Characterization of KIFAP3, a Modifier of Survival in Sporadic ALS

描述(申请人提供)：肌萎缩侧索硬化症(ALS)是一种一致致命的、与年龄相关的神经退行性疾病，典型的生存时间为2-5年。除了SMN基因拷贝数减少或SOD1A4V基因突变的可能例外，影响ALS生存的遗传因素尚未被描述。我们最近报道，散发性ALS的存活率通过减少KIFAP3的表达而提高，KIFAP3是激动素II复合体的一种蛋白质成分，介导快速顺行轴突运输。携带有利等位基因的纯合子有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ALS的单一药物(利鲁唑)的益处幅度。最近的一项研究证明，KIFAP3在ALS小鼠中与错误折叠的SOD1G93A结合，并与突变的SOD1蛋白在SOD1G93A小鼠和携带SOD1基因突变的ALS患者的脊髓中以聚集体的形式共存。这些发现支持轴突运输蛋白，尤其是KIFAP3，是运动神经元活性的决定因素的观点。这项建议将探讨KIFAP3表达减少提高ALS患者存活率的机制。本研究的具体目的是：(1)分析KIFAP3、SOD1与人类散发性ALS脊髓中其他物质之间的相互作用。假设：在散发性肌萎缩侧索硬化症中，错误折叠的野生型SOD1与KIFAP3结合，但不是对照脊髓。(2)检测KIFAP3基因表达降低对转基因SOD1G93A小鼠运动神经元活性和存活的影响。假设：类似于人类ALS的存活，KIFAP3的表达减少将提高转基因ALS小鼠的运动神经元活性和存活率。(3)分析肌萎缩侧索硬化症小鼠和正常和低水平KIFAP3小鼠脊髓中KIFAP3、SOD1与其他物质的相互作用。假设：KIFAP3的表达减少将改变KIFAP3运输的货物的类型和数量。(4)检测KIFAP3表达水平的改变对ALS和对照组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转运率的决定因素。我们提出的研究将阐明KIFAP3表达调节ALS患者生存的机制。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。 公共卫生相关性：肌萎缩侧索硬化症(ALS)，也被称为Lou Gehrig病，是一种一致致命的、与年龄相关的神经退行性疾病，典型的生存时间为2至5年。通过我们的努力，我们已经发现了一个基因，它可以影响散发性ALS患者14.0个月的生存优势，在这种疾病中大幅增加了42%。这项建议的目的是了解该基因如何影响生存，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.