Toll-like receptors differentially regulate GPCR kinases and arrestins in primary macrophages.
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.
Loniewski
Katie
K
Department of Physiology, Division of Pathology, Michigan State University, East Lansing, MI 48824, USA.
Shi
Yuhui
Y
Pestka
James
J
Parameswaran
Narayanan
N
D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054768:G-Protein-Coupled Receptor Kinases / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051193:Toll-Like Receptors / Q000378:metabolism*; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605258:Arrb2 protein, mouse; D019390:Arrestins; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C082333:arrestin3; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D051550:I-kappa B Kinase; D054768:G-Protein-Coupled Receptor Kinases