Cytoskeletal Mechanisms of Cocaine-Induced Neuroplasticity

描述(由申请人提供)：有充分的证据表明，长期接触可卡因会导致树突内结构的变化。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，长期接触可卡因会导致单体球状G-肌动蛋白和聚合的丝状F-肌动蛋白之间的肌动蛋白循环增加，并改变树突棘对急性可卡因注射的结构反应。这些变化与一些与突触后结构和肌动蛋白循环调控相关的蛋白质水平的变化有关，特别是Arp3。Arp2/3蛋白作为新肌动蛋白细丝的模板，是肌动蛋白聚合过程中重要的多蛋白复合体的组成部分。在慢性可卡因治疗和戒断后接受可卡因刺激后，突触后密度部分的Arp3蛋白水平短暂但显著上调(&gt；300%)。因此，Arp水平和活性的调节可能提供了一种重要的手段，通过蛋白质动力学调节脊柱结构对经验的反应变化。这里提出的实验将使用寻求可卡因的恢复模型来研究细胞骨架蛋白动力学与强调成瘾的长期细胞变化的发展之间的关系。特别是，我将寻求确定与长期使用可卡因相关的结构可塑性的分子机制(S)。由于Arp2/3复合体是肌动蛋白细丝聚合的关键成分，我将利用已发现的Arp3对可卡因的上调作为研究这些机制的起点。Arp2/3肌动蛋白核核心由五种蛋白质(WASP、N-WASP、WAVE-1、WAVE-2和WAVE-3)组成的WASP/WAVE家族激活。许多研究结果表明，N-WASP或WAVE-1激活Arp2/3可能是可卡因反应肌动蛋白循环的基础。因此，我将解决这样的假设，即WASP蛋白对Arp2/3的激活是对可卡因的反应，而Arp2/3成核核心的激活是可卡因恢复诱导的树突棘结构可塑性和寻找可卡因的关键步骤。我还将研究N-乙酰半胱氨酸(NAC)作为一种候选药物寻找药物的可能性，它可以防止观察到的脊椎形态变化，以及Arp3和其他肌动蛋白周期标志物表达的变化。这项提案的数据将探索肌动蛋白相关的机制，这些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.