Opposing effects of Bad phosphorylation at two distinct sites by Akt1 and JNK1/2 on ischemic brain injury.
Increasing evidence suggests that the Bcl-2 family proteins play pivotal roles in regulation of the mitochondria cell-death pathway on transient cerebral ischemia. Bad, a BH3-only proapoptotic Bcl-2 family protein, has been shown to be phosphorylated extensively on serine by kinds of kinases. However, the exact mechanisms of the upstream kinases in regulation of Bad signaling pathway remain unknown. Here, we reported that Bad could be phosphorylated not only by Akt1 but also by JNK1/2 after transient global ischemia in rat hippocampal CA1 region. Our data demonstrated that Akt1 mediated the phosphorylation of Bad at serine 136, which increased the interaction of serine 136-phosphorylated Bad with 14-3-3 proteins and prevented the dimerization of Bad with Bcl-Xl, inhibited the release of cytochrome c to the cytosol and the death effector caspase-3 activation, leading to the survival of neuron. In contrast, JNK1/2 induced the phosphorylation of Bad at a novel site of serine 128 after brain ischemia/reperfusion, which inhibited the interaction of PI3K/Akt-induced serine 136-phosphorylated Bad with 14-3-3 proteins, thereby promoted the apoptotic effect of Bad. In addition, activated Akt1 inhibited the activation of Bad(S128) through downregulating JNK1/2 activation, thus inhibiting JNK-mediated Bad apoptosis pathway. Furthermore, the fate of cell to survive or to die was determined by a balance between prosurvival and proapoptotic signals. Taken together, our studies reveal that Bad phosphorylation at two distinct sites induced by Akt1 and JNK1/2 have opposing effects on ischemic brain injury, and present the possibility of Bad as a potential therapeutic target for stroke treatment.
Wang
Xiao-Tian
XT
Research Center for Biochemistry and Molecular Biology, Xuzhou Medical College, Xuzhou 221002, China.
Pei
Dong-Sheng
DS
Xu
Jing
J
Guan
Qiu-Hua
QH
Sun
Ya-Feng
YF
Liu
Xiao-Mei
XM
Zhang
Guang-Yi
GY
D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002545:Brain Ischemia / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism*; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009942:Organometallic Compounds / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051025:bcl-Associated Death Protein / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism
D048948:14-3-3 Proteins; D000873:Anthracenes; D018696:Neuroprotective Agents; D009942:Organometallic Compounds; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C119540:oxodiperoxo(pyridine-2-carboxylate)vanadate(V); D010768:Phosphoserine; C432165:pyrazolanthrone; D048056:Mitogen-Activated Protein Kinase 9; D051057:Proto-Oncogene Proteins c-akt; D048055:Mitogen-Activated Protein Kinase 8