title: Intracellular transactivation of epidermal growth factor receptor by α1A-adrenoceptor is mediated by phosphatidylinositol 3-kinase independently of activation of extracellular signal regulated kinases 1/2 and serine-threonine kinases in Chinese hamster ovary cells.
abstract: Transactivation of epidermal growth factor receptor (EGFR) by α1-adrenoceptor (α1-AR) is implicated in contraction and hypertrophy of vascular smooth muscle (VSM). We examine whether all α1-AR subtypes transactivate EGFR and explore the mechanism of transactivation. Chinese hamster ovary (CHO) cells stably expressing one subtype of α1-AR were transiently transfected with EGFR. The transactivation mechanism was examined both by coexpression of a chimeric erythropoietin (EPO)-EGFR with an extracellular EPO and intracellular EGFR domain, and by pharmacologic inhibition of external and internal signaling routes. All three α1-AR subtypes transactivated EGFR, which was dependent on the increase in intracellular calcium. The EGFR kinase inhibitor AG1478 [4-(3'-chloroanilino)-6,7-dimethoxyquinazoline] abrogated α1A-AR and α1D-AR induced phosphorylation of EGFR, but both the inhibition of matrix metalloproteinases by GM6001 [(R)-N4-hydroxy-N(1)-[(S)-2-(1H-indol-3-yl)-1-methylcarbamoyl-ethyl]-2-isobutyl-succinamide] or blockade of EGFR by cetuximab did not. Stimulation of α1A-AR and α1D-AR also induced phosphorylation of EPO-EGFR chimeric receptors. Moreover, α1A-AR stimulation enhanced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 and serine-threonine kinases (Akt), which were both unaffected by AG1478, indicating that ERK1/2 and Akt phosphorylation is independent of EGFR transactivation. Accordingly, inhibitors of ERK1/2 or Akt did not influence the α1A-AR-mediated EGFR transactivation. Inhibition of calcium/calmodulin-dependent kinase II (CaMKII), phosphatidylinositol 3-kinase (PI3K), and Src, however, did block EGFR transactivation by α1A-AR and α1D-AR. These findings demonstrate that all α1-AR subtypes transactivate EGFR, which is dependent on an intracellular signaling route involving an increase in calcium and activation of CaMKII, PI3K, and Src, but not the of ERK1/2 and Akt pathways.
authors.affiliation: Department of Clinical Pharmacology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands (N.U., R.H.H., M.D.); Department of Medical Pharmacology, Faculty of Medicine, University of Ufuk, Ankara, Turkey (S.G.); and Department of Medical Pharmacology, Faculty of Medicine, University of Ankara, Ankara, Turkey (T.Z., B.D., H.G.).
authors.forename: Nadir
authors.initials: N
authors.lastname: Ulu
authors.forename: Robert H
authors.initials: RH
authors.lastname: Henning
authors.forename: Sahika
authors.initials: S
authors.lastname: Guner
authors.forename: Teuta
authors.initials: T
authors.lastname: Zoto
authors.forename: Basak
authors.initials: B
authors.lastname: Duman-Dalkilic
authors.forename: Marry
authors.initials: M
authors.lastname: Duin
authors.forename: Hakan
authors.initials: H
authors.lastname: Gurdal
mesh_terms: D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D066246:ErbB Receptors / Q000096:biosynthesis / Q000378:metabolism*; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000201:enzymology / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D010053:Ovary / Q000166:cytology* / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation / Q000502:physiology*
chemical_list: D018340:Receptors, Adrenergic, alpha-1; D058539:Phosphatidylinositol 3-Kinase; D066246:ErbB Receptors; D017346:Protein Serine-Threonine Kinases