title: Regulation of radiation-induced protein kinase Cdelta activation in radiation-induced apoptosis differs between radiosensitive and radioresistant mouse thymic lymphoma cell lines.
abstract: Protein kinase Cdelta (PKCdelta) has an important role in radiation-induced apoptosis. The expression and function of PKCdelta in radiation-induced apoptosis were assessed in a radiation-sensitive mouse thymic lymphoma cell line, 3SBH5, and its radioresistant variant, XR223. Rottlerin, a PKCdelta-specific inhibitor, completely abolished radiation-induced apoptosis in 3SBH5. Radiation-induced PKCdelta activation correlated with the degradation of PKCdelta, indicating that PKCdelta activation through degradation is involved in radiation-induced apoptosis in radiosensitive 3SBH5. In radioresistant XR223, radiation-induced PKCdelta activation was lower than that in radiosensitive 3SBH5. Cytosol PKCdelta levels in 3SBH5 decreased markedly after irradiation, while those in XR223 did not. There was no apparent change after irradiation in the membrane fractions of either cell type. In addition, basal cytosol PKCdelta levels in XR223 were higher than those in 3SBH5. These results suggest that the radioresistance in XR223 to radiation-induced apoptosis is due to a difference in the regulation of radiation-induced PKCdelta activation compared to that of 3SBH5. On the other hand, Atm(-/-) mouse thymic lymphoma cells were more radioresistant to radiation-induced apoptosis than wild-type mouse thymic lymphoma cells. Irradiated wild-type cells, but not Atm(-/-) cells, had decreased PKCdelta levels, indicating that the Atm protein is involved in radiation-induced apoptosis through the induction of PKCdelta degradation. The decreased Atm protein levels induced by treatment with Atm small interfering RNA had no effect on radiation-induced apoptosis in 3SBH5 cells. These results suggest that the regulation of radiation-induced PKCdelta activation, which is distinct from the Atm-mediated cascade, determines radiation sensitivity in radiosensitive 3SBH5 cells.
authors.affiliation: Research Center for Radiation Safety, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan. otetsu@nirs.go.jp
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nakajima
authors.forename: Osami
authors.initials: O
authors.lastname: Yukawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Tsuji
authors.forename: Harumi
authors.initials: H
authors.lastname: Ohyama
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.forename: Kouichi
authors.initials: K
authors.lastname: Tatsumi
authors.forename: Isamu
authors.initials: I
authors.lastname: Hayata
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hama-Inaba
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects*; D064007:Ataxia Telangiectasia Mutated Proteins; D001578:Benzopyrans / Q000494:pharmacology; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins / Q000172:deficiency; D004789:Enzyme Activation / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D008223:Lymphoma / Q000201:enzymology / Q000473:pathology; D051379:Mice; D051745:Protein Kinase C-delta / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency; D034741:RNA, Small Interfering / Q000235:genetics; D011827:Radiation; D011836:Radiation Tolerance / Q000528:radiation effects; D013347:Subcellular Fractions; D013953:Thymus Neoplasms / Q000201:enzymology* / Q000473:pathology*; D025521:Tumor Suppressor Proteins / Q000172:deficiency
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C085746:rottlerin; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases; D051745:Protein Kinase C-delta