NOVEL ERYTHROBLAST/MACROPHAGE CONTACT PROTEIN

红细胞与巨噬细胞的结合起着核心作用。 在形成称为红母细胞的不同解剖单位中 岛屿。尽管这些岛屿已经被很好地描述了 从形态上讲，几乎没有什么是关于结构和 红细胞岛内细胞接触的功能基础。 我们之前已经证明，红细胞和红细胞之间的身体接触 巨噬细胞促进红细胞的终末成熟， 到它们的体外去核。重要的是，我们确定了一部小说 一种被称为“麦地黄素”的蛋白质，它介导了 有巨噬细胞的红细胞。梅德辛细胞的破坏 黏附功能显著抑制了细胞的终末成熟 红系细胞。我们的工作假设是，麦地黄素介导的 红细胞与巨噬细胞黏附促进红系成熟 对红细胞去核是必不可少的。我们最近做了 测定了人麦地黄素的完整氨基酸序列 巨噬细胞c DNA文库。这项提案的目的是将 麦地黄素在红细胞-巨噬细胞中作用的分子基础 协会。具体而言，将解决以下问题：(1) 依赖麦地黄素的红细胞-巨噬细胞接触是否足以 红细胞成熟？我们将调查麦地黄素介导的 仅细胞接触就足以产生红系终末 成熟或额外的巨噬细胞衍生因子是必需的。(2) 麦地黄素介导的红细胞与巨噬细胞之间的接触 促进终末期红系成熟？要定义分子基础， 要发挥麦地黄素的功能，一个重要的必要条件就是确定 红细胞中与麦地黄素相关的分子。这 鉴定将使用免疫沉淀、亲和力- 层析和酵母菌两种杂交试验。(3)做好动力学研究 麦地黄素的合成、组装和周转与红细胞相关 成熟？我们建议量化麦地黄素的合成速度， 在可溶部分和颗粒部分中的组装和周转 处于特定分化阶段的红细胞。精准的 时间调节的MEDHESSIN表达的定义将提供 红细胞-巨噬细胞接触基础的线索 红血球生成。总之，拟议中的关于麦地黄素的研究可能会开始 揭示红细胞岛形成的分子基础 哺乳动物的红细胞生成。

The association of erythroblasts with macrophages plays a central role in the formation of distinct anatomic units called erythroblastic islands. Although these islands have been well characterized morphologically, virtually nothing is about the structural and functional basis of cellular contacts within erythroblastic islands. We have previously shown that physical contact between erythroblasts and macrophages promotes the terminal maturation of erythroblasts, leading to their enucleation in vitro. Importantly, we identified a novel protein termed "medhesin" which mediates the association of erythroblasts with macrophages. The disruption of medhesin's cell adhesion function dramatically inhibited the terminal maturation of erythroid cells. Our working hypothesis is that the medhesin-mediated attachment of erythroblasts to macrophages promotes erythroid maturation and is essential for erythroblast enucleation. We have recently determined the complete amino acid sequence of human medhesin from the macrophage cDNA library. The aim of this proposal is to characterize the molecular basis of medhesin function in erythroblast-macrophage association. Specifically, the following issues will be addressed: (1) Is medhesin-dependent erythroblast-macrophage contact sufficient for erythroblast maturation? We will investigate whether medhesin-mediated cellular contact alone is sufficient to produce erythroblastic terminal maturation or additional macrophage-derived factors are required. (2) How does medhesin-mediated contact between erythroblasts and macrophages promote terminal erythroid maturation? To define the molecular basis of medhesin function, an important requisite will be to identify the molecules with which medhesin associates in erythroblasts. This identification will be accomplished using immunoprecipitation, affinity- chromatography, and the yeast two hybrid assays. (3) Do the kinetics of medhesin synthesis, assembly, and turnover correlate with erythroblast maturation? We propose to quantify the rates of medhesin synthesis, assembly, and turnover in the soluble and particulate fractions of erythroblasts at defined stages of differentiation. The precise definition of temporally-regulated medhesin expression will provide clues to the basis of erythroblast-macrophage contact during erythropoiesis. Together, the proposed studies on medhesin may begin to reveal the molecular basis of erythroblastic island formation during mammalian erythropoiesis.