Molecular regulation of LRRK2 in Parkinson's disease

帕金森病(PD)是公认的最常见的运动障碍。主要症状 帕金森病是由黑质多巴胺能神经元进行性变性引起的 Compacta(SNPC)及其伴发的纹状体病理学。LRRK2的突变是已知的最多的 帕金森病的常见遗传原因。鉴于其强大的遗传联系和令人信服的药物能力，LRRK2代表着一种 明确治疗发展的目标。然而，调节LRRK2功能的机制仍然存在 不清楚。此外，LRRK2在纹状体病理和纹状体依赖行为中的调节在很大程度上仍然存在 尽管LRRK2在纹状体中高表达，但仍难以捉摸。LRRK2蛋白包括两个重要的 酶结构域：ROC(RAS Of Complex)GTP酶结构域和KK结构域。致病 在GTP酶和激酶结构域中都发现了突变，这表明GTP酶和 LRRK2的激酶活性。到目前为止，研究主要集中在LRRK2的激酶活性上，而 人们对GTPase结构域的关注有限。LRRK2是一种鸟嘌呤核苷酸结合蛋白，但其机制 对其GTPase结构域的直接调控尚不清楚。传统的鸟嘌呤核苷酸结合蛋白是 通常由GTP酶激活蛋白(GAP)和鸟嘌呤核苷酸交换因子(GEF)调节。 一些鸟嘌呤核苷酸结合蛋白可以被核苷酸依赖二聚体(GAD)激活。 LRRK2是受到GAP和GEF的调控，还是受到GAD的调控，已经得到了积极的研究。我们有 先前在体外和体内首次发现了LRRK2的GAP ArfGAP1。最近我们发现了一种潜在的 LRRK2的生理环境。它与LRRK2在黑质纹状体通路中有相似的表达模式，相互作用 与LRRK2结合，调节LRRK2神经毒性。根据初步观察，我们的中心假设 是该环境基金作为LRRK2的生理环境基金，增加LRRK2的GTP结合活性，调节 LRRK2细胞功能和LRRK2诱导的纹状体病理及相关行为缺陷。的目标是 本研究的目的是(1)鉴定和鉴定LRRK2的第一个生理全环，(2)确定LRRK2是如何 (3)从纹状体病理角度探讨该环境因子对LRRK2的调节作用 以及相关的行为。这项研究的完成将有助于理解GTP酶是如何发挥作用的 LRRK2被调控，并确定这一调控是否影响LRRK2在纹状体中的作用。这个 LRRK2 GTP酶、GAP或全球环境基金活性将被作为新的治疗靶点，这与 直接抑制LRRK2的激酶活性。关于LRRK2生物学这一方面的新知识将促进我们的 了解LRRK2的生理和病理生理作用，以及潜在的鉴定 未来药物干预的新靶点。

Parkinson's disease (PD) is recognized as the most common movement disorder. The cardinal symptoms of PD are caused by the progressive degeneration of dopaminergic (DA) neurons in substantia nigra pars compacta (SNpc) and accompanying striatal pathology. Mutations in LRRK2 are known to be the most common genetic causes of PD. Given its strong genetic links and compelling drug ability, LRRK2 represents a clear target for therapeutic development. However, the mechanisms that regulate LRRK2 function remain unclear. Moreover, LRRK2 regulation in striatal pathology and striatal-dependent behaviors remains largely elusive despite high expression of LRRK2 in the striatum. The LRRK2 protein includes two important enzymatic domains: a ROC (Ras of Complex) GTPase domain and a kinase domain. Disease causing mutations are found in both GTPase and kinase domains, indicating the importance of both GTPase and kinase activities of LRRK2. To date studies have focused largely on the kinase activity of LRRK2 while attention on the GTPase domain is limited. LRRK2 is a guanine nucleotide-binding protein, but the mechanism of direct regulation of its GTPase domain is unclear. Conventional guanine nucleotide-binding proteins are typically regulated by GTPase-activating proteins (GAPs) and guanine nucleotide-exchange factors (GEFs). Some guanine nucleotide-binding proteins can be activated by nucleotide-dependent dimerization (GAD). Whether LRRK2 is regulated by GAPs and GEFs or by GAD has been actively investigated. We have previously identified the first GAP ArfGAP1 for LRRK2 in vitro and in vivo. Recently we discovered a potential physiological GEF for LRRK2. It has similar expression patterns with LRRK2 in nigrostriatal pathway, interacts with LRRK2 and regulates LRRK2 neurotoxicity. Based on the preliminary observations, our central hypothesis is that this GEF serves as a physiological GEF for LRRK2 to increase LRRK2 GTP binding activity, regulate LRRK2 cellular function and LRRK2-induced striatal pathology and related behavioral deficits. The objective of this study is (1) to identify and characterize the first physiological GEF for LRRK2, (2) to determine how this GEF regulates LRRK2 function, and (3) to explore the regulation of this GEF on LRRK2 in striatal pathology and related behavior. Accomplishment of this study will lead to understanding how the GTPase function of LRRK2 is regulated and to determining whether this regulation affects the actions of LRRK2 in striatum. The LRRK2 GTPase, GAP or GEF activities would be served as new therapeutic targets, which is distinct from direct kinase inhibition of LRRK2. New knowledge regarding this aspect of LRRK2 biology will advance our understanding of the physiologic and pathophysiologic actions of LRRK2 as well as potential identification of novel targets for future pharmacologic intervention.