Knock-down of POSH expression is neuroprotective through down-regulating activation of the MLK3-MKK4-JNK pathway following cerebral ischaemia in the rat hippocampal CA1 subfield.
We investigated the expression and subcellular localization of the multidomain protein POSH (plenty of SH3s) by immunohistochemistry and western blot analysis, as well as its role in the selective activation of mixed-lineage kinases (MLKs) 3, MAP kinase kinase (MKK) 4, c-Jun N-terminal kinases (JNKs) and the c-Jun signalling cascade in the rat hippocampal CA1 region following cerebral ischaemia. Our results indicated that the cytosol immunoreactivity of POSH was strong in the CA1-CA3 pyramidal cell but weak in the DG granule cell of the rat hippocampus both in sham control and after reperfusion. Co-immunoprecipitation experiments showed that the interactions of MLK3, MKK4 and phospho-JNKs with POSH were persistently enhanced during the early (30 min) and the later reperfusion period (from 1 to 3 days) compared with sham controls. Consistently, MLK3-MKK4-JNK activation was rapidly increased with peaks both at 30 min and 3 days of reperfusion. Intracerebroventricular infusion of POSH antisense oligodeoxynucleotides (AS-ODNs) not only significantly reduced the protein level of POSH, markedly decreased its interactions with MLK3, MKK4 and phospho-JNKs, but also attenuated the activation of the JNK signalling pathway. In addition, infusion of POSH AS-ODNs significantly increased the neuronal density in the CA1 region at 5 days of reperfusion. Our results suggest that POSH might serve as a scaffold mediating JNK signalling activation in the hippocampal CA1 region following cerebral ischaemia, and POSH AS-ODNs exerts its protective effects on ischaemic injury through a mechanism of inhibition of the MLK3-MKK4-JNK signalling pathway, involving c-Jun and caspase 3 activation.
Zhang
Quan-Guang
QG
Department of Neurobiology and Biophysics, University of Science and Technology of China, Hefei, Anhui, China.
Wang
Rui-Min
RM
Yin
Xiao-Hui
XH
Pan
Jing
J
Xu
Tian-Le
TL
Zhang
Guang-Yi
GY
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism* / Q000503:physiopathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense; D017966:Pyramidal Cells / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology; D015398:Signal Transduction / Q000502:physiology; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
D048868:Adaptor Proteins, Signal Transducing; D053148:Caspase 3; D020169:Caspases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020319:Oligodeoxyribonucleotides, Antisense; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C506024:Sh3rf1 protein, rat; C505410:Casp3 protein, rat