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，人们已经认识到某些红细胞多态性，如血红蛋白S（HbS）和血红蛋白C（HbC），可以预防严重的疟疾。最近的发展表明，这些血红蛋白病是在逃避恶性疟原虫感染的红细胞在微血管系统中的细胞粘附引起的严重疾病和死亡的选择性压力下出现的。与血红蛋白A型的正常红细胞相比，含有HbS和HbC的寄生红细胞表现出受损的细胞粘附表型，其与红细胞表面上改变的显示和减少的疾病介导粘附素PfEMP 1的量相关。为了解释这种改变的表型，我们假设，出口和转移的粘附素的宿主红细胞的表面是受损的HbS和HbC含有红细胞。我们将通过研究HbS和HbC红细胞中的蛋白质输出途径来研究我们的工作假设，包括输出的时间框架、毛雷尔裂隙的发展以及这些膜轮廓和细胞粘附复合物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，荧光显微镜的GFP标记的出口蛋白质，有条件的蛋白质出口系统，以监测蛋白质出口在真实的时间，和生化方法来研究毛雷尔的裂缝和细胞粘附复合物与红细胞膜骨架的相互作用。

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.