Characterization of KIFAP3, a Modifier of Survival in Sporadic ALS

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS）是一种致命的、年龄依赖性的神经退行性疾病，典型生存期为2-5年。可能除了SMN基因拷贝数减少或SOD1A4V基因突变的存在外，影响ALS患者生存的遗传因素尚未被描述。我们最近报道，散发性ALS患者的生存率通过降低KIFAP3表达的遗传变异而提高，KIFAP3是一种介导快速顺行轴突运输的激酶II复合体的蛋白质成分。有利等位基因的纯合子具有14.0个月的生存优势，这是一个显著的改善（~42%），超过了FDA批准用于治疗ALS的单一药物（利鲁唑）的获益幅度。最近的一项研究表明，在ALS小鼠中，KIFAP3结合错误折叠的SOD1G93A，并与突变的SOD1蛋白共定位，聚集在SOD1G93A小鼠和SOD1基因突变的ALS患者脊髓中。这些发现支持轴突转运蛋白，特别是KIFAP3，是运动神经元活力的决定因素的观点。本研究将探讨KIFAP3表达降低提高ALS患者生存率的机制。本提案的具体目的是：(1)分析人类散发性ALS脊髓中KIFAP3、SOD1和其他基因的相互作用。假设：在散发性ALS中，错误折叠的野生型SOD1与KIFAP3结合，但不控制脊髓。(2)测定KIFAP3表达降低对转基因SOD1G93A小鼠运动神经元活力和存活的影响。假设：与人类ALS的存活类似，通过降低KIFAP3的表达，可以提高转基因ALS小鼠的运动神经元活力和存活。(3)分析ALS脊髓中KIFAP3、SOD1与其他物质的相互作用，并对照KIFAP3水平正常和降低的小鼠。假设：KIFAP3表达的降低会改变由KIFAP3运输的货物的种类和数量。(4)确定KIFAP3表达水平改变对ALS和对照小鼠胚胎运动神经元轴突转运率的影响。假设：KIFAP3表达水平的改变不是轴突运输速率的决定因素。我们提出的研究将阐明KIFAP3表达调节ALS生存的机制。从长远来看，了解KIFAP3如何影响生存将有助于开发延长ALS患者寿命的治疗方法。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a uniformly lethal, age-dependent neurodegenerative disorder with a typical survival of 2-5 years. With the possible exception of reduced numbers of copies of the SMN gene, or the presence of the SOD1A4V gene mutation, genetic factors that influence survival in ALS have not been described. We recently reported that survival in sporadic ALS is enhanced by genetic variants that reduce expression of KIFAP3, a protein constituent of a kinesin II complex that mediates fast anterograde axonal transport. Homozygotes for the favorable allele have a survival advantage of 14.0 months, a substantial improvement (~42%) that surpasses the magnitude of benefit of the single drug (riluzole) that is FDA approved for ALS in ALS. A recent study documents that KIFAP3 binds misfolded SOD1G93A in ALS mice and is co-localized with the mutant SOD1 protein in aggregates both in the SOD1G93A mouse and in spinal cords of ALS patients bearing mutations in the SOD1 gene. These findings support the view that axonal transport proteins, and KIFAP3 in particular, are determinants of motor neuron viability. This proposal will investigate the mechanisms by which decreased expression of KIFAP3 increases survival in ALS. The Specific Aims of this proposal are to: (1) Analyze the interactions between KIFAP3, SOD1 and other cargoes in human sporadic ALS spinal cords. Hypothesis: Misfolded, wild-type SOD1 binds to KIFAP3 in sporadic ALS but not control spinal cords. (2) Determine the effect of reduced KIFAP3 expression on motor neuron viability and survival in transgenic SOD1G93A mice. Hypothesis: By analogy with survival in human ALS, motor neuron viability and survival in transgenic ALS mice will be enhanced by reduced expression of KIFAP3. (3) Analyze the interactions between KIFAP3, SOD1 and other cargoes in spinal cord from ALS and control mice with normal and reduced levels of KIFAP3. Hypothesis: Decreased expression of KIFAP3 will alter the types and quantities of cargoes transported by KIFAP3. (4) Determine the influence of altered expression levels of KIFAP3 on axonal transport rates in embryonic motor neurons from ALS and control mice. Hypothesis: Altered levels of KIFAP3 expression are not determinants of axonal transport rates. Our proposed studies will elucidate the mechanisms whereby KIFAP3 expression modulates survival in ALS. In the long term, understanding how KIFAP3 influences survival will facilitate the development of therapies to extend the lifespan of ALS patients. PUBLIC HEALTH RELEVANCE: Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a uniformly lethal, age-dependent neurodegenerative disorder with a typical survival of 2 to 5 years. Through our efforts, we have identified a gene which can influence the survival advantage of sporadic ALS by 14.0 months, a substantial increment (42%) in this disease. The purpose of this proposal is to understand how this gene influences survival, which will aid in the development of treatment strategies to extend the lifespan of patients afflicted with ALS.