Extracellular phosphorylation of proteins was suggested in the late 1800s when it was demonstrated that casein contains phosphate. More recently, extracellular kinases that phosphorylate extracellular serine, threonine, and tyrosine residues of numerous proteins have been identified. However, the functional significance of extracellular phosphorylation of specific residues in the nervous system is poorly understood. Here we show that synaptic accumulation of GluN2B-containing N-methyl-D-aspartate receptors (NMDARs) and pathological pain are controlled by ephrin-B-induced extracellular phosphorylation of a single tyrosine (p*Y504) in a highly conserved region of the fibronectin type III (FN3) domain of the receptor tyrosine kinase EphB2. Ligand-dependent Y504 phosphorylation modulates the EphB-NMDAR interaction in cortical and spinal cord neurons. Furthermore, Y504 phosphorylation enhances NMDAR localization and injury-induced pain behavior. By mediating inducible extracellular interactions that are capable of modulating animal behavior, extracellular tyrosine phosphorylation of EphBs may represent a previously unknown class of mechanism mediating protein interaction and function.

当证明酪蛋白含有磷酸盐时，在1800年代后期提出了蛋白质的细胞外磷酸化。最近，已经鉴定出磷酸化许多蛋白质的胞外丝氨酸，苏氨酸和酪氨酸残基的胞外激酶。但是，人们对神经系统中特定残基的细胞外磷酸化的功能意义了解得很少。在这里，我们显示含GluN2B的N-甲基-D-天冬氨酸受体（NMDARs）的突触积累和病理性疼痛是由ephrin-B诱导的酪氨酸高度保守区域中单个酪氨酸的细胞外磷酸化（p * Y504）控制的。受体酪氨酸激酶EphB2的III型纤连蛋白（FN3）域。依赖配体的Y504磷酸化调节皮质和脊髓神经元中的EphB-NMDAR相互作用。此外，Y504磷酸化增强NMDAR定位和损伤引起的疼痛行为。通过介导能够调节动物行为的诱导性细胞外相互作用，EphB的细胞外酪氨酸磷酸化可能代表了介导蛋白质相互作用和功能的机制的未知领域。