Bombesin receptors interact with Gi and p21ras proteins in plasma membranes from rat pancreatic acinar cells.
This study investigates interaction of bombesin receptors with heterotrimeric guanosine triphosphate (GTP)-binding proteins (G proteins) and monomeric small molecular weight GTP-binding proteins (smg proteins), respectively, in plasma membranes (PM) of rat pancreatic acinar cells. Addition of bombesin to isolated PM stimulated the incorporation of the photoaffinity analogue [alpha-32P]GTP-gamma-azidoanilide into Gi proteins of 40-41 kDa and reduced the pertussis toxin-induced ADP ribosylation of three 40-41 kDa proteins, which had been previously identified as Gi1, Gi2, and Gi3 (30). In PM isolated from bombesin-prestimulated acinar cells, binding of [alpha-32P]-GTP to PM proteins of 21-22 kDa and of a monoclonal antibody against p21ras proteins was increased. Two-dimensional separation of PM proteins revealed the presence of 18 or 19 differently charged smg proteins. The p21ras proteins could be separated into two differently charged proteins with isoelectric points of 5.58 and 5.79. In microsomal membranes (MM), [alpha-32P]GTP binding to yet unidentified 21-22 kDa smg proteins was decreased compared with membranes from unstimulated acinar cells. The data suggest that Gi proteins as well as p21ras proteins are involved in bombesin receptor-mediated signal transduction in the PM. Furthermore, 21-22 kDa smg proteins in MM might play a role in bombesin-induced stimulation of intracellular pathways that lead to enzyme secretion from pancreatic acinar cells.
Pröfrock
A
A
Max-Planck-Institut für Biophysik, Frankfurt am Main, Federal Republic of Germany.
Zimmermann
P
P
Schulz
I
I
D000345:Affinity Labels; D000818:Animals; D001386:Azides; D001839:Bombesin / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D008027:Light; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008970:Molecular Weight; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D037342:Pertussis Toxin; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000345:Affinity Labels; D001386:Azides; D008565:Membrane Proteins; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter; D010566:Virulence Factors, Bordetella; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D001839:Bombesin