The bombesin/GRP receptor transfected into Rat-1 fibroblasts couples to phospholipase C activation, tyrosine phosphorylation of p125FAK and paxillin and cell proliferation
Charlesworth, A.; Broad, S.; Rozengurt, E.
Oncogene 12(6): 1337-1345
1996
ISSN/ISBN: 0950-9232 PMID: 8649836 Document Number: 467920
Bombesin elicits multiple signalling pathways in various cell types. It is not clear, however, whether these responses are mediated by a single receptor subtype or by different subtypes that couple preferentially to specific pathways. To resolve this we transfected the mouse bombesin/GRP receptor into Rat-1 fibroblasts and investigated the pathways activated by bombesin. Expression of the transfected receptors was verified by binding of (125I)GRP and two clones were selected, BOR5 and BOR15. Bombesin stimulation of BOR5 and BOR15 cells caused intracellular Ca-2+ mobilisation and increased the phosphorylation of 80K/MARCKS, a prominent protein kinase C substrate. The transfected receptor conferred a proliferative response to bombesin demonstrated by incorporation of (3H)thymidine after 18 h and an increase in total cell numbers after 1-2 days. In BOR5 and BOR15 cells, bombesin rapidly stimulated the tyrosine phosphorylation of multiple proteins M-r 110000-130000 and 70000-80000 including p125-FAK and paxillin, at low concentrations (half maximum 0.3 nM). The specific bombesin/GRP receptor antagonist, D-F-5-Phe-6, D-Ala-11-Bombesin(613)OMe, inhibited all the above responses. These results show that phospholipase C activation, cell growth and tyrosine phosphorylation emanate from a single class of bombesin receptor.