mayer, DCG;Miller, LH
恶性疟原虫根尖膜抗原1 （AMA1）位于卵裂子微粒中，这是一种含有入侵受体的细胞器，表明AMA1可能在这一过程中发挥作用。然而，缺乏恶性疟原虫AMA1与人红细胞结合的直接证据。在本研究中，我们确定AMA1的结构域III与红细胞膜蛋白Kx结合，并且Kx（null）红细胞的侵袭率降低，这表明AMA1和Kx在寄生虫侵袭红细胞中的作用显著但不是唯一的。CHO-K1细胞表面表达AMA1结构域I/II和结构域III，并确定其结合红细胞的能力。我们观察到这些结构域中的每一个都不能结合未经处理的人红细胞。相反，AMA1的结构域III，而不是其他结构域，与胰蛋白酶处理的人红细胞结合。我们测试了AMA1与胰蛋白酶处理的基因突变的人红细胞的结合，缺失了各种红细胞膜蛋白。AMA1不能结合胰蛋白酶处理的缺乏Kx蛋白的Kx(null) （McLeod）红细胞。此外，先用胰蛋白酶处理人红细胞，然后用α -凝乳胰蛋白酶处理，可切割Kx并破坏AMA1与人红细胞的结合。最后，恶性疟原虫对Kx阴性红细胞的侵袭率明显低于表达Kx的红细胞。综上所述，我们的数据表明，AMA1在人类红细胞的侵袭过程中起着重要的作用，但不是唯一的作用，这一过程涉及一种胰蛋白酶样酶对红细胞表面蛋白Kx的暴露或修饰。
Plasmodium falciparum apical membrane antigen 1 (AMA1) is located in the merozoite micronemes, an organelle that contains receptors for invasion, suggesting that AMA1 may play a role in this process. However, direct evidence that A falciparum AMA1 binds to human erythrocytes is lacking. In this study, we determined that domain III of AMA1 binds to the erythrocyte membrane protein, Kx, and that the rate of invasion of Kx(null) erythrocytes is reduced, indicating a significant but not unique role of AMA1 and Kx in parasite invasion of erythrocytes. Domains domains I/II and domain III of AMA1 were expressed on the surface of CHO-K1 cells, and their ability to bind erythrocytes was determined. We observed that each of these domains failed to bind untreated human erythrocytes. In contrast, domain III, but not the other domains of AMA1, bound to trypsin-treated human erythrocytes. We tested the binding of AMA1 to trypsin-treated genetically mutant human erythrocytes, missing various erythrocyte membrane proteins. AMA1 failed to bind trypsin-treated Kx(null) (McLeod) erythrocytes, which lack the Kx protein. Furthermore, treatment of humanerythrocytes with trypsin, followed by alpha-chymotrypsin, cleaved Kx and destroyed the binding of AMA1 to human erythrocytes. Lastly, the rate of invasion of Kx null erythrocytes by A falciparum was significantly lower than Kx-expressing erythrocytes. Taken together, our data suggest that AMA1 plays an important, but not exclusive, role in invasion of human erythrocytes through a process that involves exposure or modification of the erythrocyte surface protein, Kx, by a trypsin-like enzyme.