The role of OCRL1 in endocytic membrane traffic

我们体内的细胞由内部膜封闭的隔室组成，称为细胞器，每个隔室都有自己的身份和特定的功能。物质在细胞器之间以及某些细胞器和细胞外部之间通过称为膜运输的过程转移。主要的膜运输途径之一是内吞途径，其中物质通过在细胞表面的膜封闭囊泡中的吞噬而从细胞外部被摄取。然后，内化的材料被分选到各个下游隔室或再循环回到细胞表面。内吞途径对所有细胞都是至关重要的，当有缺陷时会引起人类许多疾病。此外，致病病毒和细菌利用这一途径进入细胞引起感染。因此，重要的是我们了解如何内吞途径的功能在分子水平上。该建议集中在两种酶上，它们位于内吞途径中的细胞器中，称为OCRL 1和INPP 5 B。这些酶作用于一类称为磷酸肌醇的脂质，其对于控制细胞行为的各个方面（包括内吞膜运输）是重要的。OCRL 1的突变导致人类两种疾病，称为Lowe综合征和Dent-2疾病，其特征是大脑，眼睛和肾脏功能缺陷。OCRL 1突变导致Lowe和Dent患者发生病理变化的机制尚不清楚。我们已经确定了OCRL 1和INPP 5 B的一个新的结合伙伴，称为IPIP 27 A，它是内吞途径中运输所必需的。该提案的目的是确定IPIP 27 A如何与其相互作用伙伴一起调节内吞运输。我们的假设是OCRL 1/INPP 5 B和IPIP 27 A参与内吞细胞器上膜载体的形成，以确保以适当控制的方式进行运输。这个过程是如何发生的仍然知之甚少。我们计划使用实验方法的组合来剖析所涉及的机制。这将需要使用各种已建立的方法，包括活细胞的真实的实时成像来分析组织培养细胞中的内吞运输。我们的工作将提供重要的知识，如何在所有细胞的内吞途径的功能，以及揭示Lowe综合征，登特病和其他疾病的机制所造成的缺陷内吞运输。

The cells in our body are made up of internal membrane-enclosed compartments called organelles, each with their own identity and specific functions. Material is transferred between the organelles and between certain organelles and the outside of the cell via a process termed membrane traffic. One of the major membrane traffic pathways is the endocytic pathway, where material is taken up from the cell exterior via engulfment in membrane-enclosed vesicles at the cell surface. The internalised material is then sorted to various downstream compartments or recycled back to the cell surface. The endocytic pathway is fundamentally important to all cells, and when defective gives rise to numerous diseases in humans. Moreover, this pathway is exploited by pathogenic viruses and bacteria to gain entry into cells to cause infection. It is therefore important we understand how the endocytic pathway functions at the molecular level. This proposal is focussed on two enzymes that are localised to organelles within the endocytic pathway, called OCRL1 and INPP5B. These enzymes act on a class of lipids called phosphoinositides that are important for controlling various aspects of cell behaviour including endocytic membrane traffic. Mutation of OCRL1 causes two diseases in humans, called Lowe syndrome and Dent-2 disease, which are characterised by defective brain, eye and kidney function. The mechanisms by which mutation of OCRL1 brings about the pathological changes seen in Lowe and Dent patients remain unclear. We have identified a new binding partner for OCRL1 and INPP5B called IPIP27A that is essential for trafficking within the endocytic pathway. The aim of this proposal is now to determine how IPIP27A functions together with its interaction partners to regulate endocytic trafficking. Our hypothesis is that OCRL1/INPP5B and IPIP27A participate in the formation of membrane carriers on endocytic organelles to ensure trafficking occurs in a properly controlled manner. How this process occurs remains poorly understood. We plan to use a combination of experimental approaches to dissect the mechanisms involved. This will entail analysis of endocytic trafficking in tissue culture cells using various established methods including imaging of living cells in real time. Our work will provide important knowledge as to how the endocytic pathway functions in all cells, as well as reveal the mechanisms underlying Lowe syndrome, Dent disease and other disorders caused by defects in endocytic trafficking.