The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1
The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1
复制标题
DOI：
10.1101/391789
复制
发表时间：
2018-08
期刊：
影响因子：
7.7
通讯作者：
Sam A. Menzies;Norbert Volkmar;D. J. van den Boomen;R. Timms;Anna S Dickson;J. Nathan;P. Lehner
中科院分区：
文献类型：
--
作者：
Sam A. Menzies;Norbert Volkmar;D. J. van den Boomen;R. Timms;Anna S Dickson;J. Nathan;P. Lehner
HMG-CoA还原酶（HMGCR）是胆固醇生物合成途径的限速酶，也是他汀类药物的治疗靶点，受固醇加速降解的转录后调节。在胆固醇充足的条件下，HMGCR被泛素化和降解，但负责哺乳动物HMGCR周转的E3泛素连接酶的身份仍有争议。使用系统的，无偏见的CRISPR/Cas9全基因组筛选与甾醇敏感的内源性HMGCR报告，我们全面绘制了甾醇加速HMGCR降解所需的E3连接酶景观。我们发现，RNF 145和gp 78，独立协调HMGCR泛素化和降解。RNF 145是一种甾醇响应性ER驻留E3连接酶，不稳定，但在甾醇耗尽后积累。甾醇添加触发RNF 145募集到HMGCR和Insig-1，促进HMGCR泛素化和蛋白酶体介导的降解。在RNF 145和gp 78都不存在的情况下，第三种UBE 2G 2依赖性连接酶Hrd 1部分调节HMGCR活性。我们的研究结果揭示了一个关键的作用，甾醇响应RNF 145在HMGCR调节和阐明甾醇加速HMGCR降解的复杂性。
HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78, independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR and Insig-1, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent ligase partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation.