The Gα13-Rho Signaling Axis Is Required for SDF-1-induced Migration through CXCR4

Wenfu Tan,Daniel Martin,J Silvio Gutkind

doi:10.1074/jbc.m609062200

Abstract

The CXC chemokine stromal cell-derived factor-1alpha (SDF-1) binds to CXCR4, a seven-transmembrane G protein-coupled receptor that plays a critical role in many physiological processes that involve cell migration and cell fate decisions, ranging from stem cell homing, angiogenesis, and neuronal development to immune cell trafficking. CXCR4 is also implicated in various pathological conditions, including metastatic spread and human immunodeficiency virus infection. Although SDF-1-induced cell migration in CXCR4-expressing cells is sensitive to pertussis toxin treatment, hence involving heterotrimeric G proteins of the G(i) family, whether other G proteins participate in the chemotactic response to SDF-1 is still unknown. In this study, we took advantage of the potent chemotactic activity of SDF-1 in Jurkat T-cells to examine the nature of the heterotrimeric G protein subunits contributing to CXCR4-mediated cell migration. We observed that whereas G(i) and Gbetagamma subunits are involved in SDF-1-induced Rac activation and cell migration, CXCR4 can also stimulate Rho potently leading to the phosphorylation of myosin light chain through the Rho effector, Rho kinase, but independently of G(i). Furthermore, we found that Galpha(13) mediates the activation of Rho by CXCR4 and that the functional activity of both Galpha(13) and Rho is required for directional cell migration in response to SDF-1. Collectively, our data indicate that signaling by CXCR4 to Rho through Galpha(13) contributes to cell migration when stimulated by SDF-1, thus identifying the Galpha(13)-Rho signaling axis as a potential pharmacological target in many human diseases that involve the aberrant function of CXCR4.

Highlights

Chemokines are a group of chemoattractant cytokines that are involved in key developmental and homeostatic events, including leukocyte trafficking, angiogenesis, hematopoiesis, inflammation, immune response, and organogenesis, as well as in tumor progression and metastasis [1]
We used Jurkat T-cells that express CXCR4 endogenously as an experimental model system to examine the contribution of heterotrimeric G proteins and their downstream targets in cell migration induced by stromal cell-derived factor-1␣ (SDF-1)
This response was abolished by treatment with pertussis toxin (PTX), confirming the key role for G proteins of the Gi family in lymphocyte migration toward chemokine gradients [36]

Summary

Introduction

Chemokines are a group of chemoattractant cytokines that are involved in key developmental and homeostatic events, including leukocyte trafficking, angiogenesis, hematopoiesis, inflammation, immune response, and organogenesis, as well as in tumor progression and metastasis [1]. We observed that whereas Gi and G␤␥ subunits are involved in SDF1-induced Rac activation and cell migration, CXCR4 can stimulate Rho potently leading to the phosphorylation of myosin light chain through the Rho effector, Rho kinase, but independently of Gi. we found that G␣13 mediates the activation of Rho by CXCR4 and that the functional activity of both G␣13 and Rho is required for directional cell migration in response to SDF-1.

Results

Conclusion