Activation of ERK1/2 by platelet-activating factor receptor is independent of receptor internalisation and G-protein activation.
Platelet-activating factor (PAF) is a potent pro-inflammatory phospholipid mediator involved in a broad range of physiological and pathophysiological processes. The receptor of PAF (PAFR) is a heptahelical G-protein-coupled receptor. We have shown previously that upon agonist stimulation, PAFR internalised through clathrin-coated vesicles in an arrestin-dependent, but G-protein-coupling-independent manner. In the current report, we demonstrate that PAF stimulates Erk1/2 phosphorylation and: (1). dominant negative mutants of arrestins and dynamin do not influence Erk1/2 activation, (2). hypertonic conditions do not decrease the extent of Erk1/2 phosphorylation, (3). internalisation-deficient and/or G-protein-coupling-deficient mutants of PAFR activate Erk1/2 as efficiently as the wild-type PAFR, and (4). inhibition of epidermal growth factor receptor (EGFR) does not block Erk1/2 activation. Taken together, our results suggest that PAFR-mediated activation of mitogen-activated protein kinases Erk1/2 does not require receptor endocytosis, receptor tyrosine kinase transactivation or G-protein activation. In addition, our studies reveal that PAFR-mediated signals of G-protein activation, receptor internalisation and MAPK activation are differentially regulated by receptor structure and/or conformation.
Chen
Zhangguo
Z
Department of Pediatrics, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
Rola-Pleszczynski
Marek
M
Stankova
Jana
J
D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D034281:Dynamins / Q000235:genetics / Q000502:physiology; D004705:Endocytosis; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007975:Leukotriene B4 / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D037342:Pertussis Toxin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D011799:Quinazolines; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013395:Sucrose / Q000494:pharmacology; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases
D019390:Arrestins; D010980:Platelet Membrane Glycoproteins; D011799:Quinazolines; D043562:Receptors, G-Protein-Coupled; D020032:Tyrphostins; C039351:platelet activating factor receptor; C101044:RTKI cpd; D007975:Leukotriene B4; D013395:Sucrose; D037342:Pertussis Toxin; D066246:ErbB Receptors; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D034281:Dynamins; D007545:Isoproterenol