An actin-based protrusion originating from a podosome-enriched region initiates macrophage fusion

• DOI: 10.1091/mbc.e19-01-0009
• Publication Date: 2019-06-26T17:18:43Z
• Authors: James J. Faust; Arnat Balabiyev; John M. Heddleston; Nataly P. Podolni...; D. Page Baluch; Teng-Leong Chew; Tatiana P. Ugarova
• Keywords: Podosome; Cell fusion; Multinucleate; Live cell imaging; Fusion mechanism; Wiskott–Aldrich syndrome protein

Macrophage fusion resulting in the formation of multinucleated giant cells occurs a variety chronic inflammatory diseases, yet mechanism responsible for initiating this process is unknown. Here, we used live cell imaging to show that actin-based protrusions at leading edge initiate macrophage fusion. Phase-contrast video microscopy demonstrated majority events, short (∼3 µm) between two closely apposed initiated fusion, but occasionally observed long (∼12 µm). Using macrophages isolated from LifeAct mice and with lattice light sheet microscopy, further found fusion-competent formed sites enriched podosomes. Inducing mixed populations GFP- mRFP-LifeAct showed rapid spatial overlap GFP RFP signal site Cytochalasin B strongly reduced when rare events occurred, were not observed. Fusion deficient Wiskott-Aldrich syndrome protein Cdc42, key molecules involved podosomes, was also impaired both vitro vivo. Finally, inhibiting activity Arp2/3 complex decreased podosome formation. Together these data suggest an protrusion initiates