Caulfield Thomas R, Fiesel Fabienne C, Springer Wolfdieter
*Department of Neuroscience, Mayo Clinic Jacksonville, 4500 San Pablo Road, Jacksonville, FL 32224, U.S.A.
Biochem Soc Trans. 2015 Apr;43(2):269-74. doi: 10.1042/BST20140321.
The PINK1 (phosphatase and tensin homologue-induced putative kinase 1)/Parkin-dependent mitochondrial quality control pathway mediates the clearance of damaged organelles, but appears to be disrupted in Parkinson's disease (PD) [Springer and Kahle (2011) Autophagy 7, 266-278]. Upon mitochondrial stress, PINK1 activates the E3 ubiquitin (Ub) ligase Parkin through phosphorylation of the Ub-like (UBL) domain of Parkin and of the small modifier Ub itself at a conserved residue [Sauvé and Gehring (2014) Cell Res. 24, 1025-1026]. Recently resolved partial crystal structures of Parkin showed a 'closed', auto-inhibited conformation, consistent with its notoriously weak enzymatic activity at steady state [Wauer and Komander (2013) EMBO J. 32, 2099-2112; Riley et al. (2013) Nat. Commun. 4, 1982; Trempe et al. (2013) Science 340, 1451-1455; Spratt et al. (2013) Nat. Commun. 4, 1983]. It has thus become clear that Parkin must undergo major structural rearrangements in order to unleash its catalytic functions. Recent published findings derived from X-ray structures and molecular modelling present a complete structural model of human Parkin at an all-atom resolution [Caulfield et al. (2014) PLoS Comput. Biol. 10, e1003935]. The results of the combined in silico simulations-based and experimental assay-based study indicates that PINK1-dependent Ser65 phosphorylation of Parkin is required for its activation and triggering of 'opening' conformations. Indeed, the obtained structures showed a sequential release of Parkin's intertwined domains and allowed docking of an Ub-charged E2 coenzyme, which could enable its enzymatic activity. In addition, using cell-based screening, select E2 enzymes that redundantly, cooperatively or antagonistically regulate Parkin's activation and/or enzymatic functions at different stages of the mitochondrial autophagy (mitophagy) process were identified [Fiesel et al. (2014) J. Cell Sci. 127, 3488-3504]. Other work that aims to pin-point the particular pathogenic dysfunctions of Parkin mis-sense mutations have been recently disseminated (Fabienne C. Fiesel, Thomas R. Caulfield, Elisabeth L. Moussaud-Lamodiere, Daniel F.A.R. Dourado, Kotaro Ogaki, Owen A. Ross, Samuel C. Flores, and Wolfdieter Springer, submitted). Such a structure-function approach provides the basis for the dissection of Parkin's regulation and a targeted drug design to identify small-molecule activators of this neuroprotective E3 Ub ligase.
磷酸酶及张力蛋白同源物诱导的假定激酶1（PINK1）/帕金蛋白依赖性线粒体质量控制途径介导受损细胞器的清除，但在帕金森病（PD）中似乎受到破坏[施普林格和卡勒（2011年），《自噬》第7卷，第266 - 278页]。在线粒体应激时，PINK1通过磷酸化帕金蛋白的泛素样（UBL）结构域以及小修饰泛素自身的一个保守残基来激活E3泛素（Ub）连接酶帕金蛋白[索维和格林（2014年），《细胞研究》第24卷，第1025 - 1026页]。最近解析的帕金蛋白部分晶体结构显示出一种“封闭”的、自我抑制的构象，这与其在稳态时众所周知的较弱酶活性一致[瓦尔和科曼德（2013年），《欧洲分子生物学组织杂志》第32卷，第2099 - 2112页；莱利等人（2013年），《自然通讯》第4卷，第1982页；特伦普等人（2013年），《科学》第340卷，第1451 - 1455页；斯普拉特等人（2013年），《自然通讯》第4卷，第1983页]。因此很明显，帕金蛋白必须经历重大的结构重排才能释放其催化功能。最近发表的来自X射线结构和分子建模的研究结果呈现了全原子分辨率下人类帕金蛋白的完整结构模型[考菲尔德等人（2014年），《公共科学图书馆·计算生物学》第10卷，e1003935]。基于计算机模拟和实验分析相结合的研究结果表明，帕金蛋白的丝氨酸65位点依赖PINK1的磷酸化是其激活和触发“开放”构象所必需的。实际上，所获得的结构显示帕金蛋白相互缠绕的结构域依次释放，并允许对接一个携带泛素的E2辅酶，这可能使其具有酶活性。此外，通过基于细胞的筛选，鉴定出了在不同阶段的线粒体自噬（mitophagy）过程中以冗余、协同或拮抗方式调节帕金蛋白激活和/或酶功能的特定E2酶[菲塞尔等人（2014年），《细胞科学杂志》第127卷，第3488 - 3504页]。最近还发表了其他旨在确定帕金蛋白错义突变的特定致病功能障碍的研究（法比安娜·C·菲塞尔、托马斯·R·考菲尔德、伊丽莎白·L·穆索 - 拉莫迪埃、丹尼尔·F·A·R·杜拉多、小垣宏、欧文·A·罗斯、塞缪尔·C·弗洛雷斯和沃尔迪特·施普林格，已提交）。这种结构 - 功能方法为剖析帕金蛋白的调控以及识别这种神经保护E3泛素连接酶的小分子激活剂的靶向药物设计提供了基础。
