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Cyclic AMP-dependent protein kinase regulates sensitivity of cells to multiple drugs
I Abraham1, R J Hunter, K E Sampson
1Cell Biology Department, Upjohn Co., Kalamazoo, Michigan 49001.
Abstract:
The isolation of mutant cell lines affecting the activity of cyclic AMP (cAMP)-dependent protein kinase (PK-A) has made it possible to determine the function of this kinase in mammalian cells. We found that both a CHO cell mutant with a defective regulatory subunit (RI) for PK-A and a transfectant cell line expressing the same mutant kinase were sensitive to multiple drugs, including puromycin, adriamycin, actinomycin D, and some antimitotic drugs. The mutant and transfectant cells, after treatment with a concentration of the antimitotic drug colcemid that had no marked effect on the wild-type parent cell, had a severely disrupted microtubule network. The phenotype of hypersensitivity to the antimitotic drug colcemid was used to select revertants of the transfectant and the original mutant. These revertants simultaneously regained normal multiple drug resistance and cAMP sensitivity, thus establishing that the characteristics of colcemid sensitivity and cAMP resistance are linked. Four revertants of the transfectant reverted because of loss or rearrangement of the transfected mutant RI gene. These revertants, as well as one revertant selected from the original mutant, had PK-A activities equal to or higher than that of the parent. In these genetic studies, in which linkage of expression of a PK-A mutation with drug sensitivity is demonstrated, it was established that the PK-A system is involved in regulating resistance of mammalian cells to multiple drugs.
Insights
Mutant cell lines with altered cyclic AMP (cAMP)-dependent protein kinase (PK-A) activity show increased sensitivity to multiple drugs. This study links PK-A function to mammalian cell resistance to various drug treatments.
Area of Science:
- Cell Biology
- Molecular Genetics
- Biochemistry
Background:
- Cyclic AMP (cAMP)-dependent protein kinase (PK-A) plays crucial roles in mammalian cell function.
- Understanding PK-A's role requires studying cellular responses to genetic alterations.
Purpose of the Study:
- To investigate the function of PK-A in mammalian cells by analyzing mutant cell lines.
- To determine the relationship between PK-A activity and cellular drug resistance.
Main Methods:
- Isolation and characterization of mutant cell lines with defective PK-A regulatory subunit (RI).
- Analysis of drug sensitivity (puromycin, adriamycin, actinomycin D, colcemid) in wild-type, mutant, and transfectant cells.
- Selection and genetic analysis of revertant cell lines.
Main Results:
- Mutant and transfectant cells expressing defective PK-A were hypersensitive to multiple drugs, including the antimitotic agent colcemid.
- Colcemid treatment severely disrupted the microtubule network in mutant cells.
- Revertant cell lines simultaneously regained normal drug resistance and cAMP sensitivity, indicating a linkage.
Conclusions:
- The PK-A system is involved in regulating mammalian cell resistance to multiple drugs.
- Genetic studies demonstrate a linkage between PK-A mutation expression and drug sensitivity.
- PK-A plays a significant role in cellular defense mechanisms against toxic compounds.