HLA-E surface expression depends on binding of TAP-dependent peptides derived from certain HLA class I signal sequences.
Previous studies showed that HLA-E was expressed in lymphoblastoid cell line (LCL) 721.221 cells, but surface expression was lacking. To determine the signals controlling surface expression, we constructed a series of hybrid genes using complementary portions derived from the HLA-E and HLA-A2 genes. In this manner, a hybrid of HLA-E was identified, designated AEH, which differed from HLA-E by having the HLA-A2 signal sequence substituting for the HLA-E leader peptide. Transfection of LCL 721.221 cells with AEH induced HLA-E surface expression. Analysis of peptides bound to HLA-E revealed that a nonamer peptide derived from the A2 signal sequence was the predominant peptide bound. LCL 721.221 cells transfected with certain class I genes, including HLA-G, were also sufficient to promote peptide binding and HLA-E surface expression without increasing the level of HLA-E heavy chain synthesis. Peptides bound to HLA-E consisted of nine amino acids, with methionine at position 2 and leucine in the carboxyl-terminal position, and were nearly identical to the leader sequence-derived peptide previously shown to be a predominant peptide bound to the murine Qa-1 Ag. Signal peptides derived from certain HLA-B proteins with threonine in position 2 only marginally up-regulated HLA-E surface expression in .221 cells. An examination of HLA-E peptide binding in the TAP negative cell line .134 indicated that peptide binding to HLA-E was dependent on a functional TAP heterodimer regardless of whether peptide was available in cis, as in the AEH construct, or in trans, as in the class I transfectants of .221 cells.
Lee
N
N
The Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98104, USA.
Goodlett
D R
DR
Ishitani
A
A
Marquardt
H
H
Geraghty
D E
DE
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D006680:HLA Antigens / Q000032:analysis* / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000032:analysis* / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000502:physiology*; D014162:Transfection; D000097625:HLA-E Antigens
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D021382:Protein Sorting Signals; D000097625:HLA-E Antigens; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; C489516:Tap2 protein, mouse; C071692:TAP2 protein, human