Cellular mechanisms of NLRP3 activation by ALCAT1 in diet-induced obesity

肥胖会导致慢性“不孕不育”炎症，这与胰岛素抵抗和 其他代谢并发症。NLRP3(NLRP3)是一种胞内结构域 传感器的各种“危险”信号来自微生物感染和代谢应激。激活 NLRP3炎性小体通过促进caspase-1依赖性诱导宿主防御反应 释放IL-1、β和其他促炎细胞因子。有趣的是，NLRP3的激活 炎症小体也与饮食诱导的“不孕症”炎症和胰岛素抵抗有关 肥胖(DIO)，然而导致NLRP3在肥胖症中激活的“危险”信号仍然难以捉摸。 Prion是一种错误折叠的蛋白质，能够将错误折叠的形状自我传递到 相同蛋白质的正常变种。该领域的最新进展已确定了240多个 哺乳动物中的非传染性类病毒蛋白。尽管这些蛋白质中的一些与 在神经退行性疾病的发病机制中，令人惊讶的是人们对此知之甚少 大多数类病毒蛋白在人类健康和疾病中的潜在作用。在这里，我们 建议研究一种新的途径，即一种可能的普恩样蛋白通过其调节NLRP3 在DIO中激活。这一途径是由ALCAT1酶介导的，ALCAT1酶是第一个依赖酰辅酶A的酶 溶心磷脂酰基转移酶是我们之前发现的。我们在这一领域的开创性工作 显示ALCAT1通过催化促进年龄相关代谢性疾病的发展 超长链多不饱和脂肪酸对心磷脂的病理重塑 即二十二碳六烯酸(DHA)。富含DHA使CL对氧化高度敏感 活性氧(ROS)损伤(CL-Ox)，导致CL耗竭和线粒体 代谢性疾病中的功能障碍。值得注意的是，我们的初步研究也发现了一个关键 ALCAT1在连接DIO和NLRP3激活中作为一种可能的普恩样蛋白的作用，包括 ALCAT1在氧化应激的作用下形成类病毒蛋白聚集体，这是由 2)脂肪组织中ALCAT1的表达显著增加 DIO上调；3)脂肪细胞中ALCAT1的靶向缺失显著减弱 NLRP3通过阻止巨噬细胞在白色脂肪组织中的渗透而激活。加在一起，这些 令人兴奋的发现让我们假设ALCAT1促进DIO中NLRP3的激活 推定的普恩样蛋白，将通过三个特定目标进行测试：目标1将确定 ALCAT1是否通过线粒体功能障碍促进NLRP3激活；AIM 2将 确定ALCAT1促进NLRP3激活的分子机制 AIM 3将评估ALCAT1是否将脂肪组织中的细胞衰老与 DIO小鼠的慢性炎症反应。成功完成拟议的研究不仅将 验证ALCAT1作为治疗慢性炎症的新药靶点，但也提供概念证据 靶向酶治疗肥胖症及其相关并发症的研究。

Obesity causes chronic “sterile” inflammation, which is implicated in insulin resistance and other metabolic complications. NLRP3 (NLR family pyrin domain containing 3) is an intracellular sensor for various “danger” signals from microbial infection and metabolic stress. Activation of NLRP3 inflammasomes elicits host defense responses by promoting caspase 1-dependent release of IL-1β and other pro-inflammatory cytokines. Intriguingly, activation of NLRP3 inflammasomes is also implicated in “sterile” inflammation and insulin resistance in diet-induced obesity (DIO), yet the “danger” signals that lead to NLRP3 activation in obesity remains elusive. Prions are misfolded proteins that are capable of self-transmitting their misfolded shape onto normal variants of the same protein. Recent progress in the field has identified more than 240 non-infectious prion-like proteins in mammals. Although a few of these proteins are well implicated in the pathogenesis of neurodegenerative diseases, surprisingly little information is known about majority of the prion-like proteins’ potential involvement in human health and disease. Here, we propose to investigate a novel pathway by which a putative prion-like protein regulates NLRP3 activation in DIO. This pathway is mediated by the ALCAT1 enzyme, the first acyl-CoA dependent lysocardiolipin acyltransferase previously identified by us. Our groundbreaking work in the field shows that ALCAT1 promotes the development of age-related metabolic diseases by catalyzing pathological remodeling of cardiolipin (CL) with very long-chain polyunsaturated fatty acids, such as docosahexaenoic acid (DHA). Enrichment of DHA renders CL highly sensitive to oxidative damage (CL-Ox) by reactive oxygen species (ROS), leading to CL depletion and mitochondrial dysfunction in metabolic diseases. Remarkably, our preliminary studies also identified a pivotal role of ALCAT1 in linking DIO to NLRP3 activation as a putative prion-like protein, including 1) ALCAT1 forms prion-like protein aggregates in response to oxidative stress, which is mediated by a prion-like domain at the N-terminus; 2) ALCAT1 expression in adipose tissue is dramatically upregulated by DIO; and 3)Targeted deletion of ALCAT1 in adipocytes significantly attenuates NLRP3 activation by preventing macrophage infiltration in white adipose tissue. Together, these exciting findings let us to hypothesize that ALCAT1 promotes NLRP3 activation in DIO as a putative prion-like protein, which will be tested by three Specific Aims: AIM 1 will determine whether ALCAT1 promotes NLRP3 activation through mitochondrial dysfunction; AIM 2 will identify molecular mechanisms by which ALCAT1 promotes NLRP3 activation as a prion-like protein; and AIM 3 will assess whether ALCAT1 links cellular senescence in adipose tissue to chronic inflammation in DIO mice. Successful completion of the proposed studies will not only validate ALCAT1 as a novel drug target of chronic inflammation, but also provide proof of concept studies of targeting the enzyme for the treatment of obesity and its related complications.