MECHANISMS OF LONG TERM SYNAPTIC PLASTICITY

分析记忆的细胞基础的一个基本问题是，在短期记忆和长期记忆之间的转换中，调节细胞机制的不同角色的重要性。突触的短期可塑性和长期可塑性之间的主要区别之一是对蛋白质合成的要求。这项拟议研究的目的是调查与长期突触可塑性相关的细胞变化中涉及的特定蛋白质的参与。已经鉴定出许多蛋白质，它们的水平是由于海兔防御性撤退反射的长期敏化而改变的，海兔是一种研究得很好的长期记忆形成模型。其中一种蛋白最近被鉴定为Aplysia tolloid/bone Morphenetic Protein Like-1(apTBL-1)。在其他系统中，apTBL-1的同系物作为生长因子的TGFβ超家族的激活剂。先前的一项研究表明，应用转化生长因子β可以在分离的神经节中诱导海兔感觉-运动联系的长期易化。在具体目标1中，将测试apTBL-1诱导培养神经元长期突触易化的能力，这部分地介导了长期敏化。此外，针对apTBL-1的特定抗体的能力将被测试，以确定其是否有能力阻止已知的神经调节剂5-羟色胺诱导的长期易化。在具体目标2中，将测试转化生长因子β对培养的感觉-运动连接产生长期促进作用的能力。这项研究将定位TGFbeta对感觉神经元或运动神经元的作用。转化生长因子β受体的分布也将通过免疫组织化学技术来确定。将进行Western blotting以确认用于染色的抗体的特异性。在特定的目标3中，将研究将转化生长因子β信号转导到细胞核的信号机制。具体地说，将分析MAPK和SMAD转录因子家族的活性，以确定它们在TGFbeta信号中的作用。这个项目将提供对简单形式学习背后的分子机制的见解。

A fundamental issue in the analysis of the cellular basis of memory is the importance of the differential roles of regulatory cellular mechanisms in the transition between short- and long-term memory. One of the main differences between short- and long-term synaptic plasticity is the requirement for protein synthesis. The objective of the proposed research is to investigate the involvement of specific proteins that have been implicated in the cellular changes associated with long-term synaptic plasticity. Many proteins have been identified whose levels are altered as a result of long-term sensitization of defensive withdrawal reflexes of Aplysia, a well-studied model for long-term memory formation. One of these proteins has recently been identified as Aplysia tolloid/bone morphogenetic protein like-1 (apTBL-1). In other systems, homologues of apTBL-1 act as activators of the TGFbeta superfamily of growth factors. A previous study has shown that application of TGFbeta induces long-term facilitation of Aplysia sensory-motor connections in isolated ganglia. In Specific Aim 1, the ability of apTBL-1 to induce long-term synaptic facilitation, which partly mediates long-term sensitization, of cultured neurons will be tested. Further, the ability of a specific antibody against apTBL-1 will be tested for its ability to block the induction of long-term facilitation by 5-HT, a known neuromodulator. In Specific Aim 2, the ability of TGFbeta to produce long-term facilitation of cultured sensory-motor connections will be tested. This study will localize TGFbeta's action to either or both the sensory or motor neuron. The distribution of TGFbeta receptors will also be determined using immunohistochemical techniques. Western blots will be performed to confirm the specificity of the antibodies used for the staining. In Specific Aim 3, the signaling mechanisms which transduce TGFbeta signals to the nucleus will be investigated. Specifically, the activities of MAPK and the SMAD family of transcription factors will be analyzed for their roles in TGFbeta signaling. This project will provide insights into the molecular mechanisms underlying simple forms of learning.