Ufd1-Npl4 is a negative regulator of cholera toxin retrotranslocation.
The A1 chain of the cholera toxin (CT) undergoes retrotranslocation to the cytosol across the endoplasmic reticulum (ER) membrane by hijacking ER-associated degradation (ERAD). In the cytosol the CT A1 chain stimulates adenylyl cyclase. The VCP(Ufd1-Npl4) complex mediates retrotranslocation of emerging ER proteins. While one group reported that VCP is required for CT retrotranslocation, another group concluded the opposite. We show that VCP is dispensable for CT retrotranslocation, however RNAi of either Ufd1 or Npl4 induces an increase in adenylyl cyclase activity induced by CT. RNAi of VCP, Ufd1 or Npl4 did not affect adenylyl cyclase activity induced by forskolin. These findings are coherent with our previous report showing that depletion of Ufd1-Npl4 accelerates ERAD of reporter substrates. To integrate contradictory results we propose a new model, where Ufd1-Npl4 is a negative regulator of retrotranslocation, delaying the retrotranslocation of ERAD substrates independently of its association with VCP.
McConnell
Elizabeth
E
Department of Anatomy and Cell Biology, Indiana University School of Medicine, 8600 University Blvd., Evansville, IN 47712, USA.
Lass
Agnieszka
A
Wójcik
Cezary
C
D033942:Adaptor Proteins, Vesicular Transport; D002772:Cholera Toxin / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics
D033942:Adaptor Proteins, Vesicular Transport; D047908:Intracellular Signaling Peptides and Proteins; C514112:NPLOC4 protein, human; D009687:Nuclear Proteins; D011506:Proteins; D034741:RNA, Small Interfering; C491497:UFD1 protein, human; D002772:Cholera Toxin