title: Apratoxin Kills Cells by Direct Blockade of the Sec61 Protein Translocation Channel.
abstract: Apratoxin A is a cytotoxic natural product that prevents the biogenesis of secretory and membrane proteins. Biochemically, apratoxin A inhibits cotranslational translocation into the ER, but its cellular target and mechanism of action have remained controversial. Here, we demonstrate that apratoxin A prevents protein translocation by directly targeting Sec61α, the central subunit of the protein translocation channel. Mutagenesis and competitive photo-crosslinking studies indicate that apratoxin A binds to the Sec61 lateral gate in a manner that differs from cotransin, a substrate-selective Sec61 inhibitor. In contrast to cotransin, apratoxin A does not exhibit a substrate-selective inhibitory mechanism, but blocks ER translocation of all tested Sec61 clients with similar potency. Our results suggest that multiple structurally unrelated natural products have evolved to target overlapping but non-identical binding sites on Sec61, thereby producing distinct biological outcomes.
authors.affiliation: Institute of Biotechnology, University of Helsinki, Viikinkaari 1, Biocenter 3, Helsinki 00014, Finland.
authors.forename: Anja O
authors.initials: AO
authors.lastname: Paatero
authors.affiliation: Institute of Biotechnology, University of Helsinki, Viikinkaari 1, Biocenter 3, Helsinki 00014, Finland.
authors.forename: Juho
authors.initials: J
authors.lastname: Kellosalo
authors.affiliation: Department of Pharmaceutical Chemistry, Institute for Neurodegenerative Disease, University of California at San Francisco, San Francisco, CA 94038, USA.
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Dunyak
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: Jehad
authors.initials: J
authors.lastname: Almaliti
authors.affiliation: Department of Pharmaceutical Chemistry, Institute for Neurodegenerative Disease, University of California at San Francisco, San Francisco, CA 94038, USA.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Gestwicki
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Gerwick
authors.affiliation: Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94158, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Taunton
authors.affiliation: Institute of Biotechnology, University of Helsinki, Viikinkaari 1, Biocenter 3, Helsinki 00014, Finland. Electronic address: ville.paavilainen@helsinki.fi.
authors.forename: Ville O
authors.initials: VO
authors.lastname: Paavilainen
mesh_terms: D016923:Cell Death / Q000187:drug effects; D047630:Depsipeptides / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D045325:HCT116 Cells; D006801:Humans; D015394:Molecular Structure; D021381:Protein Transport / Q000187:drug effects; D000069816:SEC Translocation Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D047630:Depsipeptides; D000069816:SEC Translocation Channels; C000613244:SEC61A1 protein, human; C442201:apratoxin A