title: Cap-dependent translation initiation factor, eIF4E, is the target for Ouabain-mediated inhibition of HIF-1α.
abstract: Hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor that mediates the adaptation of tumor cells and tissues to the hypoxic microenvironment, has attracted considerable interest as a potential therapeutic target. Recently, HIF-1α has been recognized as the critical target of cardiac glycosides for cancer therapy, but the molecular mechanism of cardiac glycosides' inhibition of HIF-1α is still poorly understood. In the present study, we observed that neither HIF-1α mRNA levels nor HIF-1α protein degradation are affected by Ouabain. However, Ouabain was found to be associated with the regulation of HIF-1α translation. Basing on in silico, in vitro and ex vivo models of translation processing, further studies revealed that eIF4E plays a critical role in the inhibitory effect of Ouabain on HIF-1α protein synthesis, rather than mTORC1, eIF2α signaling or Na(+)/K(+)-ATPase inhibition. Mechanistically, Ouabain directly binds eIF4E, disrupts eIF4E/eIF4G association (200 μM, Inhibit rate =61 ± 3%) but not the eIF4E/mRNA complex formation (200 μM, Inhibit rate =18 ± 5%) both in vitro and in cells, thereby inhibiting the intracellular cap-dependent translation. The association between Ouabain and eIF4E not only raises the hope of using cardiac glycosides for cancer therapeutics more rational, but also offers a pharmacologic means for developing novel anti-cancer HIF-1α antagonists.
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Cao
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Lingjuan
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Guanyu
authors.initials: G
authors.lastname: Lin
authors.affiliation: ZJU-ENS Joint Laboratory of Medicinal Chemistry, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Chunqi
authors.initials: C
authors.lastname: Hu
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Dong
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.affiliation: ZJU-ENS Joint Laboratory of Medicinal Chemistry, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Yongzhou
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Chemistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Carston R
authors.initials: CR
authors.lastname: Wagner
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Qiaojun
authors.initials: Q
authors.lastname: He
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China. Electronic address: xryang@yahoo.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D039561:Eukaryotic Initiation Factor-4E / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000187:drug effects* / Q000235:genetics; D010042:Ouabain / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D017931:DNA Primers; D039561:Eukaryotic Initiation Factor-4E; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D010042:Ouabain
keywords: Cancer therapy; Hypoxia; Hypoxia inducible factor; Translation; eIF4E