Le Hoa T, Maksumova Lola, Wang Jing, Pallen Catherine J
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
J Neurochem. 2006 Sep;98(6):1798-809. doi: 10.1111/j.1471-4159.2006.04075.x. Epub 2006 Aug 8.
Mice lacking protein tyrosine phosphatase alpha (PTPalpha) exhibited defects in NMDA receptor (NMDAR)-associated processes such as learning and memory, hippocampal neuron migration, and CA1 hippocampal long-term potentiation (LTP). In vivo molecular effectors linking PTPalpha and the NMDAR have not been reported. Thus the involvement of PTPalpha as an upstream regulator of NMDAR tyrosine phosphorylation was investigated in synaptosomes of wild-type and PTPalpha-null mice. Tyrosine phosphorylation of the NMDAR NR2A and NR2B subunits was reduced upon PTPalpha ablation, indicating a positive effect of this phosphatase on NMDAR phosphorylation via intermediate molecules. The NMDAR is a substrate of src family tyrosine kinases, and reduced activity of src, fyn, yes and lck, but not lyn, was apparent in the absence of PTPalpha. In addition, autophosphorylation of proline-rich tyrosine kinase 2 (Pyk2), a tyrosine kinase linked to NMDAR signaling, was also reduced in PTPalpha-deficient synaptosomes. Altered protein tyrosine phosphorylation was not accompanied by altered expression of the NMDAR or the above tyrosine kinases at any stage of PTPalpha-null mouse development examined. In a human embryonic kidney (HEK) 293 cell expression system, PTPalpha enhanced fyn-mediated NR2A and NR2B tyrosine phosphorylation by several-fold. Together, these findings provide evidence that aberrant NMDAR-associated functions in PTPalpha-null mice are due to impaired NMDAR tyrosine phosphorylation resulting from the reduced activity of probably more than one of the src family kinases src, fyn, yes and lck. Defective NMDAR activity in these mice may also be linked to the loss of PTPalpha as an upstream regulator of Pyk2.
缺乏蛋白酪氨酸磷酸酶α（PTPα）的小鼠在与N-甲基-D-天冬氨酸受体（NMDAR）相关的过程中表现出缺陷，如学习和记忆、海马神经元迁移以及海马CA1区的长时程增强（LTP）。尚未有关于体内连接PTPα和NMDAR的分子效应器的报道。因此，在野生型和PTPα基因敲除小鼠的突触体中研究了PTPα作为NMDAR酪氨酸磷酸化上游调节因子的作用。PTPα缺失后，NMDAR的NR2A和NR2B亚基的酪氨酸磷酸化减少，表明该磷酸酶通过中间分子对NMDAR磷酸化有正向作用。NMDAR是src家族酪氨酸激酶的底物，在缺乏PTPα的情况下，src、fyn、yes和lck的活性降低，但lyn的活性未降低。此外，与NMDAR信号传导相关的酪氨酸激酶富含脯氨酸的酪氨酸激酶2（Pyk2）的自磷酸化在PTPα缺陷的突触体中也降低。在所检测的PTPα基因敲除小鼠发育的任何阶段，蛋白酪氨酸磷酸化的改变均未伴随着NMDAR或上述酪氨酸激酶表达的改变。在人胚肾（HEK）293细胞表达系统中，PTPα使fyn介导的NR2A和NR2B酪氨酸磷酸化增强了几倍。总之，这些发现提供了证据，表明PTPα基因敲除小鼠中与NMDAR相关的异常功能是由于可能不止一种src家族激酶src、fyn、yes和lck的活性降低导致NMDAR酪氨酸磷酸化受损。这些小鼠中NMDAR活性缺陷也可能与作为Pyk2上游调节因子的PTPα缺失有关。
