Coupling of β2 integrins to actin by a mechanosensitive molecular clutch drives complement receptor-mediated phagocytosis

Nat Cell Biol. 2019 Nov;21(11):1357-1369. doi: 10.1038/s41556-019-0414-2. Epub 2019 Oct 28.

Abstract

αMβ2 integrin (complement receptor 3) is a major receptor for phagocytosis in macrophages. In other contexts, integrins' activities and functions are mechanically linked to actin dynamics through focal adhesions. We asked whether mechanical coupling of αMβ2 integrin to the actin cytoskeleton mediates phagocytosis. We found that particle internalization was driven by formation of Arp2/3 and formin-dependent actin protrusions that wrapped around the particle. Focal complex-like adhesions formed in the phagocytic cup that contained β2 integrins, focal adhesion proteins and tyrosine kinases. Perturbation of talin and Syk demonstrated that a talin-dependent link between integrin and actin and Syk-mediated recruitment of vinculin enable force transmission to target particles and promote phagocytosis. Altering target mechanical properties demonstrated more efficient phagocytosis of stiffer targets. Thus, macrophages use tyrosine kinase signalling to build a mechanosensitive, talin- and vinculin-mediated, focal adhesion-like molecular clutch, which couples integrins to cytoskeletal forces to drive particle engulfment.

MeSH terms

  • Actin Cytoskeleton / immunology
  • Actin Cytoskeleton / ultrastructure
  • Actin-Related Protein 2-3 Complex / genetics
  • Actin-Related Protein 2-3 Complex / immunology
  • Actins / genetics
  • Actins / immunology
  • Animals
  • Extracellular Matrix / immunology
  • Extracellular Matrix / metabolism
  • Focal Adhesions / immunology
  • Focal Adhesions / ultrastructure
  • Formins / genetics
  • Formins / immunology
  • Gene Expression Regulation
  • Humans
  • Macrophage-1 Antigen / genetics
  • Macrophage-1 Antigen / immunology
  • Macrophages / cytology
  • Macrophages / immunology*
  • Mechanotransduction, Cellular*
  • Mice
  • Mice, Inbred C57BL
  • Microspheres
  • Phagocytosis / immunology*
  • Phagosomes / immunology
  • Phagosomes / ultrastructure
  • Polystyrenes
  • Primary Cell Culture
  • RAW 264.7 Cells
  • Syk Kinase / genetics*
  • Syk Kinase / immunology
  • THP-1 Cells
  • Talin / genetics*
  • Talin / immunology
  • Vinculin / genetics*
  • Vinculin / immunology

Substances

  • Actin-Related Protein 2-3 Complex
  • Actins
  • Formins
  • Macrophage-1 Antigen
  • Polystyrenes
  • Talin
  • Vcl protein, mouse
  • Vinculin
  • Syk Kinase
  • Syk protein, mouse