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Pactamycin resistance in CHO cells: morphological changes induced by the drug in the wild-type and mutant cells
Abstract:
Stable mutants resistant to pactamycin (PacR), a polypeptide chain initiation inhibitor, have been selected in a single step in Chinese hamster ovary (CHO) cells. The sensitivity of protein synthesis in mutant cell extracts to pactamycin indicates that resistance involves an alteration in the permeability of this drug. The failure of PacR mutants to show cross-resistance to other compounds provides further indication that the lesion is presumably specific for pactamycin. Cell hybrids formed between PacR X PacS lines show intermediate sensitivity towards pactamycin, suggesting that the PacR lesion behaves codominantly under these conditions. In the presence of subinhibitory concentrations of pactamycin, CHO cells, which are normally short, polygonal and disoriented, became greatly elongated and aligned themselves in parallel fashion to produce highly oriented colony morphologies, reminiscent of normal diploid fibroblasts. This effect of pactamycin on cellular morphology was seen much more clearly with the PacR mutants, although somewhat higher concentrations of the drug were required to produce this change.
Insights
Stable Chinese hamster ovary (CHO) cells resistant to pactamycin (PacR) were developed. These PacR mutants exhibit altered drug permeability, with resistance being codominant and specific to pactamycin.
Area of Science:
- Cell Biology
- Molecular Pharmacology
- Drug Resistance Mechanisms
Background:
- Pactamycin is a polypeptide antibiotic that inhibits protein synthesis by targeting translation initiation.
- Understanding drug resistance mechanisms is crucial for developing effective cancer therapies and studying cellular processes.
- Chinese hamster ovary (CHO) cells are a widely used model system in toxicology and genetic studies.
Purpose of the Study:
- To select and characterize stable pactamycin-resistant mutants in CHO cells.
- To investigate the underlying mechanism of pactamycin resistance.
- To explore the effect of pactamycin on cell morphology and colony formation.
Main Methods:
- Single-step selection of pactamycin-resistant mutants (PacR) from CHO cells.
- Analysis of protein synthesis sensitivity to pactamycin in cell extracts.
- Assessment of cross-resistance to other compounds.
- Formation and analysis of cell hybrids (PacR x PacS).
- Microscopic observation of cell and colony morphology in the presence of pactamycin.
Main Results:
- Stable pactamycin-resistant CHO cell mutants (PacR) were successfully selected.
- Resistance appears to be due to altered drug permeability, specific to pactamycin.
- PacR mutation exhibits codominant inheritance in cell hybrids.
- Pactamycin induces significant changes in CHO cell morphology, promoting elongation and parallel alignment, an effect more pronounced in PacR mutants.
Conclusions:
- Pactamycin resistance in CHO cells is likely mediated by a specific defect in drug uptake.
- The codominant nature of the resistance suggests a simple genetic basis.
- Pactamycin influences cell morphology, offering a potential tool to study cellular organization and differentiation.