ENDOTHELIAL CELL-STEM CELL INTERACTIONS

在造血微环境的细胞成分中， 内皮细胞定义了血管和内皮细胞之间的界面。 造血区室及其在造血调节中的作用 直到最近才被很好地研究。我的实验室报告说 骨髓微血管分离及鉴定 内皮细胞（BMEC）及其长期维持 多系造血使用BMEC衍生的表达文库， 已经鉴定了一种分泌的糖基化形式的L-铁蛋白， 皮摩尔范围内的血浆浓度，其在 支持多能干细胞的增殖。 有趣的是， 与许多造血活性细胞因子一样，糖基化L-铁蛋白 是蛋白质的四螺旋束家族的成员。生物学 这种新认识的干细胞活性分子的主题是 这个提议。我们的数据表明，糖基化L-铁蛋白是 由骨髓微血管内皮细胞和支持物分泌 干细胞自我更新我们的表达克隆表明了这一点 数据以及通过用纯化的重组体进行的初步研究， 糖基化L-铁蛋白。糖基化L-铁蛋白的活性是 与试剂盒-配体（KL）协同作用。为了探索这种生物学 分子和它的信号机制，我们将定义 糖基化L-铁蛋白的生物学， 在增殖测定中的祖细胞存活和扩增，在模型中 骨髓重建，并在研究旨在阐明其 在造血发育生物学中的作用。我们将定义 糖基化L-铁蛋白信号传导机制的研究， 定义了它与细胞相互作用的性质。的机理 糖基化L-铁蛋白与KL的协同作用将使用 转染模型来定义伴随的信号转导事件， 糖基化L-铁蛋白结合。 受体负责 将定义糖基化L-铁蛋白结合和信号传导。这些 研究将定义新认识的造血干细胞的生物学， 具有潜在治疗重要性的细胞因子。

Of the cellular components of the hematopoietic microenvironment, the endothelial cell defines the interface between the vascular and hemopoietic compartments, and its role in the regulation of hemopoiesis has until recently, not been well studied. My laboratory has reported the isolation and characterization of bone marrow microvascular endothelial cells (BMEC) and their ability to sustain long term multilineage hemopoiesis. Using a BMEC-derived expression library we have identified a secreted, glycosylated form of L-ferritin with a plasma concentration in the picomolar range, that is active in supporting the proliferation of pluripotent stem cells. Interestingly, like many hematopoietically active cytokines, glycosylated L-ferritin is a member of the four-helix bundle family of proteins. The biology of this newly recognized stem cell active molecule is the subject of this proposal. Our data suggest that glycosylated L-ferritin is secreted by bone marrow microvascular endothelial cells and supports stem cell self renewal. This is suggested by our expression cloning data as well as by preliminary studies with purified recombinant glycosylated L-ferritin. The activity of glycosylated L-ferritin is synergistic with kit-ligand (KL). To explore the biology of this molecule and the mechanism by which it signals, we will define the biology of glycosylated L-ferritin with respect to its support of progenitor survival and expansion in proliferation assays, in a model of marrow reconstitution, and in studies designed to shed light on its role in the developmental biology of hematopoiesis. We will define the mechanism of glycosylated L-ferritin signaling in studies that will define the nature of its interaction with cells. The mechanism of glycosylated L-ferritin's synergy with KL will be explored using transfection models to define signal transduction events that accompany glycosylated L-ferritin binding. The receptor responsible for glycosylated L-ferritin binding and signaling will be defined. These studies will define the biology of a newly recognized hematopoietic cytokine of potential therapeutic importance.