The Rho-guanine nucleotide exchange factor Trio controls leukocyte transendothelial migration by promoting docking structure formation

Mol Biol Cell. 2012 Aug;23(15):2831-44. doi: 10.1091/mbc.E11-11-0907. Epub 2012 Jun 13.


Leukocyte transendothelial migration involves the active participation of the endothelium through the formation of apical membrane protrusions that embrace adherent leukocytes, termed docking structures. Using live-cell imaging, we find that prior to transmigration, endothelial docking structures form around 80% of all neutrophils. Previously we showed that endothelial RhoG and SGEF control leukocyte transmigration. In this study, our data reveal that both full-length Trio and the first DH-PH (TrioD1) domain of Trio, which can activate Rac1 and RhoG, interact with ICAM-1 and are recruited to leukocyte adhesion sites. Moreover, upon clustering of ICAM-1, the Rho-guanine nucleotide exchange factor Trio activates Rac1, prior to activating RhoG, in a filamin-dependent manner. We further show that docking structure formation is initiated by ICAM-1 clustering into ring-like structures, which is followed by apical membrane protrusion. Interestingly, we find that Rac1 is required for ICAM-1 clustering, whereas RhoG controls membrane protrusion formation. Finally, silencing endothelial Trio expression or reducing TrioD1 activity without affecting SGEF impairs both docking structure formation and leukocyte transmigration. We conclude that Trio promotes leukocyte transendothelial migration by inducing endothelial docking structure formation in a filamin-dependent manner through the activation of Rac1 and RhoG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Cell Adhesion
  • Cell Tracking
  • Chlorocebus aethiops
  • Contractile Proteins / chemistry
  • Contractile Proteins / metabolism
  • Electric Impedance
  • Filamins
  • Guanine Nucleotide Exchange Factors* / chemistry
  • Guanine Nucleotide Exchange Factors* / metabolism
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Intercellular Adhesion Molecule-1* / metabolism
  • Leukocytes* / cytology
  • Leukocytes* / metabolism
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / metabolism
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases* / chemistry
  • Protein-Serine-Threonine Kinases* / metabolism
  • Transendothelial and Transepithelial Migration*
  • rac1 GTP-Binding Protein / metabolism
  • rho GTP-Binding Proteins / chemistry
  • rho GTP-Binding Proteins / metabolism


  • ARHGEF26 protein, human
  • Contractile Proteins
  • Filamins
  • Guanine Nucleotide Exchange Factors
  • Microfilament Proteins
  • Intercellular Adhesion Molecule-1
  • RHOG protein, human
  • Protein-Serine-Threonine Kinases
  • TRIO protein, human
  • rac1 GTP-Binding Protein
  • rho GTP-Binding Proteins