THE MACROPHAGE MANNOSE RECEPTOR IN PNEUMOCYSTIS CARINII INFECTION

肺泡巨噬细胞在一线宿主中起着关键作用 在肺部进行防御。巨噬细胞甘露糖受体高度 表达于肺泡巨噬细胞，但不表达于循环 单核细胞。尽管最初的特征是内吞 一种快速循环到内小体表面的受体，其 主要的生理作用似乎是吞噬 微生物。编码基因的cDNA的特征 人和鼠的甘露糖受体揭示了一种预测的多肽 它具有由NH2末端组成的胞外结构域 富含半胱氨酸的第二型纤维连接蛋白重复序列最多 突出的特征是8个碳水化合物的串联阵列 平均具有30%同源性的识别结构域 又一个。一个短的疏水跨膜区后面跟着一个 45个氨基酸的胞质尾巴。甘露糖的瞬时表达 Cos细胞的受体与人鼻的竞争抑制 肺泡巨噬细胞中的受体活性表明 甘露糖受体足以结合和摄取 卡氏肺孢子虫的包囊和滋养体形式。这些研究 强调肺泡巨噬细胞甘露糖受体在 对肺孢子虫的一线宿主防御。 在提案中概述的初步实验中，我们有 证明从艾滋病患者体内分离的肺泡巨噬细胞 肺孢子虫肺炎几乎完全下调 它们的表面甘露糖受体的表达。一种能力 这些细胞对吞噬肺孢子虫的作用几乎完全 被废除，尽管他们能够摄入乳胶珠和 调光颗粒。用适度上调的方法培养 巨噬细胞甘露糖受体活性，导致部分 甘露糖受体表达的恢复和卡氏肺孢子虫 吞噬作用。我们假设MR功能障碍是导致 卡氏肺孢子虫的胞外积累和脱落细胞壁 产品。我们的目标是(L)定义MR的机制 下调调控；(2)检查MR的潜在上调因子 活动，如IL-13，能够恢复MR活动；(3) 确定单个HIV基因在MR中起什么作用(如果有的话) 降低监管。我们计划利用FC的观察结果 HIV感染的巨噬细胞的受体功能被保留，而MR 通过构建可溶的甘露糖受体来下调 在COOH末端含有Fc片段。我们的目标是建立一个 甘露糖受体基因敲除小鼠作为终极体内试验 甘露糖受体在卡氏肺孢子虫感染中的作用这个项目 需要与核心9001、9002和9004密切协作， 项目0008和0010如果我们要实现我们的最终目标 卡氏肺孢子虫新疗法的基础研究 感染。

The alveolar macrophage plays a pivotal role in first line host defense in the lung. The macrophage mannose receptor is highly expressed on alveolar macrophages, but not on circulating monocytes. Although originally characterized as an endocytic receptor that is rapidly recycled to the surface of endosomes, its predominant physiological role appears to be in the phagocytosis of microorganisms. The characterization of cDNAs that encode for the human and murine mannose receptors reveal a predicted polypeptide that has ectodomain that is comprised of an NH2 terminus that is cysteine rich followed by a type 2 fibronectin repeat with the most outstanding feature being a tandem array of 8 carbohydrate recognition domains which bear, on average, 30% homology to one another. A short hydrophobic transmembrane region is followed by a 45 amino acid cytoplasmic tail. Transient expression of the mannose receptor in Cos cells and competitive inhibition of man nose receptor activity in alveolar macrophages have indicated that the mannose receptor is sufficient for the binding and up take of the cyst and trophozoite forms of Pneumocystis carinii. These studies emphasize the role for the alveolar macrophage mannose receptor in first line host defense against Pneumocystis. In preliminary experiments outlined in the proposal, we have demonstrated that alveolar macrophages isolated from AIDS patients with Pneumocystis pneumonia have an almost complete downregulation in the expression of their surface mannose receptors. The ability of these cells to phagocytose Pneumocystis is almost entirely abolished although they are able to ingest latex beads and opsonized particles. Cultivation with modest upregulators of macrophage mannose receptor activity, results in a partial restoration of mannose receptor expression and P. carinii phagocytosis. We hypothesize that MR dysfunction contributes to the extracellular accumulation of P. carinii and shed cell wall products. Our goals are (l) to define the mechanisms of MR downregulation; (2) to examine if potential upregulators of MR activity, like IL-13, are able to restore MR activity; (3) determine what role, if any, individual HIV gene plays in MR downregulation. We plan to make use of the observation that Fc receptor function is preserved in HIV infected macrophages while MR is downregulated by constructing soluble mannose receptors that contain an Fc fragment in COOH terminus. We aim to establish a mannose receptor knockout mouse as the ultimate in vivo test of mannose receptor function in P. carinii infection. This project requires close collaboration with Cores 9001, 9002, and 9004 and Projects 0008 and 0010 if we are to achieve our ultimate goal of translating basic inquiry into novel therapies for P. carinii infection.