The bombesin/GRP receptor transfected into Rat-1 fibroblasts couples to phospholipase C activation, tyrosine phosphorylation of p125FAK and paxillin and cell proliferation.
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 Ca2+ 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 Mr 110 000-130 000 and 70 000-80 000 including p125fak and paxillin, at low concentrations (half maximum 0.3 nM). The specific bombesin/GRP receptor antagonist, D-F5-Phe6, D-Ala11-Bombesin (6-13)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.
Charlesworth
A
A
Imperial Cancer Research Fund, London, UK.
Broad
S
S
Rozengurt
E
E
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D051379:Mice; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D018004:Receptors, Bombesin / Q000819:agonists / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013268:Stimulation, Chemical; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; C496063:Pxn protein, rat; D018004:Receptors, Bombesin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; C496052:Ptk2 protein, rat; D010738:Type C Phospholipases; D001839:Bombesin