THE MACROPHAGE MANNOSE RECEPTOR IN PNEUMOCYSTIS CARINII INFECTION

肺泡巨噬细胞在一线宿主中起着举足轻重的作用 肺的防御。巨噬细胞甘露糖受体高度 在肺泡巨噬细胞上表达，但在循环中不表达。 单核细胞虽然最初被描述为内吞 受体迅速回收到内体表面，其 主要的生理作用似乎是在吞噬 微生物的对编码该蛋白的cDNA进行表征。 人和鼠甘露糖受体揭示了一种预测的多肽 其具有由NH 2末端组成的胞外域， 富含半胱氨酸，其次是2型纤连蛋白重复， 一个突出的特点是8个碳水化合物的串联阵列 识别结构域平均与一个具有30%同源性的 另短的疏水跨膜区之后是短的疏水跨膜区。 45个氨基酸的胞质尾。甘露糖的瞬时表达 Cos细胞的受体与人鼻竞争性抑制 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 包囊和滋养体形式的卡氏肺孢子虫。这些研究 强调肺泡巨噬细胞甘露糖受体在 抵御肺孢子虫的第一道防线 在提案中概述的初步实验中，我们 证明从艾滋病患者中分离的肺泡巨噬细胞 肺孢子虫肺炎患者几乎完全下调 它们表面甘露糖受体的表达。的能力 这些细胞吞噬肺孢子虫几乎完全 尽管它们能够摄取乳胶珠， 调理素颗粒用温和的 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功能障碍有助于 卡氏肺孢子虫细胞外积累和脱落细胞壁 产品.我们的目标是：（1）明确MR的机制 下调;（2）检查MR的潜在上调剂 活性，如IL-13，能够恢复MR活性;（3） 确定单个HIV基因在MR中起什么作用（如果有的话） 下调我们计划利用观察结果， 受体功能在HIV感染的巨噬细胞中保留，而MR 通过构建可溶性甘露糖受体下调， 在COOH末端含有Fc片段。我们的目标是建立一个 甘露糖受体敲除小鼠作为最终的体内试验， 甘露糖受体在卡氏肺孢子虫感染中的功能这个项目 需要与Cores 9001、9002和9004密切合作， 项目0008和0010，如果我们要实现我们的最终目标， 将基础研究转化为针对卡氏肺孢子虫的新疗法 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.