Takagi N, Cheung H H, Bissoon N, Teves L, Wallace M C, Gurd J W
Division of Life Sciences, University of Toronto at Scarborough, West Hill, Ontario, Canada.
J Cereb Blood Flow Metab. 1999 Aug;19(8):880-8. doi: 10.1097/00004647-199908000-00007.
Transient ischemia increases tyrosine phosphorylation of N-methyl-D-aspartate (NMDA) receptor subunits NR2A and NR2B in the rat hippocampus. The authors investigated the effects of this increase on the ability of the receptor subunits to bind to the Src homology 2 (SH2) domains of Src and Fyn expressed as glutathione-S-transferase-SH2 fusion proteins. The NR2A and NR2B bound to each of the SH2 domains and binding was increased approximately twofold after ischemia and reperfusion. Binding was prevented by prior incubation of hippocampal homogenates with a protein tyrosine phosphatase or by a competing peptide for the Src SH2 domain. Ischemia induced a marked increase in the tyrosine phosphorylation of several proteins in the postsynaptic density (PSD), including NR2A and NR2B, but had no effect on the amounts of individual NMDA receptor subunits in the PSD. The level of Src and Fyn in PSDs, but not in other subcellular fractions, was increased after ischemia. The ischemia-induced increase in the interaction of NR2A and NR2B with the SH2 domains of Src and Fyn suggests a possible mechanism for the recruitment of signaling proteins to the PSD and may contribute to altered signal transduction in the postischemic hippocampus.
短暂性脑缺血可增加大鼠海马中N-甲基-D-天冬氨酸（NMDA）受体亚基NR2A和NR2B的酪氨酸磷酸化水平。作者研究了这种增加对受体亚基与以谷胱甘肽-S-转移酶-SH2融合蛋白形式表达的Src和Fyn的Src同源2（SH2）结构域结合能力的影响。NR2A和NR2B与每个SH2结构域结合，缺血再灌注后结合增加约两倍。预先用蛋白酪氨酸磷酸酶孵育海马匀浆或用Src SH2结构域的竞争肽可阻止结合。缺血导致突触后致密物（PSD）中几种蛋白质的酪氨酸磷酸化显著增加，包括NR2A和NR2B，但对PSD中单个NMDA受体亚基的量没有影响。缺血后，PSD中Src和Fyn的水平升高，但其他亚细胞组分中未升高。缺血诱导的NR2A和NR2B与Src和Fyn的SH2结构域相互作用增加，提示信号蛋白募集到PSD的一种可能机制，可能导致缺血后海马中信号转导改变。
