Mkp1 is a c-Jun target gene that antagonizes JNK-dependent apoptosis in sympathetic neurons.
Developing sympathetic neurons depend on NGF for survival. When sympathetic neurons are deprived of NGF in vitro, a well documented series of events, including c-Jun N-terminal kinase (JNK) pathway activation, release of cytochrome c from the mitochondria, and caspase activation, culminates in the death of the neuron by apoptosis within 24-48 h. This process requires de novo gene expression, suggesting that increased expression of specific genes activates the cell death program. Using rat gene microarrays, we found that NGF withdrawal induces the expression of many genes, including mkp1, which encodes a MAPK phosphatase that can dephosphorylate JNKs. The increase in mkp1 mRNA level requires the MLK-JNK-c-Jun pathway, and we show that Mkp1 is an important regulator of JNK-dependent apoptosis in sympathetic neurons. In microinjection experiments, Mkp1 overexpression can inhibit JNK-mediated phosphorylation of c-Jun and protect sympathetic neurons from apoptosis, while Mkp1 knockdown accelerates NGF withdrawal-induced death. Accordingly, the number of superior cervical ganglion (SCG) neurons is reduced in mkp1-/- mice at P1 during the period of developmental sympathetic neuron death. We also show that c-Jun and ATF2 bind to two conserved ATF binding sites in the mkp1 promoter in vitro and in chromatin. Both of these ATF sites contribute to basal promoter activity and are required for mkp1 promoter induction after NGF withdrawal. These results demonstrate that Mkp1 is part of a negative feedback loop induced by the MLK-JNK-c-Jun signaling pathway that modulates JNK activity and the rate of neuronal death in rat sympathetic neurons following NGF withdrawal.
Kristiansen
Mark
M
Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London, and Department of Histopathology, Great Ormond Street Hospital, London WC1N 1EH, United Kingdom.
Hughes
Rosie
R
Patel
Pritika
P
Jacques
Thomas S
TS
Clark
Andrew R
AR
Ham
Jonathan
J
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation / Q000379:methods; D054638:Dual Specificity Phosphatase 1 / Q000172:deficiency / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D018274:Electroporation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008845:Microinjections / Q000379:methods; D009154:Mutation / Q000235:genetics; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology; D009474:Neurons; D011485:Protein Binding / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*; D017783:Superior Cervical Ganglion / Q000166:cytology*
C469298:CEP-11004; D002227:Carbazoles; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C106592:3,9-bis((ethylthio)methyl)-K-252a; D020932:Nerve Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse