Department of Neurobiology, University of Chicago, Chicago IL 60637, USA.
J Neurosci. 2013 Jul 17;33(29):12067-76. doi: 10.1523/JNEUROSCI.0816-13.2013.
SAP97 interacts with AMPA receptors (AMPARs) and NMDA receptors (NMDARs) during sorting and trafficking to synapses. Here we addressed how SAP97 distinguishes between AMPARs and NMDARs and what role the adaptor/scaffold protein, CASK, plays in the process. Using intramolecular SAP97 Förster resonance energy transfer sensors, we demonstrated that SAP97 is in "extended" or "compact" conformations in vivo. SAP97 conformation was regulated by a direct interaction between SAP97 and CASK through L27 protein-interaction domains on each protein. Unbound SAP97 was mostly in the compact conformation, while CASK binding stabilized it in an extended conformation. In HEK cells and rat hippocampal neurons, SAP97 in the compact conformation preferentially associated and colocalized with GluA1-containing AMPARs, and in the extended conformation colocalized with GluN2B-containing NMDARs. Altogether, our findings suggest a molecular mechanism by which CASK binding regulates SAP97 conformation and its subsequent sorting and synaptic targeting of AMPARs and NMDARs during trafficking to synapses.
SAP97 在分选和转运到突触的过程中与 AMPA 受体 (AMPAR) 和 NMDA 受体 (NMDAR) 相互作用。在这里，我们研究了 SAP97 如何区分 AMPAR 和 NMDAR，以及衔接/scaffold 蛋白 CASK 在该过程中扮演的角色。使用分子内 SAP97Förster 共振能量转移传感器，我们证明 SAP97 在体内处于“伸展”或“紧凑”构象。SAP97 构象受 SAP97 和 CASK 之间的直接相互作用调节，这种相互作用通过两种蛋白上的 L27 蛋白相互作用域发生。未结合的 SAP97 主要处于紧凑构象，而 CASK 结合稳定了其伸展构象。在 HEK 细胞和大鼠海马神经元中，处于紧凑构象的 SAP97 优先与包含 GluA1 的 AMPAR 结合并共定位，而处于伸展构象的 SAP97 则与包含 GluN2B 的 NMDAR 共定位。总之，我们的研究结果表明了一种分子机制，即 CASK 结合调节 SAP97 构象及其随后的分选和转运到突触时的 AMPAR 和 NMDAR 的突触靶向。
