Format

Send to

Choose Destination
J Biol Chem. 2018 Sep 7;293(36):14022-14039. doi: 10.1074/jbc.RA118.003097. Epub 2018 Jul 17.

GRK2 mediates TCR-induced transactivation of CXCR4 and TCR-CXCR4 complex formation that drives PI3Kγ/PREX1 signaling and T cell cytokine secretion.

Author information

1
From the Mayo IMM Ph.D. Training Program, Mayo Clinic Graduate School of Biomedical Sciences, and.
2
Department of Immunology, Mayo Clinic College of Medicine and Science, Mayo Clinic, Rochester, Minnesota 55905.
3
Department of Immunology, Mayo Clinic College of Medicine and Science, Mayo Clinic, Rochester, Minnesota 55905 hedin.karen@mayo.edu.

Abstract

The immune system includes abundant examples of biologically-relevant cross-regulation of signaling pathways by the T cell antigen receptor (TCR) and the G protein-coupled chemokine receptor, CXCR4. TCR ligation induces transactivation of CXCR4 and TCR-CXCR4 complex formation, permitting the TCR to signal via CXCR4 to activate a phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1 protein (PREX1)-dependent signaling pathway that drives robust cytokine secretion by T cells. To understand this receptor heterodimer and its regulation, we characterized the molecular mechanisms required for TCR-mediated TCR-CXCR4 complex formation. We found that the cytoplasmic C-terminal domain of CXCR4 and specifically phosphorylation of Ser-339 within this region were required for TCR-CXCR4 complex formation. Interestingly, siRNA-mediated depletion of G protein-coupled receptor kinase-2 (GRK2) or inhibition by the GRK2-specific inhibitor, paroxetine, inhibited TCR-induced phosphorylation of CXCR4-Ser-339 and TCR-CXCR4 complex formation. Either GRK2 siRNA or paroxetine treatment of human T cells significantly reduced T cell cytokine production. Upstream, TCR-activated tyrosine kinases caused inducible tyrosine phosphorylation of GRK2 and were required for the GRK2-dependent events of CXCR4-Ser-339 phosphorylation and TCR-CXCR4 complex formation. Downstream of TCR-CXCR4 complex formation, we found that GRK2 and phosphatidylinositol 3-kinase γ (PI3Kγ) were required for TCR-stimulated membrane recruitment of PREX1 and for stabilization of cytokine mRNAs and robust cytokine secretion. Together, our results identify a novel role for GRK2 as a target of TCR signaling that is responsible for TCR-induced transactivation of CXCR4 and TCR-CXCR4 complex formation that signals via PI3Kγ/PREX1 to mediate cytokine production. Therapeutic regulation of GRK2 or PI3Kγ may therefore be useful for limiting cytokines produced by T cell malignancies or autoimmune diseases.

KEYWORDS:

CXC chemokine receptor type 4 (CXCR-4); G protein-coupled receptor (GPCR); G protein-coupled receptor kinase-2 (GRK2); IL-10; IL-2; PI3 kinase γ (PI3Kγ); T-cell receptor (TCR); cytokine; fluorescence resonance energy transfer (FRET); phosphorylation; proximity ligation assay (PLA)

PMID:
30018141
PMCID:
PMC6130939
[Available on 2019-09-07]
DOI:
10.1074/jbc.RA118.003097
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for HighWire Icon for University of Colorado, Strauss Health Sciences Library
Loading ...
Support Center