Cullin 7 mediates proteasomal and lysosomal degradations of rat Eag1 potassium channels.
Cullin 7 mediates proteasomal and lysosomal degradations of rat Eag1 potassium channels.
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DOI：
10.1038/srep40825
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发表时间：
2017-01-18
影响因子：
4.6
通讯作者：
Jeng CJ
中科院分区：
文献类型：
--
作者：
Hsu PH;Ma YT;Fang YC;Huang JJ;Gan YL;Chang PT;Jow GM;Tang CY;Jeng CJ
哺乳动物Eag1 （Kv10.1）钾离子通道在大脑中广泛表达。编码人类eag1k +通道的几个基因突变与先天性神经发育异常有关。目前对介导Eag1通道蛋白合成和降解的分子知之甚少。本实验旨在确定大鼠Eag1 （rEag1）蛋白降解机制。我们发现cullin 7 （Cul7）是基于cullin的E3泛素连接酶家族的一员，是一种新的rEag1结合伙伴。免疫沉淀分析证实了Cul7和rEag1在异源细胞和神经组织中的相互作用。Cul7和rEag1在神经元突触区也表现出显著的共定位。过表达Cul7导致蛋白水平降低，泛素化增强，蛋白翻转加速，rEag1通道电流密度降低。我们提供了进一步的生化和形态学证据，表明Cul7分别靶向内质网（ER）和质膜定位的rEag1到蛋白酶体和溶酶体，以进行蛋白质降解。Cul7也有助于疾病相关的rEag1突变体的蛋白质降解。总之，这些结果表明Cul7介导了rEag1的蛋白酶体和溶酶体降解。我们的发现为内质网和外周蛋白质量控制Eag1通道的机制提供了新的见解。
Mammalian Eag1 (Kv10.1) potassium (K+) channels are widely expressed in the brain. Several mutations in the gene encoding human Eag1 K+ channel have been associated with congenital neurodevelopmental anomalies. Currently very little is known about the molecules mediating protein synthesis and degradation of Eag1 channels. Herein we aim to ascertain the protein degradation mechanism of rat Eag1 (rEag1). We identified cullin 7 (Cul7), a member of the cullin-based E3 ubiquitin ligase family, as a novel rEag1 binding partner. Immunoprecipitation analyses confirmed the interaction between Cul7 and rEag1 in heterologous cells and neuronal tissues. Cul7 and rEag1 also exhibited significant co-localization at synaptic regions in neurons. Over-expression of Cul7 led to reduced protein level, enhanced ubiquitination, accelerated protein turn-over, and decreased current density of rEag1 channels. We provided further biochemical and morphological evidence suggesting that Cul7 targeted endoplasmic reticulum (ER)- and plasma membrane-localized rEag1 to the proteasome and the lysosome, respectively, for protein degradation. Cul7 also contributed to protein degradation of a disease-associated rEag1 mutant. Together, these results indicate that Cul7 mediates both proteasomal and lysosomal degradations of rEag1. Our findings provide a novel insight to the mechanisms underlying ER and peripheral protein quality controls of Eag1 channels.