Activated heterotrimeric G protein αi subunits inhibit Rap-dependent cell adhesion and promote cell migration

J Biol Chem. 2018 Feb 2;293(5):1570-1578. doi: 10.1074/jbc.RA117.000964. Epub 2017 Dec 19.


Our recent work uncovered novel roles for activated Gαi signaling in the regulation of neutrophil polarity and adhesion. GαiGTP-mediated enhancement of neutrophil polarization was dependent on inhibition of cAMP/PKA signaling, whereas reversal of Gβγ-stimulated adhesion was cAMP/PKA independent. To uncover the mechanism for Gαi regulation of adhesion, we analyzed the effects of constitutively active Gαi1(Q204L) expression on adhesion driven by constitutively active Rap1a(G12V) or its downstream effector Radil in neutrophil-like HL-60 cells, or in HT-1080 fibrosarcoma cells. In HT-1080 cells, Rap1a(G12V) or Radil cause an increase in cell spreading and adhesion to fibronectin, which are both reversed by Gαi1(Q204L) but not WT Gαi1 In contrast, Gαi1(Q204L) did not reverse Rap1-GTP-interacting adaptor molecule (RIAM)-dependent increases in cell adhesion. This indicates that adhesion regulation by Gαi-GTP occurs downstream of Rap1a and Radil, but is upstream of components such as integrins and talin that are regulated by both Radil and RIAM. HL-60 neutrophil-like cells expressing Rap1a(G12V) or Radil have an elongated phenotype because of enhanced uropod adhesion as they attempt to migrate on fibronectin. This elongated phenotype driven by Rap1a(G12V) or Radil is reversed by Gαi1(Q204L), but not by WT Gαi1 expression, suggesting that Gαi-GTP also regulates adhesion in immune cells at the level of, or downstream of, Radil. These data identify a novel role of Gαi-GTP in regulation of cell adhesion and migration. Cell migration involves cycles of adhesion and de-adhesion, and we propose that the dynamic spatiotemporal balance between Gβγ-promoted adhesion and Gαi-GTP reversal of adhesion is important for this process.

Keywords: G protein; G protein–coupled receptor (GPCR); adhesion; cell migration; cell signaling; chemokines; integrin.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Adhesion
  • Cell Movement*
  • Fibronectins / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go / genetics
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism*
  • GTP-Binding Protein beta Subunits / genetics
  • GTP-Binding Protein beta Subunits / metabolism
  • GTP-Binding Protein gamma Subunits / genetics
  • GTP-Binding Protein gamma Subunits / metabolism
  • HL-60 Cells
  • Humans
  • Mutation, Missense*
  • rap1 GTP-Binding Proteins / genetics
  • rap1 GTP-Binding Proteins / metabolism*


  • Carrier Proteins
  • Fibronectins
  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • RADIL protein, human
  • RAP1A protein, human
  • GNAI1 protein, human
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • rap1 GTP-Binding Proteins