Functional Characterization and Physiological Consequences of Human Longevity-Associated IGF1R Variants

 描述（由申请方提供）：虽然有压倒性的证据表明，在无脊椎动物和小鼠模型中，胰岛素/胰岛素样生长因子-1（IGF 1）信号转导（IIS）减少可延长寿命，但这种进化保守途径对人类寿命的影响仍不清楚。Suh实验室的研究已经导致在IGF-1受体基因（IGF 1 R）中发现两个百岁老人富集的错义突变，A37 T（M1）和R407 H（M2），与非携带者相比，与从携带者建立的淋巴细胞中IIS降低相关（Suh et al.，PNAS，2008）。当在Igf 1 r缺失小鼠胚胎成纤维细胞中表达时，显示M1和M2变体相对于野生型人IGF 1 R引起IGF 1信号传导的减弱、IGF 1活化基因的表达降低和细胞周期进展延迟（Tazearslan等人，Aging Cell，2011）。虽然IIS与寿命的关联是已知的，但IIS在调节人类寿命中的具体作用，包括IIS组分中的错义突变如何改变生存和疾病风险，尚不清楚。本提案的目的是阐明IGF-1受体错义突变促进长寿的分子和生理机制，使用表达百岁老人富集变体受体的细胞和携带百岁老人相关变体敲入的小鼠。已经在小鼠中研究了IGF-1受体与衰老的关系，但仅在敲除或杂合缺陷的情况下进行。IGF-1受体在调节细胞和生物体生理学中具有多种作用，包括非受体功能和通过二聚化修饰其他膜结合受体。此外，IGF-1受体的刺激通过特异性配体-受体相互作用激活多个不同的细胞内信号级联，我们的初步数据显示，IGF-1受体中的百岁老人相关突变以组织特异性方式差异性地影响这些下游信号通路。为了实现这一目标，我们将（1）在基于细胞的测定中检查IGF 1 R变体的加工、组装、蛋白质-蛋白质相互作用以及对信号传导的影响;（2）使用我们产生的敲入模型来确定百岁老人相关IGF 1 R变体对小鼠生长、代谢和体内胰岛素/IGF-1信号传导的影响;（3）确定百岁老人相关IGF 1 R变体对高脂饮食反应的影响，这是年龄相关代谢疾病的模型。我们假设百岁老人相关的IGF 1 R变异体对细胞和生物体生理学具有功能相关的影响，这是由于蛋白质功能的变化。我们进一步假设，这些作用在功能上部分不同于简单降低IGF-1受体水平，包括对下游信号传导和IGF 1 R非受体功能的差异作用。最后，我们预测这些分子变化和细胞效应将导致小鼠基因敲入模型中有益的系统功能变化，这些变化是与人类长寿相关的基础，包括高脂饮食模式中对代谢应激的抵抗力。了解自然发生的百岁老人相关IGF 1 R遗传变异的生理作用，将为基于我们描述的分子机制预防和治疗年龄相关疾病的治疗策略的未来发展铺平道路。

 DESCRIPTION (provided by applicant): While there is overwhelming evidence that reduced insulin/insulin like growth factor-1 (IGF1) signaling (IIS) extends lifespan in invertebrate and murine models, the impact of this evolutionarily conserved pathway on human longevity remains unclear. Research in the Suh lab has led to the discovery of two centenarian- enriched missense mutations in the IGF-1 receptor gene (IGF1R), A37T (M1) and R407H (M2), associated with decreased IIS in lymphocytes established from carriers as compared to non-carriers (Suh et al., PNAS, 2008). The M1 and M2 variants were shown to cause attenuation of IGF1 signaling, reduced expression of IGF1-activated genes, and delayed cell cycle progression relative to wild-type human IGF1R when expressed in Igf1r null mouse embryonic fibroblasts (Tazearslan et al., Aging Cell, 2011). While the association of IIS with longevity is known, the specific role of IIS in regulating human lifespan, including how missense mutations in IIS components modify survival and disease risk, is not known. The goal of this proposal is to elucidate the molecular and physiological mechanisms of longevity promotion by missense mutations in the IGF-1 receptor using cells expressing centenarian enriched variant receptor and mice carrying a knock-in of a centenarian associated variant. The IGF-1 receptor has been studied in mice in respect to aging but only in the context of knockout, or heterozygous deficiency. The IGF-1 receptor has multiple roles in regulating cellular and organism physiology including non-receptor functions and modification of other membrane bound receptors through dimerization. In addition, stimulation of the IGF-1 receptor activates multiple distinct intracelluar signaling cascades through specific ligand-receptor interactions and our preliminary data shows that centenarian associated mutations in IGF-1 receptor differentially affect these downstream signaling pathways in a tissue specific manner. In order to address this goal we will (1) examine IGF1R variant processing, assembly, protein-protein interaction, and impact on signaling in cell based assays; (2) define the effects of a centenarian associated IGF1R variant on growth, metabolism, and in vivo insulin/IGF-1 signaling in mice using the knock-in model we have produced; (3) determine the impact of the centenarian associated IGF1R variant on the response to high- fat diet, a model for age-related metabolic disease. We hypothesize that centenarian associated IGF1R variants have functionally relevant effects on cellular and organism physiology resulting from changes to protein function. We further hypothesize that these effects will be partly functionally distinct from simply reducing levels of IGF-1 receptor, including differential effects on downstream signaling and non-receptor functions of IGF1R. Lastly, we predict that these molecular changes and cellular effects will lead to beneficial systemic functional changes in the mouse knock-in model that underlie the association to human longevity, including resistance to metabolic stress in the high-fat diet paradigm. Understanding the physiological role of naturally occurring centenarian associated IGF1R genetic variation will pave the way for future development of therapeutic strategies for preventing and treating age-related disease based on the molecular mechanisms we describe.