The p97 ATPase dislocates MHC class I heavy chain in US2-expressing cells via a Ufd1-Npl4-independent mechanism.
The human cytomegalovirus (HCMV) protein US2 hijacks the endoplasmic reticulum (ER)-associated degradation machinery to dispose of MHC class I heavy chain (HC) at the ER. This process requires retrotranslocation of newly synthesized HC molecules from the ER membrane into the cytosol, but the mechanism underlying the dislocation reaction has been elusive. Here we establish an in vitro permeabilized cell assay that recapitulates the retrotranslocation of MHC HC in US2-expressing cells. Using this assay, we demonstrate that the dislocation process requires ATP and ubiquitin, as expected. The retrotranslocation also involves the p97 ATPase. However, the mechanism by which p97 dislocates MHC class I HC in US2 cells is distinct from that in US11 cells: the dislocation reaction in US2 cells is independent of the p97 cofactor Ufd1-Npl4. Our results suggest that different retrotranslocation mechanisms can employ distinct p97 ATPase complexes to dislocate substrates.
Soetandyo
Nia
N
Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ye
Yihong
Y
D033942:Adaptor Proteins, Vesicular Transport; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D005805:Genes, MHC Class I; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000166:cytology; D008285:Major Histocompatibility Complex; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011506:Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
D033942:Adaptor Proteins, Vesicular Transport; D047908:Intracellular Signaling Peptides and Proteins; C514112:NPLOC4 protein, human; D009687:Nuclear Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; C491497:UFD1 protein, human; C118670:US2 protein, Varicellovirus; D025801:Ubiquitin; D014759:Viral Envelope Proteins; D000251:Adenosine Triphosphatases; C404942:p97 ATPase