Open AccessAn actin-based protrusion originating from a podosome-enriched region initiates macrophage fusion
Author(s) -
James J. Faust,
Arnat Balabiyev,
John M. Heddleston,
Nataly P. Podolnikova,
D. Page Baluch,
Teng Leong Chew,
Tatiana P. Ugarova
Publication year - 2019
Publication title -
molecular biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.463
H-Index - 225
eISSN - 1939-4586
pISSN - 1059-1524
DOI - 10.1091/mbc.e19-01-0009
Subject(s) - podosome , microbiology and biotechnology , biology , cell fusion , actin , multinucleate , live cell imaging , fusion protein , macrophage , fusion mechanism , wiskott–aldrich syndrome protein , fusion , actin cytoskeleton , lipid bilayer fusion , cytoskeleton , cell , in vitro , immunology , biochemistry , recombinant dna , gene , virus , linguistics , philosophy
Macrophage fusion resulting in the formation of multinucleated giant cells occurs in a variety of chronic inflammatory diseases, yet the mechanism responsible for initiating this process is unknown. Here, we used live cell imaging to show that actin-based protrusions at the leading edge initiate macrophage fusion. Phase-contrast video microscopy demonstrated that in the majority of events, short protrusions (∼3 µm) between two closely apposed cells initiated fusion, but occasionally we observed long protrusions (∼12 µm). Using macrophages isolated from LifeAct mice and imaging with lattice light sheet microscopy, we further found that fusion-competent protrusions formed at sites enriched in podosomes. Inducing fusion in mixed populations of GFP- and mRFP-LifeAct macrophages showed rapid spatial overlap between GFP and RFP signal at the site of fusion. Cytochalasin B strongly reduced fusion and when rare fusion events occurred, protrusions were not observed. Fusion of macrophages deficient in Wiskott-Aldrich syndrome protein and Cdc42, key molecules involved in the formation of actin-based protrusions and podosomes, was also impaired both in vitro and in vivo. Finally, inhibiting the activity of the Arp2/3 complex decreased fusion and podosome formation. Together these data suggest that an actin-based protrusion formed at the leading edge initiates macrophage fusion.