Competitive oxidation and ubiquitylation on the evolutionarily conserved cysteine confer tissue-specific stabilization of Insig-2

Zhang-Sen Zhou,Hengwu Jiao,Jie Luo,Jie Liu,Bao-Liang Song,Liping Chu,Mei-Xin Li,Xiong-Jie Shi,Jingrong Liu,Jing-Ming Xia,Huabin Zhao,Wei Qi

doi:10.1038/s41467-019-14231-w

Zhang-Sen Zhou, Hengwu Jiao + Show 10 more

Open Access

https://doi.org/10.1038/s41467-019-14231-w

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Journal: Nature Communications	Publication Date: Jan 17, 2020
Citations: 12	License type: open-access

Affiliation: Wuhan University, ShanghaiTech University

Abstract

Insig-2 is an ER membrane protein negatively controlling lipid biosynthesis. Here, we find that Insig-2 is increased in the tissues, including liver, but unaltered in the muscle of gp78-deficient mice. In hepatocytes and undifferentiated C2C12 myoblasts, Insig-2 is ubiquitylated on Cys215 by gp78 and degraded. However, the C215 residue is oxidized by elevated reactive oxygen species (ROS) during C2C12 myoblasts differentiating into myotubes, preventing Insig-2 from ubiquitylation and degradation. The stabilized Insig-2 downregulates lipogenesis through inhibiting the SREBP pathway, helping to channel the carbon flux to ATP generation and protecting myotubes from lipid over-accumulation. Evolutionary analysis shows that the YECK (in which C represents Cys215 in human Insig-2) tetrapeptide sequence in Insig-2 is highly conserved in amniotes but not in aquatic amphibians and fishes, suggesting it may have been shaped by differential selection. Together, this study suggests that competitive oxidation-ubiquitylation on Cys215 of Insig-2 senses ROS and prevents muscle cells from lipid accumulation.

Highlights

Insulininduced gene (Insig)-2 is an ER membrane protein negatively controlling lipid biosynthesis
We demonstrate that Insig-2 is ubiquitylated on Cys[215] by gp[78]
Since Insig[2] negatively regulates sterol regulatory element-binding proteins (SREBPs) processing[1], we analyzed the expression of an array of SREBP target genes in the liver and skeletal muscle by quantitative polymerase chain reaction

Summary

Introduction

Insig-2 is an ER membrane protein negatively controlling lipid biosynthesis. Here, we find that Insig-2 is increased in the tissues, including liver, but unaltered in the muscle of gp78deficient mice. The C215 residue is oxidized by elevated reactive oxygen species (ROS) during C2C12 myoblasts differentiating into myotubes, preventing Insig-2 from ubiquitylation and degradation. This study suggests that competitive oxidation-ubiquitylation on Cys[215] of Insig-2 senses ROS and prevents muscle cells from lipid accumulation. Genetic deletion of Insigs resulted in robust increases in mRNA abundance of lipogenic genes and HMGCR protein level, as well as overaccumulation of cholesterol and triglyceride in the liver. Oxidization of Cys[215] in myotubes by reactive oxygen species (ROS) outcompetes ubiquitylation and protectes Insig-2 from degradation, which prevents muscle cells from lipid overaccumulation. Our study reveals a tissue-specific regulation of Insig-2 stability through oxidation and ubiquitylation on Cys[215] residue and implicates a link between metabolic oxidative state and lipid biosynthesis

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