Mechanisms of regulation of tyrosine phosphorylation of NMDA receptor subunit 2B after cerebral ischemia/reperfusion.
キーワード
概要
OBJECTIVE
To study the mechanisms of the regulation of the tyrosine phosphorylation of N-methyl-D-aspartate (NMDA) receptor subunit 2B(NR2B) in the gerbil hippocampal synaptosomes following ischemia/reperfusion (I/R).
METHODS
Transient (15 min) cerebral ischemia was produced by bilateral carotid artery occlusion procedure. The tyrosine phosphorylation of NR2B was analyzed by immunoprecipitation and immunoblot assay.
RESULTS
Transient forebrain ischemia for 15 min caused a marked decrease in the levels of tyrosine phosphorylation of many protein bands including 180 kDa protein. Transient ischemia followed by reperfusion induced rapid (within 15 min of reperfusion), and sustained (for at least 48 h) increase in the tyrosine phosphorylation of many protein bands including 180 kDa protein. Immunoprecipitation and immunoblot confirmed that NR2B is among the phosphorylated 180 kDa protein. Maximal phosphorylation of 180 kDa band corresponding to NR2B (1.8 fold relative to sham-operated controls) was reached at 6 h of reperfusion following 15 min of cerebral ischemia. But the level of protein expression of NR2B did not change. Administration of ketamine (KT), a non-competitive NMDA receptor antagonist, or nifedipine (ND), an L-type voltage gated calcium channel (L-type VGCC) blocker, 20 min before ischemia attenuated stimulation of the tyrosine phosphorylation of NR2B without affecting the level of protein expression of NR2B. Under these conditions, non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) had no effect on the level of tyrosine phosphorylation. Protein tyrosine phosphatase (PTP) inhibitor vanadate and protein tyrosine kinase (PTK) inhibitor genestein resulted in the increase and the decrease of the tyrosine phosphorylation of NR2B, respectively. Src coprecipitated with NR2B protein.
CONCLUSIONS
The increase of the tyrosine phosphorylation of NR2B induced by I/R has relation to NR and L-type VGCC; PTK and PTP participate in the regulation of the tyrosine phosphorylation of NR2B during I/R. Src that associates with NR2B may play an important role in the regulation of the tyrosine phosphorylation of NR2B during I/R.
