TRIB2 desensitizes ferroptosis via \u03b2TrCP-mediated TFRC ubiquitiantion in liver cancer cells

Susu Guo,Yueyue Yang,Yongxia Qiao,Lifang Ma,Xiao Zhang,Jiayi Wang,Xiangfei Xue,Shiyu Qiu,Yuxin Chen,Yikun Wang,Jiangtao Cui

doi:10.1038/s41420-021-00574-1

Abstract

Tribbles homolog 2 (TRIB2) is known to boost liver tumorigenesis via regulating Ubiquitin (Ub) proteasome system (UPS). At least two ways are involved, i.e., acts as an adaptor protein to modulate ubiquitination functions of certain ubiquitin E3 ligases (E3s) and reduces global Ub levels via increasing the proteolysis activity of proteasome. Recently, we have identified the role of TRIB2 to relieve oxidative damage via reducing the availability of Ub that is essential for the ubiquitination and subsequent degradation of Glutathione peroxidase 4 (GPX4). Although GPX4 is a critical antioxidant factor to protect against ferroptosis, the exact evidence showing that TRIB2 desensitizes ferroptosis is lacking. Also, whether such function is via E3 remains unclear. Here, we demonstrated that deletion of TRIB2 sensitized ferroptosis via lifting labile iron in liver cancer cells. By contrast, overexpression of TRIB2 led to the opposite outcome. We further demonstrated that transferrin receptor (TFRC) was required for TRIB2 to desensitize the cells to ferroptosis. Without TFRC, the labile iron pool could not be reduced by overexpressing TRIB2. We also found that beta-transducin repeat containing E3 ubiqutin protein ligase (βTrCP) was a genuine E3 for the ubiquitination of TFRC, and TRIB2 was unable to decline labile iron level once upon βTrCP was knocked out. In addition, we confirmed that the opposite effects on ferroptosis and ferroptosis-associated lipid reactive oxygen species (ROS) generation resulted from knockout and overexpression of TRIB2 were all indispensible of TFRC and βTrCP. Finally, we demonstrated that TRIB2 exclusively manipulated RSL3- and erastin-induced-ferroptosis independent of GPX4 and glutathione (GSH). In conclusion, we elucidated a novel role of TRIB2 to desensitize ferroptosis via E3 βTrCP, by which facilitates TFRC ubiquitiation and finally decreases labile iron in liver cancer cells.

Highlights

Tribbles homolog 2 (TRIB2) is a pseudokinase that has a major function to act as a molecular adaptor mediating protein ubiquitination and followed destabilization via E3 ligases (E3s) [1]
We demonstrated that TRIB2 acts as an adaptor protein, which is essential for E3 βTrCP-mediated whether TRIB2 influences the levels of arachidonic acid (AA) and adrenic acid (AdA) in the membrane
To investigate whether TRIB2 desensitizes liver cancer cells to transferrin receptor (TFRC) was essential for TRIB2 to reduce labile iron in liver ferroptosis, a serial of liver cancer cell lines including Bel-7404, Bel- cancer cells

Summary

Introduction

TRIB2 is a pseudokinase that has a major function to act as a molecular adaptor mediating protein ubiquitination and followed destabilization via E3s [1]. An unique feature distinguishing TRIB2 from other genuine protein kinases is that TRIB2 has an atypical pseudokinase domain retaining a regulated binding platform for context-specific E3s to ubiquitinate substrates [1]. Vast majority of studies have suggested that TRIB2 can interact with a serial of E3s, such as βTrCP [2], SMAD specific E3 ubiquitin protein ligase 1 (Smurf1, [3]) and COP1 E3 ubiquitin ligase (COP1, [4]) at its C terminus. The roles of TRIB2 are expanded by our study demonstrating that TRIB2 can modulate proteasome function for the reduction of global Ub and protection of liver cancer cells against oxidative stress [5]. Whether TRIB2 modulates the sensitivity of cells to the induction of ferroptosis is not known far

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Results

Conclusion