Human Blood Monocyte Receptor Expression and Modulation

巨噬细胞Fey受体(FcyR)在宿主防御和自身免疫中起重要作用。跟随他们的集群 通过免疫球蛋白复合体，巨噬细胞FcyR及其免疫球蛋白配体的内化可以通过几种途径进行。 小路。受体通过小的免疫球蛋白聚集导致内吞作用的内化，并且 通过大颗粒复合体(例如，包被免疫球蛋白的细胞)聚集导致吞噬作用的内化。 虽然这两个过程都涉及由相同的配体(免疫球蛋白Fc部分)激活相同的受体， 我们观察到调节这些内化的分子机制有很大的不同。 通向不同功能结果的途径。 例如，FcyRIIA ITAM的C末端酪氨酸(Y298)对于最佳吞噬作用是关键的，但 对于内吞作用是可有可无的。相比之下，N端的ITAM酪氨酸(Y282)似乎对两者都是必不可少的 流程。此外，通过Src家族激酶(SRTKs)对ITAM中的酪氨酸进行磷酸化是一种重要的功能。 吞噬的起始步骤，我们的证据表明内吞作用不依赖于受体 酪氨酸的磷酸化是由Src激酶引起的，也不涉及Syk激酶。我们还观察到， 泛素化不是FcyRIIA介导的吞噬作用的初始步骤，但对FcyRIIA是必不可少的 介导的内吞作用。此外，FcyriIA Y282XXL亮氨酸(L)(Y282完整)的突变完全抑制 FcyRIIA的内吞作用，表明Y282和L.285都是这一过程所必需的。这一观察结果 支持Y282XXL与笼状蛋白适配器AP-2的相互作用作为潜在的机制 受体介导的内吞作用，因为YXXL基序与细胞骨架蛋白介导的内吞作用有关。 使用细胞和分子生物学方法，我们将追求我们的长期目标，以定义分子 Fey受体介导的吞噬和吞噬作用的机制(S)。具体来说，我们将 确定：1)FcyRIIA序列是否构成AP-2的结合位点；2)哪些泛素连接酶是 在FcyRIIA介导的吞噬和吞噬作用中起重要作用，3)抑制受体的潜在作用 PC/RUB在调节内吞作用中的作用，4)脂筏在FcvRIIA介导的吞噬作用中的作用，5)序列 负责Fc/RIIA脂筏定位，最后6)泛素化在吞噬体内的作用 成熟。由于Fey受体介导的吞噬和内吞免疫球蛋白复合体起着重要的作用 在宿主防御和自身免疫性疾病中的作用，了解不同的分子是至关重要的 这些过程中涉及的机制。

Macrophage Fey receptors (FcyR) are important in host defense and autoimmunity. Following their clustering by IgG complexes, the internalization of macrophage FcyR and their IgG ligand can proceed by several pathways. Receptor clustering by small IgG aggregates leads to internalization via endocytosis, and clustering via large particulate complexes (e.g. IgG coated cells) leads to internalization via phagocytosis. Although both processes involve activation of identical receptors by the same ligand (theFc portion ofIgG), we have observed profound differences in the molecular mechanisms mediating these internalization pathways leading to distinct functional outcomes. For example, the C-terminal tyrosine (Y298), of the FcyRIIA ITAM is critical for optimal phagocytosis, but is dispensable for endocytosis. By contrast, the N-terminal ITAM tyrosine (Y282) appears essential for both processes. Also, while phosphorylation of tyrosines in the ITAM by Src family kinases (SRTKs) is an essen- tial step for initiation of phagocytosis, our evidence indicates that endocytosis is not dependent on receptor tyrosine phosphorylation by Src kinases, nor does it involve Syk kinase. We have also observed that ubiquitination is not required for the initial step of FcyRIIA mediated phagocytosis, but is essential for FcyRIIA mediated endocytosis. Further, mutation of the FcyRIIA Y282XXL leucine (L) (Y282 intact) completely inhibits endocytosis by FcyRIIA, suggesting that both Y282 and L.285 are required for this process. This observation argues in favor of interaction of Y282XXL with the clathrin adaptor AP-2as the mechanism underlying receptor mediated endocytosis, since YXXL motifs have been implicated in clathrin-mediated endocytosis. Using cellular and molecular biology approaches, we will pursue our long term goal to define the molecular mechanism(s) underlying Fey receptor mediated endocytosis and phagocytosis. Specifically, we will determine: 1) if a FcyRIIA sequence constitutes a binding site for AP-2, 2) which ubiquitin ligases are important in FcyRIIA mediated endocytosis and phagocytosis, 3) the potential role of the inhibitory receptor Pc/RUB in regulating endocytosis, 4) the role of lipid rafts in FcvRIIA mediated phagocytosis, 5) sequences responsible for Fc/RIIA lipid raft localization, and finally 6) the role of ubiquitination in phagosomal maturation. Since Fey receptor mediated phagocytosisand endocytosisof IgG complexes play an important role in host defense and autoimmune disorders, it is essential to understand the distinct molecular mechanisms involved in these processes.