title: Sustained activation of Src-family tyrosine kinases by ischemia: a potential mechanism mediating extracellular signal-regulated kinase cascades in hippocampal dentate gyrus.
abstract: In the present report, we investigated the association between the sustained activation of Src family tyrosine kinases (primarily Src kinase) with the biphasic phosphorylation of extracellular signal-regulated kinase (ERK) induced by ischemia in the rat hippocampal CA3/dentate gyrus subfield. Post-ischemia reperfusion resulted in the phosphorylation of ERK in a Ras-dependent manner; down-regulation of NMDA receptors or Src family protein kinases by ketamine or 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo[3,4-d] pyrimidine (PP2) potently antagonized the activation of ERK, indicating that NMDA receptors and Src family tyrosine kinases are essential for the up-regulation of ERK activity following ischemic stimuli. Additionally, an ischemia-induced association between RKIP and Raf-1 resulted in the inhibition of the ERK signaling cascade through an inhibition of Src-mediated Raf-1 phosphorylation at Tyr340/341 residues. This ischemia-induced inhibition of ERK was not associated with other downstream pathways involving Raf-1 phosphorylation at Ser 259 elicited by protein kinase B (Akt). Dissociation of Raf-1 from RKIP by 24 h reperfusion or (4S)-3-[(E)-but-2-enoyl]-4-benzyl-2-oxazolidinone (locostatin) influenced the second phase of ERK activation elicited by the Src-Raf cassette. We propose that, following ischemia, the Src family tyrosine kinases are critical for modulation of the Ras/Raf/MEK/ERK cascade, in which RKIP is involved in biphasic phosphorylation of ERK via a blockade of Src-Raf cascades.
authors.affiliation: Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, China. guoj69@yahoo.com
authors.forename: J
authors.initials: J
authors.lastname: Guo
authors.forename: H W
authors.initials: HW
authors.lastname: Wu
authors.forename: G
authors.initials: G
authors.lastname: Hu
authors.forename: X
authors.initials: X
authors.lastname: Han
authors.forename: W
authors.initials: W
authors.lastname: De
authors.forename: Y J
authors.initials: YJ
authors.lastname: Sun
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D018891:Dentate Gyrus / Q000201:enzymology*; D015536:Down-Regulation / Q000187:drug effects / Q000528:radiation effects; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047468:Immunoprecipitation / Q000379:methods; D007511:Ischemia / Q000201:enzymology / Q000473:pathology*; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D023303:Oxazolidinones / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015424:Reperfusion / Q000379:methods; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: C412373:AG 1879; D004791:Enzyme Inhibitors; D023303:Oxazolidinones; D011743:Pyrimidines; D019061:src-Family Kinases; D048052:Mitogen-Activated Protein Kinase 3