Title: Tyrosine Phosphorylation in a Model of Ischemia Using the Rat Hippocampal Slice: Specific, Long‐Term Decrease in the Tyrosine Phosphorylation of the Postsynaptic Glycoprotein PSD‐GP180
Abstract: Abstract: The effects of the exposure of hippocampal slices to brief periods of ischemic‐like conditions on the tyrosine phosphorylation of proteins and glycoproteins were investigated. Freshly prepared hippocampal slices contained a range of tyrosine‐phosphorylated proteins and two prominent tyrosine‐phosphorylated glycoproteins of apparent M r 110,000 (GP110) and 180,000, which we have previously shown to correspond to the postsynaptic density (PSD)‐associated glycoprotein PSD‐GP180. When hippocampal slices were incubated in oxygenated Krebs‐Ringer buffer containing 10 m M glucose (KRB), there was a transient increase in the tyrosine phosphorylation of a protein of M r 42,000 (p42) and a pronounced increase in the tyrosine phosphorylation of GP110. After these initial changes, the tyrosine phosphorylation of all proteins remained constant for at least 60 min. In vitro “ischemia” was achieved by transferring slices that had been preincubated for 60 min in KRB to KRB that had been equilibrated with N 2 instead of O 2 and that did not contain glucose. Tyrosine‐phosphorylated GP110 and PSD‐GP180 could no longer be detected after 10 min of exposure of the slices to ischemic‐like conditions. GP110 was rapidly rephosphorylated on tyrosine after transfer of slices back to oxygenated, glucose‐containing buffer. In contrast, short periods of ischemia (5 or 10 min) resulted in the long‐term loss of phosphotyrosine [Tyr(P)]‐PSD‐GP180 so that it was not detected even after 60 min of reincubation in oxygenated KRB. The sustained decrease in tyrosine phosphorylation of PSD‐GP180 after ischemia was Ca 2+ dependent, the levels of Tyr(P)‐PSD‐GP180 slowly increasing to preischemic values if Ca 2+ was omitted from the incubation media. Reoxygenation of ischemic slices also resulted in the Ca 2+ ‐dependent, transient tyrosine phosphorylation of p42. The major PSD‐associated, tyrosine‐phosphorylated glycoprotein of molecular mass 180 kDa has recently been identified as the NR2B subunit of the NMDA receptor. The results suggest that changes in tyrosine phosphorylation after an ischemic insult may modulate the NMDA receptor or signal transduction pathways in the postsynaptic cell and are consistent with a role for tyrosine phosphorylation in the sequence of events leading to neuronal cell damage and death.
Publication Year: 1995
Publication Date: 1995-10-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 11
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