Wu Hai-Yan, Hsu Fu-Chun, Gleichman Amy J, Baconguis Isabelle, Coulter Douglas A, Lynch David R
Departments of Pediatrics and Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Biol Chem. 2007 Jul 13;282(28):20075-87. doi: 10.1074/jbc.M700624200. Epub 2007 May 25.
Cleavage of the intracellular carboxyl terminus of the N-methyl-d-aspartate (NMDA) receptor 2 subunit (NR2) by calpain regulates NMDA receptor function and localization. Here, we show that Fyn-mediated phosphorylation of NR2B controls calpain-mediated NR2B cleavage. In cultured neurons, calpain-mediated NR2B cleavage is significantly attenuated by blocking NR2B phosphorylation of Tyr-1336, but not Tyr-1472, via inhibition of Src family kinase activity or decreasing Fyn levels by small interfering RNA. In HEK cells, mutation of Tyr-1336 eliminates the potentiating effect of Fyn on calpain-mediated NR2B cleavage. The potentiation of NR2B cleavage by Fyn is limited to cell surface receptors and is associated with calpain translocation to plasma membranes during NMDA receptor activation. Finally, reducing full-length NR2B by calpain does not decrease extrasynaptic NMDA receptor function, and truncated NR1/2B receptors similar to those generated by calpain have electrophysiological properties matching those of wild-type receptors. Thus, the Fyn-controlled regulation of NMDA receptor cleavage by calpain may play critical roles in controlling NMDA receptor properties during synaptic plasticity and excitotoxicity.
钙蛋白酶对N-甲基-D-天冬氨酸（NMDA）受体2亚基（NR2）细胞内羧基末端的切割作用可调节NMDA受体的功能和定位。在此，我们表明Fyn介导的NR2B磷酸化作用可控制钙蛋白酶介导的NR2B切割。在培养的神经元中，通过抑制Src家族激酶活性或利用小干扰RNA降低Fyn水平来阻断Tyr-1336（而非Tyr-1472）的NR2B磷酸化，可显著减弱钙蛋白酶介导的NR2B切割。在人胚肾（HEK）细胞中，Tyr-1336的突变消除了Fyn对钙蛋白酶介导的NR2B切割的增强作用。Fyn对NR2B切割的增强作用仅限于细胞表面受体，且与NMDA受体激活过程中钙蛋白酶向质膜的转位有关。最后，钙蛋白酶对全长NR2B的切割不会降低突触外NMDA受体的功能，并且与钙蛋白酶产生的类似截短型NR1/2B受体具有与野生型受体相匹配的电生理特性。因此，Fyn控制的钙蛋白酶对NMDA受体切割的调节作用可能在突触可塑性和兴奋性毒性过程中控制NMDA受体特性方面发挥关键作用。
