Morova Jana, Osicka Radim, Masin Jiri, Sebo Peter
Institute of Microbiology of the Academy of Sciences of the Czech Republic, Videnska 1083, CZ-142 20 Prague 4, Czech Republic.
Proc Natl Acad Sci U S A. 2008 Apr 8;105(14):5355-60. doi: 10.1073/pnas.0711400105. Epub 2008 Mar 28.
Bordetella pertussis adenylate cyclase (AC) toxin-hemolysin (Hly) (CyaA, ACT, or AC-Hly) is a cytotoxin of the RTX (repeat in toxin) family. It delivers into target cells an AC domain that catalyzes uncontrolled conversion of ATP to cAMP, a key signaling molecule subverting phagocyte functions. CyaA utilizes a heavily N-glycosylated beta(2) integrin receptor CD11b/CD18 (alpha(M)beta(2), Mac-1, or CR3). We show that deglycosylation of cell surface proteins by glycosidase treatment, or inhibition of protein N-glycosylation by tunicamycin, ablates CyaA binding and penetration of CD11b-expressing cells. Furthermore, binding of CyaA to cells was strongly inhibited in the presence of free saccharides occurring as building units of integrin oligosaccharide complex, whereas saccharides absent from integrin oligosaccharide chains failed to inhibit CyaA binding to CD11b/CD18-expressing cells. CyaA, hence, selectively recognized sugar residues of N-linked oligosaccharides of integrins. Moreover, glycosylation of CD11a/CD18, another receptor of the beta(2) integrin family, was also essential for cytotoxic action of other RTX cytotoxins, the leukotoxin of Aggregatibacter actinomycetemcomitans (LtxA) and the Escherichia coli alpha-Hly (HlyA). These results show that binding and killing of target cells by CyaA, LtxA, and HlyA depends on recognition of N-linked oligosaccharide chains of beta(2) integrin receptors. This sets a new paradigm for action of RTX cytotoxins.
百日咳博德特氏菌腺苷酸环化酶（AC）毒素 - 溶血素（Hly）（CyaA、ACT或AC - Hly）是RTX（毒素重复序列）家族的一种细胞毒素。它将一个AC结构域递送至靶细胞，该结构域催化ATP不受控制地转化为cAMP，cAMP是一种破坏吞噬细胞功能的关键信号分子。CyaA利用高度N - 糖基化的β2整合素受体CD11b/CD18（αMβ2、Mac - 1或CR3）。我们发现，通过糖苷酶处理使细胞表面蛋白去糖基化，或用衣霉素抑制蛋白质N - 糖基化，可消除CyaA与表达CD11b的细胞的结合及穿透。此外，在作为整合素寡糖复合物构建单元的游离糖类存在的情况下，CyaA与细胞的结合受到强烈抑制，而整合素寡糖链中不存在的糖类则不能抑制CyaA与表达CD11b/CD18的细胞的结合。因此，CyaA选择性地识别整合素N - 连接寡糖的糖残基。此外，β2整合素家族的另一种受体CD11a/CD18的糖基化对于其他RTX细胞毒素——伴放线聚集杆菌的白细胞毒素（LtxA）和大肠杆菌α - Hly（HlyA）的细胞毒性作用也至关重要。这些结果表明，CyaA、LtxA和HlyA对靶细胞的结合和杀伤取决于对β2整合素受体N - 连接寡糖链的识别。这为RTX细胞毒素的作用设定了一个新的范例。
