The Plasmodial Surface Anion Channel And Malaria Parasit

Apicomplexan分子生理学单位对离子和营养物质穿过感染疟疾寄生虫的人类红细胞的各种膜的运输进行基础研究。这项工作结合了分子生物学和信息学，蛋白质和脂质生物化学，膜蛋白的免疫荧光定位，各种运输试验，生物物理学，化合物库的高通量筛选，以及小分子抑制剂的结构-活性关系的检查。 我们最近使用电生理学方法来鉴定感染恶性疟原虫的人类红细胞上的一种不寻常的离子通道，恶性疟原虫是最致命的疟疾。这种通道，疟原虫表面阴离子通道（PSAC），是目前在1000个拷贝/细胞，具有不寻常的门控特性，并渗透到一系列的阴离子和营养素已知是寄生虫生长所需的。我们提出，PSAC介导的第一步，在一个连续的扩散途径的养分收购。实验室目前的项目包括：1）表征通过PSAC的渗透机制，2）开发和测试可能作为未来抗疟药的特异性PSAC阻断剂，3）克隆编码PSAC和其他转运蛋白的基因，以及4）这些转运蛋白的异源表达。这些项目旨在探索PSAC如何实现其不寻常的功能特性，了解寄生虫的细胞生物学和生理学，并开发控制疟疾的新策略。 在过去的一个财政年度里，该实验室为这一重要领域做出了几项基本贡献。最重要的是，我们解决了关于感染疟疾寄生虫的红细胞上诱导了多少不同离子通道的争论。测量与同位素通量，渗透溶解运输试验，和两个独立的配置膜片钳表明，一个单一的离子通道，PSAC，可以充分考虑各种小溶质的摄取增加。我们还确定了，第一次，多态性PSAC门控行为时，红细胞与地理上不同的寄生虫分离株培养，表明PSAC是寄生虫编码。在一项单独的研究中，我们研究了PSAC对各种营养溶质的广泛选择性，尽管其对钠离子的渗透性非常低。我们发现，这种组合，无与伦比的任何已知的人类渠道，主要是通过赖氨酸残基或附近的PSAC？的细胞外孔口。这些功能研究对我们理解溶质如何渗透通过PSAC，深入了解寄生虫生物学和针对新寄生虫靶点的药物开发具有重要意义。

The Apicomplexan Molecular Physiology Unit conducts basic research on the transport of ions and nutrients across various membranes of human red blood cells infected with malaria parasites. This work incorporates molecular biology and informatics, protein and lipid biochemistry, immunofluorescent localization of membrane proteins, various transport assays, biophysics, high-throughput screening of compound libraries, and examination of structure-activity relationships for small molecule inhibitors. We recently used electrophysiological methods to identify an unusual ion channel on human red blood cells infected with P. falciparum, which causes the deadliest form of malaria. This channel, the plasmodial surface anion channel (PSAC), is present at 1000 copies/cell, has unusual gating properties, and is permeable to a range of anions and nutrients known to be required for parasite growth. We proposed that PSAC mediates the first step in a sequential diffusive pathway of nutrient acquisition. Current projects in the lab include: 1) characterizing the mechanism of permeation through PSAC, 2) developing and testing specific PSAC blockers that may function as future antimalarials, 3) cloning the gene(s) encoding PSAC and other transporters, and 4) heterologous expression of these transporters. These projects aim to probe how PSAC achieves its unusual functional properties, to understand the parasite's cell biology and physiology, and to develop new strategies for the control of malaria. In the past fiscal year, the lab made several fundamental contributions to this important field. Most importantly, we addressed debates about how many different ion channels are induced on red blood cells infected with the malaria parasite. Measurements with isotope flux, osmotic lysis transport assays, and two independent configurations of patch-clamp indicate that a single ion channel, PSAC, can adequately account for the increased uptake of various small solutes. We also identified, for the first time, polymorphisms in PSAC gating behavior when red cells are cultured with geographically distinct parasite isolates, suggesting that PSAC is parasite-encoded. In a separate study, we examined PSAC's broad selectivity for diverse nutrient solutes in spite of its very low permeability to sodium ions. We found that this combination, unparalleled by any known human channel, is largely achieved by lysine residues in or near PSAC?s extracellular pore mouth. These functional studies have important implications for our understanding of how solutes permeate through PSAC, for insights into parasite biology, and for drug development against novel parasite targets.