Research ArticleImmunology

Genetic diversity affects the nanoscale membrane organization and signaling of natural killer cell receptors

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Science Signaling  17 Dec 2019:
Vol. 12, Issue 612, eaaw9252
DOI: 10.1126/scisignal.aaw9252

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Diversity starts at the gene level

Natural killer (NK) cells are immune cells with potent antiviral and antitumor activities. These cells express several germline-encoded inhibitory receptors (KIRs) that prevent NK cells from killing healthy cells but enable the targeting of infected and transformed cells. Using various imaging techniques and functional assays, Kennedy et al. investigated the effects of genetic diversity in KIR-encoding genes on receptor organization and activity. They found that KIRs encoded by distinct genes were present at varying abundances and in clusters of varying sizes, which led to differences in downstream signaling that affected NK cell function. Together, these data suggest that genetic diversity in KIR-encoding genes affects receptor organization, signaling, and functional outcomes.

Abstract

Genetic diversity in human natural killer (NK) cell receptors is linked to resistance and susceptibility to many diseases. Here, we tested the effect of this diversity on the nanoscale organization of killer cell immunoglobulin-like receptors (KIRs). Using superresolution microscopy, we found that inhibitory KIRs encoded by different genes and alleles were organized differently at the surface of primary human NK cells. KIRs that were found at low abundance assembled into smaller clusters than those formed by KIRs that were more highly abundant, and at low abundance, there was a greater proportion of KIRs in clusters. Upon receptor triggering, a structured interface called the immune synapse assembles, which facilitates signal integration and controls NK cell responses. Here, triggering of low-abundance receptors resulted in less phosphorylation of the downstream phosphatase SHP-1 but more phosphorylation of the adaptor protein Crk than did triggering of high-abundance receptors. In cells with greater KIR abundance, SHP-1 dephosphorylated Crk, which potentiated NK cell spreading during activation. Thus, genetic variation modulates both the abundance and nanoscale organization of inhibitory KIRs. That is, as well as the number of receptors at the cell surface varying with genotype, the way in which these receptors are organized in the membrane also varies. Essentially, a change in the average surface abundance of a protein at the cell surface is a coarse descriptor entwined with changes in local nanoscale clustering. Together, our data indicate that genetic diversity in inhibitory KIRs affects membrane-proximal signaling and, unexpectedly, the formation of activating immune synapses.

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