Lasting N-terminal phosphorylation of c-Jun and activation of c-Jun N-terminal kinases after neuronal injury.
Transcription factor c-Jun is proposed to control neuronal cell death and survival, but its activation by N-terminal phosphorylation and the underlying activity of the c-Jun N-terminal kinases (JNKs) remain to be elucidated in the adult mammalian brain. We generated a polyclonal antiserum that specifically recognizes c-Jun phosphorylated at its serine 73 (S73) residue after UV irradiation of 3T3 cells. Disruption of the c-jun locus in 3T3 cells abolished this reaction, and retransfection of the human c-jun at the c-jun-/- background restored it. The phospho-c-Jun antiserum was used to visualize N-terminally phosphorylated c-Jun in the adult rat brain with cellular resolution. Prolonged c-Jun S73 phosphorylation was detected in affected neurons up to 5 d after transient occlusion of medial cerebral artery or up to 50 d after transection of central nerve fiber tracts. After cerebral ischemia-reperfusion, phosphorylation of c-Jun was linked with induced expression of Fas-ligand (APO-1, CD95-ligand), whose gene is a putative c-Jun/AP-1 target, and with terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) reactivity, a marker for apoptosis. After nerve fiber transection, however, lasting c-Jun phosphorylation occurred in axotomized neurons negative for Fas-ligand or TUNEL and regardless of degeneration or survival. In contrast to these lasting phosphorylation patterns, transient seizure activity by pentylenetetrazole provoked only a brief c-Jun phosphorylation and JNK activation. In extracts from ischemic or axotomized brain compartments, c-Jun phosphorylation correlated with enhanced long-term JNK activity, and in-gel kinase assays visualized proteins with sizes corresponding to JNK isoforms as the only c-Jun N-terminally phosphorylating enzymes. These results demonstrate that lasting c-Jun S73 phosphorylation and JNK activity are part of neuronal stress response after neurodegenerative disorders in the adult mammalian brain with Fas-ligand as a putative apoptotic effector.
Herdegen
T
T
Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA.
Claret
F X
FX
Kallunki
T
T
Martin-Villalba
A
A
Winter
C
C
Hunter
T
T
Karin
M
M
D016475:3T3 Cells; D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D009410:Nerve Degeneration / Q000378:metabolism*; D009412:Nerve Fibers / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D009419:Nerve Tissue Proteins; D016755:Proto-Oncogene Proteins c-jun; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases