title: Preventing the unfolded protein response via aberrant activation of 4E-binding protein 1 by versipelostatin.
abstract: We recently isolated a macrocyclic compound, versipelostatin (VST), that exerts in vivo antitumor activity. VST shows unique, selective cytotoxicity to glucose-deprived tumor cells by preventing the unfolded protein response (UPR). Here we show that eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), a negative regulator of eukaryotic initiation factor 4E-mediated protein translation, plays a role in the UPR-inhibitory action of VST. Indeed, 4E-BP1 is aberrantly activated by VST. This activation occurs specifically during glucose deprivation and results in profound translation repression and prevents induction of the typical UPR markers glucose-regulated protein (GRP) 78 and activating transcription factor (ATF) 4. Our overexpression and knockdown experiments showed that 4E-BP1 can regulate GRP78 and ATF4 expression. These mechanisms appear to be specific for VST. By contrast, rapamycin, which activates 4E-BP1 regardless of cellular glucose availability, has only marginal effects on the expression of GRP78 and ATF4. Our present findings demonstrate that aberrant 4E-BP1 activation can contribute to UPR preventing by VST, possibly through a mechanism that does not operate in rapamycin-treated cells.
authors.affiliation: Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 3-10-6 Ariake, Koto-ku, Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Matsuo
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tsukumo
authors.forename: Junko
authors.initials: J
authors.lastname: Sakurai
authors.forename: Satomi
authors.initials: S
authors.lastname: Tsukahara
authors.forename: Hae-Ryong
authors.initials: HR
authors.lastname: Park
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shin-ya
authors.forename: Toshiki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuruo
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tomida
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000091342:Endoplasmic Reticulum Chaperone BiP; D005786:Gene Expression Regulation / Q000187:drug effects*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology*; D009844:Oligosaccharides / Q000494:pharmacology*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D020123:Sirolimus / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects*
chemical_list: C497109:ATF4 protein, human; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D007166:Immunosuppressive Agents; D018942:Macrolides; D009844:Oligosaccharides; D010750:Phosphoproteins; D034741:RNA, Small Interfering; C490154:versipelostatin; D051701:Activating Transcription Factor 4; D008156:Luciferases; D020123:Sirolimus