Impaired trafficking and transfer of virulence factors to the surface of P. falciparum-infected erythrocytes containing the hemoglobin polymorphisms HbS and HbC

长期以来，人们一直认为某些红细胞多态，如血红蛋白S(HbS)和血红蛋白C(Hbc)，可以预防严重疟疾。最近的发展表明，这些血红蛋白疾病是在选择性压力下出现的，以逃避恶性疟原虫感染的红细胞在微血管系统中的细胞黏附引起的严重疾病和死亡。与正常的A型血红蛋白红细胞相比，含有HBS和HBC的寄生红细胞表现出细胞黏附表型受损，这与红细胞表面介导疾病的粘附素PfEMP1的显示改变和数量减少有关。为了解释这种改变的表型，我们假设在含有红细胞的HBS和HBC中，粘附素向宿主红细胞表面的输出和转移受到损害。我们将通过研究HBS和HBC红细胞中的蛋白质输出途径来验证我们的工作假设，包括输出的时间框架、毛雷尔裂隙的发育以及这些膜轮廓和细胞黏附复合体与红细胞膜骨架的锚定。我们的方法将包括冷冻电子断层扫描，GFP标记的输出蛋白质的荧光显微镜，实时监测蛋白质输出的条件蛋白质输出系统，以及研究毛雷氏裂隙和细胞黏附复合体与红细胞膜骨架相互作用的生物化学方法。

It has long been appreciated that certain erythrocyte polymorphisms, such as hemoglobin S (HbS) and hemoglobin C (HbC), protect against severe malaria. Recent developments have now suggested that these hemoglobinopathies have emerged under the selective pressure to escape severe disease and death resulting from the cytoadhesion of P. falciparum-infected erythrocytes in the microvasculature. Parasitized erythrocytes containing HbS and HbC exhibit an impaired cytoadhesive phenotype that correlates with an altered display and a reduced amount of the disease-mediating adhesin PfEMP1 on the erythrocyte surface, as compared to normal erythrocytes of the hemoglobin A type. To explain this altered phenotype, we hypothesize that export and transfer of the adhesin to the surface of the host erythrocyte is impaired in HbS and HbC containing erythrocytes. We will investigate our working hypothesis by studying, in HbS and HbC erythrocytes, the protein export pathway, including the time frame of export, the development of the Maurer’s clefts and the anchoring of these membrane profiles and the cytoadhesion complex to the erythrocyte membrane skeleton. Our approach will include cryo-electron tomography, fluorescence microscopy of GFP-tagged exported proteins, a conditional protein export system to monitor protein export in real time, and a biochemical approach to study the interactions of the Maurer’s clefts and the cytadhesion complex with the erythrocyte membrane skeleton.