The pavA gene of Streptococcus pneumoniae encodes a fibronectin-binding protein that is essential for virulence
The pavA gene of Streptococcus pneumoniae encodes a fibronectin-binding protein that is essential for virulence
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DOI：
10.1046/j.1365-2958.2001.02610.x
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发表时间：
2001-09-01
影响因子：
3.6
通讯作者：
Jenkinson, HF
中科院分区：
文献类型：
--
作者：
Holmes, AR;McNab, R;Jenkinson, HF
肺炎链球菌在高达40%的健康受试者的鼻咽中定殖，并且是中耳感染（中耳炎）、脑膜炎和肺炎的主要原因。肺炎球菌粘附于上皮细胞上的糖苷受体和固定的纤连蛋白，但介导这些反应的细菌粘附素在很大程度上是未知的。在这份报告中，我们描述了一种新的肺炎球菌蛋白PavA，它结合纤连蛋白，并与肺炎球菌的粘附和毒力。pavA基因存在于64个独立的S. pneumoniae的Fbp 54蛋白编码551个氨基酸残基的多肽，与酿脓链球菌中的Fbp 54蛋白具有67%的氨基酸同源性。免疫电子显微镜显示，尽管一级序列内缺乏常规的分泌或细胞表面锚定信号，但PavA定位于肺炎球菌细胞外表面。全长重组PavA多肽结合固定化的人纤连蛋白优先于液相纤连蛋白，在肝素敏感的相互作用，并阻止野生型肺炎球菌细胞与纤连蛋白的结合。然而，C-末端截短的PavA'多肽（362个氨基酸残基）未能结合纤连蛋白或阻断肺炎球菌细胞粘附。pavA在粪肠球菌JH 2 -2中的表达赋予超过对照JH 2 -2细胞的> 6倍的增加的细胞对纤连蛋白的粘附水平。S. pneumoniae，要么废除PavA表达，要么产生42 kDa的C-末端截短的蛋白质，表现出高达50%的减少结合固定化纤连蛋白。pavA的灭活对生长速率、细胞形态、细胞表面物理化学性质、肺炎球菌溶血素、自溶素或表面蛋白PspA和PsaA的产生没有影响。包囊S. pneumoniae D39在小鼠脓毒症模型中的毒力约减弱10（4）倍。这些结果提供了证据，PavA纤连蛋白结合蛋白在肺炎球菌感染的发病机制中起着直接的作用。
Streptococcus pneumoniae colonizes the nasopharynx in up to 40% of healthy subjects, and is a leading cause of middle ear infections (otitis media), meningitis and pneumonia. Pneumococci adhere to glycosidic receptors on epithelial cells and to immobilized fibronectin, but the bacterial adhesins mediating these reactions are largely uncharacterized. In this report we describe a novel pneumococcal protein PavA, which binds fibronectin and is associated with pneumococcal adhesion and virulence. The pavA gene, present in 64 independent isolates of S. pneumoniae tested, encodes a 551 amino acid residue polypeptide with 67% identical amino acid sequence to Fbp54 protein in Streptococcus pyogenes. PavA localized to the pneumococcal cell outer surface, as demonstrated by immunoelectron microscopy, despite lack of conventional secretory or cell-surface anchorage signals within the primary sequence. Full-length recombinant PavA polypeptide bound to immobilized human fibronectin in preference to fluid-phase fibronectin, in a heparin-sensitive interaction, and blocked binding of wild-type pneumococcal cells to fibronectin. However, a C-terminally truncated PavA' polypeptide (362 aa residues) failed to bind fibronectin or block pneumococcal cell adhesion. Expression of pavA in Enterococcus faecalis JH2-2 conferred > sixfold increased cell adhesion levels to fibronectin over control JH2-2 cells. Isogenic mutants of S. pneumoniae, either abrogated in PavA expression or producing a 42 kDa C-terminally truncated protein, showed up to 50% reduced binding to immobilized fibronectin. Inactivation of pavA had no effects on growth rate, cell morphology, cell-surface physico-chemical properties, production of pneumolysin, autolysin, or surface proteins PspA and PsaA. Isogenic pavA mutants of encapsulated S. pneumoniae D39 were approximately 10(4)-fold attenuated in virulence in the mouse sepsis model. These results provide evidence that PavA fibronectin-binding protein plays a direct role in the pathogenesis of pneumococcal infections.