Lipophosphoglycan is a virulence factor distinct from related glycoconjugates in the protozoan parasite leishmania major
Lipophosphoglycan is a virulence factor distinct from related glycoconjugates in the protozoan parasite leishmania major
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DOI：
10.1073/pnas.160257897
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发表时间：
2000-08-01
影响因子：
11.1
通讯作者：
Beverley, SM
中科院分区：
文献类型：
--
作者：
Späth, GF;Epstein, L;Beverley, SM
利什曼原虫属的原生动物寄生虫经历了复杂的生命周期，包括通过叮咬沙蝇进行传播以及在哺乳动物巨噬细胞吞噬溶酶体中进行复制。利什曼原虫表面涂层的主要成分是糖基磷脂酰肌醇 (GPI) 锚定的多糖，称为脂磷酸聚糖 (LPG)。 LPG 已被认为在感染周期中发挥多种作用，包括针对补体和氧化剂的保护，作为巨噬细胞粘附的主要配体，以及作为通过灭活巨噬细胞信号通路来减轻宿主反应的关键因素。然而，LPG 的所有结构域都由其他主要表面或分泌产物共享，从而提供了生化冗余，从而损害了体外测试确定 LPG 本身是否是毒力因子的能力。为了研究真正的 Ipg(-) 寄生虫，我们通过有针对性的基因破坏产生了缺乏基因 LPG1 [编码假定的呋喃半乳糖基 (Gal(f)) 转移酶] 的重大利什曼原虫。 lpg1(-)寄生虫缺乏LPG，但含有正常水平的相关糖缀合物和GPI锚定蛋白。体外对易感小鼠和巨噬细胞的感染表明，这些lpg(-)利什曼原虫是高度减毒的。与之前的 LPG 突变体相比，显着的是，将 LPG1 重新引入 lpg(-) 寄生虫中恢复了毒力。因此，遗传学方法可以剖析这个相互关联的寄生虫毒力因子的复杂家族的作用，并明确确定 LPG 本身作为寄生虫毒力因子的作用。因为lpg1(-)突变体继续合成大量GPI锚定的含Gal(f)的糖脂而不是LPG，所以必须存在不同于高尔基体相关LPG合成区室的第二条途径。
Protozoan parasites of the genus Leishmania undergo a complex life cycle involving transmission by biting sand flies and replication within mammalian macrophage phagolysosomes. A major component of the Leishmania surface coat is the glycosylphosphatidylinositol (GPI)-anchored polysaccharide called lipophosphoglycan (LPG). LPG has been proposed to play many roles in the infectious cycle, including protection against complement and oxidants, serving as the major ligand for macrophage adhesion, and as a key factor mitigating host responses by deactivation of macrophage signaling pathways. However, all structural domains of LPG are shared by other major surface or secretory products, providing a biochemical redundancy that compromises the ability of in vitro tests to establish whether LPG itself is a virulence factor. To study truly Ipg(-) parasites, we generated Leishmania major lacking the gene LPG1 [encoding a putative galactofuranosyl (Gal(f)) transferase] by targeted gene disruption. The lpg1(-) parasites lacked LPG but contained normal levels of related glycoconjugates and GPI-anchored proteins. Infections of susceptible mice and macrophages in vitro showed that these lpg(-) Leishmania were highly attenuated. Significantly and in contrast to previous LPG mutants, reintroduction of LPG1 into the lpg(-) parasites restored virulence. Thus, genetic approaches allow dissection of the roles of this complex family of interrelated parasite virulence factors, and definitively establish the role of LPG itself as a parasite virulence factor. Because the lpg1(-) mutant continue to synthesize bulk GPI-anchored Gal(f)-containing glycolipids other than LPG, a second pathway distinct from the Golgi-associated LPG synthetic compartment must exist.