Receptor sorting through tubular microdomains of Rab7-positive endosomes in Charcot- Marie-Tooth disease 2B

通过 Charcot-Marie-Tooth 病 2B 中 Rab7 阳性内体的管状微结构域进行受体分选

• 批准号: 427899738
• 负责人: Dr. Katja Burk, Ph.D.
• 金额: --
• 依托单位: School of Biochemistry and Cell Biology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427899738?language=en
• 关键词: Receptor; sorting; through; tubular; microdomains

Charcot-Marie-Tooth (CMT) disease is an inherited neuropathy which affects the peripheral nervous system, leading to neurodegeneration. Disease onset occurs generally during adolescence or adulthood and is manifested by muscle weakness, loss of fine motor control and sensation in the extremities. In autosomal dominant Charcot-Marie Tooth type 2B (CMT2B), disease is caused by mutations in the late endosomal Rab7-GTPase. In neurons, Rab7- endosomes are important for the trafficking of growth-factors: Following activation by their respective ligand, growth-factor receptors are endocytosed, subsequently sorted into Rab7-positive endosomes and transported retrogradely to the soma where they regulate gene expression of pro-survival genes. Finally, receptors are degraded through the lysosomal pathway. Intriguingly, recent studies have linked CMT2B to impairments in trafficking of Rab7-positive late endosomes, but how mutations in Rab7-GTPase contribute to growth- factor receptors trafficking in CMT2B remains elusive. I hypothesize that endosomes in CMT2B-Rab7 mutants show perturbed sorting abilities due to disturbed formation of tubular microdomains into which receptors are routed during the sorting/trafficking process. Generally, it is considered that sorting occurs on early endosomes where receptors are sorted into the recycling pathways- either directly back to the plasma membrae or through the trans-golgi network (TGN). However, I hypothesize that these tubular microdomains on late endosomes also facilitate receptor sorting, potentially into lysosomes which would be a process uncoupled/in parallel from the process of endosomal maturation. The perturbation in forming such tubular microdomains could therefore affect sorting from Rab7-positive endosomes into lysosomes, defective receptor signalling, a delay in receptor degradation and ultimately downregulation of transcription genes which regulate innervation and/ or survival. All of these effects would explain several of the observed phenotypes in CMT2B, which includes prolonged growth-factor signaling, delay in growth factor sorting into lysosomes and defects in Rab7-endosome trafficking.The main goal of this project is to elucidate the pathogenic mechanisms leading to Charcot-Marie-Tooth type 2B, by focusing on mutations in Rab7-positive late endosomes within the endosomal sorting machinery. I will decipher interactions of Rab7-mutations in CMT2B with the cellular sorting machinery and I will follow subcellular localization of activated growth-factor receptors using high resolution imaging to visualize disturbed trafficking routes. I will address this in mouse DRG neurons as well as iPSC-derived motor- and sensory neurons from CMT2B patients. This proposed work will unravel sorting malfunctions in CMT2B and contribute to the evaluation of new therapeutic approaches by revealing possible target proteins.

腓骨肌萎缩症（CMT）是一种遗传性神经病，影响周围神经系统，导致神经变性。疾病发作通常发生在青春期或成年期，表现为肌肉无力、精细运动控制和四肢感觉丧失。在常染色体显性Charcot-Marie Tooth 2B型（CMT 2B）中，疾病是由晚期内体Rab 7-GT3突变引起的。在神经元中，Rab 7-内体对于生长因子的运输是重要的：在被它们各自的配体激活后，生长因子受体被内吞，随后被分选到Rab 7-阳性内体中，并逆行运输到索马，在那里它们调节促存活基因的基因表达。最后，受体通过溶酶体途径降解。有趣的是，最近的研究已经将CMT 2B与Rab 7阳性晚期内体运输的损伤联系起来，但是Rab 7-GT3中的突变如何有助于CMT 2B中的生长因子受体运输仍然是难以捉摸的。我假设CMT 2B-Rab 7突变体中的内体显示干扰的分选能力，这是由于在分选/运输过程中受体被路由到的管状微区的干扰形成。通常，认为分选发生在早期内体上，其中受体被分选到再循环途径中-直接回到质膜或通过trans-golgi网络（TGN）。然而，我假设晚期内体上的这些管状微结构域也促进受体分选，可能进入溶酶体，这将是与内体成熟过程解耦/平行的过程。因此，形成这种管状微结构域的扰动可能影响从Rab 7阳性内体到溶酶体的分选、缺陷的受体信号传导、受体降解的延迟以及调节神经支配和/或存活的转录基因的最终下调。 所有这些影响将解释几个观察到的表型CMT 2B，其中包括延长生长因子信号，延迟生长因子分选到溶酶体和Rab 7-内体trafficking.The主要目标的缺陷本项目的主要目标是阐明致病机制，导致Charcot-Marie-Tooth型2B，通过专注于突变Rab 7阳性内体内的内体分选机器。我将破译CMT 2B中Rab 7突变与细胞分选机制的相互作用，我将使用高分辨率成像来观察受干扰的贩运途径，从而跟踪活化的生长因子受体的亚细胞定位。我将在小鼠DRG神经元以及来自CMT 2B患者的iPSC衍生的运动和感觉神经元中解决这一问题。这项拟议的工作将解开CMT 2B中的分选故障，并通过揭示可能的靶蛋白来评估新的治疗方法。