Release of MIF protein complexes in vivo: inflammation

描述（由申请人提供）：巨噬细胞迁移抑制因子（MIF）是一种由尿路上皮产生的促炎细胞因子。在膀胱炎症期间，膀胱中MIF的产生上调，MIF被释放到腔内空间，通过激活下游炎症介质对尿路上皮产生促炎作用。一项新的发现是，MIF不是作为未结合的单聚体蛋白释放，而是以与α -1抑制剂3 （α - 2-巨球蛋白家族中的蛋白酶抑制剂）的高分子量复合物释放。此外，在另一项新发现中，MIF-alpha1抑制剂3复合物与膀胱中表面葡萄糖相关蛋白78相关，可能导致信号转导途径的激活。本研究的总体目标是通过研究这两个新发现来继续研究MIF介导的膀胱炎症的机制。根据我们最近的实验证据，我们的工作假设是，在神经源性炎症期间，MIF被释放到膀胱腔中，并与尿路上皮上的特定细胞表面蛋白（CD74或葡萄糖调节蛋白78）相互作用，激活信号转导通路，导致其他促炎介质的产生。因此，尽管速激肽（如P物质）对膀胱的作用是短暂的，但MIF的激活会导致炎症循环，如果不加以控制，则会调节其他炎症介质并维持炎症状态。在本提案中描述的新研究方向中，我们将更详细地研究MIF释放的机制，尿路上皮中与MIF相关的特定细胞表面分子的阻断作用，以及MIF复合物在体外系统中激活信号转导的能力。鉴定与MIF相关的新型细胞表面蛋白的作用将增加对MIF促炎功能的基本机制的了解，因此该建议的发现可能扩展到MIF已被证明发挥作用的其他炎症条件。

DESCRIPTION (provided by applicant): Macrophage migration inhibitory factor (MIF), is a pro-inflammatory cytokine produced by the urothelium. During bladder inflammation, MIF production is upregulated in the bladder and MIF is released into the intraluminal space where it exerts proinflammatory effects on the urothelium by activating downstream inflammatory mediators. A novel finding is that MIF is released, not as an unbound momeric protein, but in high-molecular weight complexes with alpha-1 inhibitor 3, a protease inhibitor in the family of alpha2- macroglobulins. In addition, in another novel finding, MIF-alpha1 inhibitor 3 complexes associate with surface glucose related protein 78 in the bladder which likely results in activation of signal transduction pathways. The overall goal of the present proposal is to continue to investigate the mechanism of MIF- mediated inflammation in the bladder by investigating these two novel findings. Based on our recent experimental evidence, our working hypothesis is that during neurogenic inflammation, MIF is released into the bladder lumen and interacts with specific cell-surface proteins (either CD74 or glucose regulated protein 78) on the urothelium to activate signal transduction pathways resulting in the production of other pro- inflammatory mediators. Thus, even though the effects of tachykinins (e.g. Substance P; SP) on the bladder are short-lived, activation of MIF results in an inflammatory loop that, if left unchecked, regulates other inflammatory mediators and maintains an inflammatory condition. In the new line of research described in the present proposal, we will examine in greater detail the mechanisms of MIF release, the effects of blockade of specific cell-surface molecules associated with MIF in the urothelium and the ability of MIF complexes to activate signal transduction in well-described in vitro systems. Identification of the effect of novel cell-surface proteins associated with MIF will add to knowledge of basic mechanisms of MIF's pro- inflammatory functions, and thus the findings of this proposal may extend to other inflammatory conditions where MIF has been demonstrated to play a role.