5-Azacytidine engages an IRE1α-EGFR-ERK1/2 signaling pathway that stabilizes the LDL receptor mRNA

• Published in: Biochimica et biophysica acta. Gene regulatory mechanisms 2018-01, Vol.1861 (1), p.29-40
• Main Authors: Mnasri, Nourhen, Mamarbachi, Maya, Allen, Bruce G., Mayer, Gaétan
• Format: Article
• Language: English
• Subjects: 3' Untranslated Regions - genetics; 3′-UTR; 5-Azacytidine; AU Rich Elements - genetics; AU-rich elements; Azacitidine - administration & dosage; Cell Line, Tumor; Cholesterol, LDL - genetics; Endoribonucleases - genetics; Gene Expression Regulation - drug effects; Hepatocytes; Hepatocytes - drug effects; Hepatocytes - metabolism; Humans; IRE1α/EGFR; JNK Mitogen-Activated Protein Kinases - genetics; Low-density lipoprotein receptor (LDLR); MAP Kinase Signaling System - drug effects; mRNA stabilization; Myelodysplastic Syndromes - drug therapy; Myelodysplastic Syndromes - genetics; Myelodysplastic Syndromes - pathology; Protein-Serine-Threonine Kinases - genetics; Receptor, Epidermal Growth Factor - genetics; Receptors, LDL - genetics; RNA Stability - genetics; RNA, Messenger - drug effects; RNA, Messenger - genetics
• ISSN: 1874-9399; 1876-4320
• DOI: 10.1016/j.bbagrm.2017.11.010

Hepatic low-density lipoprotein receptor (LDLR) is the primary conduit for the clearance of plasma LDL-cholesterol and increasing its expression represents a central goal for treating cardiovascular disease. However, LDLR mRNA is unstable and undergoes rapid turnover mainly due to the three AU-rich elements (ARE) in its proximal 3′-untranslated region (3′-UTR). Herein, our data revealed that 5-azacytidine (5-AzaC), an antimetabolite used in the treatment of myelodysplastic syndrome, stabilizes the LDLR mRNA through a previously unrecognized signaling pathway resulting in a strong increase of its protein level in human hepatocytes in culture. 5-AzaC caused a sustained activation of the inositol-requiring enzyme 1α (IRE1α) kinase domain and c-Jun N-terminal kinase (JNK) independently of endoplasmic reticulum stress. This resulted in activation of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase1/2 (ERK1/2) that, in turn, stabilized LDLR mRNA. Systematic mutation of the AREs (ARE1-3) in the LDLR 3′UTR and expression of each mutant coupled to a luciferase reporter in Huh7 cells demonstrated that ARE1 is required for rapid LDLR mRNA decay and 5-AzaC-induced mRNA stabilization via the IRE1α-EGFR-ERK1/2 signaling cascade. The characterization of this pathway will help to reveal potential targets to enhance plasma LDL clearance and novel cholesterol-lowering therapeutic strategies. •A mechanism for LDL receptor mRNA stabilization induced by 5-Azacytidine is proposed.•5-Azacytidine activates IRE1α kinase domain independently of ER stress.•An IRE1α kinase domain-EGFR-ERK1/2 signaling cascade stabilizes LDLR mRNA.•LDLR 3′UTR ARE1 is required for 5-AzaC-induced LDLR mRNA stabilization.