Abstract 16570: The Interaction Between Gα13 and Integrin β1 Cytoplasmic Domain Mediates Cell Migration
Cell migration is critical to inflammation, angiogenesis and development of atherosclerosis. Cell migration on extracellular matrix proteins is mediated by integrin family of adhesion receptors. Among the various integrin family members, β1 integrins are expressed in most cell types, and mediate cell adhesion and migration on matrix proteins such as laminin, collagen, and fibronectin. Ligand binding to integrins initiates “outside-in” signal leading to cell spreading, retraction, and migration. However, the mechanisms of integrin outside-in signaling leading to cell migration remain poorly understood. We have recently shown that Gα13 directly interacts with integrin β1 and β3 subunits. In this study, we have further determined the binding site of Gα13 in the membrane-proximal region of the cytoplasmic domains of integrin β subunits, in which a conserved ExE motif is critically important. To determine whether Gα13-integrin interaction is important in mediating integrin outside-in signaling leading to cell migration, we have developed Gα13 binding-deficient mutants of β1 by mutating the ExE motif. GD25 cells (a β1-deficient cell line) were transfected with wild type β1 or Gα13 binding-deficient β1 mutants. As expected, β1-deficient GD25 cells migrated poorly while GD25 cells expressing wild type β1 migrated as normal cells in scratched wound healing analysis and in transwell migration assay, indicating β1-dependent cell migration. In contrast to wild type β1-expressing cells, GD25 cells expressing Gα13 binding-deficient mutants of β1 showed significantly diminished migration both in scratched wound healing analysis and transwell migration. Furthermore, a myristoylated synthetic peptide corresponding to the Gα13 binding site of β1 inhibited binding of Gα13 to β1 and also inhibited β1-dependent cell migration. The inhibitory effect of Gα13 binding-deficient mutations and the Gα13 binding-blocking peptide is not caused by their effect on inside-out signaling, because they did not affect the ligand binding function of β1 integrins. Thus, we conclude that Gα13-integrin interaction plays a critical role in mediating integrin signaling leading to cell migration.
- © 2011 by American Heart Association, Inc.