Toll-like receptors differentially regulate GPCR kinases and arrestins in primary macrophages

Mol Immunol. 2008 Apr;45(8):2312-22. doi: 10.1016/j.molimm.2007.11.012. Epub 2008 Jan 4.

Abstract

G-protein coupled receptor kinases (GRKs) and arrestins (ARRs) are ubiquitously distributed crucial signaling proteins that are critical in the regulation of responsiveness of G-protein coupled receptors (GPCRs). Toll-like receptors (TLRs) (class of pattern recognition receptors) play a vital role in macrophage biology and innate immunity. Because GPCR responsiveness is regulated in part by the expression levels of GRKs/ARRs, the focus of this work was to uncover potential cross-talk mechanisms between TLRs and GPCRs via regulation of GRK/ARR expression in primary mouse macrophages. We demonstrate here that activation of TLR2 and 4 (but not TLR3 and 7) significantly decrease ARR2 but not ARR3 protein levels in macrophages. Compared to this, activation of TLR2, 4, and 7 (but not TLR3) significantly decrease GRK5 and 6 protein levels. Surprisingly, GRK2 protein levels are markedly increased by TLR2, 3, 4 and 7. Mechanistically, expression of ARR2 and GRK5 are regulated at transcriptional as well as post-translational levels. Downregulation of GRK6 by LPS is regulated primarily at the post-translational level. TLR4-induced GRK2 level, however, is both transcriptionally and post-transcriptionally regulated. Our results demonstrate previously unknown crucial regulatory mechanisms that alter ARR/GRK expression levels in macrophages that might modify many, if not all, GPCR-mediated innate immune responses.

Publication types

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

MeSH terms

  • Animals
  • Arrestins / metabolism*
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • G-Protein-Coupled Receptor Kinases / genetics
  • G-Protein-Coupled Receptor Kinases / metabolism*
  • Gene Expression Regulation, Enzymologic / drug effects
  • I-kappa B Kinase / antagonists & inhibitors
  • Lipopolysaccharides / pharmacology
  • MAP Kinase Signaling System / drug effects
  • Macrophages / drug effects
  • Macrophages / enzymology*
  • Mice
  • Mice, Inbred C57BL
  • Protein Processing, Post-Translational / drug effects
  • RNA Stability / drug effects
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Toll-Like Receptor 2 / metabolism
  • Toll-Like Receptor 4 / metabolism
  • Toll-Like Receptors / metabolism*
  • beta-Arrestin 2
  • beta-Arrestins

Substances

  • Arrb2 protein, mouse
  • Arrestins
  • Enzyme Inhibitors
  • Lipopolysaccharides
  • RNA, Messenger
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • arrestin3
  • beta-Arrestin 2
  • beta-Arrestins
  • I-kappa B Kinase
  • G-Protein-Coupled Receptor Kinases