HLA-G peptide preferences change in transformed cells: impact on the binding motif

Alexander A Celik,Gwendolin S Simper,Christina Bade-Döding,Wiebke Hiemisch,Rainer Blasczyk

doi:10.1007/s00251-018-1058-2

Alexander A Celik, Gwendolin S Simper + Show 3 more

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https://doi.org/10.1007/s00251-018-1058-2

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Journal: Immunogenetics	Publication Date: Mar 30, 2018
Citations: 15	License type: open-access

Affiliation: Hannover Medical School

Abstract

HLA-G is known for its strictly restricted tissue distribution. HLA-G expression could be detected in immune privileged organs and many tumor entities such as leukemia, multiple myeloma, and non-Hodgkin and Hodgkin’s lymphoma. This functional variability from mediation of immune tolerance to facilitation of tumor immune evasion strategies might translate to a differential NK cell inhibition between immune-privileged organs and tumor cells. The biophysical invariability of the HLA-G heavy chain and its contrary diversity in immunity implicates a strong influence of the bound peptides on the pHLA-G structure. The aim was to determine if HLA-G displays a tissue-specific peptide repertoire. Therefore, using soluble sHLA-G technology, we analyzed the K562 and HDLM-2 peptide repertoires. Although both cell lines possess a comparable proteome and recruit HLA-G-restricted peptides through the same peptide-loading pathway, the peptide features appear to be cell specific. HDLM-2 derived HLA-G peptides are anchored by an Arg at p1 and K562-derived peptides are anchored by a Lys. At p2, no anchor motif could be determined while peptides were anchored at pΩ with a Leu and showed an auxiliary anchor motif Pro at p3. To appreciate if the peptide anchor alterations are due to a cell-specific differential peptidome, we performed analysis of peptide availability within the different cell types. Yet, the comparison of the cell-specific proteome and HLA-G-restricted ligandome clearly demonstrates a tissue-specific peptide selection by HLA-G molecules. This exclusive and unexpected observation suggests an exquisite immune function of HLA-G.

Highlights

Human leukocyte antigen (HLA)-G, a non-classical HLA class Ib molecule, plays an important role in immune protection and is in contrast to HLA class Ia molecules exclusively expressed at immune privileged sites (Kovats et al 1990)
Using the methods established by Bade-Doeding et al (2011), K562 and T2 cells were stably transduced with full-length HLA-G*01:01, K562 and HDLM-2 cells were stably transduced with sHLAG*01:01
To determine the HLA-G*01:01 restricted peptide repertoire, HDLM-2 or K562 cells were stably transduced with sHLAG*01:01 and, after cultivation in bioreactors, soluble HLA molecules were affinity purified

Summary

Introduction

Human leukocyte antigen (HLA)-G, a non-classical HLA class Ib molecule, plays an important role in immune protection and is in contrast to HLA class Ia molecules exclusively expressed at immune privileged sites (Kovats et al 1990). HLA-G interacts with different subsets of immune effector cells (NK, T, B, macrophages), usually resulting in inhibition of Immunogenetics (2018) 70:485–494 these cells (Bainbridge et al 2000; Li et al 2009; Naji et al 2014; Rouas-Freiss et al 1997). T cell activity is inhibited by interaction of HLA-G with ILT-2 and ILT-4 (Riteau et al 1999) and leads to unresponsive and suppressive CD4+ T cell phenotypes (LeMaoult et al 2004). Purified soluble HLA-G was shown to lead to apoptosis in activated CD8+ T cells (Fournel et al 2000) and suppression of proliferation in CD4+ T cells (Bainbridge et al 2000). It was shown that interaction of ILT-4 can occur with β2m free forms of HLA-G (Gonen-Gross et al 2005)

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