The ERdj5-Sel1L complex facilitates cholera toxin retrotranslocation.
Cholera toxin (CT) traffics from the host cell surface to the endoplasmic reticulum (ER), where the toxin's catalytic CTA1 subunit retrotranslocates to the cytosol to induce toxicity. In the ER, CT is captured by the E3 ubiquitin ligase Hrd1 via an undefined mechanism to prepare for retrotranslocation. Using loss-of-function and gain-of-function approaches, we demonstrate that the ER-resident factor ERdj5 promotes CTA1 retrotranslocation, in part, via its J domain. This Hsp70 cochaperone regulates binding between CTA and the ER Hsp70 BiP, a chaperone previously implicated in toxin retrotranslocation. Importantly, ERdj5 interacts with the Hrd1 adaptor Sel1L directly through Sel1L's N-terminal lumenal domain, thereby linking ERdj5 to the Hrd1 complex. Sel1L itself also binds CTA and facilitates toxin retrotranslocation. By contrast, EDEM1 and OS-9, two established Sel1L binding partners, do not play significant roles in CTA1 retrotranslocation. Our results thus identify two ER factors that promote ER-to-cytosol transport of CTA1. They also indicate that ERdj5, by binding to Sel1L, triggers BiP-toxin interaction proximal to the Hrd1 complex. We postulate this scenario enables the Hrd1-associated retrotranslocation machinery to capture the toxin efficiently once the toxin is released from BiP.
Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48103, USA.
Jeffrey M
JM
Williams
Takamasa
T
Inoue
Lindsey
L
Banks
Billy
B
Tsai
D000906:Antibodies / Q000276:immunology; D002460:Cell Line; D002772:Cholera Toxin / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism*; D021381:Protein Transport; D011506:Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014734:Vibrio cholerae / Q000472:pathogenicity
D000906:Antibodies; C539791:Bax-inhibiting peptide, BIP; C471179:DNAJC10 protein, human; C486654:EDEM1 protein, human; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D037102:Lectins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; C098898:OS9 protein, human; D009842:Oligopeptides; D011506:Proteins; D034741:RNA, Small Interfering; C117384:SEL1L protein, human; D002772:Cholera Toxin; C482345:SYVN1 protein, human; D044767:Ubiquitin-Protein Ligases