Increased acute inflammation, leukotriene B4-induced chemotaxis, and signaling in mice deficient for G protein-coupled receptor kinase 6.
Directed migration of polymorphonuclear neutrophils (PMN) is required for adequate host defense against invading organisms and leukotriene B(4) (LTB(4)) is one of the most potent PMN chemoattractants. LTB(4) exerts its action via binding to BLT1, a G protein-coupled receptor. G protein-coupled receptors are phosphorylated by G protein-coupled receptor kinases (GRK) in an agonist-dependent manner, resulting in receptor desensitization. Recently, it has been shown that the human BLT1 is a substrate for GRK6. To investigate the physiological importance of GRK6 for inflammation and LTB(4) signaling in PMN, we used GRK6-deficient mice. The acute inflammatory response (ear swelling and influx of PMN into the ear) after topical application of arachidonic acid was significantly increased in GRK6(-/-) mice. In vitro, GRK6(-/-) PMN showed increased chemokinetic and chemotactic responses to LTB(4). GRK6(-/-) PMN respond to LTB(4) with a prolonged increase in intracellular calcium and prolonged actin polymerization, suggesting impaired LTB(4) receptor desensitization in the absence of GRK6. However, pre-exposure to LTB(4) renders both GRK6(-/-) as well as wild-type PMN refractory to restimulation with LTB(4), indicating that the presence of GRK6 is not required for this process to occur. In conclusion, GRK6 deficiency leads to prolonged BLT1 signaling and increased neutrophil migration.
Kavelaars
Annemieke
A
Laboratory for Psychoneuroimmunology, University Medical Center Utrecht, Utrecht, The Netherlands.
Vroon
Anne
A
Raatgever
Roel P
RP
Fong
Alan M
AM
Premont
Richard T
RT
Patel
Dhavalkumar D
DD
Lefkowitz
Robert J
RJ
Heijnen
Cobi J
CJ
D000199:Actins / Q000378:metabolism; D000208:Acute Disease; D000287:Administration, Topical; D000818:Animals; D016718:Arachidonic Acid / Q000633:toxicity; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology*; D004431:Ear, External / Q000473:pathology*; D004487:Edema / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D054768:G-Protein-Coupled Receptor Kinases; D007249:Inflammation / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D007975:Leukotriene B4 / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
D000199:Actins; D043562:Receptors, G-Protein-Coupled; D007975:Leukotriene B4; D016718:Arachidonic Acid; D017346:Protein Serine-Threonine Kinases; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6