Cytoskeletal Mechanisms of Cocaine-Induced Neuroplasticity

描述（由申请人提供）：有充分的证据表明，长期暴露于可卡因会导致树突棘的结构变化。然而，这些变化发生的机制在很大程度上是未知的。最近的研究结果表明，长期暴露于可卡因导致肌动蛋白在单体球状g -肌动蛋白和聚合丝状f -肌动蛋白之间的循环增加，以及树突棘对急性可卡因注射的结构反应性改变。这些变化与一些与突触后结构和肌动蛋白循环调节相关的蛋白质水平的变化有关，特别是Arp3。Arp2/3蛋白作为新的肌动蛋白细丝的模板，是肌动蛋白聚合的重要多蛋白复合物的组成部分。慢性可卡因治疗和戒断后，在可卡因刺激后的突触后密度部分中，Arp3蛋白水平短暂但显著上调（>300%）。因此，Arp水平和活性的调节可能提供了一个重要的手段，通过蛋白质动力学调节脊柱结构的变化，以响应经验。本文提出的实验将使用可卡因寻求的恢复模型来研究细胞骨架蛋白动力学与强调成瘾的持久细胞变化的发展之间的关系。特别是，我将试图确定与慢性可卡因使用相关的结构可塑性的分子机制。由于Arp2/3复合物是肌动蛋白丝聚合的关键组成部分，我将利用已确定的Arp3在可卡因反应中的上调作为研究这些机制的起点。Arp2/3肌动蛋白成核核由WASP/WAVE家族的5个蛋白（WASP、N-WASP、WAVE-1、WAVE-2和WAVE-3）激活。许多研究结果表明，N-WASP或WAVE-1激活Arp2/3可能是对可卡因反应的肌动蛋白循环的基础。因此，我将提出一种假设，即WASP蛋白激活Arp2/3参与了对可卡因的反应，而Arp2/3核核的激活是可卡因恢复诱导树突棘结构可塑性和可卡因寻求的关键步骤。我还将研究n -乙酰半胱氨酸（NAC）作为药物寻找的一种候选药物治疗方法，可能会阻止脊柱中观察到的形态学变化，以及观察到的Arp3和其他肌动蛋白循环标志物表达的变化。来自该提案的数据将探索肌动蛋白相关机制，该机制是可卡因诱导的神经可塑性的基础，有助于可卡因成瘾者的复发。

DESCRIPTION (provided by applicant): It is well documented that chronic exposure to cocaine leads to structural changes within dendritic spines. However, the mechanisms by which these changes occur are largely unknown. Recent findings indicate that chronic exposure to cocaine leads to an increase in actin cycling between monomeric globular G-actin and polymerized filamentous F-actin, as well as a change in the structural responsiveness of dendritic spines to an acute cocaine injection. These changes are correlated with changes in the levels of a number of proteins associated with the postsynaptic structure and regulation of actin cycling, in particular Arp3. Arp2/3 proteins serve as templates for new actin filaments, and are components of a multi-protein complex important for actin polymerization. Arp3 protein levels are transiently but strikingly upregulated (>300%) in a postsynaptic density fraction following a cocaine challenge after chronic cocaine treatment and withdrawal. Thus, regulation of Arp levels and activity may provide an important means by which protein dynamics regulate changes in spine architecture in response to experience. The experiments proposed herein will use the reinstatement model of cocaine-seeking to investigate the relationship between cytoskeletal protein dynamics and the development of long-lasting cellular changes which underscore addiction. In particular, I will seek to identify the molecular mechanism(s) that underlie the structural plasticity associated with chronic cocaine use. As the Arp2/3 complex is a critical component of the polymerization of actin filaments, I will take advantage of the identified upregulation of Arp3 in response to cocaine as a starting point at which to investigate these mechanisms. The Arp2/3 actin nucleation core is activated by the WASP/WAVE family of five proteins (WASP, N-WASP, WAVE-1, WAVE-2, and WAVE-3). A number of findings indicate that activation of Arp2/3 by N-WASP or WAVE-1 may underlie actin cycling in response to cocaine. Thus, I will address the hypothesis that the Arp2/3 activation by WASP proteins is engaged in response to cocaine, and that activation of the Arp2/3 nucleation core is a critical step in the structural plasticity of dendritic spines and cocaine-seeking induced by cocaine reinstatement. I will also investigate the possibility that N-acetylcysteine (NAC), a candidate pharmacotherapy for drug seeking, may prevent the morphological changes observed in spines, as well as the changes observed in expression of Arp3 and other markers of actin cycling. The data from this proposal will explore actin-related mechanisms that underlie the cocaine-induced neuroplasticity that contributes to relapse in cocaine addicts.