Phosphoinositide signaling: novel potential targets for Huntington disease

亨廷顿氏病（Huntington's disease，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中的三核苷酸重复扩增。没有有效的治疗方法 这种致命的疾病。因此，鉴定新的靶向途径以减轻亨廷顿病是至关重要的。我们 发现了两个降低突变HTT蛋白（mHTT）的靶点，从而具有改善疾病的潜力。 疗法在无偏高通量筛选中，我们发现了PIP 4K γ-INH，一种PIP 4K γ的变构抑制剂。 用PIP 4K γ-INH处理HdhQ 111敲入小鼠纹状体神经元，降低了HTTQ 111的水平。 此外，将亨廷顿病患者成纤维细胞暴露于PIP 4 K γ的抑制或敲低，降低了突变型PIP 4 K γ的表达。 亨廷顿蛋白PIP 4K γ将PI 5 P转化为PI（4，5）P2。我们确定了哪些磷酸肌醇脂质 受PIP 4K γ-INH的影响，并确定了一种正交方法来诱导这些脂质的类似变化。 值得注意的是，这种新方法也可能降低突变HTT聚集体。事实上，亨廷顿蛋白的共同表达 外显子1-polyQ 74-GFP（httQ 74-GFP）与脂质激酶的激活结合，通过以下方式减少httQ 74聚集体： > 35%。因此，改变磷酸肌醇脂质的正交方法有可能降低HD水平。 本提案的总体目标是确定PIP 4K γ的抑制和/或脂质激酶的激活是否 应该测试改善HD相关表型的潜力。这一目标将与 以下目的：1）确定特定脂质激酶的活化对突变HTT的细胞水平的影响。 2)确定抑制PIP 4K γ或激活特定脂质激酶降低突变的机制 HTT。3)确定PIP 4K γ的抑制和/或特定脂质激酶的激活是否减轻疾病 HD动物模型的发病机制。我们预测，这些研究的结果将揭示， 这两种脂质激酶靶点都是进一步测试作为可能的疾病修饰剂的有吸引力的选择， 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.