Effect of Protein Kinase C Inhibitor (PKCI) on Radiation Sensitivity and c-fos Transcription Activity.
- Author:
Eun Kyung CHOI
1
;
Hyesook CHANG
;
Yun Hee RHEE
;
Kun Koo PARK
Author Information
1. Department of Radiation Oncology, Asan Medical Center, College of Medicine, University of Ulsan, Korea.
- Publication Type:Original Article
- Keywords:
Radiation sensitivity;
Ataxia-Telangiectasia;
PKCI;
c-fos
- MeSH:
Animals;
Apoptosis;
Ataxia Telangiectasia;
Blotting, Northern;
Catalytic Domain;
Cats;
Gene Expression;
Genes, fos;
Genes, Reporter;
Humans;
In Situ Nick-End Labeling;
Phosphatidylinositol 3-Kinase;
Plasmids;
Polymerase Chain Reaction;
Protein Kinase C*;
Protein Kinases*;
Radiation Tolerance*;
Radiation, Ionizing;
Signal Transduction;
Transfection
- From:The Journal of the Korean Society for Therapeutic Radiology and Oncology
1999;17(4):299-306
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
PURPOSE: The human genetic disorder ataxia-telangiectasia (AT) is a multisystem disease characterized by extreme radiosensitivity. The recent identification of the gene mutated in AT, ATM, and the demonstration that it encodes a homologous domain of phosphatidylinositol 3-kinase (PI3-K), the catalytic subunit of an enzyme involved in transmitting signals from the cell surface to the nucleus, provide support for a role of this gene in signal transduction. Although ionizing radiation was known to induce c-fos transcription, nothing is known about how ATM or PKCI mediated signal transduction pathway modulates the c-fos gene transcription and gene expression. Here we have studied the effect of PKCI on radiation sensitivity and c-fos transcription in normal and AT cells. MATERIALS AND METHODS: Normal (LM217) and AT (AT5BIVA) cells were transfected with PKCI expression plasmid and the overexpression and integration of PKCI was evaluated by northern blotting and polymerase chain reaction, respectively. 5 Gy of radiation was exposed to LM and AT cells transfected with PKCI expression plasmid and cells were harvested 48 hours after radiation and investigated apoptosis with TUNEL method. The c-fos transcription activity was studied by performing CAT assay of reporter gene after transfection of c-fos CAT plasmid into AT and LM cells. RESULTS: Our results demonstrate for the first time a role of PKCI on the radiation sensitivity and c-fos expression in LM and AT cells. PKCI increased radiation induced apoptosis in LM cells but reduced apoptosis in AT cells. The basal c-fos transcription activity is 70 times lower in AT cells than that in LM cells. The c-fos transcription activity was repressed by overexpression of PKCI in LM cells but not in AT cells. After induction of c-fos by Ras protein, overexpression of PKCI repressed c-fos transcription in LM cells but not in AT cells CONCLUSION: Overexpression of PKCI increased radiation sensitivity and repressed c-fos transcription in LM cells but not in AT cells. The results may be a reason of increased radiation sensitivity of AT cells. PKCI may be involved in an ionizing radiation induced signal transduction pathway responsible for radiation sensitivity and c-fos transcription. The data also provided evidence for novel transcriptional difference between LM and AT cells.
