Staphylococcus aureus, a Gram-positive bacterial pathogen, is an urgent health threat causing a wide range of clinical infections. Originally viewed as a strict extracellular pathogen, accumulating evidence has revealed S. aureus to be a facultative intracellular pathogen subverting host cell signalling to support invasion. The majority of clinical isolates produce fibronectin-binding proteins A and B (FnBPA and FnBPB) to interact with host integrin α5β1, a key component of focal adhesions. S. aureus binding of integrin α5β1 promotes its clustering on the host cell surface, triggering activation of focal adhesion kinase (FAK) and cytoskeleton rearrangements to promote bacterial invasion into non-phagocytic cells. Here, we discover that septins, a component of the cytoskeleton that assembles on membranes, are recruited as collar-like structures with actin to S. aureus invasion sites engaging integrin α5β1. To investigate septin recruitment to the plasma membrane in a bacteria-free system, we used FnBPA-coated latex beads and showed that septins are recruited upon activation of integrin α5β1. SEPT2 depletion reduced S. aureus invasion, but increased surface expression of integrin α5 and adhesion of S. aureus to host cells. Consistent with this, SEPT2 depletion increased cellular protein levels of integrin α5 and β1 subunits, as well as FAK. Collectively, these results provide insights into regulation of integrin α5β1 and invasion of S. aureus by the septin cytoskeleton.

金黄色葡萄球菌是一种革兰氏阳性细菌病原体，是一种紧迫的健康威胁，可引起广泛的临床感染。最初被视为严格的细胞外病原体，越来越多的证据表明金黄色葡萄球菌是一种兼性细胞内病原体，可破坏宿主细胞信号传导以支持入侵。大多数临床分离株产生纤连蛋白结合蛋白 A 和 B（FnBPA 和 FnBPB），与宿主整合素 α5β1（粘着斑的关键成分）相互作用。金黄色葡萄球菌与整合素α5β1的结合促进其在宿主细胞表面聚集，触发粘着斑激酶（FAK）的激活和细胞骨架重排，从而促进细菌侵入非吞噬细胞。在这里，我们发现脓毒蛋白（在膜上组装的细胞骨架的一个组成部分）被招募为领状结构，肌动蛋白与整合素α5β1结合到金黄色葡萄球菌入侵位点。为了研究无菌系统中隔膜蛋白向质膜的募集，我们使用了 FnBPA 包被的乳胶珠，结果表明隔膜蛋白在整合素 α5β1 激活后被募集。SEPT2耗竭减少了金黄色葡萄球菌的侵袭，但增加了整合素α5的表面表达以及金黄色葡萄球菌与宿主细胞的粘附。与此一致的是，SEPT2 缺失增加了整合素 α5 和 β1 亚基以及 FAK 的细胞蛋白水平。总的来说，这些结果为整合素 α5β1 的调节和脓毒症细胞骨架对金黄色葡萄球菌的侵袭提供了见解。