Understanding the molecular pathways that underlie dectin-1 mediated cytokine responses

侵袭性真菌感染在健康个体中并不常见，但有几种情况会大大增加发生这些感染的风险。例如，接受免疫抑制治疗的患者，无论是在器官移植后还是在治疗癌症和自身免疫性疾病等疾病时，都更有可能发生侵袭性真菌感染。由于艾滋病毒等感染或由于调节免疫的关键蛋白质的遗传突变而导致免疫系统受到抑制的人，患真菌感染的风险也要大得多。在这些患者群体中，当侵袭性真菌感染发生时，它们很难治疗，死亡率很高。随着高风险群体人数的增加以及对现有抗真菌药物的耐药性增加，这一问题日益严重。因此，了解免疫系统如何检测和响应真菌病原体是一个重要的问题。感染后，首先检测真菌病原体的细胞类型之一是免疫系统中称为抗原呈递细胞（APCs）的特化细胞。一旦这些细胞感知到真菌病原体的存在，它们就会承担一些功能，其中关键的是产生细胞因子，免疫细胞释放的小蛋白质，需要协调免疫反应。apc能够检测真菌病原体，因为它们表达某些特定的受体，这些受体对真菌病原体表面上发现的分子有特异性，但对人体自身细胞没有特异性。其中一种受体是一种叫做dectin-1的蛋白质。dectin-1基因敲除小鼠和携带dectin-1基因失活突变的人对真菌感染更敏感，这一观察结果证实了dectin-1与真菌感染的相关性。在本提案中概述的研究中，我们将使用各种技术来研究dectin-1的激活促进所需细胞反应和控制细胞因子产生的方式。关键是了解dectin-1如何影响细胞内信号网络，其中许多信号网络是由一个被称为蛋白质磷酸化的过程控制的。这些过程对于细胞将探测素-1检测到的真菌病原体转化为正确的免疫反应至关重要。这项研究的一个主要部分将是使用最先进的质谱方法来绘制在dectin-1激活后细胞内发生的蛋白质磷酸化的全局变化。这将使我们能够建立起激活的信号网络的图像。然后，我们将检查该网络的特定部分对细胞因子产生控制的贡献。这项工作将增加我们对免疫系统如何处理真菌感染的理解，并可能提出免疫系统可以靶向增强其对抗真菌感染能力的方法。此外，由真菌病原体诱导的几种细胞因子在其他情况下可能具有病理作用，例如在关节炎等自身免疫性疾病中。因此，了解它们的产生是如何被控制的，对于解释免疫系统的功能以及未来针对许多免疫相关疾病的药物开发计划也具有更广泛的意义。

Invasive fungal infections are uncommon in healthy individuals however several conditions can greatly increase the risk of developing these infections. For example patients undergoing immunosuppressive therapies, either following organ transplant or for the treatment of diseases such as cancer and autoimmune conditions, are much more likely to develop invasive fungal infections. People with a suppressed immune system either as a result of infections such as HIV or due to inherited mutations in key proteins that regulate immunity are also at much greater risk of acquiring fungal infections. In these patient groups when invasive fungal infections occur they are difficult to treat and have a high mortality rate. This represents an increasing problem as the numbers of people in high-risk groups grows and as resistance to existing antifungals increases. Understanding how the immune system detects and responds to fungal pathogens is therefore an important issue.Following infection, one of the first cell types to detect fungal pathogens are specialized cells in the immune system termed antigen-presenting cells (APCs). Once these cells sense the presence of a fungal pathogen they undertake several functions, key amongst which is the production of cytokines, small proteins that are released from immune cells and that are required to co-ordinate the immune response. APCs are able to detect fungal pathogens as they express certain specialized receptors that are specific for molecules that are found on the surface of fungal pathogens but not on the body's own cells. One such receptor is a protein called dectin-1. The relevance of dectin-1 to fungal infection has been demonstrated by the observations that both dectin-1 knockout mice and people that carry an inactivating mutation in the dectin-1 gene are more sensitive to fungal infection.In the research outlined in this proposal we will use a variety of techniques to study the way in which the activation of dectin-1 promotes the required cellular response and controls the production of cytokines. Key to this is understanding how dectin-1 affects intracellular signaling networks, many of which are controlled by a process known as protein phosphorylation. These processes are essential for the cell to translate the detection of a fungal pathogen by dectin-1 into the correct immune response. A major part of this study will be to use sate of the art mass spectrometry methods to map global changes in protein phosphorylation that occur inside the cell following the activation of dectin-1. This will allow us to build up a picture of the signaling networks activated. We will then examine the contribution of specific parts of this network to the control of cytokine production.This work will increase our understanding of how the immune system deals with fungal infections, and may suggest ways in which the immune system could be targeted to increase its ability to combat fungal infections. In addition several of the cytokines that are induced by fungal pathogens can, in other circumstances, have pathological roles such as in autoimmune diseases like arthritis. Understanding how their production is controlled therefore also has wider implications for interpreting how the immune system functions and for future drug development programs for a number of immune related diseases.