Mechanisms underlying calcium dependent activation of the Raf-1/ERK cascade following cerebral ischemia

AIM: To investigate the relationship between Raf-1 phosphorylation and calcium-dependent ERK activation following cerebral ischemia. METHODS: Four-vessel occlusion method was used to induce forebrain ischemia in rats. Immunoblotting assay was employed to observe the phosphorylation level of Raf-1 and ERK in hippocampus after ischemia-reperfusion, and their activity after the treatment of ketamine. RESULTS: The activation of ERK exhibited a significant elevation in response to 15 min reperfusion in hippocampus after ischemia, while the phosphorylation of Raf-1 at Ser259 rather than Ser338 or Tyr340 decreased significantly. Ketamine blocked the dephosphorylation of Ser259 on Raf-1 after ischemia, and then suppressed the activation of Raf-1/ERK.CONCLUSION: Cerebral ischemia induces the dephosphorylation of Raf-1 at the site of Ser259 in calcium-dependent manner, induces the formation of its catalytic domain, and finally results in up-regulation of ERK cascade.