title: Valine-286 residue in the third intracellular loop of the cholecystokinin 2 receptor exerts a pivotal role in cholecystokinin 2 receptor mediated intracellular signal transduction in human colon cancer cells.
abstract: Although expression of the gastrin/cholecystokinin-2 receptor (CCK2R) is widely reported in human colorectal cancer, little is known on its role in mediating mature amidated gastrin (gastrin-17 amide, G-17) induced intracellular signal transduction in colon cancer cells. The purpose of this study was to explore the intracellular events of colorectal cancer cells after gastrin binding to CCK2R. Meanwhile, the influence of a natural point mutation 286V-->F in the third intracellular loop of CCK2R on gastrin-envoked intracellular signal transduction was also investigated. Firstly, Colo320 cells were stably transfected with wild type (Colo320 WT) and mutant CCK2R (Colo320 M), respectively. The intracellular signal transduction events in response to gastrin were investigated in both Colo320 WT and Colo320 M cells. In Colo320 WT cells, G-17 induced formation of intracellular cyclic AMP and inositol 1,4,5-trisphosphate, and stimulated intracellular calcium mobilization. G-17 also stimulated tyrosine phosphorylation of ERKl/2, p38, FAK, and paxillin, and up-regulated the mRNA expression of early response gene c-Jun and c-Fos. However, G-17 inhibited proliferation and induced apoptosis in Colo320 WT cells. Mutation 286V-->F in the third intracellular loop of CCK2R blocked G-17 induced biological without affecting binding affinity of CCK2R to G-17. Our results suggest that activation of CCK2R by gastrin stimulates heterotrimeric G-protein Gq and G(12/13) mediated intracellular signal transduction pathway in colon cancer cells. The valine-287 residue in third intracellular loop of CCK2R plays a pivotal role in CCK2R mediated intracellular signal transduction.
authors.affiliation: Laboratory for Experimental Gastroenterology, Department of Medicine I, St. Josef-Hospital, Ruhr-University of Bochum, Gudrunstr. 56, D-44791 Bochum.
authors.forename: Hong-Gang
authors.initials: HG
authors.lastname: Yu
authors.forename: Heiner
authors.initials: H
authors.lastname: Schäfer
authors.forename: Stefan
authors.initials: S
authors.lastname: Mergler
authors.forename: Susanne
authors.initials: S
authors.lastname: Müerköster
authors.forename: Torsten
authors.initials: T
authors.lastname: Cramer
authors.forename: Michael
authors.initials: M
authors.lastname: Höcker
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Herzig
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Schmidt
authors.forename: Frank
authors.initials: F
authors.lastname: Schmitz
mesh_terms: D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D005755:Gastrins / Q000378:metabolism; D017781:Genes, Immediate-Early; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000378:metabolism; D043887:Receptor, Cholecystokinin B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation; D014633:Valine / Q000378:metabolism*
chemical_list: D005755:Gastrins; D051419:Paxillin; D012333:RNA, Messenger; D043887:Receptor, Cholecystokinin B; D014443:Tyrosine; C013550:gastrin 17; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D014633:Valine