Molecular mechanisms of voltage-gated proton channels

描述（由申请人提供）：在许多哺乳动物细胞类型中发现了电压门控质子（HV）通道，包括血细胞、肺上皮细胞、骨骼肌和小胶质细胞。特别重要的是，HV通道已被证明在血细胞中起着至关重要的作用：巨噬细胞中的HV通道对于呼吸爆发期间活性氧的产生是必不可少的，这对吞噬作用和破坏外来病原体的过程至关重要。我们的长期目标是了解巨噬细胞和其他细胞类型中HV通道功能的分子机制。近年来，HV通道的分子鉴定被发现。发现HV与电压门控钾（Kv）通道的电压敏感域（VSD）同源。Kv通道是具有6个跨膜（TM）区段和孔结构域的四聚体通道。然而，HV通道仅具有前4个TM并且缺乏典型的孔域。我们最近发现HV通道是二聚体，每个亚基都有自己的质子通路。关于它们的分子功能的许多问题仍然没有答案。两个HV亚基如何结合在一起形成二聚体HV通道？电压如何激活HV通道，巨噬细胞激活如何改变HV通道的活性？HV通道中的质子渗透途径是什么？该基金的研究目标是确定HV亚基二聚化的机制，确定二聚化如何影响HV亚基的活性和协同性，并确定HV通道中质子传导途径的残基。拟议的工作的结果将提供电压门控质子通道HV的结构的更好的理解，并将提供了解这种蛋白质的活性是如何调节的第一步。这项工作对于理解先天免疫的基础以及哮喘的病理基础具有重要意义。HV是免疫系统吞噬细胞功能的重要组成部分，也是哮喘期间肺部的重要因素。因此，对HV的结构和调控的更深入了解将为这种蛋白质在疾病和正常免疫功能中所起的作用提供新的见解，并可以为许多病理学的治疗干预提供新的途径。最重要的是，HV的调节可能是调节免疫系统炎症反应以及治疗哮喘的潜在药物靶点。

DESCRIPTION (provided by applicant): Voltage-gated proton (HV) channels have been found in many mammalian cell types, including blood cells, lung epithelia, skeletal muscle, and microglia. Of particular importance, HV channels have been shown to play a crucial role in blood cells: HV channels in macrophages are essential for the generation of reactive oxygen species during the respiratory burst, which is critical to the process of phagocytosis and the destruction of foreign pathogens. Our long-term goal is to understand the molecular mechanism of HV channel function in macrophages and other cell types. Recently, the molecular identify of HV channels was discovered. HV was found to be homologous to the voltage-sensing domain (VSD) of voltage-gated potassium (Kv) channels. Kv channels are tetrameric channels with 6 transmembrane (TM) segments and a pore domain. However, HV channels have only the first 4 TMs and lack a typical pore domain. We recently showed that HV channels are dimers, with each subunit having its own proton pathway. Many questions about their molecular function remain unanswered. How do two HV subunits come together to form a dimeric HV channel? How does voltage activate HV channels and how does macrophage activation alter the activity of HV channels? What constitutes the proton permeation pathway in HV channels? The research objectives of this grant are to determine the mechanism of dimerization of HV subunits, to determine how dimerization affects the activity and cooperativity of HV subunits, and to identify residues lining the proton conduction pathway in HV channels. The results of the proposed work will provide a greater understanding of the structure of the voltage-gated proton channel HV and will provide a first step in understanding how the activity of this protein is regulated. The proposed work is highly significant to understanding the basis of innate immunity as well as the pathology underlying asthma. HV is a crucial component in the function of phagocytes of the immune system, and it is also an important factor in the lungs during asthma. A greater understanding of the structure and regulation of HV will therefore provide new insight into the role that this protein plays in both disease and in normal immune function, and could provide novel avenues for therapeutic intervention in a number of pathologies. Most significantly, the regulation of HV could be a potential drug target for modulating the inflammatory response of the immune system as well as for the treatment of asthma.