Phosphatidylinositol Metabolism and Trafficking in Atherosclerosis and Inflammation

PIP2是一种次要磷脂（PL），在多种细胞功能中起关键作用，但PIP2在动脉粥样硬化和Nlrp3/ IL-1β炎症小体途径中的作用尚不清楚。我之前已经证明，ABCA1也可以作为磷脂酰肌醇4,5 -二磷酸（PIP2）转运酶，将PIP2从质膜的内小叶转运到外小叶。ABCA1是一种细胞胆固醇外排转运蛋白，通过从细胞中外排多余的脂质/胆固醇和阻断促炎途径，在预防动脉粥样硬化和炎症中发挥重要作用。Abca1基因突变的人类患者会出现早期动脉粥样硬化，Ldlr KO小鼠中巨噬细胞特异性敲除Abca1 /G1可促进动脉粥样硬化和斑块炎症。CANTOS试验强调了促炎Nlrp3/IL-1β通路在动脉粥样硬化中的作用，表明抗IL-1β治疗达到了主要试验终点，减少了心脏病发作、中风和心血管死亡。最近的研究表明，新发现的炎症小体底物Gasdermin D （GsdmD）与质膜上的PIP2结合并寡聚，生成孔以释放成熟的IL-1β。这些研究将揭示PIP2在这些通路中的新作用，并可能为预防心血管疾病（CVD）的治疗干预打开新的窗口。本研究将进一步证实PIP2是细胞胆固醇外排的主要调节因子，并鉴定出反过来调节胆固醇外排和炎症的PIP2翻转酶（p4型atp酶，将PIP2从细胞膜的外叶转运到内叶）。该提案将确定GsdmD在动脉粥样硬化、逆转胆固醇转运（RCT）以及逆转炎症对RCT的负面影响中的作用。该提案的三个主要目标是；1)确立PIP2作为主要的细胞胆固醇外排调节因子，2)鉴定和表征PIP2翻转酶，确定p4型atp酶在胆固醇外排和炎症中的作用，3)确定Gasdermin D在动脉粥样硬化中的作用和RCT。

PIP2 is a minor phospholipid (PL) and plays a critical role in variety of cellular functions but the role of PIP2 in atherosclerosis and Nlrp3/ IL-1β inflammasome pathway is not well characterized. I have previously shown that ABCA1 also functions as a phosphatidylinositol 4, 5-bisphosphate (PIP2) floppase, transporting PIP2 from the inner to the outer leaflet of the plasma membrane. ABCA1, a cellular cholesterol efflux transporter, plays a major role in preventing atherosclerosis and inflammation by effluxing excess lipids/cholesterol from cells and by blocking pro-inflammatory pathways. Human patients with mutations in Abca1 suffer from premature atherosclerosis and macrophage specific knockout of ABCA1/G1 in Ldlr KO mice promotes atherosclerosis and plaque inflammation. The role of pro-inflammatory Nlrp3/IL-1β pathway in atherosclerosis was highlighted by CANTOS trial showing that anti-IL-1β therapy met the primary trial endpoint, a reduction in a composite of heart attack, stroke and cardiovascular death. Recent studies have shown that, Gasdermin D (GsdmD), a newly discovered substrate of inflammasome, binds to PIP2 on plasma membrane and oligomerize, generating pores for releasing mature IL-1β. The proposed studies will unravel the novel roles of PIP2 in these pathways and may open new windows for therapeutic intervention to prevent cardiovascular disease (CVD). This proposal will further establish PIP2 as a major regulator of cellular cholesterol efflux and identify the PIP2 flippases (P4-type ATPases that transport PIP2 from the outer to the inner leaflet of the plasma membrane) that in turn regulate cholesterol efflux and inflammation. The proposal will identify the role of GsdmD in atherosclerosis, reverse cholesterol transport (RCT), and in reversing the negative effects of inflammation on RCT. The three main goals of this proposal are; 1) to establish PIP2 as a major cellular cholesterol efflux regulator, 2) to identify and characterize the PIP2 flippase and determine role of P4-type ATPases in cholesterol efflux and inflammation, and 3) to determine role of Gasdermin D in atherosclerosis and RCT.