title: Gastrointestinal hormones cause rapid c-Met receptor down-regulation by a novel mechanism involving clathrin-mediated endocytosis and a lysosome-dependent mechanism.
abstract: The activated c-Met receptor has potent effects on normal tissues and tumors. c-Met levels are regulated by hepatocyte growth factor (HGF); however, it is unknown if they can be regulated by gastrointestinal (GI) hormones. c-Met is found in many GI tissues/tumors that possess GI hormone receptors. We studied the effect of GI hormones on c-Met in rat pancreatic acini, which possess both receptors. CCK-8, carbachol, and bombesin, but not VIP/secretin, decreased c-Met. CCK-8 caused rapid and potent c-Met down-regulation and abolished HGF-induced c-Met and Gab1 tyrosine phosphorylation, while stimulating c-Met serine phosphorylation. The effect of cholecystokinin (CCK) was also seen in intact acini using immunofluorescence, in a biotinylated fraction representing membrane proteins, in single acinar cells, in Panc-1 tumor cells, and in vivo in rats injected with CCK. CCK-8 did not decrease cell viability or overall responsiveness. GF109203X, thapsigargin, or their combination partially reversed the effect of CCK-8. In contrast to HGF-induced c-Met down-regulation, the effect of CCK was decreased by a lysosome inhibitor (concanamycin) but not the proteasome inhibitor lactacystin. Inhibitors of clathrin-mediated endocytosis blocked the effect of CCK. HGF but not CCK-8 caused c-Met ubiquitination. These results show CCK and other GI hormones can cause rapid c-Met down-regulation, which occurs by a novel mechanism. These results could be important for c-Met regulation in normal as well as in neoplastic tissue in the GI tract.
authors.affiliation: Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1804, USA.
authors.forename: K Martin
authors.initials: KM
authors.lastname: Hoffmann
authors.forename: Jose A
authors.initials: JA
authors.lastname: Tapia
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Berna
authors.forename: Michelle
authors.initials: M
authors.lastname: Thill
authors.forename: Till
authors.initials: T
authors.lastname: Braunschweig
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Mantey
authors.forename: Terry W
authors.initials: TW
authors.lastname: Moody
authors.forename: Robert T
authors.initials: RT
authors.lastname: Jensen
mesh_terms: D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004705:Endocytosis; D005768:Gastrointestinal Hormones / Q000494:pharmacology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D066298:In Vitro Techniques; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000494:pharmacology
chemical_list: D002966:Clathrin; D005768:Gastrointestinal Hormones; D017228:Hepatocyte Growth Factor; D002217:Carbachol; D019859:Proto-Oncogene Proteins c-met; D011493:Protein Kinase C; D012844:Sincalide; D001839:Bombesin; D002118:Calcium