Structural and functional studies of ubiquitin kinases

生物体及其组成细胞必须对环境信号作出反应以适应和生存。虽然反应主要是通过基因介导蛋白质水平的缓慢变化，但通过化学修饰蛋白质以调节其在细胞中的作用可以实现快速变化。这些翻译后修饰（PTMs）对地球上所有形式的生命都是必不可少的，并且有不同的形式。最常见的两种是：1)磷酸化，由蛋白激酶进行；2)泛素化，由泛素连接酶进行。最近，我的实验室和其他人发现分子泛素本身也会被磷酸化。这种修饰是由一种名为PINK1的激酶进行的，该激酶参与神经元长期存活所必需的质量控制途径。从昆虫到人类，几乎所有动物体内都含有这种蛋白质。磷酸化的泛素是细胞中激活帕金的关键信号，帕金是一种泛素连接酶，参与许多细胞过程，包括蛋白质质量控制、神经元存活、对细菌病原体的抗性和糖/脂质代谢。

Living organisms and their constituent cells must respond to environmental cues to adapt and survive. Whereas responses are mostly mediated by slow changes in protein levels through genes, rapid changes can be achieved by chemically modifying proteins in order to modulate their roles in the cell. These post-translational modifications (PTMs) are essential to all forms of life on Earth and come in different flavours. Two of the most common are: 1) phosphorylation, carried out by protein kinases, and 2) ubiquitination, carried out by ubiquitin ligases. Recently, my laboratory and others discovered that the molecule ubiquitin itself is subject to phosphorylation. The modification is carried out by a kinase named PINK1 that is involved in a quality control pathway essential for the long-term survival of neurons. This protein can be found in nearly all animals, from insects to humans. Phosphorylated ubiquitin is a key signal in cells for the activation of parkin, a ubiquitin ligase that is involved in a number of cellular processes including protein quality control, neuronal survival, resistance to bacterial pathogens, and sugar/lipid metabolism. I hypothesize that PINK1 is the first member of a family of kinases that phosphorylate ubiquitin. The long-term objective of my research program is to characterize the family of ubiquitin kinases at the molecular structure level. My laboratory uses a wide-range of structural biology methods including X-ray crystallography, which enables us to determine the 3D structure of enzymes with very high definition. My first aim is to determine how PINK1 recognizes ubiquitin and adds a phosphate on a specific residue. My second aim is to identify and study other ubiquitin kinases, by characterizing where and how they modify ubiquitin. These studies define my research program on understanding how enzymes like ligases and kinases alter other proteins, and how PTMs regulate cell survival and function.