Heat-shock protein 25 (Hspb1) regulates manganese superoxide dismutase through activation of Nfkb (NF-kappaB).
We previously demonstrated that overexpression of HSP25 (now known as Hspb1) conferred increased resistance to ionizing radiation (Radiat Res. 154, 421-428, 2000). In the present study, L929 cells overexpressing Hspb1 were shown to have increased expression of the manganese superoxide dismutase gene (now known as SOD2) and its enzyme activity. To elucidate Hspb1-induced pathways leading to activation of these antioxidant enzymes, the production of the tumor necrosis factor alpha (Tnf) and interleukin 1 beta (Il1b) genes was examined. Increased expression of Tnf and Il1b resulting from Hspb1 overexpression was detected by RT-PCR. Increased activation of Nfkb (degradation of Ikb, a member of the Nfkb family) was also found in Hspb1-overexpressing cells. When treated with Tnf, Nfkb activation and SOD2 gene expression were increased more by Hspb1 overexpression. Moreover, transfection with the Hspb1 antisense gene abrogated all of the Hspb1-mediated phenomena. To further elucidate the exact relationship between induction of SOD2 and Nfkb activation, a dominant negative I-kBalpha (now known as Nfkb1a) construct was transfected into Hspb1-overexpressing cells. The dominant negative Nfkb1a inhibited Hspb1-mediated SOD2 gene expression. In addition, Hspb1-mediated radioresistance was blocked by dominant negative Nfkb1a transfection. When the SOD2 gene was transfected into L929 cells, a somewhat increased radioresistance was detected by a clonogenic survival assay compared to control cells. Hspb1 produced Tnf and Il1b and facilitated SOD2 gene expression through Nfkb activation, possibly resulting in Hspb1-mediated radioresistance.
Yi
Min-Jeong
MJ
Laboratory of Radiation Effect, Korea Cancer Center Hospital, Seoul 139-706, Korea.
Park
Sang-Hee
SH
Cho
Hye-Nyun
HN
Yong Chung
Hee
H
Kim
Jong-Il
JI
Cho
Chul-Koo
CK
Lee
Su-Jae
SJ
Lee
Yun-Sil
YS
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays / Q000009:adverse effects; D005786:Gene Expression Regulation / Q000528:radiation effects; D006360:Heat-Shock Proteins; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D000099156:Superoxide Dismutase 2
D006360:Heat-Shock Proteins; D007375:Interleukin-1; D018832:Molecular Chaperones; D016328:NF-kappa B; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D013482:Superoxide Dismutase; D014409:Tumor Necrosis Factor-alpha; D000099156:Superoxide Dismutase 2; C486113:Hsbp1 protein, mouse