Hepatic PPARα function is controlled by polyubiquitination and proteasome‐mediated degradation through the coordinated actions of PAQR3 and HUWE1

Abstract

Peroxisome proliferator‐activated receptor α (PPARα) is a key transcriptional factor that regulates hepatic lipid catabolism by stimulating fatty acid oxidation and ketogenesis in an adaptive response to nutrient starvation. However, how PPARα is regulated by posttranslational modification is poorly understood. In this study, we identified that progestin and adipoQ receptor 3 (PAQR3) promotes PPARα ubiquitination through the E3 ubiquitin ligase HUWE1, thereby negatively modulating PPARα functions both in vitro and in vivo. Adenovirus‐mediated Paqr3 knockdown and liver‐specific deletion of the Paqr3 gene reduced hepatic triglyceride levels while increasing fatty acid oxidation and ketogenesis upon fasting. PAQR3 deficiency enhanced the fasting‐induced expression of PPARα target genes, including those involved in fatty acid oxidation and fibroblast growth factor 21, a key molecule that mediates the metabolism‐modulating effects of PPARα. PAQR3 directly interacted with PPARα and increased the polyubiquitination and proteasome‐mediated degradation of PPARα. Furthermore, the E3 ubiquitin ligase HUWE1 was identified to mediate PPARα polyubiquitination. Additionally, PAQR3 enhanced the interaction between HUWE1 and PPARα. Conclusion: Ubiquitination modification through the coordinated action of PAQR3 with HUWE1 plays a crucial role in regulating the activity of PPARα in response to starvation. (Hepatology 2018;68:289‐303).

PAQR3 Regulates Endoplasmic Reticulum-to-Golgi Trafficking of COPII Vesicle via Interaction with Sec13/Sec31 Coat Proteins

“…We also investigated the structural domain of PAQR3 involved in the interaction by constructing a series of PAQR3 deletion mutants. By co-immunoprecipitation assays, we found that deletion of N-terminal 1–70 amino acids of PAQR3 led to loss of the binding capacity of PAQR3 with Sec13 and Sec31A ( Figures 5 F and 5G), consistent with our previous studies showing that the N-terminus of PAQR3 is required for Golgi localization and is important for its functions by interacting with multiple proteins ( Luo et al., 2008 , Xu et al., 2015 , Xu et al., 2016 , You et al., 2017 , Zhao et al., 2018 ). Moreover, deletion of the N-terminal end of PAQR3 disrupted its interactions with endogenous Sec13 and Sec31A ( Figure 5 H), indicating that the N-terminal 1–70 amino acid residues of PAQR3 are required for the interaction of PAQR3 with these two COPII coat proteins.…”

“…PAQR3 also plays a critical role in DNA damage repair by affecting the function of RAD23B-XPC ( You et al., 2017 ). Moreover, PAQR3 has an important effect on hepatic lipid catabolism by promoting PPARα ubiquitination through the E3 ubiquitin ligase HUWE1 ( Zhao et al., 2018 ).…”

SRC fine‐tunes ADAM10 shedding activity to promote pituitary adenoma cell progression

“…To induce SRC (K295A) or SRC (E387G) expression, the cells were incubated with 0.5 μg·mL −1 Dox for the indicated time as described. Transient transfection was conducted by Lipofectamine 2000 (Thermo Fisher Scientific) or polyethylenime (Sigma‐Aldrich) transfection reagents based on the manufacturers’ instructions, as previously reported .…”

<p>Characterization of the Golgi scaffold protein PAQR3, and its role in tumor suppression and metabolic pathway compartmentalization</p>

“…PAQR3 is critical in regulating lipid catabolism in response to starvation via PPARα modulation. 68 PAQR3 interacts directly with PPARα to increase para-polyubiquitination and proteasome-mediated degradation. Further, E3 ubiquitin ligase HECT, UBA and WWE domain containing E3 ubiquitin protein ligase 1 (HUWE1) mediates para-polyubiquitination.…”

“…Moreover, PAQR3 enhances HUWE1-PPARα interaction. 68 Histone modifications are highly involved in several physiological processes, including development and tumorigenesis. Histone H3 lysine 4 (H3K4) methylation is often involved in gene induction at the transcriptional level.…”