Abstract
The natural cytotoxicity receptors are a unique set of activating proteins expressed mainly on the surface of natural killer (NK) cells. The human natural cytotoxicity receptor family comprises the three type I membrane proteins NKp30, NKp44, and NKp46. Especially NKp30 is critical for the cytotoxicity of NK cells against different targets including tumor, virus-infected, and immature dendritic cells. Although the crystal structure of NKp30 was recently solved (Li, Y., Wang, Q., and Mariuzza, R. A. (2011) J. Exp. Med. 208, 703-714; Joyce, M. G., Tran, P., Zhuravleva, M. A., Jaw, J., Colonna, M., and Sun, P. D. (2011) Proc. Natl. Acad. Sci. U.S.A. 108, 6223-6228), a key question, how NKp30 recognizes several non-related ligands, remains unclear. Therefore, we investigated the parameters that impact ligand recognition of NKp30. Based on various NKp30-hIgG1-Fc fusion proteins, which were optimized for minimal background binding to cellular Fcγ receptors, we identified the flexible stalk region of NKp30 as an important but so far neglected module for ligand recognition and related signaling of the corresponding full-length receptor proteins. Moreover, we found that the ectodomain of NKp30 is N-linked glycosylated at three different sites. Mutational analyses revealed differential binding affinities and signaling capacities of mono-, di-, or triglycosylated NKp30, suggesting that the degree of glycosylation could provide a switch to modulate the ligand binding properties of NKp30 and NK cell cytotoxicity.
Highlights
NKp30 is a major activating receptor of natural killer (NK) cells
The ligand binding properties of the various Ig fusion proteins were assayed by flow cytometry on K-562 cells, which express a cellular ligand of NKp30 [19, 24, 41] and high levels of Fc␥ receptor (Fc␥R) [42, 43] (Fig. 1B)
Previous studies were performed with Ig fusion proteins of a partial ectodomain of NKp30 [16, 24, 41]
Summary
Results: The stalk domain of NKp30 increases ligand binding affinity, which is modulated by glycosylation of the ectodomain of NKp30. NKp30 is critical for the cytotoxicity of NK cells against different targets including tumor, virus-infected, and immature dendritic cells. The major activating receptors on human NK cells include NKG2D and the natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46 [7]. Stalk Domain-dependent Ligand Binding of NKp30 ing healthy cells and tumor cells [10]; their expression level is critical for the ability of NK cells to destroy target cells [8, 12,13,14,15]. Detailed studies revealed that differential glycosylation impacts the ligand binding properties of NKp30 and might be a switch to modulate NK cell cytotoxicity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
