KIR2DL4 differentially signals downstream functions in human NK cells through distinct structural modules.
KIR2DL4 (2DL4) is a member of the killer cell Ig-like receptor (KIR) family in human NK cells. It can stimulate potent cytokine production and weak cytolytic activity in resting NK cells, but the mechanism for 2DL4-mediated signaling remains unclear. In this study we characterized the signaling pathways stimulated by 2DL4 engagement. In a human NK-like cell line, KHYG-1, cross-linking of 2DL4 activated MAPKs including JNK, ERK, and p38. Furthermore, 2DL4 cross-linking resulted in phosphorylation of IkappaB kinase beta (IKKbeta) and the phosphorylation and degradation of IkappaBalpha, which indicate activation of the classical NF-kappaB pathway. Engagement of 2DL4 was also shown to activate the transcription and translation of a variety of cytokine genes, including TNF-alpha, IFN-gamma, MIP1alpha, MIP1beta, and IL-8. Pharmacological inhibitors of JNK, MEK1/2 and p38, blocked IFN-gamma, IL-8, and MIP1alpha production, suggesting that MAPKs are regulating 2DL4-mediated cytokine production in a nonredundant manner. Activation of both p38 and ERK appear to be upstream of the stimulation of NF-kappaB. Mutation of a transmembrane arginine in 2DL4 to glycine (R/G mutant) abrogated FcepsilonRI-gamma association, as well as receptor-mediated cytolytic activity and calcium responses. Surprisingly, the R/G mutant still activated MAPKs and the NF-kappaB pathway and selectively stimulated the production of MIP1alpha, but not that of IFN-gamma or IL-8. In conclusion, we provide evidence that the activating functions of 2DL4 can be compartmentalized into two distinct structural modules: 1) through transmembrane association with FcepsilonRI-gamma; and 2) through another receptor domain independent of the transmembrane arginine.
Miah
S M Shahjahan
SM
Fox Chase Cancer Center, Division of Basic Science, Institute for Cancer Research, Philadelphia, PA 19111, USA.
Hughes
Tracey L
TL
Campbell
Kerry S
KS
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001120:Arginine / Q000235:genetics; D045744:Cell Line, Tumor; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D006801:Humans; D007694:Killer Cells, Natural / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000276:immunology; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D017455:Receptors, IgE / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054345:Receptors, KIR2DL4 / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*
D016328:NF-kappa B; D017455:Receptors, IgE; D054345:Receptors, KIR2DL4; D001120:Arginine; D048049:Extracellular Signal-Regulated MAP Kinases