Nuclear MT1-MMP and Macrophage Immune Function

描述(申请人提供)：在从宿主防御到慢性炎症性疾病状态的一系列事件中，巨噬细胞(MO)渗透到受影响的间质组织，在那里它们可以参与细胞外基质的蛋白水解性重塑和局部免疫反应。长期以来，人们一直认为MOS可以动员蛋白水解酶(特别是那些属于基质金属蛋白酶基因家族的酶)来重塑细胞外基质。然而，越来越多的证据表明，MMPs也可以独立于其基质重塑活动来调节细胞功能。为了研究基质金属蛋白酶在MOS中的依赖和非依赖功能，我们最近将注意力集中在膜锚定的蛋白水解酶MT1-MMPs上，MT1-MMPs是一个单一的MMP家族成员，在小鼠体内的缺失会导致发病率和死亡率的显著增加。在最近报道的旨在比较和对比野生型MOS和MT1-MMP零MOS的功能的研究中，我们发现MO来源的MT1-MMPs是一种先前未被怀疑的MO炎症反应中心基因网络的反式激活因子。Mt1-MMPs通过控制一个新的调节轴来影响MO的功能，在这个轴上，LPSTLR4相互作用触发Mt1-MMPs的表达，而Mt1-MMPs则是PI3K�/Akt/Gsk3信号和核小体重构因子的Mi-2/NuRd复合体所必需的激活物。重要的是，但出乎意料的是，MT1-基质金属蛋白酶通过运输到与PI3K�启动子相关联的核间隔室来控制MO免疫反应。虽然类似的--如果不是相同的--过程在人类细胞中起作用，但控制MT1-MMP核运输和易位的机制仍然不清楚，控制MT1-MMPDNA结合相互作用或靶基因选择的过程也是如此。此外，除了核室中MT1-MMPs的功能外，该酶还是MO介导的细胞外基质周转的关键效应器，特别是那些与基底膜相关的成分，基底膜是构成所有上皮细胞和内皮细胞的特殊结缔组织屏障。因此，我们建议：1)研究MT1-MMP核转运和核质转位的调控机制；2)确定介导MT1-MMP核转录激活的DNA结合伙伴；3)确定MT1-MMPs作为细胞外基质重塑的主要介体；4)研究M0 MT1-MMP3在体内调节免疫反应中的作用。这些研究应该为新发现的、依赖MO的核小体重构途径提供新的见解，这些途径标志着作为宿主防御中心的慢性炎症事件以及炎症性疾病状态。由于MT-MMPs和PI3K�在几乎所有的免疫细胞群中都有表达，这些结果应该有助于勾勒出炎症和控制机制的新范式，这可能被证明有助于治疗干预。

DESCRIPTION (provided by applicant): During events ranging from host defense to chronic inflammatory disease states, macrophages (MOs) infiltrate affected interstitial tissues where they can participate in both the proteolytic remodeling of the extracellular matrix and local immune responses. MOs have long been assumed to mobilize proteolytic enzymes (particularly those belonging to the matrix metalloproteinase gene family) in order to remodel the extracellular matrix. However, increasing evidence suggests that MMPs can also regulate cell function independently of their matrix remodeling activities. In an attempt to characterize matrix metalloproteinase-dependent versus -independent functions in MOs, we have recently focused our attention on the membrane-anchored protease, MT1-MMP - the single MMP family member whose deletion in mice results in a profound increase in morbidity and mortality. In recently reported studies designed to compare and contrast the function of wild-type and MT1- MMP-null MOs, we discovered that MO-derived MT1-MMP acts as a previously unsuspected transactivator of the gene networks central to MO inflammatory responses. MT1-MMP exerts these effects on MO function by controlling a novel regulatory axis wherein LPS-TLR4 interactions trigger MT1-MMP expression which then acts as a required activator of PI3K�/Akt/GSK3 signaling and the Mi-2/NuRD complex of nucleosome remodeling factors. Importantly, but unexpectedly, MT1-MMP exerts control over MO immune responses by trafficking into the nuclear compartment where it associates with the PI3K� promoter. While similar - if not identical - processes are operative in human cells, the mechanisms that control MT1-MMP nuclear trafficking and translocation remain undefined as do the processes that control MT1-MMP-DNA binding interactions or target gene selection. Furthermore, independent of MT1-MMP function in the nuclear compartment, the proteinase also serves as a key effector of MO-mediated turnover of the extracellular matrix, particularly those components associated with basement membranes, the specialized connective tissue barriers that underlies all epithelial and endothelial cells. As such, we propose to i) characterize the regulatory mechanisms underlying MT1-MMP nuclear trafficking and nucleoplasm translocation, ii) identify the DNA-binding partners that mediate MT1-MMP-mediated nuclear transcriptional activation iii) define the role of MT1-MMP as the dominant mediator of extracellular matrix remodeling and iv) characterize the role of MO MT1-MMP in regulating immune responses in vivo. These studies should provide novel insights into newly identified, MO- dependent nucleosomal remodeling pathways that mark chronic inflammatory events central to host defense as well as inflammatory disease states. As MT-MMPs and PI3K� are expressed in almost all immune cell populations, these results should serve to outline a new paradigm in inflammation and identification of control mechanisms that may prove conducive to therapeutic intervention.