Phosphatidylinositol Metabolism and Trafficking in Atherosclerosis and Inflammation

PIP2是一种次要的磷脂，在多种细胞功能中发挥重要作用，但PIP2在动脉粥样硬化和Nlrp3/IL-1β炎性小体通路中的作用尚不清楚。我以前已经证明ABCA1还作为磷脂酰肌醇4，5-二磷酸(PIP2)Floppase发挥作用，将PIP2从质膜的内叶运输到外叶。ABCA1是一种细胞胆固醇外流转运体，通过将多余的脂类/胆固醇从细胞中排出并阻断促炎途径，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患有过早的动脉粥样硬化，Ldlr KO小鼠中巨噬细胞特异的ABCA1/G1基因敲除促进了动脉粥样硬化和斑块炎症。CANTOS试验表明，抗IL-1β治疗达到了主要的试验终点，减少了心脏病发作、中风和心血管死亡的综合发生率，突显了促炎因子Nlrp3/IL-1β通路在动脉粥样硬化中的作用。最近的研究表明，新发现的炎症体底物Gasdermin D(GsdmD)与质膜上的PIP2结合并寡聚，产生释放成熟IL-1β的孔道。这项拟议的研究将揭开PIP2在这些途径中的新角色，并可能为预防心血管疾病(CVD)的治疗干预打开新的窗口。这项提议将进一步确立PIP2作为细胞胆固醇外流的主要调节因子，并确定PIP2翻转酶(P4型ATPase，将PIP2从质膜的外部转运到内叶)，进而调节胆固醇外流和炎症。该提案将确定GsdmD在动脉粥样硬化、反向胆固醇运输(RCT)以及逆转炎症对RCT的负面影响方面的作用。该提案的三个主要目标是：1)建立PIP2作为主要的细胞胆固醇外流调节器；2)鉴定和表征PIP2翻转酶并确定P4型ATPase在胆固醇外流和炎症中的作用；3)确定Gasdermin D在动脉粥样硬化和RCT中的作用。

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.