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Tumour promoter-mediated reversible inhibition of cell-cell communication (electrical coupling). Relationship with
Abstract:
A tumour promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA), reversibly inhibits the onset and maintenance of cell-cell communication measured by electrophysiological method. We have now studied the mechanism by which TPA inhibits communication of human cells (FL) in culture. Using [3H]phorbol-12,13-dibutyrate [( 3H]PDBu), we found a class of specific, high-affinity, saturable binding sites in intact FL cells; they have a dissociation constant of 15.4 nM, and at saturation about 3 X 10(5) PDBu molecules were bound to each cell. The binding of [3H]PDBu to FL cells was inhibited by TPA, phorbol-12-13-didecanoate and mezerein, whereas phorbol and 4 alpha-phorbol-12-13-didecanoate had no effect. There is a close correlation between the ability of the former compounds to inhibit [3H]PDBu binding and their capacity to inhibit cell-cell communication. When FL cells are dispersed with EDTA and plated onto a culture dish, they start to couple electrically within 2 h; such cell coupling was not affected by the presence of cycloheximide or actinomycin D. TPA inhibits the formation of electrical cell coupling as well as its maintenance, even in the presence of cycloheximide; the recovery of cell-cell communication after the removal of TPA was not significantly affected by the addition of cycloheximide or actinomycin D. Taken together, these results suggest that TPA-mediated reversible inhibition of intercellular communication is mediated by specific binding of TPA to cellular receptors and that macromolecular synthesis is not necessary.
Insights
12-O-tetradecanoyl phorbol-13-acetate (TPA) reversibly inhibits cell-cell communication by binding to specific cellular receptors. This inhibition does not require macromolecular synthesis, suggesting a direct mechanism of action.
Area of Science:
- Cell Biology
- Molecular Pharmacology
- Biochemistry
Background:
- Cell-cell communication is crucial for tissue function.
- Tumor promoters can disrupt normal cellular processes.
- 12-O-tetradecanoyl phorbol-13-acetate (TPA) is a known tumor promoter that affects cell communication.
Purpose of the Study:
- To investigate the mechanism by which TPA inhibits intercellular communication in human FL cells.
- To identify the cellular targets and requirements for TPA's inhibitory effects.
Main Methods:
- Electrophysiological measurements to assess cell-cell communication.
- Binding assays using radiolabeled phorbol ester ([3H]PDBu) to identify and characterize TPA receptors.
- Experiments with inhibitors of macromolecular synthesis (cycloheximide, actinomycin D).
Main Results:
- TPA reversibly inhibits both the onset and maintenance of electrophysiologically measured cell-cell communication.
- Specific, high-affinity binding sites for phorbol esters were identified in FL cells.
- The binding affinity and inhibitory capacity of phorbol derivatives correlated closely with their ability to inhibit cell communication.
- TPA inhibited cell coupling independently of macromolecular synthesis.
Conclusions:
- TPA-mediated inhibition of intercellular communication involves specific binding to cellular receptors.
- Macromolecular synthesis is not required for TPA to inhibit cell-cell communication.
- These findings elucidate a key mechanism of TPA's action on cellular communication.