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Changes in protein kinase C subspecies protein expression and activity in a series of multidrug-resistant human KB
1Department of Biology, University of York, England.
Abstract:
We have investigated the relationship between protein kinase C (PKC), levels of resistance and drug used for selection in a series of human KB carcinoma cell lines by comparing protein kinase C activity and PKC alpha, beta I, beta II, gamma, delta, epsilon, and zeta subspecies protein expression. PKC alpha protein expression was increased by 600% and 375% in KB-A1 and KB-C1 lines respectively over the parent KB-3-1 line; only KB-A1 cells showed increased PKC delta expression. Expression of other PKC subspecies was equal to that of KB-3-1 cells. There was considerable variation between the different KB cell lines in total cytosolic PKC activity, the KB-A1 and KB-C1 lines showing 400% and 350% increases respectively, KB-V1 and KB-8-5-11 about 180%, and KB-8-5 no increase relative to the parent KB-3-1 line. For calcium-independent PKC activity, the KB-C1 and KB-A1 lines only were increased over the KB-3-1 line. Immunoprecipitation with antisera to PKC subspecies confirmed that the increase in KB-A1 cytosolic total PKC activity was due largely to PKC alpha and partially to PKC delta. Membrane-associated PKC activity was increased by 500% and 350% in KB-A1 and KB-C1 lines respectively, by 250% and 270% in KB-V1 and KB-8-5-11, and not increased in KB-8-5 cells relative to the KB-3-1 cells. For KB-C1, KB-8-5-11, and KB-8-5 lines, which show decreasing resistance to colchicine, our results suggest a correlation between PKC and multidrug resistance in cells selected for resistance to this drug. There is no correlation between PKC and multidrug resistance for cells selected in different drugs. Our study therefore suggests that specific PKC subspecies are associated with the MDR phenotype of some KB cell lines, but that the extent of PKC involvement depends on the type of drug used for selection and its concentration.
Insights
Specific protein kinase C (PKC) subspecies correlate with multidrug resistance (MDR) in human KB carcinoma cells, but this association depends on the drug used for selection. This highlights PKC
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Protein Kinase C (PKC) is a family of enzymes involved in various cellular processes.
- Multidrug resistance (MDR) is a complex phenomenon where cancer cells develop resistance to multiple chemotherapeutic agents.
- Understanding the molecular mechanisms underlying MDR is crucial for improving cancer treatment efficacy.
Purpose of the Study:
- To investigate the relationship between protein kinase C (PKC) activity and expression of its subspecies with multidrug resistance (MDR) in human KB carcinoma cell lines.
- To determine if the type of drug used for selection influences the association between PKC and MDR.
- To identify specific PKC subspecies involved in the MDR phenotype.
Main Methods:
- Comparison of protein kinase C activity and expression of PKC alpha, beta I, beta II, gamma, delta, epsilon, and zeta subspecies in parent KB-3-1 cells and drug-selected resistant cell lines (KB-A1, KB-C1, KB-V1, KB-8-5-11, KB-8-5).
- Measurement of total cytosolic and membrane-associated PKC activity.
- Immunoprecipitation using antisera to specific PKC subspecies to confirm enzyme contributions.
Main Results:
- Increased expression of PKC alpha and, in some cases, PKC delta was observed in resistant cell lines.
- Significant variations in total cytosolic and membrane-associated PKC activity were found across different resistant cell lines.
- A correlation between PKC and MDR was suggested for cells selected for resistance to colchicine, but not for cells selected with different drugs.
Conclusions:
- Specific PKC subspecies are associated with the MDR phenotype in certain KB cell lines.
- The extent of PKC involvement in MDR is dependent on the drug used for selection and its concentration.
- PKC may play a role in MDR, but the specific mechanisms and contributing subspecies vary based on the selection pressure.