Allelic Polymorphism Determines Surface Expression or Intracellular Retention of the Human NK Cell Receptor KIR2DL5A (CD158f)

Abstract

KIR2DL5 (CD158f) is the most recently identified inhibitory member of human killer-cell Ig-like receptors (KIRs), which enable NK cells to sense self-HLA. Unlike KIR2DL1–3, recognizing HLA-C allotypes through Ig-like domains of the D1–D2 type, KIR2DL5 shares a D0–D2 configuration with KIR2DL4, and its ligands have not been identified. KIR2DL5 is encoded by two paralogous genes displaying copy number variation and allelic polymorphism—KIR2DL5A and KIR2DL5B. UP-R1 mAb, raised against the common allele KIR2DL5A*001, enables specific KIR2DL5 detection. However, not every KIR2DL5+ individual has NK cells staining with UP-R1, discrepancy explained in part by epigenetically silent KIR2DL5B alleles with a distinctive substitution in a promoter RUNX-binding site. Furthermore, we show here that the transcribed allele KIR2DL5A*005, second most common of its locus, fails to confer NK cells UP-R1 reactivity, phenotype explained by inefficacious transport of its product to the cell surface. Two amino acid substitutions distinguish the KIR2DL5A*005 and *001 coding regions. Western blot, flow cytometry, and confocal microscopy analyses of cells transfected with tagged constructs demonstrate that a serine substitution for glycine-174, conserved in most KIR, is mainly responsible for KIR2DL5A*005 intracellular retention, and it also affects mAb recognition. In contrast, substitution of aspartate for asparagine 152 has only a minor effect on surface expression, despite destroying an otherwise conserved N-glycosylation site. Our results help to explain the variable expression profile of KIR2DL5+ subjects and indicate that functional polymorphisms in both its promoter and its coding regions are critical for understanding the KIR2DL5 role in immunity and its importance for human health.

Haplotype-Based Analysis of KIR-Gene Profiles in a South European Population—Distribution of Standard and Variant Haplotypes, and Identification of Novel Recombinant Structures

“…Transcription of KIR2DL5B * 0020106 and * 0020202 provides further confirmation to our hypothesis that an intact RUNX binding site in the proximal promoter is essential for KIR-gene expression, whilst its mutation determines epigenetic silencing. The biological significance of transcribed KIR2DL5B * 002 alleles is, however, uncertain since, like KIR2DL5A * 005 (Figure 7), the encoded receptor appears not to reach the cell surface and is possibly retained intracellularly (56). The fact that nearly identical coding sequences are preceded by three highly divergent promoter sequences in alleles of two paralog genes (2DL5A * 005, 2DL5B * 0020101 and 2DL5B * 0020106/0020202) illustrates the role of recombination in KIR-gene evolution.…”

TIGIT Blockade: A Multipronged Approach to Target the HIV Reservoir

“…Less than 10% of CD56 dim NK cells and a very small fraction of the CD8 + T cells of carriers express the most common allele, 2DL5A * 001, which is detectable by mAb UP-R1 (Estefania et al, 2007;Cisneros et al, 2012). An accurate measure of KIR2DL5 prevalence in the wider population is currently unavailable as it is unknown whether this is the only allele expressed or whether polymorphisms arising in other alleles alter epitopes recognized by UP-R1 (Cisneros et al, 2012(Cisneros et al, , 2016. While multiple factors suggest that inhibiting TIGIT/PVR interactions is a suitable strategy to invigorate effector cell responses against HIV-1, PLWH expressing KIR2DL5 may be less likely to benefit from this approach.…”

Immunological Risk Stratification of Bladder Cancer Based on Peripheral Blood Natural Killer Cell Biomarkers

“…Current knowledge cannot offer a simple biological explanation for our results. Although our genetic study could not differentiate between centromeric (not expressed) and telomeric (predominance of expressed) KIR2DL5 forms [15], naturally expressed KIR2DL5 can inhibit NKc cytotoxicity to an extent comparable with classical iKIRs [29]. Besides, the ligand for KIR2DL5 still needs to be identified [14], although our results suggest that HLA-C*16 could be or may mimic the natural KIR2DL5 ligand, probably by presenting BC peptides, since the deleterious effect of the KIR2DL5/HLA-C*16 combination was not observed in other solid or hematological cancers.…”

“…The best characterized iKIR/ HLA-I licensing interactions are KIR2DL1/HLA-C2, KIR2DL2-3/HLA-C1, and KIR3DL1/HLA-Bw4 allotypes [11]. However, ligands for KIR2DL5 and their roles in immunity and human health remain elusive [14,15]. For aKIR, only interactions between KIR2DS1/HLA-C2, KIR2DS4/HLA-A*11/C*2/C*4/C*5/C* 16 allotypes, and KIR3DS1/HLA-Bw4 have been reported [16].…”