title: Cholecystokinin stimulates extracellular signal-regulated kinase through activation of the epidermal growth factor receptor, Yes, and protein kinase C. Signal amplification at the level of Raf by activation of protein kinase Cepsilon.
abstract: Cholecystokinin (CCK) and related peptides are potent growth factors in the gastrointestinal tract and may be important for human cancer. CCK exerts its growth modulatory effects through G(q)-coupled receptors (CCK(A) and CCK(B)) and activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). In the present study, we investigated the different mechanisms participating in CCK-induced activation of ERK1/2 in pancreatic AR42J cells expressing both CCK(A) and CCK(B). CCK activated ERK1/2 and Raf-1 to a similar extent as epidermal growth factor (EGF). Inhibition of EGF receptor (EGFR) tyrosine kinase or expression of dominant-negative Ras reduced CCK-induced ERK1/2 activation, indicating participation of the EGFR and Ras in CCK-induced ERK1/2 activation. However, compared with EGF, CCK caused only small increases in tyrosine phosphorylation of the EGFR and Shc, Shc-Grb2 complex formation, and Ras activation. Signal amplification between Ras and Raf in a CCK-induced ERK cascade appears to be mediated by activation of protein kinase Cepsilon (PKCepsilon), because 1) down-modulation of phorbol ester-sensitive PKCs inhibited CCK-induced activation of Ras, Raf, and ERK1/2 without influencing Shc-Grb2 complex formation; 2) PKCepsilon, but not PKCalpha or PKCdelta, was detectable in Raf-1 immunoprecipitates, although CCK activated all three PKC isoenzymes. In addition, the present study provides evidence that the Src family tyrosine kinase Yes is activated by CCK and mediates CCK-induced tyrosine phosphorylation of Shc. Furthermore, we show that CCK-induced activation of the EGFR and Yes is achieved through the CCK(B) receptor. Together, our data show that different signals emanating from the CCK receptors mediate ERK1/2 activation; activation of Yes and the EGFR mediate Shc-Grb2 recruitment, and activation of PKC, most likely PKCepsilon, augments CCK-stimulated ERK1/2 activation at the Ras/Raf level.
authors.affiliation: Department of Internal Medicine II, University of the Saarland, D-66421 Homburg/Saar, Germany. inapii@uniklinik-saarland.de
authors.forename: Albrecht
authors.initials: A
authors.lastname: Piiper
authors.forename: Robert
authors.initials: R
authors.lastname: Elez
authors.forename: Se-Jong
authors.initials: SJ
authors.lastname: You
authors.forename: Bernd
authors.initials: B
authors.lastname: Kronenberger
authors.forename: Stefan
authors.initials: S
authors.lastname: Loitsch
authors.forename: Serge
authors.initials: S
authors.lastname: Roche
authors.forename: Stefan
authors.initials: S
authors.lastname: Zeuzem
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D016466:CHO Cells; D002766:Cholecystokinin / Q000494:pharmacology*; D006224:Cricetinae; D015536:Down-Regulation; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D006801:Humans; D015151:Immunoblotting; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010703:Phorbol Esters / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D051575:Proto-Oncogene Proteins c-yes; D051381:Rats; D029589:Seminal Plasma Proteins / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013997:Time Factors; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495950:Grb2 protein, rat; D010703:Phorbol Esters; D011506:Proteins; C528024:SHC1 protein, human; D029589:Seminal Plasma Proteins; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D002766:Cholecystokinin; C497257:Prkce protein, rat; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D051575:Proto-Oncogene Proteins c-yes; C489834:YES1 protein, human; D019908:Proto-Oncogene Proteins c-raf; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins