Macrophage fusion resulting in the formation of multinucleated giant cells (MGCs) is a multistage process that requires many adhesion-dependent steps and involves the rearrangement of the actin cytoskeleton. The diversity of actin-based structures and their role in macrophage fusion is poorly understood. In this study, we revealed hitherto unrecognized actin-based zipper-like structures (ZLSs) that arise between MGCs formed on the surface of implanted biomaterials. We established an in vitro model for the induction of these structures in mouse macrophages undergoing IL-4–mediated fusion. Using this model, we show that over time MGCs develop cell–cell contacts containing ZLSs. Live-cell imaging using macrophages isolated from mRFP- or eGFP-LifeAct mice demonstrated that ZLSs are dynamic formations undergoing continuous assembly and disassembly and that podosomes are precursors of these structures. Immunostaining experiments showed that vinculin, talin, integrin α_Mβ₂, and other components of podosomes are present in ZLSs. Macrophages deficient in WASp or Cdc42, two key molecules involved in actin core organization in podosomes, as well as cells treated with the inhibitors of the Arp2/3 complex, failed to form ZLSs. Furthermore, E-cadherin and nectin-2 were found between adjoining membranes, suggesting that the transition of podosomes into ZLSs is induced by bridging plasma membranes by junctional proteins.

导致形成多核巨细胞（MGC）的巨噬细胞融合是一个多阶段过程，需要许多依赖粘附的步骤，并涉及肌动蛋白细胞骨架的重排。基于肌动蛋白的结构的多样性及其在巨噬细胞融合中的作用了解甚少。在这项研究中，我们揭示了迄今无法识别的基于肌动蛋白的拉链状结构（ZLSs），该结构出现在植入的生物材料表面上形成的MGC之间。我们建立了体外模型，用于在经历IL-4介导融合的小鼠巨噬细胞中诱导这些结构。使用该模型，我们表明，随着时间的流逝，MGC会发展出包含ZLS的细胞间接触。使用从mRFP-或eGFP-LifeAct小鼠中分离的巨噬细胞进行的活细胞成像显示ZLS是动态形成，正在经历连续的组装和拆卸，并且足小体是这些结构的前体。免疫染色实验表明，纽蛋白，塔林，整联蛋白α_中号β ₂，和足体的其它组分存在于ZLSs。缺乏WASp或Cdc42的巨噬细胞，足小体中肌动蛋白核心组织所涉及的两个关键分子，以及用Arp2 / 3复合物抑制剂处理过的细胞均未能形成ZLS。此外，在相邻的膜之间发现了E-钙粘蛋白和nectin-2，这表明通过连接蛋白桥接质膜可以诱导足小体向ZLSs的转变。