Characterization of KIFAP3, a Modifier of Survival in Sporadic ALS

描述（由申请人提供）：肌萎缩侧索硬化症（ALS）是一种致死性、年龄依赖性神经退行性疾病，典型生存期为2-5年。除了可能的SMN基因拷贝数减少或SOD 1A 4V基因突变的存在外，尚未描述影响ALS生存率的遗传因素。我们最近报道，在散发性ALS的生存率提高了基因变异，减少KIFAP 3的表达，驱动蛋白II复合体，介导快速顺行轴突运输的蛋白质成分。有利等位基因的纯合子具有14.0个月的生存优势，这是一个实质性的改善（~42%），超过了FDA批准用于ALS的单一药物（利鲁唑）的获益幅度。最近的一项研究证明，KIFAP 3在ALS小鼠中结合错误折叠的SOD 1G 93 A，并且在SOD 1G 93 A小鼠和携带SOD 1基因突变的ALS患者的脊髓中与突变的SOD 1蛋白共定位在聚集体中。这些发现支持了轴突转运蛋白，特别是KIFAP 3是运动神经元活力的决定因素的观点。该提案将研究KIFAP 3表达减少增加ALS患者生存率的机制。本研究的具体目的是：（1）分析人散发性ALS脊髓中KIFAP 3、SOD 1和其他货物之间的相互作用。假设：在散发性ALS中，错误折叠的野生型SOD 1与KIFAP 3结合，但不与对照脊髓结合。(2)确定KIFAP 3表达降低对转基因SOD 1G 93 A小鼠中运动神经元活力和存活的影响。假设：与人ALS中的存活类似，转基因ALS小鼠中的运动神经元活力和存活将通过KIFAP 3的表达减少而增强。(3)分析ALS小鼠和KIFAP 3水平正常和降低的对照小鼠脊髓中KIFAP 3、SOD 1和其他货物之间的相互作用。假设：KIFAP 3表达减少将改变KIFAP 3运输的货物的类型和数量。(4)确定KIFAP 3表达水平改变对ALS和对照小鼠胚胎运动神经元轴突转运速率的影响。假设：KIFAP 3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KIFAP 3表达调节ALS生存的机制。从长远来看，了解KIFAP 3如何影响生存将有助于开发延长ALS患者寿命的疗法。 公共卫生相关性：肌萎缩侧索硬化症（ALS），也被称为Lou Gehrig病，是一种均匀致命的，年龄依赖性神经退行性疾病，典型的生存期为2至5年。通过我们的努力，我们已经确定了一个基因，它可以影响散发性ALS的生存优势14.0个月，在这种疾病中有很大的增加（42%）。这项提案的目的是了解这种基因如何影响生存，这将有助于制定治疗策略，以延长ALS患者的寿命。

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.