Glasner A, etal., PLoS One. 2012;7(5):e36837. doi: 10.1371/journal.pone.0036837. Epub 2012 May 15.
Natural killer (NK) cells are innate cytotoxic lymphocytes that specialize in the defense against viral infection and oncogenic transformation. Their action is tightly regulated by signals derived from inhibitory and activating receptors; the later include proteins such as the Natural Cytotoxicity R
eceptors (NCRs: NKp46, NKp44 and NKp30). Among the NCRs, NKp46 is the only receptor that has a mouse orthologue named Ncr1. NKp46/Ncr1 is also a unique marker expressed on NK and on Lymphoid tissue inducer (LTI) cells and it was implicated in the control of various viral infections, cancer and diabetes. We have previously shown that human NKp46 recognizes viral hemagglutinin (HA) in a sialic acid-dependent manner and that the O-glycosylation is essential for the NKp46 binding to viral HA. Here we studied the molecular interactions between Ncr1 and influenza viruses. We show that Ncr1 recognizes influenza virus in a sialic acid dependent manner and that N-glycosylation is important for this binding. Surprisingly we demonstrate that none of the predicted N-glycosilated residues of Ncr1 are essential for its binding to influenza virus and we thus conclude that other, yet unidentified N-glycosilated residues are responsible for its recognition. We have demonstrated that N glycosylation play little role in the recognition of mouse tumor cell lines and also showed the in-vivo importance of Ncr1 in the control of influenza virus infection by infecting C57BL/6 and BALB/c mice knockout for Ncr1 with influenza.
Diab M, etal., Eur J Immunol. 2017 Apr;47(4):692-703. doi: 10.1002/eji.201646756. Epub 2017 Mar 6.
Natural killer (NK) cells are capable of killing various pathogens upon stimulation of activating receptors. Human metapneumovirus (HMPV) is a respiratory virus, which was discovered in 2001 and is responsible for acute respiratory tract infection in infants and children worldwide. HMPV infection is
very common, infecting around 70% of all children under the age of five. Under immune suppressive conditions, HMPV infection can be fatal. Not much is known on how NK cells respond to HMPV. In this study, using reporter assays and NK-cell cytotoxicity assays performed with human and mouse NK cells, we demonstrated that the NKp46-activating receptor and its mouse orthologue Ncr1, both members of the natural cytotoxicity receptor (NCR) family, recognized an unknown ligand expressed by HMPV-infected human cells. We demonstrated that MHC class I is upregulated and MICA is downregulated upon HMPV infection. We also characterized mouse NK-cell phenotype in the blood and the lungs of HMPV-infected mice and found that lung NK cells are more activated and expressing NKG2D, CD43, CD27, KLRG1, and CD69 compared to blood NK cells regardless of HMPV infection. Finally, we demonstrated, using Ncr1-deficient mice, that NCR1 plays a critical role in controlling HMPV infection.
Glasner A, etal., J Immunol. 2015 Oct 15;195(8):3959-69. doi: 10.4049/jimmunol.1501234. Epub 2015 Sep 14.
NK cells kill various cells using activating receptors, such as the natural cytotoxicity receptors (NCRs). NKp46 is a major NCR and is the only NCR expressed in mice (denoted Ncr1). Using Ncr1-deficient mice (Ncr1
nt-weight:700;'>Ncr1(gfp/pfp)) we demonstrated that Ncr1 controls various pathologies, and that in its absence Ncr1-related functions are impaired. In 2012, another Ncr1-related mouse was generated, named Noé, in which a random mutation, W32R, in position 32, impaired the Ncr1-Noé cell surface expression. Interestingly, in the Noé mice, Ncr1-dependent deficiencies were not observed. Additionally, the Noé-NK cells were hyperactivated, probably due to increased Helios expression, and the Noé mice demonstrate increased clearance of influenza and murine CMV. In contrast, in the Ncr1(gfp/pfp) mice infection with influenza was lethal and we show in the present study no difference in murine CMV infection between Ncr1(gfp/pfp) and wild-type (WT) mice. Because the foremost difference between the Noé and Ncr1(gfp/gfp) mice is the presence of a mutated Ncr1-Noé protein, we studied its properties. We show that Ncr1-Noé and various other Ncr1 mutants in position 32 can be expressed on the surface, albeit slowly and unstably, and that ligand recognition and function of the various Ncr1-Noé is similar to the WT Ncr1. We further show that the glycosylation pattern of Ncr1-Noé is aberrant, that the Ncr1-Noé proteins accumulate in the endoplasmic reticulum, and that the expression of Ncr1-Noé proteins, but not WT Ncr1, leads to increased Helios expression. Thus, we suggest that the NK hyperactivated phenotype observed in the Noé mice might result from the presence of the Ncr1-Noé protein.
Jang Y, etal., J Immunol. 2018 Mar 15;200(6):1982-1987. doi: 10.4049/jimmunol.1701676. Epub 2018 Feb 9.
B6.SJL-Ptprca Pepcb /Boy (CD45.1) mice have been used in hundreds of congenic competitive transplants, with the presumption that they differ from C57BL/6 mice only at the CD45 locus. In this study, we describe a point mutation in the natural cytotoxicity receptor 1 (Ncr1
r1) locus fortuitously identified in the CD45.1 strain. This point mutation was mapped at the 40th nucleotide of the Ncr1 locus causing a single amino acid mutation from cysteine to arginine at position 14 from the start codon, resulting in loss of NCR1 expression. We found that these mice were more resistant to CMV due to a hyper innate IFN-γ response in the absence of NCR1. In contrast, loss of NCR1 increased susceptibility to influenza virus, a result that is consistent with the role of NCR1 in the recognition of influenza Ag, hemagglutinin. This work sheds light on potential confounding experimental interpretation when this congenic strain is used as a tool for tracking lymphocyte development.
Durrenberger PF, etal., J Neuroinflammation. 2012 Jan 2;9:1. doi: 10.1186/1742-2094-9-1.
BACKGROUND: Pathogenic or regulatory effects of natural killer (NK) cells are implicated in many autoimmune diseases, but evidence in multiple sclerosis (MS) and its murine models remains equivocal. In an effort to illuminate this, we have here analysed expression of the prototypic NK cel
l marker, NCR1 (natural cytotoxicity triggering receptor; NKp46; CD335), an activating receptor expressed by virtually all NK cells and therefore considered a pan-marker for NK cells. The only definitive ligand of NCR1 is influenza haemagglutinin, though there are believed to be others. In this study, we investigated whether there were differences in NCR1+ cells in the peripheral blood of MS patients and whether NCR1+ cells are present in white matter lesions. RESULTS: We first investigated the expression of NCR1 on peripheral blood mononuclear cells and found no significant difference between healthy controls and MS patients. We then investigated mRNA levels in central nervous system (CNS) tissue from MS patients: NCR1 transcripts were increased more than 5 times in active disease lesions. However when we performed immunohistochemical staining of this tissue, few NCR1+ NK cells were identified. Rather, the major part of NCR1 expression was localised to astrocytes, and was considerably more pronounced in MS patients than controls. In order to further validate de novo expression of NCR1 in astrocytes, we used an in vitro staining of the human astrocytoma U251 cell line grown to model whether cell stress could be associated with expression of NCR1. We found up-regulation of NCR1 expression in U251 cells at both the mRNA and protein levels. CONCLUSIONS: The data presented here show very limited expression of NCR1+ NK cells in MS lesions, the majority of NCR1 expression being accounted for by expression on astrocytes. This is compatible with a role of this cell-type and NCR1 ligand/receptor interactions in the innate immune response in the CNS in MS patients. This is the first report of NCR1 expression on astrocytes in MS tissue: it will now be important to unravel the nature of cellular interactions and signalling mediated through innate receptor expression on astrocytes.
NKp46/NCR1 is an activating NK-cell receptor implicated in the control of various viral and bacterial infections. Recent findings also suggest that it plays a role in shaping the adaptive immune response to pathogens. Using NCR1
pan>-deficient (NCR1gfp/gfp ) mice, we provide evidence for the role of NCR1 in antibody response to mouse cytomegalovirus infection (MCMV). The absence of NCR1 resulted in impaired maturation, function and NK-cell migration to regional lymph nodes. In addition, CD4+ T-cell activation and follicular helper T-cell (Tfh) generation were reduced, leading to inferior germinal center (GC) B-cell maturation. As a consequence, NCR1gfp/gfp mice produced lower amounts of MCMV-specific antibodies upon infection, which correlated with lower number of virus-specific antibody secreting cells in analyzed lymph nodes.
Vitenshtein A, etal., Cell Host Microbe. 2016 Oct 12;20(4):527-534. doi: 10.1016/j.chom.2016.09.008.
Natural killer (NK) cells form an important arm of the innate immune system and function to combat a wide range of invading pathogens, ranging from viruses to bacteria. However, the means by which NK cells accomplish recognition of pathogens with a limited repertoire of receptors remain largely unkn
own. In the current study, we describe the recognition of an emerging fungal pathogen, Candida glabrata, by the human NK cytotoxic receptor NKp46 and its mouse ortholog, NCR1. Using NCR1 knockout mice, we observed that this receptor-mediated recognition was crucial for controlling C. glabrata infection in vitro and in vivo. Finally, we delineated the fungal ligands to be the C. glabrata adhesins Epa1, Epa6, and Epa7 and demonstrated that clearance of systemic C. glabrata infections in vivo depends on their recognition by NCR1. As NKp46 and NCR1 have been previously shown to bind viral adhesion receptors, we speculate that NKp46/NCR1 may be a novel type of pattern recognition receptor.
