Molecular mechanisms of Parkin-directed mitochondrial quality control

描述（由申请人提供）：帕金森病（PD）是一种毁灭性疾病，迄今为止只有对症治疗存在。原因仍然是谜，因此治疗停止或预防PD是不可用的。过去几年，由于我们的实验室和其他实验室发现了一种新的线粒体质量控制（mtQC）途径，这是非常令人兴奋的。到目前为止，这条通路连接了三个帕金森相关基因PINK1 PARKIN和FBXO7，以及参与疾病发病的两大细胞功能障碍：mt功能障碍和降解途径损伤。mtQC途径被认为有助于消除功能失调的细胞器，否则会导致进一步的细胞损伤。然而，这一途径的（病理）生理相关触发因素，特别是在疾病相关细胞和体内的触发因素尚不清楚。当激酶PINK1特异性地在受损的线粒体上积累时，Parkin被招募来催化线粒体底物的差异泛素化。然而，Parkin的酶功能，它的E2辅因子，形成的泛素链的拓扑结构及其生物学作用仍然是谜。鉴于最近Parkin的结构及其“封闭”的自抑制构象，我们认为Parkin被顺序激活以释放其泛素连接酶功能。我们已经确定了一些E2酶，它们通过不同的和相反的机制调控Parkin的激活及其酶功能。鉴于沿Parkin激活级联可能存在几种治疗机会，我们将对这种神经保护蛋白进行结构-功能分析。此外，线粒体中错误折叠蛋白的积累可能是PINK1和Parkin激活的生理刺激。引人注目的是，诱导的mt特异性未折叠蛋白反应（mtUPR）最近被描述为一种保守的长寿机制。我们拟从结构、分子、细胞和机体等层面阐明Parkin蛋白的激活机制。因此，我们将

DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a devastating disorder for which to date only symptomatic treatments exist. The causes remain enigmatic and thus therapeutics that halt or prevent PD are not available. The last few years have been extremely exciting due to the discovery of a novel mitochondrial quality control (mtQC) pathway by our laboratory and others. By now, this pathway links three parkinsonism associated genes, PINK1 PARKIN, and FBXO7, as well as the two major cellular dysfunctions involved in disease pathogenesis: mt dysfunction and impairment of degradation pathways. The mtQC pathway is thought to facilitate the elimination of dysfunctional organelles that would otherwise cause further cellular damage. However, (patho-) physiological relevant triggers of this pathway, particular in disease-relevant cells and in vivo are unclear. Upon accumulation of the kinase PINK1 specifically on damaged mitochondria, Parkin is recruited to catalyze differential ubiquitinations of mitochondrial substrates. However, Parkin's enzymatic functions, its E2 co-factors, the topologies of formed ubiquitin chains and their biological roles remain enigmatic. Given the recently resolved structure of Parkin and its 'closed' auto-inhibited conformation, we suggest that Parkin is sequentially activated to unleash its ubiquitin ligase functions. We have identified select E2 enzymes that regulate Parkin's activation and its enzymatic functions, excitingly through different and opposing mechanisms. Given that several therapeutic opportunities may exist along Parkin's activation cascade, we will perform structure-function analyses of this neuroprotective protein. Further, the accumulation of misfolded proteins in mitochondria may act as a physiological stimulus for PINK1 and Parkin activation. Strikingly, the induced mt- specific unfolded protein response (mtUPR) has very recently been described as a conserved longevity mechanism. We propose to elucidate the (in-) activation mechanisms of Parkin's functions on the structural, molecular, cellular, and organismal level. Therefore, we will use cutting-edge technologies and combine computational, functional biochemical and cell-biological with genetic methods in human iPSC-derived neurons and in vivo in C. elegans. Based on preliminary data, we hypothesize that Parkin is activated through the mtUPR, is regulated by bioenergetics and integrates with conserved aging pathways. On the molecular and structural level, Parkin is controlled by post-translational modifications, conformational rearrangements and by select E2 co-enzymes. Specifically, we will 1) unravel biological and molecular mechanism that (in)-activate Parkin in health and disease; 2) determine Parkin's physiological E2 co-enzymes, their regulatory roles and contribution to PD; 3) determine Parkin's activity(ies) and their interplay with bioenergetics and aging pathways. The proposed studies are relevant to fully appreciate the biological significance and potential of Parkin-directed mitochondrial quality control for disease intervention and to uncover important mechanistic insights that will provide the basis for rationale drug design.