Natural killer group 2 member D (NKG2D), also known as killer lectin-like receptor subfamily K member 1 (KLRK1) and CD314, is a 42 kDa type II transmembrane protein belonging to the C-type lectin superfamily and is an activating receptor for NK cells (1). NKG2D is expressed on innate and adaptive immune cells such as NK cells, NKT cells, CD8+ T cells, and gammadelta T cells (1-4). Under pathological conditions, including Crohn's disease and Rheumatoid arthritis, NKG2D expression can be induced on CD4+ cells (2,3). NKG2D is synthesized as a protein of 216 amino acids (aa) in length with a theoretical molecular weight of 25.3 kDa (5). The full NKG2D receptor is expressed on the cell surface as a disulfide-linked homodimer and, in humans, has several ligands expressed on tumor cells including MHC class I-related genes A and B (MICA and MICB) and 6 members of the UL16-binding protein (ULBP) family (1-4, 6). NKG2D interaction with its ligand results in activation of NK cells via the recruitment of adapter molecules DNAX-activating protein of 10 kDa (DAP10) or DAP12 homodimers to the intracellular tail region of NKG2D (1-4, 6). In humans, NKG2D can only bind DAP10; however, mice have both short and long NKG2D isoforms which can also bind DAP12 (2-4, 6). Following NKG2D receptor and ligand interaction, the YXXM motif of the DAP10 adapter molecule initiates a downstream signaling cascade through Grb2 and PI3K pathways, resulting in NK cell cytotoxicity (4,6).

In general, NKG2D signaling has dual functions, playing a role in both immune surveillance and immune escape (4,6). Detection of viruses or pathogens and corresponding cytokine production induces NKG2D-ligand expression on dendritic cells and macrophages as well as NKG2D receptor upregulation on NK cells to initiate an immune response (1,2,4,6). Similarly, NKG2D-ligand expression on tumor cells is upregulated in cancers such as liver cancer, ovarian cancer, colon cancer, and leukemia, and the NKG2D/NKG2D-ligand signaling axis functions in preventing progression and metastasis (1,4,6). By contrast, NKG2D signaling also mediates tumor escape through ligand shedding via proteases from the matrix metalloproteinase (MMP) and a disintegrin and metalloprotease (ADAM) families and transforming growth factor (TGF)-beta inhibition of T cell and NK cell function (4). A number of therapeutic strategies targeting the NKG2D receptor-ligand pathway have been developed for cancer immunotherapies including upregulating NKG2D expression on immune cells via soluble cytokines, modulating ligand expression with histone deacetylase (HDAC) inhibitors, or inhibiting ligand shedding molecules like ADAMs and MMPs (1,4,6). Alternatively, in instances of autoimmune diseases or inflammation, NKG2D blocking strategies are of interest (6).

References

1. Wang, J., Li, C. D., & Sun, L. (2020). Recent Advances in Molecular Mechanisms of the NKG2D Pathway in Hepatocellular Carcinoma. Biomolecules, 10(2), 301. https://doi.org/10.3390/biom10020301

2. Stojanovic, A., Correia, M. P., & Cerwenka, A. (2018). The NKG2D/NKG2DL Axis in the Crosstalk Between Lymphoid and Myeloid Cells in Health and Disease. Frontiers in immunology, 9, 827. https://doi.org/10.3389/fimmu.2018.00827

3. Wensveen, F. M., Jelencic, V., & Polic, B. (2018). NKG2D: A Master Regulator of Immune Cell Responsiveness. Frontiers in immunology, 9, 441. https://doi.org/10.3389/fimmu.2018.00441

4. Liu, H., Wang, S., Xin, J., Wang, J., Yao, C., & Zhang, Z. (2019). Role of NKG2D and its ligands in cancer immunotherapy. American journal of cancer research, 9(10), 2064-2078.

5. Uniprot (P26718)

6. Lanier L. L. (2015). NKG2D Receptor and Its Ligands in Host Defense. Cancer immunology research, 3(6), 575-582. https://doi.org/10.1158/2326-6066.CIR-15-0098

Long Name

Natural Killer G2D

Alternate Names

CD314, D12S2489E, KLRK1

Gene Symbol

KLRK1

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Sold under license from the Howard Hughes Medical Institute, Janelia Research Campus.

This product is for research use only and is not approved for use in humans or in clinical diagnosis. Primary Antibodies are guaranteed for 1 year from date of receipt.

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NKG2D/CD314 Antibody (6E5A7) [Janelia Fluor® 549] - Chimeric

Novus Biologicals, part of Bio-Techne | Catalog # NBP3-20156JF549

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Background: NKG2D/CD314