The role of TRAF6 in the regulation of neurite outgrowth

描述(由申请人提供)： 脊髓损伤后神经再生的缺乏被归因于几个因素，所有这些因素都必须被克服才能发生功能恢复。中枢神经系统而不是外周神经系统中存在生长抑制信号，导致中枢神经系统无法再生。脊髓再生的一个公认的障碍是损伤部位髓鞘抑制蛋白的表达。髓鞘抑制蛋白导致神经崩溃并从损伤部位收缩，从而阻止再生。这项工作将集中在阐明髓鞘抑制蛋白阻止中枢神经系统轴突再生的机制。髓鞘抑制蛋白通过Nogo受体(NGR)发挥作用，Nogo受体表达在生长轴突表面，并通过与p75神经营养素受体(P75)的相互作用传递信号。NGR和p75抑制轴突生长的机制尚未完全建立。P75抑制轴突生长的一个已知机制是通过涉及Rho家族GTP酶的信号级联。P75缺乏内在的催化活性，依赖于细胞内的接头蛋白来传递信号，如肿瘤坏死因子受体相关因子6(TRAF6)。我们实验室的初步数据表明，TRAF6在髓鞘抑制蛋白抑制轴突生长中发挥了作用。我们假设TRAF6是NGR-p75复合体下游生长抑制信号转导所必需的。我们研究的具体目的是：1)确定TRAF6是否是髓鞘蛋白抑制轴突生长所必需的；2)评估髓鞘抑制蛋白结合后TRAF6是否被p75招募以调节GTPase活性；3)探讨TRAF6参与抑制轴突生长的机制。将在体外和体内对缺乏TRAF6的神经元的轴突生长进行研究，以确定TRAF6在髓鞘抑制蛋白下游的作用。利用原代神经元培养，我们将评估TRAF6在调节GTPase活性中的作用。我们实验室的数据表明，TRAF6和p21激活的激酶之间可能存在功能上的相互作用，p21激活的激酶是肌动蛋白细胞骨架的已知调节者。我们将继续将这种相互作用作为TRAF6抑制轴突生长的机制。这项工作将对抑制神经再生所涉及的生化过程提供有价值的见解。这些知识将使我们能够开发治疗策略，促进脊髓损伤后神经元的生长，从而防止瘫痪。

DESCRIPTION (provided by applicant): The lack of nerve regeneration following spinal cord injury has been attributed to several factors, all of which must be overcome for functional recovery to occur. The presence of outgrowth inhibitory cues in the central nervous system, but not the peripheral nervous system, contribute to the inability of the central nervous system to regenerate. One well established obstacle in spinal cord regeneration is the expression of myelin inhibitory proteins at the site of injury. Myelin inhibitory proteins cause the nerve to collapse and retract away from the injury site, thus preventing regeneration. This work will focus on elucidating the mechanisms by which myelin inhibitory proteins prevent axon regeneration in the central nervous system. Myelin inhibitory proteins act through the Nogo receptor (NgR), which is expressed on the surface of growing axons and signals through its interaction with the p75 neurotrophin receptor (p75). The mechanisms by which NgR and p75 inhibit axon outgrowth have not been fully established. One known mechanism by which p75 inhibits axon outgrowth is through a signaling cascade involving the Rho family of GTPases. p75 lacks intrinsic catalytic activity and relies on intracellular adaptor proteins to signal, such as TNF Receptor Associated Factor 6 (TRAF6). Preliminary data from our laboratory suggests a role for TRAF6 in the inhibition of axon outgrowth by myelin inhibitory proteins. We hypothesize that TRAF6 is required for the transduction of the growth inhibitory signal downstream of the NgR-p75 complex. The specific aims of our research are to 1) Determine whether TRAF6 is required for axon outgrowth inhibition by myelin proteins 2) Evaluate whether TRAF6 is recruited by p75 following binding of the myelin inhibitory proteins to regulate GTPase activity 3) Investigate the mechanism by which TRAF6 is involved in inhibition of axon outgrowth. Axon outgrowth will be studied in neurons lacking TRAF6 both in vitro and in vivo to establish a role for TRAF6 downstream of myelin inhibitory proteins. Using primary neuron cultures, we will assess the role of TRAF6 in the regulation of GTPase activity. Data from our laboratory indicates a possible functional interaction between TRAF6 and p21-activated kinase, a known modulator of the actin cytoskeleton. We will pursue this interaction as a mechanism by which TRAF6 inhibits axonal growth. This work will provide valuable insight into the biochemical processes involved in the inhibition of nerve regeneration. This knowledge will allow us to develop therapeutic strategies to promote neuronal growth following spinal cord injury and thus prevent paralysis.