Effect of guanine and adenine nucleotides on bombesin-stimulated phospholipase C activity in membranes from Swiss 3T3 and small cell lung carcinoma cells.
In [3H]inositol-labeled membranes prepared from Swiss mouse 3T3 and human small cell lung carcinoma cells, [Tyr4]-bombesin stimulated production of water-soluble inositol phosphates. The reaction was stimulated by guanosine 5'-O-[3-thiotriphosphate] and was specifically inhibited by both [Leu13-psi-CH2NHLeu14]-bombesin and the antibombesin antibody 2A11. [Tyr4]-bombesin-induced activation of phospholipase C is most apparent in Ca2(+)-depleted conditions (less than 1 microM[Ca2+]free). The kinetics of activation by ligand also demonstrate that [Tyr4]-bombesin-dependent phospholipase C activation is most apparent at [Mg2+]free of approximately 0.2 microM. At millimolar concentrations of [Mg2+]free, there is considerably less dependence on [Tyr4]-bombesin for activation of phospholipase C. ATP is not necessary for initial activation of phospholipase C, and beta, gamma-imidoadenosine-5'-triphosphate does not inhibit the reaction. These results demonstrate that in these cell types [Tyr4]-bombesin activates phospholipase C in conjunction with guanine nucleotides. Phospholipase C-coupled guanine nucleotide regulatory proteins would be appropriately considered as novel targets for the development of therapeutic strategies in small cell lung carcinoma.
Sharoni
Y
Y
NCI-Navy Medical Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland 20814.
Viallet
J
J
Trepel
J B
JB
Sausville
E A
EA
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology*; D000818:Animals; D000906:Antibodies; D001839:Bombesin / Q000276:immunology / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D018288:Carcinoma, Small Cell; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D006150:Guanine Nucleotides / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms; D008274:Magnesium / Q000494:pharmacology; D051379:Mice; D013873:Thionucleotides / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology*; D010738:Type C Phospholipases / Q000378:metabolism*
D000906:Antibodies; D006150:Guanine Nucleotides; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D000266:Adenylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D008274:Magnesium; D001839:Bombesin; D002118:Calcium