Adipokine Signaling in Macrophages

描述(申请人提供)：肥胖中观察到的慢性炎症与医学上重要并发症的发展有关，特别是动脉粥样硬化、癌症、胰岛素抵抗和非酒精性脂肪性肝病。巨噬细胞是炎症的关键介质，已被证明对这些疾病的发展有重要贡献。然而，尽管受到了相当多的关注，但到目前为止，关于巨噬细胞受脂肪细胞分泌的各种炎症相关脂肪因子(如脂联素和抵抗素)的差异调控机制的信息很少。巨噬细胞中是否存在多种脂肪因子的共同分子介质？在巨噬细胞中，各种脂肪因子是否通过不同的途径发出信号？值得注意的是，我们最近的数据支持这样的观点，即巨噬细胞TORC2(调节CREB活性转导因子2)通过一种独特的机制控制巨噬细胞的激活，涉及TORC2在特定脂肪因子刺激下的核-胞质穿梭。我们的两个假设是：(I)脂联素和抵抗素介导的脂肪因子信号通路汇聚在巨噬细胞TORC2上；(Ii)TORC2核浆穿梭决定巨噬细胞是否被激活，这一事件控制炎症并影响胰岛素抵抗的病理生理。这些假说使TORC2成为将肥胖的全身炎症效应与胰岛素抵抗联系起来的关键参与者。我们将使用最先进的生化和免疫学方法并结合代谢表型分析方法，针对以下三个具体目标对这些假说进行验证：(1)揭示脂肪因子调控巨噬细胞中TORC2活性的信号通路，重点是确定反应激酶和磷酸酶；(2)通过表达具有固有活性的TORC2突变体的巨噬细胞特异性转基因小鼠模型，验证TORC2在炎症和胰岛素抵抗中的生理重要性；(3)在使用骨髓移植建立的功能丧失的TORC2小鼠模型中，进一步阐明TORC2在炎症和胰岛素抵抗中的作用。假说的确认将确定脂肪因子向巨噬细胞传递信号所需的关键分子，以及导致巨噬细胞激活的细胞内事件。与人类健康相关：描绘信号通路(S)将建立肥胖诱导的胰岛素抵抗和相关慢性病的关键机制。它将为因慢性炎症而恶化的情况下的药物干预提供一个或多个候选靶点，并可能建立TORC2或其相互作用的合作伙伴作为慢性炎症发病的早期标志。

DESCRIPTION (provided by applicant): Chronic inflammation observed in obesity has been implicated in the development of medically important complications, particularly atherosclerosis, cancer, insulin resistance and non-alcoholic fatty liver disease. Macrophages, key mediators of inflammation, have been shown to contribute significantly to the development of these disorders. Despite considerable attention, however, there is little information thus far on the mechanism through which macrophages are differentially regulated by various inflammation- related adipokines (e.g., adiponectin and resistin) secreted by adipocytes. Is there a common molecular mediator in macrophages for various adipokines? Do various adipokines signal through distinctive pathways in macrophages? Remarkably, our recent data support the notion that macrophage TORC2 (for Transducers Of Regulated CREB activity 2) controls macrophage activation via a unique mechanism, involving nuclear-cytosolic shuttling of TORC2, upon stimulation by specific adipokines. Our two hypotheses are: (i) the adipokine signaling pathways mediated by adiponectin and resistin converge on macrophage TORC2; (ii) nuclear-cytosolic shuttling of TORC2 determines whether macrophages are activated, an event which controls inflammation and influences the pathophysiology of insulin resistance. These hypotheses place TORC2 as the key player that links systemic inflammatory effects of obesity to insulin resistance. Using the state-of-art biochemical and immunological approaches together with metabolic phenotyping, we will test these hypotheses with the following three Specific Aims: (1) to delineate the signaling pathway by which adipokines regulate TORC2 activity in macrophages, focusing on identification of the responsive kinase and phosphatase; (2) to validate the physiological importance of TORC2 in inflammation and insulin resistance in a macrophage-specific transgenic mouse model expressing a constitutively active TORC2 mutant; (3) to further elucidate the role of TORC2 in inflammation and insulin resistance in a loss-of-function TORC2 mouse model generated using bone marrow transplantation. Confirmation of the hypotheses will identify key molecules required for adipokine signaling of the macrophages and intracellular events leading to macrophage activation. Relevance to human health: Delineating the signaling pathway(s) will establish a pivotal mechanism for obesity- induced insulin resistance and related chronic diseases. It will provide one or more candidate targets for drug intervention in conditions exacerbated by chronic inflammation, and possibly establish TORC2 or its interacting partners as early markers of the onset of chronic inflammation.