title: Thromboxane A2 receptor-mediated epidermal growth factor receptor transactivation: involvement of PKC-delta and PKC-epsilon in the shedding of epidermal growth factor receptor ligands.
abstract: We examined thromboxane A(2) receptor (TP)-mediated transactivation of epidermal growth factor receptor (EGFR) through the shedding of EGFR ligands. A TP agonist U46619 caused the phosphorylation of EGFR in 1321N1 human astrocytoma cells, which was inhibited by an EGFR selective inhibitor AG1478 and by a disintegrin and metalloproteinase (ADAM) inhibitor TAPI-2, indicating TP stimulation caused the EGFR transactivation through the EGFR ligand shedding. Since 1321N1 cells expressed heparin-binding EGF (HB-EGF) mRNA, the mechanism of TP-mediated EGFR transactivation was examined in HEK293 cells expressing alkaline phosphatase-conjugated HB-EGF and TP. U46619 caused the shedding of HB-EGF in a time- and concentration-dependent manner. The TP-mediated shedding was inhibited by a furin inhibitor CMK, TAP-2, dominant-negative G alpha(q), a G(q/11) inhibitor YM254890, and also by a non-selective PKC inhibitor GF109203X and PKC down-regulation, but not by a conventional PKC inhibitor Gö6976. Furthermore, siRNAs of PKC-delta and PKC-epsilon inhibited U46619-induced HB-EGF shedding. Although BAPTA/AM had no effect on U46619-induced shedding of HB-EGF, EGTA inhibited it. These results suggest that TP-mediated EGFR transactivation is partially caused by shedding of HB-EGF, which involves furin and ADAM via novel types of PKCs (PKC-delta and PKC-epsilon) through G alpha(q/11) proteins in an extracellular Ca(2+)-dependent manner.
authors.affiliation: Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Kotomi
authors.initials: K
authors.lastname: Uchiyama
authors.forename: Masaki
authors.initials: M
authors.lastname: Saito
authors.forename: Masako
authors.initials: M
authors.lastname: Sasaki
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Obara
authors.forename: Shigeki
authors.initials: S
authors.lastname: Higashiyama
authors.forename: Norimichi
authors.initials: N
authors.lastname: Nakahata
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002460:Cell Line; D066246:ErbB Receptors / Q000819:agonists / Q000378:metabolism / Q000502:physiology*; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D005231:Fatty Acids, Unsaturated; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D008024:Ligands; D016716:PC12 Cells; D051745:Protein Kinase C-delta / Q000502:physiology*; D051744:Protein Kinase C-epsilon / Q000502:physiology*; D051381:Rats; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D007527:Isoenzymes; D008024:Ligands; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C045749:SQ 29548; D066246:ErbB Receptors; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon