Release of find-me signals during apoptotic cell clearance

描述（由申请人提供）：在几乎所有的组织中，细胞都有一个持续的更新，通常是通过细胞凋亡的过程。在健康组织中，垂死的细胞很快被吞噬细胞识别和清除。然而，不能及时清除凋亡细胞会导致其继发性坏死、毒性细胞质内容物释放和组织内炎症。目前的证据表明，凋亡细胞在死亡过程的早期“宣传”它们的存在，通过称为“寻找我信号”的可溶性因子吸引吞噬细胞，从而促进它们的迅速清除。该提案的主要研究者的初步研究已经确定核苷酸ATP和UTP是一种“寻找我的信号”，对体外和体内凋亡细胞清除至关重要；随后的研究发现细胞膜蛋白pannexin 1 （Panx1）是介导凋亡细胞释放核苷酸的通道。本提案测试的总体假设是，pannexin通道依赖于凋亡细胞释放核苷酸find-me信号，随后被吞噬细胞感知，这对于体内适当的细胞清除是重要的，panx1介导的find-me信号通路的破坏将导致疾病。基于我们的初步研究，在Aim 1中，我们研究了一种新的Panx1激活机制的分子基础，寻求新的理解，这将允许通过这些通道操纵“找到我”信号释放。在Aim 2中，我们使用条件细胞特异性Panx1敲除小鼠来确定Panx1通道的操作是否会影响体内细胞清除。为此，我们利用了两个模型，新证据表明细胞清除在正常组织稳态和疾病（即胸腺发育和气道炎症）中很重要。总的来说，我们希望这些研究能够对find-me信号的调节释放如何影响细胞清除产生新的机制理解，并更好地定义死亡细胞和吞噬细胞之间的细胞间通信模式，对自身免疫和气道炎症具有指导意义。这些研究也为考虑Panx1通道作为治疗发展的合适靶点提供了理论依据。

DESCRIPTION (provided by applicant): In nearly all tissues, there is a continual turnover of cells, usually by the process of apoptosis. In healthy tissues, the dying cells are quickly recognized and cleared by phagocytes. However, failure to promptly clear apoptotic cells leads to their secondary necrosis, release of toxic cytoplasmic contents, and inflammation within tissues. Current evidence suggests that the apoptotic cells 'advertise' their presence early on in the death process, via soluble factors termed 'find-me signals' to attract phagocytes, and thereby promote their prompt clearance. Initial studies from the Principal Investigators of this proposal have identified the nucleotides ATP and UTP as one type of 'find-me signal' that is critical for apoptotic cell clearance in vitro and in vivo; subsequent studies led to a key discovey that the membrane protein pannexin 1 (Panx1) is the channel mediating nucleotide release from apoptotic cells. The overall hypothesis tested in this proposal is that pannexin channel-dependent release of nucleotide find-me signal from apoptotic cells, and subsequent sensing by phagocytes is important for proper cell clearance in vivo, and that disruption of the Panx1-mediated find-me signal pathway would contribute to diseases. Based on our preliminary studies, in Aim 1, we study the molecular basis of a novel Panx1 activation mechanism, seeking new understanding that will allow manipulation of 'find-me' signal release via these channels. In Aim 2, we use conditional cell-specific Panx1 knockout mice to determine if manipulation of Panx1 channels affects cell clearance in vivo. For this, we take advantage of two models for which new evidence suggests cell clearance is important in normal tissue homeostasis and in disease - i.e., thymic development and airway inflammation. Collectively, we expect these studies to yield new mechanistic understanding on how the regulated release of find-me signals influence cell clearance, and better define this mode of inter-cellular communication between dying cells and phagocytes, with implications for autoimmunity and airway inflammation. These studies can also provide a rationale for considering Panx1 channels as a suitable target for therapeutic development.