Glutamate induces phosphorylation of Elk-1 and CREB, along with c-fos activation, via an extracellular signal-regulated kinase-dependent pathway in brain slices.
In cell culture systems, the TCF Elk-1 represents a convergence point for extracellular signal-related kinase (ERK) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) subclasses of mitogen-activated protein kinase (MAPK) cascades. Its phosphorylation strongly potentiates its ability to activate transcription of the c-fos promoter through a ternary complex assembled on the c-fos serum response element. In rat brain postmitotic neurons, Elk-1 is strongly expressed (V. Sgambato, P. Vanhoutte, C. Pagès, M. Rogard, R. A. Hipskind, M. J. Besson, and J. Caboche, J. Neurosci. 18:214-226, 1998). However, its physiological role in these postmitotic neurons remains to be established. To investigate biochemically the signaling pathways targeting Elk-1 and c-fos in mature neurons, we used a semi-in vivo system composed of brain slices stimulated with the excitatory neurotransmitter glutamate. Glutamate treatment leads to a robust, progressive activation of the ERK and JNK/SAPK MAPK cascades. This corresponds kinetically to a significant increase in Ser383-phosphorylated Elk-1 and the appearance of c-fos mRNA. Glutamate also causes increased levels of Ser133-phosphorylated cyclic AMP-responsive element-binding protein (CREB) but only transiently relative to Elk-1 and c-fos. ERK and Elk-1 phosphorylation are blocked by the MAPK kinase inhibitor PD98059, indicating the primary role of the ERK cascade in mediating glutamate signaling to Elk-1 in the rat striatum in vivo. Glutamate-mediated CREB phosphorylation is also inhibited by PD98059 treatment. Interestingly, KN62, which interferes with calcium-calmodulin kinase (CaM-K) activity, leads to a reduction of glutamate-induced ERK activation and of CREB phosphorylation. These data indicate that ERK functions as a common component in two signaling pathways (ERK/Elk-1 and ERK/?/CREB) converging on the c-fos promoter in postmitotic neuronal cells and that CaM-Ks act as positive regulators of these pathways.
Vanhoutte
P
P
Laboratoire de Neurochimie-Anatomie, Institut des Neurosciences-Unité Mixte de Recherche 7624, CNRS-Universtité Pierre et Marie Curie, 75005 Paris, France.
Barnier
J V
JV
Guibert
B
B
Pagès
C
C
Besson
M J
MJ
Hipskind
R A
RA
Caboche
J
J
D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D003342:Corpus Striatum / Q000473:pathology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005110:Extracellular Space; D005786:Gene Expression Regulation; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D048369:MAP Kinase Kinase 1; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D014157:Transcription Factors; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C494114:Elk1 protein, rat; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D018698:Glutamic Acid; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases