Two novel routes of transporter associated with antigen processing (TAP)-independent major histocompatibility complex class I antigen processing.
Jaw1 is an endoplasmic reticulum (ER) resident protein representative of a class of proteins post translationally inserted into membranes via a type II membrane anchor (cytosolic NH2 domain, lumenal COOH domain) in a translocon-independent manner. We found that Jaw1 can efficiently deliver a COOH-terminal antigenic peptide to class I molecules in transporter associated with antigen processing (TAP)-deficient cells or cells in which TAP is inactivated by the ICP47 protein. Peptide delivery mediated by Jaw1 to class I molecules was equal or better than that mediated by the adenovirus E3/19K glycoprotein signal sequence, and was sufficient to enable cytofluorographic detection of newly recruited thermostabile class I molecules at the surface of TAP-deficient cells. Deletion of the transmembrane region retargeted Jaw1 from the ER to the cytosol, and severely, although incompletely, abrogated its TAP-independent peptide carrier activity. Use of different protease inhibitors revealed the involvement of a nonproteasomal protease in the TAP-independent activity of cytosolic Jaw1. These findings demonstrate two novel TAP-independent routes of antigen processing; one based on highly efficient peptide liberation from the COOH terminus of membrane proteins in the ER, the other on delivery of a cytosolic protein to the ER by an unknown route.
Snyder
H L
HL
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892-0440, USA.
Bacík
I
I
Bennink
J R
JR
Kearns
G
G
Behrens
T W
TW
Bächi
T
T
Orlowski
M
M
Yewdell
J W
JW
D017951:Antigen Presentation / Q000276:immunology*; D015153:Blotting, Western; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005786:Gene Expression Regulation; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D010455:Peptides / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D011993:Recombinant Fusion Proteins; D014170:Transformation, Genetic; D014616:Vaccinia virus / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D015395:Histocompatibility Antigens Class I; C486311:IRAG2 protein, human; D008565:Membrane Proteins; D010455:Peptides; D011480:Protease Inhibitors; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D010450:Endopeptidases