The Plasmodial Surface Anion Channel And Malaria Parasit

Apicomplexan分子生理学单位对感染疟疾寄生虫的人类红血球的各种膜上离子和营养物质的运输进行基础研究。这项工作包括分子生物学和信息学，蛋白质和脂肪生物化学，膜蛋白的免疫荧光定位，各种转运分析，生物物理学，化合物文库的高通量筛选，以及小分子抑制剂的构效关系研究。 最近，我们使用电生理学方法识别了感染恶性疟原虫的人红细胞上一种不寻常的离子通道，恶性疟原虫是最致命的疟疾形式。这种通道，即原生物质表面阴离子通道(PSAC)，存在于1000个拷贝/细胞中，具有不同寻常的门控特性，可以渗透到一系列已知的寄生虫生长所需的阴离子和营养物质中。我们认为PSAC介导了营养获得的连续扩散途径的第一步。实验室目前的工作包括：1)确定PSAC的渗透机制；2)开发和测试未来可能作为抗疟疾药物的特定PSAC阻滞剂；3)克隆编码PSAC和其他转运蛋白的基因(S)，以及4)这些转运蛋白的异源表达。这些项目旨在探索PSAC如何实现其不同寻常的功能特性，了解这种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，实验室在这一重要领域做出了几项根本性的贡献。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的离子通道的争论。同位素通量、渗透裂解转运分析和两种独立的膜片钳结构的测量表明，单个离子通道PSAC可以充分解释各种小溶质摄取的增加。我们还首次发现，当红细胞与地理上不同的寄生虫分离株培养时，PSAC门控行为存在多态，这表明PSAC是由寄生虫编码的。在另一项研究中，我们考察了PSAC对各种营养溶质的广泛选择性，尽管它对钠离子的渗透性非常低。我们发现，这种结合是任何已知的人类通道都无法比拟的，主要是通过PSAC？S胞外孔口或其附近的赖氨酸残基实现的。这些功能研究对于我们理解溶质如何渗透PSAC、深入了解寄生虫生物学以及针对新的寄生虫靶点的药物开发具有重要的意义。

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.