Release of MIF protein complexes in vivo: response to inflammation

描述(申请人提供)：巨噬细胞移动抑制因子(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，MIF在膀胱中的产生被上调，MIF被释放到腔内间隙，在那里它通过激活下游的炎症介质对尿路上皮起促炎作用。一项新的发现是，MIF不是作为一种无结合的分子蛋白质释放的，而是在与α-1抑制剂3的高分子量复合体中释放的，α-1抑制剂3是α2-巨球蛋白家族中的一种蛋白酶抑制剂。此外，在另一项新发现中，MIF-Alpha1抑制物3复合体与膀胱表面葡萄糖相关蛋白78结合，这可能导致信号转导通路的激活。本提案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，在神经源性炎症过程中，MIF被释放到膀胱腔内，并与尿路上皮上特定的细胞表面蛋白(CD74或葡萄糖调节蛋白78)相互作用，激活信号转导通路，从而产生其他促炎介质。因此，尽管速激肽(如P物质；SP)对膀胱的影响是短暂的，但MIF的激活会导致炎症循环，如果不加以控制，就会调节其他炎症介质并维持炎症状态。在本提案描述的新的研究路线中，我们将更详细地研究MIF的释放机制，与MIF相关的特定细胞表面分子在尿路上皮中的阻断作用，以及MIF复合体在体外系统中激活信号转导的能力。识别与MIF相关的新的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，因此该提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.