Impact of emperipolesis on platelet function

项目摘要 巨核细胞(MK)几十年来一直被认为参与了一种不寻常的行为，称为 红斑，白细胞--主要是中性粒细胞--在MK细胞质内完好无损。 胚乳在哺乳动物物种中是保守的。它在正常骨髓中观察到，但成为 尤其是在血小板需求增加的情况下流行，但其机制和功能 仍然默默无闻。使用一种新的体外模型系统，我们发现胚芽代表了一种高度的 中性粒细胞通过MK快速通过的吞吐量相互作用。在这一过程中，中性粒细胞脂质 膜与MK分界膜系统(DMS)合并，从而形成膜 在体外和体内，直接与巨噬细胞本身和由此产生的血小板结合。这其中的一个含义是 研究发现，一些循环中的血小板代表杂交体，既有MK成分，也有中性粒细胞成分。 这项提议的目的是开始了解这种新的生物学的生理功能。 与经验丰富的MK/血小板合作者Italiano博士和Flaumenhaft博士一起，我们提出了两个目标。 目的应用LIVE技术研究中性粒细胞向血小板转移蛋白质的过程。 细胞成像和电子显微镜，并定义了从中性粒细胞转移到血小板的蛋白质 SILAC质谱仪。AIM II继续我们的初步数据，杂交血小板可能表现出 应用体外血小板功能测定和体内血小板成像增强促凝血功能 血栓生长过程中的积聚。 总而言之，这些研究将开启一项关于月经生物学的新研究，阐明 免疫和造血系统之间相互作用的惊人途径，并定义了以前的 有可能有力地调节血小板功能的未被认识的机制。这些“高风险， 对哺乳动物物种中观察到的过程进行的高回报研究非常符合FOA的任务 PA-19-049推进NHLBI战略视野正常生物学“澄清”的新研究方向 既存在于健康人身上，也可能与HLBS疾病…相关的生物学过程。 为进一步调查这一现象奠定基础。

Project Summary Megakaryocytes (MK) have been known for decades to engage in an unusual behavior termed emperipolesis, whereby leukocytes – principally neutrophils – appear intact within the MK cytoplasm. Emperipolesis is conserved across mammalian species. It is observed in normal marrow but becomes particularly prevalent under conditions of increased platelet demand, but its mechanisms and functions remain obscure. Using a new in vitro model system, we found that emperipolesis represents a high- throughput interaction whereby neutrophils passage rapidly through MKs. During this transit, neutrophil lipid membranes merge with the MK demarcation membrane system (DMS) and thereby contribute membrane directly to MKs themselves and to the resulting platelets, both in vitro and in vivo. One implication of this finding is that some circulating platelets represent hybrids, featuring both MK and neutrophil components. The goal of this proposal is to begin to understand the physiological function of this novel biology. Together with experienced MK/platelet collaborators Dr. Italiano and Dr. Flaumenhaft, we propose two Aims. Aim I characterizes the process of protein transfer from neutrophils to platelets via emperipolesis, using live cell imaging and electron microscopy, and defines the proteins transferred from neutrophils to platelets via SILAC mass spectrometry. Aim II pursues our preliminary data that hybrid platelets are likely to exhibit enhanced procoagulant function using in vitro assays of platelet function and in vivo imaging of platelet accumulation in growing thrombi. Together, these studies will initiate a novel of research into the biology of emperipolesis, illuminating a surprising pathway of interaction between the immune and hematopoietic systems and defining a previously unappreciated mechanism that has the potential to powerfully modulate platelet function. These “high risk, high reward” studies of a process observed across mammalian species fits well within the mandate of FOA PA-19-049 New Research Directions that Advance the NHLBI Strategic Vision Normal Biology to “clarify biological processes that are both present in healthy humans and likely to be relevant in HLBS disorders…” to set the stage for an extended investigation of this phenomenon.