Endophilin A1参与树突棘急性结构可塑性的机制研究

突触可塑性是学习记忆的细胞基础，长时程增强(LTP)是突触可塑性的经典形式。由于活细胞成像技术时空分辨率的局限性，神经活性诱导的LTP起始期树突棘快速膨大的调控机制及功能尚不明晰。我们通过超高分辨活细胞成像发现，LTP起始期树突棘质膜伸展与微丝聚合在时空上高度偶联，而膜结合蛋白endophilin A1(EEN1)基因敲除抑制二者偶联及树突棘快速膨大。此外，钙/钙调蛋白调节EEN1与质膜及p140Cap的结合。树突棘快速膨大不依赖于胞吐但需内陷的质膜及分支状微丝聚合。因此我们提出假说：LTP起始期EEN1作为钙/钙调蛋白直接效应分子，结合至质膜内陷处募集p140Cap促进局部分支状微丝聚合，推动质膜伸展使树突棘快速膨大。我们拟运用超高分辨显微成像及细胞生物学、生物化学、电生理和行为学等手段，解析LTP起始期树突棘快速膨大的分子细胞机制，为急性结构可塑性的调控机制及生理功能提供新见解。

Dendritic spines of excitatory synapses undergo activity-dependent structural and functional plasticity, which are cellular correlates of learning and memory. However, mechanisms underlying the rapid morphological changes immediately following NMDAR-mediated Ca2+ influx into spines remain poorly defined due to the low temporal-spatial resolution of live-cell fluorescence microscopy. By super-resolution microscopic analysis, we found that rapid expansion of spine plasma membrane and actin polymerization in spines are spatially and temporally coupled upon chemical induction of long-term potentiation (LTP), a classic form of synaptic plasticity. Knockout of EEN1, the gene encoding the N-BAR protein endophilin A1, abolishes not only spine enlargement but also the coupling of local rapid membrane expansion and actin polymerization in the initial phase of LTP. Moreover, Ca2+/Calmodulin enhance the binding of endophilin A1 to plasma membrane and p140Cap, an actin cytoskeleton regulator. Intriguingly, rapid spine enlargement requires branched actin polymerization and invaginated plasma membrane but not exocytosis for membrane supply. Based on these preliminary findings, we hypothesize that Ca2+/CaM enhance the association of endophilin A1 with plasma membrane invaginations in spines and its recruitment of p140Cap, an actin cytoskeleton regulator, which promotes local actin polymerization to generate pushing force for rapid membrane expansion of spines in response to Ca2+ influx in the acute phase of synaptic structural plasticity. In this study, we will test the hypothesis to investigate the molecular mechanism underlying acute structural plasticity.