LZTR1 facilitates polyubiquitination and degradation of RAS-GTPases
LZTR1 facilitates polyubiquitination and degradation of RAS-GTPases
复制标题
DOI：
10.1038/s41418-019-0395-5
复制
发表时间：
2020-03-01
影响因子：
12.4
通讯作者：
Aoki, Yoko
中科院分区：
文献类型：
--
作者：
Abe, Taiki;Umeki, Ikumi;Aoki, Yoko
亮氨酸拉链样转录调节因子1（LZTR 1）编码BTB-Kelch超家族的一个成员，其与基于Cullin 3（CUL 3）的E3泛素连接酶复合物相互作用。LZTR 1突变已在胶质母细胞瘤、神经鞘瘤病和努南综合征中被鉴定。然而，LZTR 1在致癌或人类发育中的功能作用尚未完全了解。在这里，我们证明LZTR 1通过泛素-蛋白酶体途径促进RAS的多聚泛素化和降解，从而抑制RAS/MAPK信号传导。在表达MRAS、HRAS、NRAS和KRAS以及致癌RAS突变体的细胞中也观察到RAS的多泛素化和降解，并抑制ERK 1/2的活化和细胞生长。体内泛素化实验表明，MRAS-K127和HRAS-K170被LZTR 1泛素化，其多聚泛素化链主要含有Ub-K48、K63和K33连接链，提示其可能参与自噬。免疫沉淀分析显示LZTR 1和RAS-GTP酶与自噬相关蛋白，包括LC 3B和SQSTM 1/p62的相互作用。LZTR 1和RAS的共表达增加了脂化形式的LC 3B的表达。然而，氯喹的长期治疗对RAS蛋白水平几乎没有影响，表明自噬对LZTR 1介导的RAS降解的贡献很小。综上所述，这些结果表明，LZTR 1作为“RAS杀伤蛋白”主要通过泛素蛋白酶体途径发挥作用，而不管RAS GT酶的类型如何，控制下游信号转导。我们的研究结果还表明LZTR 1和RAS-GTP酶与自噬可能相关。这些发现为阐明RAS降解机制和RAS/MAPK信号级联调控提供了线索。
Leucine zipper-like transcriptional regulator 1 (LZTR1) encodes a member of the BTB-Kelch superfamily, which interacts with the Cullin3 (CUL3)-based E3 ubiquitin ligase complex. Mutations in LZTR1 have been identified in glioblastoma, schwannomatosis, and Noonan syndrome. However, the functional role of LZTR1 in carcinogenesis or human development is not fully understood. Here, we demonstrate that LZTR1 facilitates the polyubiquitination and degradation of RAS via the ubiquitin-proteasome pathway, leading to the inhibition of the RAS/MAPK signaling. The polyubiquitination and degradation of RAS was also observed in cells expressing MRAS, HRAS, NRAS, and KRAS as well as oncogenic RAS mutants and inhibited the activation of ERK1/2 and cell growth. In vivo ubiquitination assays showed that MRAS-K127 and HRAS-K170 were ubiquitinated by LZTR1 and that the polyubiquitinated-chains contained mainly Ub-K48, K63, and K33linked chains, suggesting its possible involvement in autophagy. Immunoprecipitation analyses showed the interaction of LZTR1 and RAS-GTPases with autophagy-related proteins, including LC3B and SQSTM1/p62. Co-expression of LZTR1 and RAS increased the expression of lipidated form of LC3B. However, long- term treatment with chloroquine had little effect on RAS protein levels, suggesting that the contribution of autophagy to LZTR1-mediated RAS degradation is minimal. Taken together, these results show that LZTR1 functions as a "RAS killer protein" mainly via the ubiquitinproteasome pathway regardless of the type of RAS GTPase, controlling downstream signal transduction. Our results also suggest a possible association of LZTR1 and RAS-GTPases with the autophagy. These findings provide clues for the elucidation of the mechanisms of RAS degradation and regulation of the RAS/MAPK signaling cascade.