Related Experiment Videos
Inhibition of bombesin-induced mitogenesis by pertussis toxin: dissociation from phospholipase C pathway
Abstract:
Prior incubation of quiescent cultures of Swiss 3T3 cells with pertussis toxin selectively inhibited the stimulation of DNA synthesis induced by peptides of the bombesin family. While pertussis toxin blocked mitogenesis at an early stage in the action of the peptide, the toxin did not impair the rapid stimulation of polyphosphoinositide breakdown, Ca2+ mobilization or activation of protein kinase C promoted by bombesin. Thus, inhibition of bombesin-induced mitogenesis by pertussis toxin can be dissociated from inactivation of the phospholipase C signalling pathway.
Insights
Pertussis toxin inhibits bombesin-induced cell proliferation by blocking DNA synthesis early on. However, it does not affect key signaling events like calcium mobilization or protein kinase C activation, indicating a specific dissociation in the signaling pathway.
Area of Science:
- Cellular Biology
- Molecular Signaling
- Biochemistry
Background:
- The bombesin family of peptides are potent mitogens for Swiss 3T3 cells.
- Pertussis toxin is known to ADP-ribosylate and inactivate guanine nucleotide-binding proteins (G proteins).
- G protein-coupled receptors mediate cellular responses to various signaling molecules, including bombesin.
Purpose of the Study:
- To investigate the specific mechanism by which pertussis toxin inhibits bombesin-induced mitogenesis in Swiss 3T3 cells.
- To determine if pertussis toxin affects early signaling events downstream of bombesin receptor activation.
- To elucidate the role of G proteins in mediating bombesin-induced DNA synthesis.
Main Methods:
- Quiescent Swiss 3T3 cells were pre-incubated with pertussis toxin.
- Cells were subsequently stimulated with peptides of the bombesin family.
- DNA synthesis, polyphosphoinositide breakdown, Ca2+ mobilization, and protein kinase C activation were measured.
Main Results:
- Pertussis toxin selectively inhibited bombesin-induced DNA synthesis.
- The toxin blocked mitogenesis at an early stage of peptide action.
- Pertussis toxin did not inhibit early signaling events such as polyphosphoinositide breakdown, Ca2+ mobilization, or protein kinase C activation.
Conclusions:
- Inhibition of bombesin-induced mitogenesis by pertussis toxin is dissociated from the inactivation of the phospholipase C signaling pathway.
- Pertussis toxin's effect on mitogenesis occurs downstream of initial signaling events but upstream of DNA synthesis.
- These findings suggest a complex signaling cascade where G protein-dependent and -independent pathways may contribute to bombesin-induced cellular responses.