Regulation and Function of Phosphoinositide Lipid Signalling

膜结合细胞器是细胞的“器官”。细胞器有多种类型，每一种都具有不同的生物物理、生化和功能特性。例如，内质网是蛋白质合成发生的膜小管的迷宫，而溶酶体是充满消化酶的小而圆的细胞器。细胞器如何形成或变化是细胞生物学的中心问题。 磷脂酰肌醇(PIP)脂类是细胞器特性的设计师。有7种PIP在细胞器中有不同的分布。由于每个PIP物种都结合并招募了一组独特的蛋白质，因此这就用一组独特的分子特性装饰了宿主细胞器。为了了解PIP如何帮助确定细胞器的特性，细胞生物学家需要了解A)合成和降解PIP的酶是如何被靶向和调控的，以及B)PIP及其效应蛋白是如何工作的。 在这里，我建议研究一种特殊的PIP，磷脂酰肌醇-3，5-二磷酸[PI(3，5)P2]，它控制内吞途径中细胞器的形态和膜运输。这条途径负责将蛋白质分类和运输到不同的目的地，包括细胞表面，或者负责溶酶体的降解。它还与免疫细胞用来摧毁病原体的吞噬途径相连。在NSERC支持下： I)我们将研究PI(3，5)P2及其效应分子在巨噬细胞和中性粒细胞中的作用。这些免疫细胞捕猎并将病原体吞噬到吞噬小体中，以消化和杀死它们。我们之前已经证明，吞噬小体需要PI(3，5)P2在巨噬细胞中降解。这项新的研究将试图了解PI(3，5)P2对吞噬小体成熟的重要性，并探索它在中性粒细胞中的作用，中性粒细胞是感染的第一反应者。 Ii)我们将进行前所未有的研究，以了解PI(3，5)P2如何通过遵循PI(3，5)P2耗尽导致溶酶体大量肿胀的动力学、动力学和机制来控制溶酶体的大小。溶酶体的这种戏剧性变化仍然没有得到很好的描述。 III)我们将研究细胞中两种不同的PI(3)P池的来源和功能。PI(3)P是PI(3，5)P2的前体，但这种转化发生的时间和地点尚不清楚。利用尖端研究和基因工程，我们将致力于更好地了解PI(3)P的各个池是如何发挥作用的，这将告诉我们PI(3)P到PI(3，5)P2的转变。 总体而言，我的研究将回答细胞生物学中与PIP调节和功能相关的问题。这些答案可能会对机体的健康产生影响，因为PI(3，5)P2功能障碍会导致神经退化，并可能扰乱免疫反应。我们的发现可能会为加拿大生物技术和制药行业提供新的策略，以治疗由PIP故障引起的疾病，这些疾病困扰着加拿大人。

Membrane-bound organelles are the “organs” of cells. There are many organelle types, each with distinct biophysical, biochemical and functional properties. For example, the endoplasmic reticulum is a labyrinth of membrane tubules where protein synthesis occurs, whereas lysosomes are small, round organelles full of digestive enzymes. How organelles form or change is a central question in cell biology. The phosphoinositide (PIP) lipids are architects of organelle identity. There are seven PIP species that are differentially distributed among organelles. Since each PIP species binds and recruits a unique set of proteins, then this decorates the host organelle with a unique set of molecular properties. In order to understand how PIPs help to determine organelle identity, cell biologists need to understand A) how the enzymes that synthesize and degrade PIPs are targeted and regulated and B) how PIPs and their effector proteins work. Here, I propose to study a specific PIP, phosphatidylinositol-3,5-bisphosphate [PI(3,5)P2], which controls the morphology and membrane traffic of organelles in the endocytic pathway. This pathway is responsible for sorting and trafficking proteins to various destinations including the cell surface or for degradation in lysosomes. It also interfaces with the phagocytic pathway, which immune cells use to destroy pathogens. With NSERC support: i) We will study the role of PI(3,5)P2 and its effectors in macrophages and neutrophils. These immune cells hunt and engulf pathogens into phagosomes to digest and kill them. We have previously showed that phagosomes require PI(3,5)P2 to become degradative in macrophages. The new research will seek to understand how PI(3,5)P2 is important for phagosome maturation and explore its role in neutrophils, the first responders to an infection. ii) We will perform unprecedented studies to understand how PI(3,5)p2 controls lysosome size by following the dynamics, kinetics and mechanisms by which PI(3,5)P2 depletion causes massive lysosome swelling. This dramatic change to lysosomes remains poorly uncharacterized. iii) We will study the origin and functions of two different pools of PI(3)P in cells. PI(3)P is the precursor for PI(3,5)P2, but it is unclear when and where this conversion occurs. Using cutting-edge research and genetic engineering, we will aim to better understand how individual pools of PI(3)P function, which will then inform us about the transition of PI(3)P to PI(3,5)P2. Overall, my research will answer questions in cell biology related to PIP regulation and function. These answers may then have implications for organismal well-being since PI(3,5)P2 dysfunction causes neurodegeneration and may disrupt the immune response. Our findings may provide the Canadian biotechnology and pharmaceutical industries with novel strategies to treat conditions caused by PIP malfunction that afflicts Canadians.