Uncover the role of cGAS-STING activation in megakaryocytes and platelets

我的研究计划的长期目标是了解细胞如何在不同的细胞群体中感知内源性细胞质DNA，包括多倍体细胞，以及这如何影响它们的微环境和寿命。CGAS是一种胞质受体，它识别微生物DNA，对这一应用来说，重要的是识别DNA损伤时释放到细胞质中的自身DNA。在DNA检测之后，cGAS激活I型干扰素(IFN-I)反应，这通常形成抗病毒反应，但也有助于许多其他免疫功能。从机制上讲，这是通过cGAS产生一种名为cGAMP的环二核苷酸并随后与刺适配子蛋白结合来实现的。STING的激活负责参与干扰素-I和其他促炎分子的产生。越来越多的证据表明，这一途径在提醒免疫系统在特定背景下观察到的基因组完整性丧失方面发挥了关键作用，如细胞衰老、细胞转化或DNA修复缺陷。与其他免疫受体相比，cGAS和STING的表达相当普遍。尽管如此，cGAS-STING激活的结果在不同的细胞群体中报道了显著的差异，从交叉呈递、诱导凋亡和刺激自噬。这些差异突显了在特定细胞群体中研究该途径的重要性，包括在多倍体细胞中，如巨核细胞。巨噬细胞集落刺激因子通过支持血小板内波动的需求和塑造骨髓微环境，在止血方面起着关键作用。在分化过程中，MK经历了有丝分裂，这是一个败育的有丝分裂过程，在这个过程中，MK的DNA含量预计会上升到32N左右。MK表达先天免疫受体并产生细胞因子。我们最近发现，MKs表达cGAS-STING途径的蛋白。重要的是，cGAS驱动基本的干扰素-I反应，这种反应可以通过cGAS的遗传缺失或通过药物抑制刺痛而显著减少。基于这些发现，我们的目标是调查cGAS刺痛信号对巨核细胞生物学的贡献，并发现这如何影响他们的环境，包括血小板的功能。在这一应用中，我们假设巨噬细胞中cGAS的激活影响其生物学的许多方面，包括细胞因子的产生、细胞通讯和细胞活力。这一假设将通过以下短期目标进行检验。1.破译导致cGAS-STING激活的分子事件；2.确定cGAS-STING刺激在巨核细胞中的广泛结果；3.确定cGAS在肺巨核细胞中的作用。这项研究计划有望对MKs的生物学产生重要的见解，并将为基础生物学、传染病和生物技术的新研究领域铺平道路。

The long-term objectives of my research program are to understand how cells sense endogenous cytoplasmic DNA in different cell population, including polyploid cells, and how this impact their microenvironment and lifespan. cGAS is a cytosolic receptor that recognises microbial DNA and, importantly for this application, self-DNA released into the cytoplasm upon DNA damage. Following DNA detection, cGAS activates the type-I Interferon (IFN-I) response, which usually shapes the anti-viral response but also contribute to numerous other functions in immunity. Mechanistically, this occurs through the production of a cyclic dinucleotide, named cGAMP, by cGAS and its subsequent binding to STING adaptor protein. STING activation is responsible to engage the production of IFN-I and other pro-inflammatory molecules. Growing body of evidence demonstrated the critical role of this pathway to alert the immune system of the loss of genome integrity observed during specific context such as cell senescence, cell transformation or upon DNA repair deficiency. In contrast to other immune receptors, the expression of cGAS and STING is rather ubiquitous. Nonetheless, striking differences in the outcome of cGAS-STING activation were reported for distinct cell populations ranging from cross-presentation, induction of apoptosis, and stimulation of autophagy. Such differences underline the importance to study the pathway in specific cell populations including in polyploid cells such as megakaryocytes. MKs have a critical role in haemostasis by supporting the fluctuating demand in platelets and by shaping the bone marrow microenvironment. During their differentiation, MKs undergo endomitosis, a process of abortive mitosis in which the DNA content of MKs is expected to rise to around 32 N. MKs express innate immune receptors and produce cytokines. We have recently discovered that MKs express the proteins of the cGAS-STING pathway. Importantly, cGAS drives a basal IFN-I response that can be significantly reduced by genetic depletion of cGAS or by pharmacological inhibition of STING. Based on these findings, our objectives are to investigate the contribution of cGAS-STING signalling to the biology of megakaryocytes and to discover how this impact their environment including the function of platelets. In this application, we hypothesise that cGAS activation in MKs impact many aspects of their biology, including cytokines production, cell communication and cell viability. This hypothesis will be tested with the following short-term objectives. 1. Decipher the molecular events leading to cGAS-STING activation; 2 Define the broad outcome of cGAS-STING stimulation in MKs; 3.Determine the role of cGAS in lung megakaryocytes. This research program is expected to generate important insight into the biology of MKs and will pave the way to new area of research in fundamental biology, infectious diseases and biotechnology.