Cell surface expression of HLA-E: interaction with human β2-microglobulin and allelic differences

Abstract

The formation of a trimeric complex composed of MHC class I heavy chain, beta2-microglobulin (beta2m) and peptide ligand is a prerequisite for its efficient transport to the cell surface. We have previously demonstrated impaired intracellular transport of the human class Ib molecule HLA-E in mouse myeloma X63 cells cotransfected with the genes for HLA-E and human beta2m (hbeta2m), which is most likely attributable to inefficient intracellular peptide loading of the HLA-E molecule. Here we demonstrate that cell surface expression of HLA-E in mouse cells strictly depends on the coexpression of hbeta2m and that soluble empty complexes of HLA-E and hbeta2m display a low degree of thermostability. Both observations imply that low affinity interaction of HLA-E with beta2m accounts to a considerable extent for the observed low degree of peptide uptake in the endoplasmic reticulum. Moreover, we show that the only allelic variation present in the caucasoid population located at amino acid position 107 (Gly or Arg) greatly affects intracellular transport and cell surface expression upon transfection of the respective alleles into mouse cells. No obvious difference was found with regard to the sequence of the peptide ligand.

Cutting Edge: The Human CytomegalovirusUL40Gene Product Contains a Ligand for HLA-E and Prevents NK Cell-Mediated Lysis

“…Total cellular RNA of the K-562 cells was isolated as described (15). Cellular RNA of HCMV infected fibroblasts was isolated using the High Pure RNA Isolation Kit of Roche Diagnostics (Indianapolis, IN).…”

“…Cellular RNA of HCMV infected fibroblasts was isolated using the High Pure RNA Isolation Kit of Roche Diagnostics (Indianapolis, IN). Northern blot analysis was performed on 5 g of total RNA as described (15). A full-length UL40 probe was labeled with digoxigenin dUTP by use of the PCR DIG Probe Synthesis Kit (Roche Diagnostics).…”

“…An HLA-E*01033 cDNA was amplified by RT-PCR using the primers HLA-E5ЈUT and HLA-E3ЈUT as previously described (15) and cloned into the vector pcDNA3 (Invitrogen, San Diego, CA) for transfection giving pcDNA-E.…”

“…Culturing of the HLA class I-negative chronic myelogenous leukemia cell line K-562, of the NK cell line NKL kindly provided by M. Lopez-Botet (Madrid, Spain) and the mouse CTL clone TER-1 specific for HLA-E, has been described (15)(16)(17). Transfectants were generated by electroporation and selected by adding 0.4 mg/ml G418 and/or 0.4 mg/ml hygromycin B.…”

Association Between HLA‐E *0101 Homozygosity and Recurrent Miscarriage in Egyptian Women

“…HLA-E*0103 allele differs from HLA-E*0101 by an amino acid substitution (glycine to arginine at position 107 of the a2 heavy-chain domain) and by a cell surface expression [8,9]. In the light of the possible role of HLA-E in the success of pregnancy, it is important to understand the biology of the different alleles of HLA-E [10].…”