Direct Rap1/Talin1 interaction regulates platelet and neutrophil integrin activity in mice

Blood. 2018 Dec 27;132(26):2754-2762. doi: 10.1182/blood-2018-04-846766. Epub 2018 Nov 15.

Abstract

Targeting Talin1 to the plasma membrane is a crucial step in integrin activation, which in leukocytes is mediated by a Rap1/RIAM/Talin1 pathway, whereas in platelets, it is RIAM independent. Recent structural, biochemical, and cell biological studies have suggested direct Rap1/Talin1 interaction as an alternative mechanism to recruit Talin1 to the membrane and induce integrin activation. To test whether this pathway is of relevance in vivo, we generated Rap1 binding-deficient Talin1 knockin (Tln13mut) mice. Although Tln13mut mice showed no obvious abnormalities, their platelets exhibited reduced integrin activation, aggregation, adhesion, and spreading, resulting in prolonged tail-bleeding times and delayed thrombus formation and vessel occlusion in vivo. Surprisingly, neutrophil adhesion to different integrin ligands and β2 integrin-dependent phagocytosis were also significantly impaired, which caused profound leukocyte adhesion and extravasation defects in Tln13mut mice. In contrast, macrophages exhibited no defect in adhesion or spreading despite reduced integrin activation. Taken together, our findings suggest that direct Rap1/Talin1 interaction is of particular importance in regulating the activity of different integrin classes expressed on platelets and neutrophils, which both depend on fast and dynamic integrin-mediated responses.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Platelets / metabolism*
  • Blood Platelets / pathology
  • CD18 Antigens / genetics
  • CD18 Antigens / metabolism*
  • Cell Adhesion / genetics
  • Hemorrhage / genetics
  • Hemorrhage / metabolism*
  • Hemorrhage / pathology
  • Mice
  • Mice, Mutant Strains
  • Neutrophils / metabolism*
  • Neutrophils / pathology
  • Phagocytosis / genetics
  • Talin / genetics
  • Talin / metabolism*
  • rap1 GTP-Binding Proteins / genetics
  • rap1 GTP-Binding Proteins / metabolism*

Substances

  • CD18 Antigens
  • Talin
  • Tln1 protein, mouse
  • Rap1 protein, mouse
  • rap1 GTP-Binding Proteins