Depolarization activates ERK and proline-rich tyrosine kinase 2 (PYK2) independently in different cellular compartments in hippocampal slices.
In the hippocampus, extracellular signal-regulated kinase (ERK) and the non-receptor protein proline-rich tyrosine kinase 2 (PYK2) are activated by depolarization and involved in synaptic plasticity. Both are also activated under pathological conditions following ischemia, convulsions, or electroconvulsive shock. Although in non-neuronal cells PYK2 activates ERK through the recruitment of Src-family kinases (SFKs), the link between these pathways in the hippocampus is not known. We addressed this question using K(+)-depolarized rat hippocampal slices. Depolarization increased the phosphorylation of PYK2, SFKs, and ERK. These effects resulted from Ca(2+) influx through voltage-gated Ca(2+) channels and were diminished by GF109203X, a protein kinase C inhibitor. Inhibition of SFKs with PP2 decreased PYK2 tyrosine phosphorylation dramatically, but not its autophosphorylation on Tyr-402. Moreover, PYK2 autophosphorylation and total tyrosine phosphorylation were profoundly altered in fyn-/- mice, revealing an important functional relationship between Fyn and PYK2 in the hippocampus. In contrast, ERK activation was unaltered by PP2, Fyn knock-out, or LY294002, a phosphatidyl-inositol-3-kinase inhibitor. ERK activation was prevented by MEK inhibitors that had no effect on PYK2. Immunofluorescence of hippocampal slices showed that PYK2 and ERK were activated in distinct cellular compartments in somatodendritic regions and nerve terminals, respectively, with virtually no overlap. Activation of ERK was critical for the rephosphorylation of a synaptic vesicle protein, synapsin I, following depolarization, underlining its functional importance in nerve terminals. Thus, in hippocampal slices, in contrast to cell lines, depolarization-induced activation of non-receptor tyrosine kinases and ERK occurs independently in distinct cellular compartments in which they appear to have different functional roles.
Corvol
Jean-Christophe
JC
Signal Transduction and Plasticity in the Nervous System Unit, INSERM/Université Pierre et Marie Curie U536, Institut du Fer à Moulin, 75005 Paris, France.
Valjent
Emmanuel
E
Toutant
Madeleine
M
Enslen
Hervé
H
Irinopoulou
Théano
T
Lev
Sima
S
Hervé
Denis
D
Girault
Jean-Antoine
JA
D000818:Animals; D002451:Cell Compartmentation; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D051418:Focal Adhesion Kinase 2; D006624:Hippocampus / Q000502:physiology* / Q000648:ultrastructure; D066298:In Vitro Techniques; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D011189:Potassium Chloride / Q000378:metabolism / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D051381:Rats; D017207:Rats, Sprague-Dawley; D019061:src-Family Kinases / Q000378:metabolism
D011518:Proto-Oncogene Proteins; D011189:Potassium Chloride; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C494960:Fyn protein, mouse; C494961:Fyn protein, rat; D051076:Proto-Oncogene Proteins c-fyn; C496053:Ptk2b protein, mouse; C496054:Ptk2b protein, rat; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases