Inhibition of I kappaB-alpha phosphorylation at serine and tyrosine acts independently on sensitization to DNA damaging agents in human glioma cells.
Molecular mechanisms and/or intrinsic factors controlling cellular radiosensitivity are not fully understood in mammalian cells. The recent studies have suggested that nuclear factor kappaB (NF-kappaB) is one of such factors. The activation and regulation of NF-kappaB are tightly controlled by IkappaB-alpha, a cellular inhibitory protein of NF-kappaB. Most importantly, phosphorylation regulates activity of the inhibitor IkappaB-alpha, which sequesters NF-kappaB in the cytosol. Two different pathways for the phosphorylation of IkappaB-alpha are demonstrated, such as serine (at residues 32 and 36) and tyrosine (at residue 42) phosphorylations. To assess a role of the transcription factor, NF-kappaB, on cellular sensitivity to DNA damaging agents, we constructed three different types of expression plasmids, i.e. S-IkappaB (mutations at residues 32 and 36), Y-IkappaB (mutation at residue 42) and SY-IkappaB (mutations at residues 32, 36 and 42). The cell clones expressing S-IkappaB and Y-IkappaB proteins became sensitive to X-rays as compared with the parental and vector-transfected cells. The cell clones expressing SY-IkappaB were further radiosensitive. By the treatment with herbimycin A, an inhibitor of phosphorylation, the X-ray sensitivity of cells expressing SY-IkappaB did not change, while that of the cells expressing S-IkappaB and Y-IkappaB and the parental cells was enhanced. Change in the sensitivity to adriamycin and UV in those clones was very similar to that in the X-ray sensitivity. The inhibition of IkappaB-alpha phosphorylation at serine and tyrosine acts independently on the sensitization to X-rays, adriamycin and UV. These findings suggest that the transcriptional activation induced by NF-kappaB may play a role in the DNA damage repair. The present study proposes a possibility that the inactivation of NF-kappaB by inhibition of both serine and tyrosine phosphorylations may be useful for the treatment of cancer in radio- and chemotherapies.
Miyakoshi
J
J
Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Japan.
Yagi
K
K
D000970:Antineoplastic Agents / Q000494:pharmacology; D016227:Benzoquinones; D002453:Cell Cycle / Q000187:drug effects; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005822:Genetic Vectors; D005910:Glioma / Q000201:enzymology; D006801:Humans; D051550:I-kappa B Kinase; D047029:Lactams, Macrocyclic; D008025:Ligases / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D011836:Radiation Tolerance; D017828:Rifabutin / Q000031:analogs & derivatives; D017384:Sequence Deletion; D012694:Serine / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D014466:Ultraviolet Rays
D000970:Antineoplastic Agents; D016227:Benzoquinones; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D016328:NF-kappa B; D011809:Quinones; D014409:Tumor Necrosis Factor-alpha; D017828:Rifabutin; D014443:Tyrosine; D012694:Serine; C020754:herbimycin; D004317:Doxorubicin; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases