Physiological changes in GRK2 regulate CCL2-induced signaling to ERK1/2 and Akt but not to MEK1/2 and calcium

J Neurochem. 2008 Feb;104(4):979-92. doi: 10.1111/j.1471-4159.2007.05023.x. Epub 2007 Oct 30.

Abstract

G protein-coupled receptor (GPCR) kinase 2 (GRK2) regulates G protein-coupled receptor signaling via agonist-induced receptor phosphorylation and desensitization. GRK2 can also modulate cellular activation by interacting with downstream signaling molecules. The intracellular GRK2 level changes during inflammatory conditions. We investigated how IL-1beta-induced changes in endogenous GRK2 expression influence chemokine receptor signaling in primary astrocytes. Culturing astrocytes with IL-1beta for 24 h induced a 2-3-fold increase in GRK2 and decreased C-C chemokine ligand 2 (CCL2)-induced ERK1/2 activation. Conversely, the 45% decrease in GRK2 expression in astrocytes from GRK2+/- animals resulted in a more pronounced CCL2-induced ERK1/2 phosphorylation. Increased GRK2 inhibited CCL2-induced Akt phosphorylation at Thr308 and Ser473 as well as pPDK-1 translocation. In contrast, altered GRK2 levels did not change the CCL2-induced increase in intracellular calcium or MEK1/2 phosphorylation. These data suggest that altered GRK2 expression modulates chemokine signaling downstream of the receptor. We found that GRK2 kinase activity was not required to decrease chemokine-induced ERK1/2 phosphorylation, whereas regulation of CCL2-induced Akt phosphorylation did require an active GRK2 kinase domain. Collectively, these data suggest that changes in endogenous GRK2 expression in primary astrocytes regulate chemokine receptor signaling to ERK1/2 and to PDK-1-Akt downstream of receptor coupling via kinase-dependent and kinase-independent mechanisms, respectively.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Astrocytes / enzymology
  • Astrocytes / metabolism
  • Calcium / metabolism*
  • Cell Line, Tumor
  • Cells, Cultured
  • Chemokine CCL2 / metabolism*
  • G-Protein-Coupled Receptor Kinase 2 / physiology*
  • Humans
  • MAP Kinase Kinase 1 / metabolism
  • MAP Kinase Kinase 2 / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mitogen-Activated Protein Kinases / metabolism*
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Signal Transduction / physiology*

Substances

  • Chemokine CCL2
  • Proto-Oncogene Proteins c-akt
  • GRK2 protein, mouse
  • G-Protein-Coupled Receptor Kinase 2
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • Map2k2 protein, mouse
  • Calcium