Mechanisms of IKK Regulation of Basal and Inflammatory Osteoclastogenesis

描述（由申请方提供）：转录因子NF-β B是破骨细胞生成所必需的，被认为是炎症反应的关键调节剂。NF-β B的活化需要诱导大的I β B激酶（IKK）复合物，其包含IKK 1、IKK 2和IKK（/NEMO. IKK 2和IKK 1分别激活经典（p50/p65）和非经典（p52/relB）NF-（B）通路.最近的研究表明IKK 2和IKK 1对破骨细胞的生成至关重要，但这种功能的机制仍不清楚。此外，IKK 2被认为是TNF、LPS和其他促炎剂（通过经典NF-（B途径）诱导的炎症事件的关键介质，而关于IKK 1在这种反应中的作用知之甚少。在过去的几年中，我们研究了在溶骨性反应中调节破骨细胞活性的分子途径，如炎性骨质溶解和关节炎性骨侵蚀，并揭示了调节破骨细胞前体中NF-β B活化的关键调节步骤。在这方面，我们发现NF-β B活化在多个水平的破坏减弱了破骨细胞生成和炎性骨侵蚀。具体地说，我们已经证明，施用抗IKK 2磷酸化的I（B）的显性阴性形式;以及最近使用诱饵NEMO结合域（NBD）肽抑制IKK与NEMO的组装，都是在体外和体内抑制破骨细胞生成和骨侵蚀的成功方法。最重要的是，我们有初步证据表明，1）IKK 1-null OCP诱导RANKL诱导破骨细胞生成的失败可通过重新引入IKK 1 cDNA构建体来挽救，2）OCP中IKK 2的组织特异性缺失（使用CD 11b-cre）导致骨骼畸形小鼠。很明显，在缺乏IKK 1或IKK 2的情况下，破骨细胞发生会受损，然而，IKK在基础和炎症性破骨细胞发生中的信号传导的精确机制仍然很少。此外，这两种蛋白质对这些反应的相对贡献是不确定的。还已知IKK 1和IKK 2具有相当大的序列和结构域相似性，尽管它们保持不同且不重叠的功能。因此，我们假设IKK 1和IKK 2通过替代的和经典的NF-β B活化途径，对基础和炎性破骨细胞的生成进行不同的调节。因此，通过研究IKK在破骨细胞中的分子信号传导细节，利用相关基因的种系和特定组织缺失，澄清IKK在破骨细胞生成中的个体作用，将使我们能够设计针对IKK 1和IKK 2的策略和选择性抑制剂，这些策略和选择性抑制剂可能有助于调节破骨细胞生成和减轻各种骨吸收疾病中的炎性骨质溶解。因此，我们建议研究以下具体目标：1）确定IKK 1和IKK 2在基础和炎性破骨细胞生成中的分子作用。2)确定酪氨酸磷酸化调节破骨细胞谱系中IKK 2的命运和活性的机制及其对破骨细胞生成的影响。3)确定IKK 1和IKK 2在体内炎性骨质溶解中的作用。公共卫生相关性：转录因子NF-β B对破骨细胞生成和调节炎症反应至关重要。NF-B由丝氨酸激酶I（B激酶（IKK）-1、IKK-2和IKK（/NEMO. IKK 1或IKK 2的基因缺失导致破骨细胞缺陷和炎症反应。使用IKK 1和IKK 2-null小鼠，我们建议研究IKK 1和IKK 2对破骨细胞生成和炎性骨质溶解的分子结构域贡献，就像在炎性关节炎中的情况一样。我们的建议有希望确定新的选择性抗溶骨性疗法。

DESCRIPTION (provided by applicant): The transcription factor NF-(B is essential for osteoclastogenesis and is considered a key modulator of inflammatory responses. Activation of NF-(B entails induction of a large I(B kinase (IKK) complex that comprises IKK1, IKK2, and IKK(/NEMO. IKK2 and IKK1 activate the canonical (p50/p65) and non- canonical (p52/relB) NF-(B pathways, respectively. Recent studies implicate IKK2 and IKK1 as essential for osteoclastogenesis, yet the mechanisms underling this function, remain unclear. In addition, IKK2 is considered as a key mediator of inflammatory events induced by TNF, LPS, and other pro-inflammatory agents (through the classical NF-(B pathway), whereas less is known about the role of IKK1 is such responses. In the past few years we have investigated molecular pathways regulating osteoclast activity in osteolytic responses, such as inflammatory osteolysis and arthritic bone erosion, and unveiled critical regulatory steps modulating NF-(B activation in osteoclast precursors. In this regard, we find that disruption of NF-(B activation at multiple levels attenuates osteoclastogenesis and inflammatory bone erosion. Specifically, we have shown that administration of dominant-negative forms of I(B(, that resist phosphorylation by IKK2; and most recently inhibition of IKK assembly with NEMO, using a decoy NEMO binding domain (NBD) peptide, all are successful approaches to inhibit osteoclastogenesis and bone erosion, in vitro and in vivo. Most importantly, we have preliminary evidence that, 1) failure of RANKL-induced osteoclastogenesis by IKK1-null OCPs is rescued by re-introduction of IKK1 cDNA constructs, and that 2) tissue-specific deletion of IKK2 in OCPs (using CD11b-cre) results with skeletally deformed mice. It is evident that osteoclastogenesis is impaired in the absence of IKK1 or IKK2, however, the precise mechanism(s) underlying signaling of IKKs in basal and inflammatory osteoclastogenesis remain scarce. Moreover, the relative contribution of either protein to these responses is indefinite. It is also known that IKK1 and IKK2 share considerable sequence and domain similarities, albeit they maintain distinct and non-overlapping functions. Thus, we hypothesize that IKK1 and IKK2 differentially regulate basal and inflammatory osteoclastogenesis through the alternative and classical NF-(B activation pathways. Hence, clarifying the individual roles of IKKs in osteoclastogenesis by investigating the details of their molecular signaling in osteoclasts, utilizing germ-line and specific tissue deletions of the relevant genes, will enable us to design strategies and selective inhibitors directed against IKK1 and IKK2 that may be useful for regulating osteoclastogenesis and alleviating inflammatory osteolysis in various bone resorptive disorders. Thus, we propose to investigate the following specific aims: 1) Determine the molecular role of IKK1 and IKK2 in basal and inflammatory osteoclastogenesis. 2) Determine the mechanism by which tyrosine phosphorylation regulates the fate and activity of IKK2 in the osteoclast lineage and it's impact on osteoclastogenesis. 3) Determine the role of IKK1 and IKK2 in inflammatory osteolysis, in vivo. PUBLIC HEALTH RELEVANCE: The transcription factor NF-(B is essential for osteoclastogenesis and modulates inflammatory responses. NF-(B is activated by the serine kinases, I(B kinase (IKK)-1, IKK-2, and IKK(/NEMO. Gene deletions of IKK1 or IKK2 led to defects in osteoclasts and inflammatory responses. Using IKK1 and IKK2-null mice, we propose to investigate the molecular domain contributions of IKK1 and IKK2 to osteoclastogenesis and inflammatory osteolysis, as is the case in inflammatory arthritis. Our proposal holds promise to identify novel selective anti-osteolytic therapies.