Surface Proteins and Sortases of Bacillus anthracis

描述（由申请方提供）：炭疽芽孢杆菌的休眠孢子（炭疽的病原体）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在一起。随着病原体穿过宿主上皮细胞并被巨噬细胞吞噬，孢子萌发和营养细胞的生长发生在吞噬体内。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溶解，然后杆菌在所有组织中细胞外繁殖，包括血液、肝、脾、肺、脑和肠。B的γ-D-聚谷氨酸胶囊。炭疽提供了对吞噬杀伤的抗性。水肿毒素和致死毒素的分泌诱导免疫细胞和内皮组织的凋亡。这些事件介导宿主死亡，随后是孢子形成、环境传播和传播到新宿主。该建议调查的作用，分选酶和锚定的表面蛋白在炭疽发病的四个阶段-（i）孢子进入，（ii）侵入的营养杆菌进入巨噬细胞或宿主组织，（iii）细胞外复制的杆菌，和（iv）孢子形成在死亡的主机。两种分选酶基因在营养杆菌中和在铁饥饿条件下表达（srtA和srtB），如在宿主组织中发生的。第三种分选酶基因（srtQ）仅在孢子形成期间表达。每个分选酶识别特定的分选信号并将表面蛋白质底物锚定在细菌包膜中，从而为B的感染性生命周期贡献独特的性质。炭疽病分选酶C锚定的BasH和BasI沉积在孢子肽聚糖中。一个新的和令人兴奋的机制孢子包膜组装在这里描述，作为srtC是必不可少的感染性孢子在宿主组织中的形成。分选酶B锚定的BasK是血红素铁清除所必需的，而分选酶A锚定的BasC和内化蛋白样BasJ参与巨噬细胞复制。使用B。炭疽菌株Sterne和艾姆斯进行遗传和生化分析，表面蛋白和分选酶在炭疽发病机制中的分子机制将得到解决。B。炭疽病是一种重要的生物恐怖威胁因子，这项研究提案将通过揭示炭疽病发病机制的潜在生物现象，提供未来的治疗和预防干预措施。

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.