Differential regulation of HSP70 expression by the JNK kinases SEK1 and MKK7 in mouse embryonic stem cells treated with cadmium.
JNK, a member of the mitogen-activated protein kinases (MAPKs), is activated by the MAPK kinases SEK1 and MKK7 in response to environmental stresses. In the present study, the effects of CdCl2 treatment on MAPK phosphorylation and HSP70 expression were examined in mouse embryonic stem (ES) cells lacking the sek1 gene, the mkk7 gene, or both. Following CdCl2 exposure, the phosphorylation of JNK, p38, and ERK was suppressed in sek1-/- mkk7-/- cells. When sek1-/- or mkk7-/- cells were treated with CdCl2, JNK phosphorylation, but not the phosphorylation of either p38 or ERK, was markedly reduced, while a weak reduction in p38 phosphorylation was observed in sek1-/- cells. Thus, both SEK1 and MKK7 are required for JNK phosphorylation, whereas their role in p38 and ERK phosphorylation could overlap with that of another kinase. We also observed that CdCl2-induced HSP70 expression was abolished in sek1-/- mkk7-/- cells, was reduced in sek1-/- cells, and was enhanced in mkk7-/- cells. Similarly, the phosphorylation of heat shock factor 1 (HSF1) was decreased in sek1-/- mkk7-/- and sek1-/- cells, but was increased in mkk7-/- cells. Transfection with siRNA specific for JNK1, JNK2, p38, ERK1, or ERK2 suppressed CdCl2-induced HSP70 expression. In contrast, silencing of p38 or p38 resulted in further accumulation of HSP70 protein. These results suggest that HSP70 expression is up-regulated by SEK1 and down-regulated by MKK7 through distinct MAPK isoforms in mouse ES cells treated with CdCl2.
Nishitai
Gen
G
Department of Hygiene and Public Health I, School of Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. nishitai@research.twmu.ac.jp
Matsuoka
Masato
M
D000818:Animals; D019256:Cadmium Chloride / Q000633:toxicity*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000187:drug effects* / Q000201:enzymology*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000172:deficiency / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000172:deficiency / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; C490017:Hsf1 protein, mouse; D007527:Isoenzymes; D014157:Transcription Factors; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; C482570:Map2k7 protein, mouse; D019256:Cadmium Chloride