Targeting LRH-1 - Phospholipid Signaling in Metabolic Pathways

描述(申请人提供)：糖尿病是一种日益严重的流行病，目前在美国有超过2500万人受到影响。这些病例中的大多数(90%-95%)是2型糖尿病，其特征是对胰岛素的反应能力减弱。更令人担忧的是，估计有5400万美国人患有糖尿病前期，这种情况使他们处于患2型糖尿病的高危状态。迫切需要以不依赖胰岛素的方式管理这种疾病的新方法。最近，一种不寻常的磷脂，二桂酰磷脂酰胆碱(PC 12：0-12：0；DLPC)，在口服给药时显示出良好的抗糖尿病作用--降低血脂水平，减少脂肪在肝脏中的积聚，并改善糖尿病小鼠的糖耐量。条件性基因敲除研究表明，这些作用完全依赖于孤儿核受体肝脏受体同源1(LRH-1)，从而确定了一个新的LRH-1-DLPC信号轴，参与胆汁酸代谢和葡萄糖动态平衡。我们发现DLPC直接与LRH-1结合，并且DLPC结合在体外完全阻断了辅阻遏子的结合。为了针对这一途径治疗糖尿病，关键是要确定DLPC特异性激活LRH-1的基本机制。我们测定了LRH-1-DLPC复合体的结构为1.9°，这表明DLPC与目前最好的LRH-1合成激动剂的结合方式有很大的不同。我们将利用这一结构以及我们实验室最近的几项创新来确定推动这一独特活动的机制，以增强针对LRH-1的潜在疗法的效力，用于治疗代谢性疾病。本研究的具体目的如下：1.体外测定LRH-1‘S磷脂的特异性；2.确定DLPC与LRH-1的相互作用面并将其与受体功能联系起来；3.确定载脂蛋白LRH-1-辅阻遏子复合体的结构和动力学

DESCRIPTION (provided by applicant): Diabetes is a growing epidemic that currently affects over 25 million people in the US. The majority of these cases (90-95%) are type 2 diabetes, characterized by a diminished ability to respond to insulin. More alarming is that an estimated 54 million Americans have pre-diabetes, a condition that puts them at high risk for developing type 2 diabetes. New ways to manage this disease in an insulin independent manner are urgently needed. Recently, an unusual phospholipid, dilauroylphosphatidylcholine (PC 12:0-12:0; DLPC), has shown promising antidiabetic properties - lowering serum lipid levels, reducing fat accumulation in the liver, and improving glucose tolerance in diabetic mice when administered orally. Conditional knockout studies revealed that these effects were completely dependent on the orphan nuclear receptor liver receptor homologue-1 (LRH-1), thus identifying a new LRH-1 - DLPC signaling axis involved in bile acid metabolism and glucose homeostasis. We show that DLPC binds directly to LRH-1 and that DLPC binding completely blocks corepressor binding in vitro. To target this pathway for the treatment of diabetes it is critical t determine the fundamental mechanism governing the specific activation of LRH-1 by DLPC. We have determined the structure of the LRH-1 - DLPC complex to 1.9 ¿, which shows that DLPC binds very differently than the current best LRH-1 synthetic agonists. We will capitalize on this structure along with several recent innovations in our lab to identify the mechanisms driving this unique activity to enhance the potency of potential therapeutics targeting LRH-1 for the treatment of metabolic diseases. The Specific Aims of this proposal are as follows: 1. To determine LRH-1's phospholipid specificity in vitro, 2. To define the interaction surface between DLPC and LRH-1 and to connect these interactions with receptor function, 3. To determine the structure and dynamics of the apoLRH-1 - corepressor complex