Rab7 Mutants Associated with Charcot-Marie-Tooth Disease Cause Delayed Growth Factor Receptor Transport and Altered Endosomal and Nuclear Signaling
Rab7 Mutants Associated with Charcot-Marie-Tooth Disease Cause Delayed Growth Factor Receptor Transport and Altered Endosomal and Nuclear Signaling
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DOI：
10.1074/jbc.m112.417766
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发表时间：
2013-01-11
影响因子：
4.8
通讯作者：
Wandinger-Ness, Angela
中科院分区：
文献类型：
--
作者：
BasuRay, Soumik;Mukherjee, Sanchita;Wandinger-Ness, Angela
Rab7属于小gtpase Ras超家族，是早期到晚期内吞膜运输的主要调节因子。晚期内体Rab7 GTPase的四种错义突变（L129F、K157N、N161T和V162M）导致常染色体显性周围神经病变charco - marie - tooth型2B （CMT2B）疾病。到目前为止，Rab7蛋白突变表达与神经元功能改变之间的病理机制尚不清楚。在这里，我们分析了Rab7 CMT2B突变体对表皮生长因子（EGF）依赖性细胞内信号传导和运输的影响。三种表达Rab7 CMT2B突变体并受EGF刺激的不同细胞系表现出EGF向lamp1阳性的晚期内体和溶酶体转运的延迟，并减缓了EGF受体（EGFR）的降解。所有Rab7 CMT2B突变体的表达改变了Rab7的激活周期，导致EGFR信号传导增强和延长，以及p38和ERK1/2激活的可变增加。然而，由于p38和ERK1/2的核易位减少，Elk-1的下游核激活随着疾病突变体c-fos和Egr-1等直接早期基因的表达而降低。总之，我们的研究结果表明，Rab7 CMT2B突变体损害了生长因子受体的转运，进而改变了核周围聚集性信号核内体的p38和ERK1/2信号。由此产生的egfr依赖性核转录的下调对正常轴突生长和周围神经支配至关重要，这为研究与其他神经退行性疾病相关的疾病发病机制提供了重要的新机制。
Rab7 belongs to the Ras superfamily of small GTPases and is a master regulator of early to late endocytic membrane transport. Four missense mutations in the late endosomal Rab7 GTPase (L129F, K157N, N161T, and V162M) cause the autosomal dominant peripheral neuropathy Charcot-Marie-Tooth type 2B (CMT2B) disease. As yet, the pathological mechanisms connecting mutant Rab7 protein expression to altered neuronal function are undefined. Here, we analyze the effects of Rab7 CMT2B mutants on epidermal growth factor (EGF)-dependent intracellular signaling and trafficking. Three different cell lines expressing Rab7 CMT2B mutants and stimulated with EGF exhibited delayed trafficking of EGF to LAMP1-positive late endosomes and lysosomes and slowed EGF receptor (EGFR) degradation. Expression of all Rab7 CMT2B mutants altered the Rab7 activation cycle, leading to enhanced and prolonged EGFR signaling as well as variable increases in p38 and ERK1/2 activation. However, due to reduced nuclear translocation of p38 and ERK1/2, the downstream nuclear activation of Elk-1 was decreased along with the expression of immediate early genes like c-fos and Egr-1 by the disease mutants. In conclusion, our results demonstrate that Rab7 CMT2B mutants impair growth factor receptor trafficking and, in turn, alter p38 and ERK1/2 signaling from perinuclear, clustered signaling endosomes. The resulting down-regulation of EGFR-dependent nuclear transcription that is crucial for normal axon outgrowth and peripheral innervation offers a crucial new mechanistic insight into disease pathogenesis that is relevant to other neurodegenerative diseases.