Molecular chaperones and immune tolerance

项目总结 Gp96是内质网管腔内的一种免疫伴侣，用于折叠和组装 免疫反应中的多种关键受体，包括TLRs和整合素。Gp96的调节失调已经被 与许多类风湿性疾病有关，如狼疮。我们最近发现gp96也是 对调节性T细胞的稳定性和体内抑制功能至关重要(Zhang等人，J Clin 投资2015年)。此外，我们还揭示了gp96是折叠细胞表面所必需的伴侣。 TGFb对接受体GARP(也称为LRRC32)，其表达被认为仅限于 特雷格和血小板。有趣的是，我们发现在TLR结扎后，B细胞而不是髓系细胞表达GARP， 无论是小鼠狼疮模型还是人类狼疮模型，都存在稳定状态的GARP+B细胞群 SLE患者。 从本质上讲，我们现在已经确定gp96调节免疫和耐受的几个关键方面。它是 通过陪伴TLR启动免疫反应，实现最佳树突状细胞激活所必需的。Gp96也 通过赋予Treg细胞抑制功能，在免疫耐受中发挥重要作用。豁免权与 因此，耐受命运的决定可以由gp96以上下文和细胞类型特定的方式来协调。 我们假设gp96通过调节细胞表面TGFb的生物利用度来控制免疫耐受。 树突状细胞和B细胞。这是通过gp96在折叠GARP和GARP时的内在伴侣功能实现的 整合素，前者参与从细胞外环境中抢夺和结合潜伏的TGFb。 而后者参与了TGFb的激活。这一新的假设将通过以下方式得到解决 以下两个具体目标： 我们的首要目标是了解gp96调控Treg细胞功能的机制。我们的第二个 目的将确定B细胞内源性GARP在基础B细胞生物学中的作用及其发病机制。 狼疮，通过利用我们令人兴奋的初步数据展示了GARP在减重中的作用 实验性狼疮。因此，在正常和致病条件下都将追求这两个目标。一批 将使用新的遗传模型，包括可诱导的和细胞特异性的GARP基因敲除小鼠。我们相信 充分阐明我们的假设将对理解细胞难以捉摸的角色具有根本意义。 表面TGFb在免疫耐受以及狼疮发病机制中的作用。

PROJECT SUMMARY gp96 is an immune chaperone in the lumen of the endoplasmic reticulum, for the folding and assembly of multiple key receptors in immune responses including TLRs and integrins. Dysregulation of gp96 has been linked with a number of rheumatoid diseases such as lupus. We discovered very recently that gp96 is also critically required for the stability and in vivo suppressive function of regulatory T cells (Zhang et al., J Clin Invest 2015). Furthermore, we unveiled that gp96 serves as an essential chaperone for folding the cell surface docking receptor for TGFb, GARP (known also as LRRC32), whose expression is thought to be restricted to Tregs and platelets. Intriguingly, we found that B cells but not myeloid cells express GARP upon TLR ligation, and there is a unique population of GARP+ B cells in the steady state in both mouse lupus models and human patients with SLE. In essence, we have now established that gp96 regulates several key aspects of immunity and tolerance. It is required for optimal dendritic cell activation via chaperoning TLRs to initiate immune responses. gp96 also plays essential roles for immune tolerance by endowing suppressive function of Treg cells. The immunity vs. tolerance fate determination thus could be orchestrated by gp96 in a contextual and cell type specific fashion. We hypothesize that gp96 controls immune tolerance by regulating the bioavailability of cell surface TGFb for Tregs and B cells. This is accomplished by the intrinsic chaperone function of gp96 in folding both GARP and integrins, the former is involved in snatching and binding latent TGFb from the extracellular milieu in a paracrine fashion, whereas the latter is involved in TGFb activation. This novel hypothesis will be addressed by the following two specific aims: Our first Aim will focus on understanding the mechanisms of gp96 in controlling Treg cell function. Our second Aim will determine the roles of B cell-intrinsic GARP in fundamental B cell biology and the pathogenesis of lupus, by taking advantage of our exciting preliminary data demonstrating the roles of GARP in attenuating experimental lupus. Thus, the two aims will be pursued in both normal and pathogenic conditions. A number of novel genetic models including inducible and cell-specific GARP knockout mice, will be used. We believe that full elucidation of our hypothesis will have fundamental implications in understanding the elusive roles of cell surface TGFb in immune tolerance, as well as in the pathogenesis of lupus.