alpha 2B-adrenergic receptor activates MAPK via a pathway involving arachidonic acid metabolism, matrix metalloproteinases, and epidermal growth factor receptor transactivation.
We have investigated the mechanisms whereby alpha(2B)-adrenergic receptor (alpha(2B)-AR) promotes MAPK activation in a clone of the renal tubular cell line, LLC-PK1, transfected with the rat nonglycosylated alpha(2)-AR gene. Treatment of LLC-PK1-alpha(2B) with UK14304 or dexmedetomidine caused arachidonic acid (AA) release and ERK2 phosphorylation. AA release was abolished by prior treatment of the cells with pertussis toxin, quinacrine, or methyl arachidonyl fluorophosphonate but not by the addition of the MEK inhibitor U0126. The effects of alpha(2)-agonists on MAPK phosphorylation were mimicked by cell exposure to exogenous AA. On the other hand, quinacrine abolished the effects of UK14304, but not of AA, suggesting that AA released through PLA2 is responsible for MAPK activation by alpha(2B)-AR. The effects of alpha(2)-agonists or AA were PKC-independent and were attenuated by indomethacin and nordihydroguaiaretic acid. Treatment with batimastat, CRM 197, or tyrphostin AG1478 suppressed MAPK phosphorylation promoted by alpha(2)-agonist or AA. Furthermore, conditioned culture medium from UK14304-treated LLC-PK1-alpha(2B) induced MAPK phosphorylation in wild-type LLC-PK1. Based on these data, we propose a model whereby activation of MAPK by alpha(2B)-AR is mediated through stimulation of PLA2, AA release, generation of AA derivatives, activation of matrix metalloproteinases, release of heparin-binding EGF-like growth factor, transactivation of epidermal growth factor receptor, and recruitment of Shc. Whether this pathway is particular to alpha(2B)-AR and LLC-PK1 or whether it can be extended to other cell types and/or other G-protein-coupled receptors remains to be established.
Cussac
Daniel
D
INSERM, Unité 388, Institut L. Bugnard, CHU Rangueil, 31403 Toulouse Cedex 4, France.
Schaak
Stephane
S
Denis
Colette
C
Paris
Herve
H
D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001426:Bacterial Proteins / Q000494:pharmacology; D000068438:Brimonidine Tartrate; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009570:Nitriles / Q000494:pharmacology; D037342:Pertussis Toxin; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011796:Quinacrine / Q000494:pharmacology; D011799:Quinazolines; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013552:Swine; D015533:Transcriptional Activation; D020032:Tyrphostins / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C547773:Adra2b protein, rat; D001426:Bacterial Proteins; D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; D011506:Proteins; D011799:Quinazolines; D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D020032:Tyrphostins; C113580:U 0126; D010566:Virulence Factors, Bordetella; C028581:CRM197 (non-toxic variant of diphtheria toxin); C101044:RTKI cpd; D016718:Arachidonic Acid; D000068438:Brimonidine Tartrate; D037342:Pertussis Toxin; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020782:Matrix Metalloproteinases; D011796:Quinacrine