MYCOKETIDES: M TUBERCULOSIS PKS12 PRODUCT PRESENTED BY CD1C TO T CELLS: AIDS OI

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 对CD 1c介导的T细胞应答的脂质靶点的研究最近鉴定了分枝杆菌磷脂抗原，其碳水化合物结构精确地对应于哺乳动物甘露糖基B-1-磷酸二醇（MPD），但含有不寻常的脂质部分。 在这里，我们表明，这种T细胞抗原是一个分支，烷烃脂质的长度不同（C30-34），并产生的M家族的成员。tuberculosis，M.牛卡介苗和其他在细胞内生长的分枝杆菌。 这些分枝杆菌抗原的精细结构的分析表明，区分它们与哺乳动物MPD的化学特征是必需的CD 1c限制性T细胞的激活，但不能占任何已知的脂质生物合成途径。 代谢标记和质谱分析表明，延长脂质在C5增量严格交替纳入C2和C3单位，而不是异戊烯焦磷酸缩合的机制。 检查M。结核病基因组鉴定了一个基因pks 12，预测该基因在蛋白质组中产生最大的蛋白质，并含有进行这种多步合成所必需的12个催化结构域。 基因缺失和互补表明，PKS 12是必要的和足够的抗原生产和由此产生的CD 1c介导的T细胞活化，但不影响合成的真正异戊烯醇。 这些研究建立了一种以前未知类型的分枝杆菌聚酮（称为分枝杆菌酮）的遗传和酶基础，它代表了一种与分枝杆菌病原体相关的分子模式，使分枝杆菌能够被人类免疫系统识别。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Study of the lipid targets of CD1c-mediated T cell responses recently identified a mycobacterial phospholipid antigen whose carbohydrate structure precisely corresponded to mammalian mannosyl b-1-phosphodolichols (MPD), but contained an unusual lipid moiety. Here we show that this T cell antigen is a member of a family of branched, alkane lipids that vary in length (C30-34) and are produced by M. tuberculosis, M. bovis Bacille-Calmette-Guerin and other mycobacteria that grow within cells. Analysis of the fine structures of these mycobacterial antigens showed that the chemical features that distinguished them from mammalian MPDs were necessary for activation of CD1c-restricted T cells, but could not be accounted for by any known lipid biosynthetic pathway. Metabolic labeling and mass spectrometric analyses suggested a mechanism for elongating lipids in C5 increments by strictly alternating incorporation of C2 and C3 units, rather than isopentenyl pyrophosphate condensation. Inspection of the M. tuberculosis genome identified one gene pks12, which is predicted to make the largest protein in the proteome and to contain 12 catalytic domains necessary to carry out this multi-step synthesis. Genetic deletion and complementation showed that PKS12 was necessary and sufficient for antigen production and the resulting CD1c-mediated T cell activation, but did not affect synthesis of true isoprenols. These studies establish the genetic and enzymatic basis for a previously unknown type of mycobacterial polyketide, designated mycoketide, which represents a lipidic pathogen associated molecular pattern that allows mycobacterial recognition by the human immune system.