Department of Dermatology, School of Medicine, University of California, Sacramento, California, USA.
Department of Internal Medicine, School of Medicine, University of California, Sacramento, California, USA.
Infect Immun. 2022 Jan 25;90(1):e0051621. doi: 10.1128/IAI.00516-21. Epub 2021 Oct 18.
Salmonella invades and disrupts gut epithelium integrity, creating an infection-generated electric field that can drive directional migration of macrophages, a process called galvanotaxis. Phagocytosis of bacteria reverses the direction of macrophage galvanotaxis, implicating a bioelectrical mechanism to initiate life-threatening disseminations. The force that drives direction reversal of macrophage galvanotaxis is not understood. One hypothesis is that Salmonella can alter the electrical properties of the macrophages by modifying host cell surface glycan composition, which is supported by the fact that cleavage of surface-exposed sialic acids with a bacterial neuraminidase severely impairs macrophage galvanotaxis, as well as phagocytosis. Here, we utilize N-glycan profiling by nanoLC-chip QTOF mass cytometry to characterize the bacterial neuraminidase-associated compositional shift of the macrophage glycocalyx, which revealed a decrease in sialylated and an increase in fucosylated and high mannose structures. The Salmonella gene, encoding a putative neuraminidase, is required for invasion and internalization in a human colonic epithelial cell infection model. To determine whether NanH is required for the Salmonella infection-dependent direction reversal, we constructed and characterized a deletion mutant and found that NanH is partially required for Salmonella infection in primary murine macrophages. However, compared to wild type Salmonella, infection with the mutant only marginally reduced the cathode-oriented macrophage galvonotaxis, without canceling direction reversal. Together, these findings strongly suggest that while neuraminidase-mediated N-glycan modification impaired both macrophage phagocytosis and galvanotaxis, yet to be defined mechanisms other than NanH may play a more important role in bioelectrical control of macrophage trafficking, which potentially triggers dissemination.
沙门氏菌入侵并破坏肠道上皮完整性,形成一个由感染产生的电场,可驱动巨噬细胞的定向迁移,这个过程称为趋电性。细菌的吞噬作用会逆转巨噬细胞趋电性的方向,这表明存在生物电机制来引发危及生命的扩散。然而,驱动巨噬细胞趋电性方向逆转的力尚不清楚。有一种假设是,沙门氏菌可以通过改变宿主细胞表面聚糖组成来改变巨噬细胞的电学性质,这一假设得到了以下事实的支持:用细菌神经氨酸酶切割表面暴露的唾液酸严重损害了巨噬细胞的趋电性和吞噬作用。在这里,我们利用纳米 LC 芯片 QTOF 质谱流式细胞术对 N-聚糖进行分析,以表征巨噬细胞糖萼中细菌神经氨酸酶相关的组成变化,结果表明唾液酸化结构减少,而岩藻糖化和高甘露糖化结构增加。编码一种假定神经氨酸酶的 基因是沙门氏菌在人结肠上皮细胞感染模型中入侵和内化所必需的。为了确定 NanH 是否是沙门氏菌感染依赖性方向逆转所必需的,我们构建并表征了一个 缺失突变体,发现 NanH 部分是鼠源原代巨噬细胞中沙门氏菌感染所必需的。然而,与野生型沙门氏菌相比,感染 突变体仅略微降低了阴极定向的巨噬细胞趋电性,而没有取消方向逆转。总的来说,这些发现强烈表明,尽管神经氨酸酶介导的 N-聚糖修饰损害了巨噬细胞的吞噬作用和趋电性,但除了 NanH 之外,尚未确定的其他机制可能在生物电控制巨噬细胞迁移中发挥更重要的作用,这可能触发扩散。