Phosphoinositide signaling: novel potential targets for Huntington disease

亨廷顿病(HD)是一种由CAG引起的常染色体显性遗传性神经退行性疾病 亨廷顿(Htt)基因外显子1的三核苷酸重复扩增。目前还没有有效的治疗方法 这种致命的疾病。因此，确定新的靶向途径以减轻亨廷顿病是至关重要的。我们 发现了两个靶点，它们可以降低突变的HTT蛋白(MHTT)，从而具有改变疾病的潜力 心理治疗。在无偏倚的高通量筛选中，我们发现了PIP4Kγ-INH，一种PIP4Kγ的变构抑制剂。 用PIP4Kγ-INH处理HdhQ111敲入小鼠纹状体神经元，可降低HTTQ111的表达水平。 此外，亨廷顿患者成纤维细胞暴露于抑制或击倒PIP4Kγ，减少突变 亨廷顿蛋白。PIP4Kγ将PI5P转换为PI(4，5)P2。我们确定了哪些肌醇磷脂是 受PIP4Kγ-异烟肼的影响，并确定了一种正交法来诱导这些脂类的类似变化。 值得注意的是，这种新方法可能还会降低突变的HTT聚集体。事实上，亨廷顿蛋白的共同表达 外显子1-PolyQ74-GFP(HttQ74-GFP)结合脂蛋白激酶的激活使HttQ74聚集体减少 &gt；35%。因此，改变磷脂酰肌醇脂类的正交方法有可能降低HD水平。 这项提案的总体目标是确定是否抑制PIP4Kγ和/或激活脂蛋白激酶 应测试改善HD相关表型的可能性。这一目标将与 目的如下：1)确定特定脂蛋白激酶激活对突变型HTT细胞水平的影响。 2)确定抑制PIP4Kγ或激活特定脂蛋白激酶降低突变株的机制 HTT。3)确定抑制PIP4Kγ和/或激活特定的脂蛋白激酶是否可以减轻疾病 HD动物模型的发病机制。我们预测这些研究的结果将揭示其中一项或 这两种脂激酶靶点都是有吸引力的选择，可以作为可能的疾病改良剂在 临床前研究。

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in exon 1 of the Huntingtin (HTT) gene. There are no effective treatments for this fatal disease. Thus, identification of new target pathways to mitigate Huntington's disease is critical. We discovered two targets that lower mutant HTT protein (mHTT) and thus hold potential for disease-modifying therapy. In an unbiased, high-throughput screen, we discovered PIP4Kγ-INH, an allosteric inhibitor of PIP4Kγ. Treatment of HdhQ111 knock-in mouse striatal neurons with PIP4Kγ-INH, reduced the levels of HTTQ111. Moreover, exposure of Huntington patient fibroblasts to inhibition or knock-down of PIP4Kγ, reduced mutant huntingtin protein. PIP4Kγ converts PI5P to PI(4,5)P2. We determined which phosphoinositide lipids are impacted by PIP4Kγ-INH, and identified an orthogonal approach to induce similar changes in these lipids. Notably this new approach might also lower mutant HTT aggregates. Indeed, co-expression of huntingtin exon1-polyQ74-GFP (httQ74-GFP) combined with activation of a lipid kinase reduced httQ74 aggregates by >35%. Thus, orthogonal approaches that change phosphoinositide lipids have the potential to lower HD levels. The overall goal of this proposal is to determine whether inhibition of PIP4Kγ and/or activation of a lipid kinase should be test for the potential to ameliorate phenotypes associated with HD. This goal will be pursued with the following aims: 1) Determine the effects of activation of a specific lipid kinase on cellular levels of mutant HTT. 2) Determine mechanisms whereby inhibition of PIP4Kγ or activation of a specific lipid kinase lowers mutant HTT. 3) Determine whether inhibition of PIP4Kγ and/or activation of a specific lipid kinase mitigates disease pathogenesis in animal models of HD. We predict that the outcomes of these studies will reveal that one or both lipid kinase targets are attractive options for further testing as possible disease-modifying agents in preclinical studies.