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The immunopeptidome of HLA-A*11:01 expressed K562 cell line

ABSTRACT: The K562 cell line was obtained from ATCC (American Type Culture Collection, Manassas,VA). And the K562 cell line was transduced using a highly efficient retroviral vector coding HLA-A*11:01. The vectors were transfected into a 293T packaging cell line and replication-defective virus supernatants were harvested. After infection of K562 cells with the supernatant, antibody-directed flow cytometry sorting was done to obtain high expression for HLA-A*11:01. Cells were grown in T75 flasks to a density of 1e9 cells before purification of HLA-I peptides for MS experiments.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Bo Li Le Zhang

PROVIDER: MSV000086567 | MassIVE | Mon Dec 07 02:56:00 GMT 2020

SECONDARY ACCESSION(S): PXD022951

REPOSITORIES: MassIVE

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Project description:Human leukocyte antigen (HLA) - B*51:01 and endoplasmic reticulum aminopeptidase 1 (ERAP1) are two strong predisposing genetic factors to Behçet's disease (BD). Previous studies have focused on two subgroups of HLA-B*51 peptidome containing Proline (Pro) or Alanine (Ala) at position 2 (P2). Little is known about the unconventional non-Pro/Ala2 HLA-B*51-bound peptides. We aimed to study the features of this novel sub-peptidome, and investigate its regulation by ERAP1. CRISPR-Cas9 was used to generate an HLA-ABC-knockout HeLa cell line (HeLa.ABC-KO), which was subsequently transduced to express HLA-B*51:01 (HeLa.ABC-KO.B51). ERAP1 was silenced using lentiviral shRNA. Peptides bound to HLA-B*51:01 were eluted and analyzed by Mass Spectrometry. The characteristics of non-Pro/Ala2, Pro2 and Ala2 peptides, and their alteration by ERAP1 silencing were investigated. Effects of ERAP1 silencing on cell surface expression of HLA-B*51:01 were studied using flow cytometry. More than 20% of peptides eluted from HLA-B*51:01 lacked Proline or Alanine at P2. This unconventional group of HLA-B*51:01-bound peptides was enriched for 8-mers (with fewer 9-mers) compared to Pro2 and Ala2 sub-peptidomes, and had similar N-terminal and C-terminal residue usages to Ala2 peptides with the exception of the less abundant Leucine at position Ω. Knockdown of ERAP1 increased the percentage of non-Pro/Ala2 to approximately 40%, increased the percentage of longer (10-mer and 11-mer) peptides eluted from HLA-B*51:01 complexes, and abrogated the predominance of Leucine at P1. Interestingly knockdown of ERAP1 altered the length and N-terminal residue usage of non-Ala2&Pro2 and Ala2 but not the Pro2 peptides. Finally, ERAP1 silencing regulated the expression levels of cell surface HLA-B*51 in a cell type - dependent manner. The HLA-B*51:01 peptidome includes a surprisingly high proportion of unconventional non-Pro/Ala2 peptides which are increased by ERAP1 silencing, mimicking the loss-of-function BD risk variant.

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The immunopeptidome of HLA-A*11:01 expressed K562 cell line

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