Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic.
Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague 2, Czech Republic.
Int J Mol Sci. 2020 Nov 29;21(23):9092. doi: 10.3390/ijms21239092.
The Gram-negative coccobacillus is increasingly recognized as an important invasive pediatric pathogen that causes mostly bacteremia and skeletal system infections. secretes an RtxA toxin that belongs to a broad family of the RTX (Repeats in ToXin) cytotoxins produced by bacterial pathogens. Recently, we demonstrated that membrane cholesterol facilitates interaction of RtxA with target cells, but other cell surface structures potentially involved in toxin binding to cells remain unknown. We show that deglycosylation of cell surface structures by glycosidase treatment, or inhibition of protein N- and O-glycosylation by chemical inhibitors substantially reduces RtxA binding to target cells. Consequently, the deglycosylated cells were more resistant to cytotoxic activity of RtxA. Moreover, experiments on cells expressing or lacking cell surface integrins of the β family revealed that, unlike some other cytotoxins of the RTX family, RtxA does not bind target cells via the β integrins. Our results, hence, show that RtxA binds cell surface oligosaccharides present on all mammalian cells but not the leukocyte-restricted β integrins. This explains the previously observed interaction of the toxin with a broad range of cell types of various mammalian species and reveals that RtxA belongs to the group of broadly cytolytic RTX hemolysins.
革兰氏阴性球杆菌越来越被认为是一种重要的侵袭性儿科病原体，主要引起菌血症和骨骼系统感染。它分泌一种 RtxA 毒素，属于广泛的 RTX（重复毒素）细胞毒素家族，由细菌病原体产生。最近，我们证明了膜胆固醇有助于 RtxA 与靶细胞的相互作用，但其他可能涉及毒素与细胞结合的细胞表面结构仍不清楚。我们表明，糖苷酶处理对细胞表面结构的去糖基化，或化学抑制剂对蛋白质 N 和 O 糖基化的抑制，可显著降低 RtxA 与靶细胞的结合。因此，去糖基化的细胞对 RtxA 的细胞毒性活性更具抗性。此外，在表达或缺乏β家族细胞表面整合素的细胞上进行的实验表明，与 RTX 家族的其他一些细胞毒素不同，RtxA 不通过β整合素来结合靶细胞。因此，我们的结果表明，RtxA 结合存在于所有哺乳动物细胞表面的寡糖，但不结合白细胞受限的β整合素。这解释了先前观察到的毒素与各种哺乳动物物种的广泛细胞类型的相互作用，并表明 RtxA 属于广泛细胞溶解 RTX 溶血素组。
