Complex regulation of human NKG2D-DAP10 cell surface expression: opposing roles of the γc cytokines and TGF-β1

Abstract

Natural killer (NK) cells help protect the host against viral infections and tumors. NKG2D is a vital activating receptor, also expressed on subsets of T cells, whose ligands are up-regulated by cells in stress. Ligation of NKG2D leads to phosphorylation of the associated DAP10 adaptor protein, thereby activating immune cells. Understanding how the expression of NKG2D-DAP10 is regulated has implications for immunotherapy. We show that IL-2 and TGF-β1 oppositely regulate NKG2D-DAP10 expression by NK cells. IL-2 stimulation increases NKG2D surface expression despite a decrease in NKG2D mRNA levels. Stimulation with IL-2 results in a small increase of DAP10 mRNA and a large up-regulation of DAP10 protein synthesis, indicating that IL-2-mediated effects are mostly posttranscriptional. Newly synthesized DAP10 undergoes glycosylation that is required for DAP10 association with NKG2D and stabilization of NKG2D expression. TGF-β1 has an opposite and dominant effect to IL-2. TGF-β1 treatment decreases DAP10, as its presence inhibits the association of RNA polymerase II with the DAP10 promoter, but not NKG2D mRNA levels. This leads to the down-regulation of DAP10 expression and, as a consequence, NKG2D protein as well. Finally, we show that other γ(c) cytokines act similarly to IL-2 in up-regulating DAP10 expression and NKG2D-DAP10 surface expression.

TGF-β–inducible microRNA-183 silences tumor-associated natural killer cells

“…Thus, DAP12 depletion via TGF-β-induced miR-183 profoundly affects the NK cell response to cancer cells. Of note, TGF-β also represses DAP10 (35). However, the DAP10 3′ UTR lacks miR-183 binding sites (Fig.…”

A Chimeric Receptor with NKG2D Specificity Enhances Natural Killer Cell Activation and Killing of Tumor Cells

“…There is strong evidence in vitro and in animal models for an important role of NKG2D in NK cell-mediated antitumor activity (1,4,(6)(7)(8)(9)(10)(11)(12)(13). NKG2D is associated with DNAX-activating protein 10 (DAP10), which promotes and stabilizes its surface membrane expression (14)(15)(16)(17)(18). NKG2D lacks a signaling motif in its cytoplasmic domain and signal transduction upon ligation occurs via the phosphorylation of DAP10, which recruits downstream signaling effector molecules and, ultimately, cytotoxicity (14,19).…”

Dendritic Cell–Derived IL-32α: A Novel Inhibitory Cytokine of NK Cell Function

“…Most studies focused on the IL-32g, which is known to synergize with other cell activators such as LPS (TLR4 ligand) or muramyldipeptide (NOD2 ligand) (42,43). IL-32g can trigger TNF-a and IL-6 production, the maturation of DCs (24), and the activation of NK cell cytotoxicity through cell death receptor 3 (44). Furthermore, IL-32g has been shown to be protective in tuberculosis (30,45,46).…”

“…For example, IL-6 has been shown to antagonize NK cytotoxicity by reducing granzyme B and perforin in the systemic juvenile idiopathic arthritis murine model, and its presence in patient sera was correlated with lower NK activity (58). TGF-b is known to reduce NK cell function by repressing the mTor pathway (59) and downregulating NKG2D or DAP10 expression, leading to an impaired cytotoxic activity of human NK cells (44,60). Our findings show that IL-32a can act directly on NK cells and on DCs to reduce their capacity to prime cytolytic NK cells and their IL-18 production.…”