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Engagement of natural cytotoxicity programs regulates AP-1 expression in the NKL human NK cell line
K Bernard1, A Cambiaggi, S Guia
1Centre d'Immunologie, Institut National de la Santé et de la Recherche Médicale (INSERM)/Centre National de la Recherche Scientifique (CNRS) de Marseille-Luminy, France.
Abstract:
NK cell cytotoxicity is a fast and efficient mechanism of target cell lysis. Using transcription analysis, such as multiplex messenger assays, we show here that natural cytotoxicity exerted by the human NKL cell line correlates with mRNA accumulation of very early activator protein (AP)-1 transcription factor genes such as JunB, FosB and c-Fos. In addition, DNA-binding activities of Jun-Fos heterodimers were observed by electrophoretic mobility shift assays during the course of natural cytotoxicity. Interaction between immunoglobulin-like transcript-2/leukocyte Ig-like receptor 1 on NKL cells and HLA-B27 on target cells leads to an impairment of NKL natural cytotoxicity, which correlates with an absence of JunB, FosB, and c-Fos transcription, as well as an absence of their DNA-binding activity. Our studies thus indicate that, despite the rapidity of NK cell-mediated lysis, AP-1 transcription factor is activated during the early stage of NK cell cytolytic programs and that engagement of NK cell inhibitory receptors for MHC class I molecules impairs the very early activation of AP-1.
Insights
Natural killer (NK) cell cytotoxicity relies on early activation of Activator Protein-1 (AP-1) transcription factors. Inhibitory signals from target cells block this crucial early AP-1 activation, impairing NK cell function.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- Natural killer (NK) cells are crucial for innate immunity, mediating rapid target cell lysis.
- NK cell cytotoxicity involves complex signaling pathways that remain incompletely understood.
- Activator Protein-1 (AP-1) is a transcription factor family known to regulate cellular responses.
Purpose of the Study:
- To investigate the role of AP-1 transcription factors in the early stages of NK cell-mediated cytotoxicity.
- To determine how NK cell inhibitory receptor engagement affects AP-1 activation during cytotoxicity.
Main Methods:
- Multiplex messenger assays were used to analyze mRNA accumulation of AP-1 genes.
- Electrophoretic mobility shift assays (EMSA) were employed to assess DNA-binding activities of Jun-Fos heterodimers.
- NKL cell line and target cells expressing HLA-B27 were utilized to study inhibitory receptor interactions.
Main Results:
- NK cell cytotoxicity correlated with increased mRNA levels of AP-1 genes (JunB, FosB, c-Fos).
- DNA-binding activity of Jun-Fos heterodimers was detected during active NK cell cytotoxicity.
- Engagement of the ILT-2/LIR-1 receptor on NKL cells by HLA-B27 on target cells inhibited cytotoxicity and prevented AP-1 gene transcription and DNA-binding activity.
Conclusions:
- AP-1 transcription factors are rapidly activated during the early phase of NK cell-mediated cytolytic programs.
- Engagement of NK cell inhibitory receptors, such as ILT-2/LIR-1, by MHC class I molecules on target cells impairs the early activation of AP-1.
- This impairment of early AP-1 activation likely contributes to the inhibition of NK cell cytotoxicity by specific target cell interactions.