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

James J. Faust, Arnat Balabiyev, John M. Heddleston, Nataly P. Podolnikova, D. Page Baluch, Teng Leong Chew, Tatiana P. Ugarova

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)2254-2267
Number of pages14
JournalMolecular biology of the cell
Issue number17
StatePublished - Aug 1 2019

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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