Mechanisms of regulation of tyrosine phosphorylation of NMDA receptor subunit 2B after cerebral ischemia/reperfusion

AIM: To study the mechanisms of the regulation of the tyrosine phosphorylat ion of N-methyl-D-aspartate (NMDA) receptor subunit 2B(NR2B) in the gerbil hippocampal synaptosomes following ischemia/reperfusion (VR). METHODS: Tran sient (15 min) cerebral ischemia was produced by bilateral carotid artery o cclusion procedure. The tyrosine phosphorylation of NR2B was analyzed by im munoprecipitation and immunoblot assay. RESULTS: Transient forebrain ischem ia for 15 min caused a marked decrease in the levels of tyrosine phosphoryl ation of many protein bands including 180 kDa protein. Transient ischemia f ollowed by reperfusion induced rapid (within 15 min of reperfusion), and su stained (for at least 48 h) increase in the tyrosine phosphorylation of man y protein bands including 180 kDa protein. Immunoprecipitation and immunobl ot confirmed that NR2B is among the phosphorylated 180 kDa protein. Maximal phosphorylation of 180 kDa band corresponding to NR2B (1.8 fold relative t o sham-operated controls) was reached at 6 h of reperfusion following 15 mi n of cerebral ischemia. But the level of protein expression of NR2B did not change. Administration of ketamine (KT), a noncompetitive NMDA receptor an tagonist, or nifedipine (ND), an L-type voltage gated calcium channel (L-ty pe VGCC) blocker, 20 min before ischemia attenuated stimulation of the tyro sine phosphorylation of NR2B without affecting the level of protein express ion of NR2B. Under these conditions, non-NMDA receptor antagonist 6,7-dinit roquinoxaline-2,3-dione (DNQX) had no effect on the level of tyrosine phosp horylation. Protein tyrosine phosphatase (PTP) inhibitor vanadate and prote in tyrosine kinase (PTK) inhibitor genestein resulted in the increase and t he decrease of the tyrosine phosphorylation of NR2B, respectively. Src copr ecipitated with NR2B protein. CONCLUSION: The increase of the tyrosine phos phorylation of NR2B induced by VR has relation to NR and L-type VGCC; PTK a nd PTP participate in the regulation of the tyrosine phosphorylation of NR2 B during I/R. Src that associates with NR2B may play an important role in t he regulation of the tyrosine phosphorylation of NR2B during VR.