Delayed activation and regulation of MKK7 in hippocampal CA1 region following global cerebral ischemia in rats.
c-Jun N-terminal protein kinase (JNK) activation and subsequent c-Jun phosphorylation which stimulates its transcriptional activity have been well studied in cerebral ischemia. To determine whether mitogen-activated protein kinase kinase 7 (MKK7) play a role in JNK activation in response to the stress of global cerebral ischemia, we tested the activation of such a kinase by using phospho-Ser and phospho-Thr antibodies. Immunoprecipitation and Western blot analysis revealed that MKK7 was expressed at similar levels in all conditions, whereas phospho-MKK7 was highly augmented from 1 to 5 days and reached its peak at 3 days after 15 min of ischemia. Consistent with the active phase, the interaction of MLK3, ASK1 and phospho-JNK with MKK7 was increased compared with sham control, as shown by coimmunoprecipitation experiments. Moreover, MKK7 activation was markedly reduced by pretreatment of the free radical scavenging thiol antioxidant N-acetylcysteine (NAC). Together with previous studies, the late activation of MKK7 in hippocampal CA1 region may contribute to delayed cell death, and the protective effects of antioxidant against ischemia-induced injury may be partially mediated by the down-regulation of JNK signal pathway.
Zhang
Quanguang
Q
Research Center for Biochemistry and Molecular Biology, Xuzhou Medical College, 84 West Huai-hai Road, Xuzhou, Jiangsu, 221002, PR China.
Tian
Hui
H
Fu
Xinzhen
X
Zhang
Guangyi
G
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D002545:Brain Ischemia / Q000201:enzymology*; D004789:Enzyme Activation; D006624:Hippocampus / Q000201:enzymology*; D048688:MAP Kinase Kinase 7; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
D048688:MAP Kinase Kinase 7; D020929:Mitogen-Activated Protein Kinase Kinases; D000111:Acetylcysteine