Sinha B, Francois P, Que Y A, Hussain M, Heilmann C, Moreillon P, Lew D, Krause K H, Peters G, Herrmann M
Institute of Medical Microbiology, University of Münster, D-48129 Münster, Germany.
Infect Immun. 2000 Dec;68(12):6871-8. doi: 10.1128/IAI.68.12.6871-6878.2000.
Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureus fibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin alpha(5)beta(1) (B. Sinha et al., Cell. Microbiol. 1:101-117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp. cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any known S. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactis harboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors.
金黄色葡萄球菌对包括上皮细胞、内皮细胞和成纤维细胞在内的哺乳动物细胞的侵袭，关键取决于金黄色葡萄球菌纤连蛋白结合蛋白（FnBPs）与宿主纤连蛋白受体整合素α(5)β(1)之间的纤连蛋白桥接作用（B.辛哈等人，《细胞微生物学》1:101 - 117，1999年）。然而，尚不清楚这种机制是否足以使金黄色葡萄球菌实现侵袭。为解决这个问题，在肉葡萄球菌和乳酸乳球菌亚种cremoris中表达了各种金黄色葡萄球菌黏附素（FnBPA、FnBPB和凝聚因子[ClfA]）。这两种非侵袭性革兰氏阳性微生物在基因上与金黄色葡萄球菌不同，缺乏任何已知的金黄色葡萄球菌表面蛋白，且不结合纤连蛋白。携带编码各种金黄色葡萄球菌表面蛋白（FnBPA、FnBPB和ClfA）的质粒的肉葡萄球菌和乳酸乳球菌转化体功能性地表达了黏附素（通过血浆中的细菌凝聚、特异性乳胶凝集、Western配体印迹以及与固定化和可溶性纤连蛋白的结合来确定）。FnBPA或FnBPB而非ClfA赋予了肉葡萄球菌和乳酸乳球菌侵袭性。转化体对293细胞的侵袭与强侵袭性金黄色葡萄球菌菌株考恩1相当。可溶性和固定化纤连蛋白的结合与侵袭性平行，表明可及表面FnBPs的量是限速因素。因此，金黄色葡萄球菌FnBPs赋予非侵袭性、无致病性的革兰氏阳性球菌侵袭性。此外，FnBP包被的聚苯乙烯珠被293细胞内化，表明FnBPs足以实现对宿主细胞的侵袭，而无需（金黄色葡萄球菌特异性）共受体。
