Circadian regulation of phagocytosis

描述(申请人提供)：免疫系统功能的昼夜节律调节知之甚少，但对人类健康有重大影响。免疫系统功能的许多指标，如细胞因子肿瘤坏死因子和干扰素-γ的基线水平，都会随着一天中的不同时间而变化。昼夜节律的丧失也与免疫系统功能差和感染易感性有关。我们已经建立了一个系统来研究果蝇的昼夜节律免疫功能。我们发现，感染肺炎链球菌的苍蝇在一天中的不同时间段死亡的存活率不同，这是由于昼夜节律蛋白的影响。我们进一步确定了一种受昼夜节律调节的特定免疫反应：细菌的吞噬作用。虽然吞噬作用的细胞生物学在单细胞生物体和培养细胞中已经得到了很好的研究，但多细胞生物体中吞噬作用的分子调控还不是很清楚。同样，尽管人们对昼夜节律的了解很多，但主要关注的是分子机制和昼夜节律神经元(起搏器神经元)--而不是效应器组织。我们需要了解相关效应组织的昼夜节律，才能将这些发现转化为医学实践。在初步数据中，我们发现，抑制起搏神经元或吞噬细胞免疫细胞的昼夜节律时钟可以增加对肺炎链球菌感染的抵抗力。我们假设，起搏器神经元调节吞噬免疫细胞的昼夜节律，决定这些细胞的时钟活动以及吞噬活动的振荡。在本提案中，我们将通过三种方式检验这一假设： 我们将确定昼夜节律调节吞噬作用的细胞机制(目标1)；我们还将研究细胞自主昼夜节律调节器如何控制吞噬细胞功能(目标2)以及起搏神经元非细胞自主调节吞噬细胞功能(目标3)。因此，拟议的实验将在分子、细胞和系统水平上分析免疫系统功能的昼夜调节。由于先天免疫和昼夜节律生物学的高度进化保守性，阐明果蝇的分子机制将有助于深入了解如何改善人类先天免疫系统的功能。

DESCRIPTION (provided by applicant): Circadian regulation of immune system function is poorly understood but has significant impact on human health. Many measures of immune system function, such as baseline levels of the cytokines TNF and IFN- gamma, vary with time of day. Loss of circadian regulation is also associated with poor immune system function and susceptibility to infection. We have established a system to study circadian-regulated immune function in Drosophila. We found that flies infected at different times of day with S. pneumoniae die with different survival rates and that this is due to the effects of circadian regulatory protens. We further identified a specific immune response that is circadian-regulated: phagocytosis of bacteria. Though the cell biology of phagocytosis is well studied in unicellular organisms and in cultured cells, the molecular regulation of phagocytosis in multicellular organisms is less clear. Similarly, though much is known about circadian regulation, the major focus has been on molecular mechanisms and circadian regulatory neurons (pacemaker neurons)-not on effectors tissues. We need to understand the circadian regulation of relevant effectors tissues to translate these discoveries into medical practice. In preliminary data, we found that inhibition of the circadian regulator Clock in either pacemaker neurons or phagocytic immune cells increases resistance to infection by S. pneumoniae. We hypothesize that pacemaker neurons regulate the circadian rhythms of phagocytic immune cells, dictating the oscillation of Clock activity in those cells as well as phagocytic activity. In this proposal, we will test this hypothesis in three ways: we will identify cellular mechanisms underlying circadian-regulated phagocytosis (Aim 1); we will also examine how cell-autonomous circadian regulators control phagocyte function (Aim 2) and how pacemaker neurons non cell-autonomously regulate phagocyte function (Aim 3). Thus the proposed experiments will analyze circadian regulation of immune system function on molecular, cellular, and systemic levels. Because of the high evolutionary conservation of both innate immunity and circadian biology, defining the molecular mechanisms in Drosophila will provide insight into ways to improve human innate immune system function.