The eukaryotic plasmid that expresses
cholecystokinin 2 receptor (CCK2R) stably, named pCR3.1/CCK2R, was transfected into Colo320 to construct an up-regulated gastrin-CCK2R signal pathway; the
gastrin antagonist was used to down-regulate the signal pathway. Thus, including the normal control, there were three signal pathways with different CCK2R levels. Different doses of
gastrin were used to stimulate FAK in the different time. FAK
tyrosine phosphorylation and FAK expression in different groups were detected by immunoprecipitation and Western-blotting assays, and analyzed with Labimage software.
RESULTS: RT-PCR result showed that Colo320 transfected with CCK2R had a
mRNA level four times higher than that normal Colo320 did, and which suggested that up-regulated signal transduction pathway was constructed. After stimulated by
gastrin with 0, 0.1, 1, 10 and 100 nmol/
L, tyrosine phosphorylation levels of Colo320 were 24.0%, 39.7%, 46.2%, 50.4% and 44.5%, and those of Colo320 transfected with CCK2R were 24.6%, 70.7%, 90.1%, 100% and 88.6%. When incubated with
gastrin at 0, 2.5, 5, 10 and 20 min, the
tyrosine phosphorylation levels of Colo320 were 23.9%, 63.6%, 58.6%, 45.5% and 40.9%, and those of Colo320 transfected with CCK2R were 24.5%, 84.6%, 100%, 98.6% and 97.9%. The increases of
tyrosine phosphorylation in both Colo320 and Colo320 transfected with CCK2R were dose dependence of
gastrin. In Colo320, the time of phosphorylation had a tendency of exhaustion at 2.5 min; but in Colo320 transfected with CCK2R, it was
at 10 min.
Gastrin had no effects on FAK
protein expression in different cell groups. An up-regulated level of CCK2R could enhance the effect of
gastrin on FAK
tyrosine phosphorylation. The
gastrin antagonist showed an effect of competitive inhibition on
tyrosine phosphorylation of FAK.
CONCLUSIONS: FAK is a signal transducer in downstream of CCK(2)R; FAK exerts its functions by
tyrosine phosphorylation, but dose not increase FAK
protein. Gastrin-CCK2R-FAK signal pathway is a pivotal one in the cell growth and proliferation caused by
gastrin.