Surface Proteins and Sortases of Bacillus anthracis

描述（由申请人提供）：炭疽杆菌（炭疽的病原体）的休眠孢子感染人类或动物宿主，并将微生物发育与疾病发病机制联系起来。在病原体穿过宿主上皮并被巨噬细胞吞噬后，吞噬体内发生孢子萌发和营养细胞的生长。杆菌随后逃离吞噬体膜并在巨噬细胞的细胞质中复制。感染的巨噬细胞最终被溶解，然后杆菌在所有组织中细胞外繁殖，包括血液、肝脏、脾脏、肺、脑和肠。y- d -聚谷氨酸胶囊对炭疽芽胞杆菌具有抗吞噬作用。水肿毒素和致死毒素的分泌诱导免疫细胞和内皮组织凋亡。这些事件介导寄主死亡，随后孢子形成，环境传播和传播给新寄主。本研究研究了分选酶和锚定表面蛋白在炭疽发病的四个阶段中的作用——孢子进入，营养杆菌侵入巨噬细胞或宿主组织，杆菌的细胞外复制，以及死亡宿主的孢子形成。两个分选酶基因在营养杆菌和铁饥饿条件下表达（srtA和srtB），发生在宿主组织中。第三种分选酶基因（srtQ）仅在孢子形成过程中表达。每种分选酶识别特定的分选信号并将表面蛋白底物锚定在细菌包膜中，从而为炭疽芽孢杆菌的感染生命周期贡献独特的特性。分选酶C锚定的BasH和Basl沉积在孢子肽聚糖中。本文描述了一种新的令人兴奋的孢子包膜组装机制，因为srtC对宿主组织中感染性孢子的形成至关重要。排序酶B锚定的BasK是清除血红素铁所必需的，而排序酶A锚定的BasC和内部样蛋白BasJ则参与巨噬细胞复制。通过对炭疽芽孢杆菌Sterne和Ames菌株进行遗传和生化分析，探讨表面蛋白和分选酶功能在炭疽发病中的分子机制。炭疽芽孢杆菌是一种重要的生物恐怖威胁因子，本研究将通过揭示炭疽芽孢杆菌发病机制的潜在生物学现象，为今后的治疗和预防措施提供依据。

DESCRIPTION (provided by applicant): The dormant spores of Bacillus anthracis, the causative agent of anthrax, infect human or animal hosts and tether microbial development to disease pathogenesis. Following pathogen crossing of host epithelia and engulfment by macrophages, spore germination and outgrowth of vegetative cells occurs within phagosomes. Bacilli subsequently escape phagosomal membranes and replicate in the cytoplasm of macrophages. Infected macrophages are eventually lysed, and bacilli then multiply extracellularly in all tissues, including blood, liver, spleen, lungs, brain and intestines. The y-D-polyglutamic acid capsule of B. anthracis provides for resistance to phagocytic killing. Secretion of edema toxin as well as lethal toxin induces apoptosis of immune cells and endothelial tissues. These events mediate host killing, which is followed by spore formation, environmental dissemination and transmission to new hosts. This proposal investigates the role of sortases and anchored surface proteins during the four stages of anthrax pathogenesis - (i) spore entry, (ii) invasion of vegetative bacilli into macrophages or host tissues, (iii) extracellular replication of bacilli, and (iv) spore formation in deceased hosts. Two sortase genes are expressed in vegetative bacilli and under iron starvation conditions (srtA and srtB), as occurs in host tissues. A third sortase gene (srtQ is only expressed during spore formation. Each sortase recognizes specific sorting signals and anchors surface protein substrates in the bacterial envelope, thereby contributing unique properties to the infectious life cycle of B. anthracis. Sortase C anchored BasH and Basl are deposited in spore peptidoglycan. A new and exciting mechanism of spore envelope assembly is described here, as srtC is essential for the formation of infectious spores in host tissues. Sortase B anchored BasK is required for heme-iron scavenging, whereas sortase A anchored BasC and internalin-like BasJ are involved in macrophage replication. Using B. anthracis strains Sterne and Ames for genetic and biochemical analysis, the molecular mechanisms of surface protein and sortase function in anthrax pathogenesis will be addressed. B. anthracis is an important bioterror threat agent and this research proposal will provide future therapeutic and preventive interventions by revealing the underlying biological phenomena of anthrax pathogenesis.