Department and Center of Neuroscience, Geneva University Medical Center, CH-1211 Geneva, Switzerland.
Hippocampus. 2011 Sep;21(9):990-8. doi: 10.1002/hipo.20811. Epub 2010 May 20.
Synaptic scaffolding proteins from membrane-associated guanylate kinases (MAGUK) family are implicated in synapse formation and functioning. To better understand the role of one of the proteins of this family, SAP97, we studied with electron microscopy the effects of its overexpression on spine and synapse morphology in CA1 pyramidal neurons of rat organotypic hippocampal slice cultures. Dramatic spine enlargement induced by SAP97 overexpression was accompanied by marked morphological changes, with spines enwrapping and engulfing presynaptic terminals. The size and complexity of the PSD was also significantly increased. Similar to PSD-95, SAP97 promoted formation of multi-innervated spines (MIS). In addition, both MAGUK proteins induced multiple excitatory contacts on dendritic shafts suggesting a mechanism for shaft synapse formation. Formation of MIS and shaft synapses was blocked by the nitric oxide synthase (NOS) inhibitor L-NAME. Immunochemistry revealed that overexpression of SAP97 was associated with overexpression of PSD-95 and recruitment of nNOS to the synapse. These data provide evidence for both common and distinct structural alterations produced by overexpression of SAP97 and PSD-95 and demonstrate strong interactions between these two proteins to regulate contact formation through nitric oxide signaling.
突触相关膜鸟苷酸激酶 (MAGUK) 家族的突触支架蛋白参与突触的形成和功能。为了更好地了解该家族的一种蛋白质 SAP97 的作用，我们通过电子显微镜研究了其过表达对大鼠器官型海马切片培养物 CA1 锥体神经元中棘突和突触形态的影响。SAP97 过表达诱导的棘突显著增大伴随着明显的形态变化，棘突包裹和吞噬突触前末端。PSD 的大小和复杂性也显著增加。与 PSD-95 相似，SAP97 促进多神经支配棘突 (MIS) 的形成。此外，两种 MAGUK 蛋白均在树突干上诱导形成多个兴奋性接触，提示形成杆状突触的机制。NOS 抑制剂 L-NAME 阻断了 MIS 和杆状突触的形成。免疫化学显示 SAP97 的过表达与 PSD-95 的过表达和 nNOS 向突触的募集有关。这些数据为 SAP97 和 PSD-95 过表达产生的共同和独特的结构改变提供了证据，并证明了这两种蛋白质之间的强烈相互作用，通过一氧化氮信号调节接触的形成。
