ABSTRACT
Interleukin-1 (IL-1) is a major proinflammatory cytokine mediating local and systemic responses of the immune system. Two types of IL-1 receptors are known, but only the IL-1 receptor type I initiates biological responses. Here we show that two proteins with nucleic acid binding potential and mortalin, a member of the HSP70-family, are associated with the IL-1 receptor type I irrespective of IL-1 binding. The association of mortalin with the IL-1 receptor type I is specifically reversed by ATP concentrations in the physiological range. Other nucleotides are not or much less effective. The in vitro dissociation of mortalin effects neither the receptor association nor the activity of IRAK, which initiates the IL-1-dependent phosphorylation cascade. The roles of the receptor-associated proteins are therefore discussed in the context of receptor internalisation.
Subject(s)
Adenosine Triphosphate/pharmacology , CCAAT-Enhancer-Binding Proteins , HSP70 Heat-Shock Proteins/metabolism , RNA-Binding Protein FUS , Receptors, Interleukin-1/metabolism , Amino Acid Sequence , Animals , Carrier Proteins , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , Dose-Response Relationship, Drug , HSP70 Heat-Shock Proteins/chemistry , Humans , Interleukin-1/metabolism , Interleukin-1/pharmacology , Interleukin-1 Receptor-Associated Kinases , Mice , Mitochondrial Proteins , Molecular Sequence Data , Molecular Weight , Nuclear Proteins/chemistry , Nuclear Proteins/metabolism , Nucleotides/pharmacology , Oncogene Proteins, Fusion/chemistry , Oncogene Proteins, Fusion/metabolism , Phosphorylation/drug effects , Protein Binding/drug effects , Protein Kinases/metabolism , Receptors, Interleukin-1 Type I , Sequence Homology, Amino Acid , Signal Transduction , Transcription Factor CHOP , Tumor Cells, CulturedABSTRACT
Mycoplasmas are potent macrophage stimulators. The active principle are lipopeptides or lipoproteins with a characteristic N-terminal S-[dihydroxypropyl]-cysteinyl group bearing two ester-bound fatty acids and lacking the amide-bound one common to other bacterial lipoproteins. Using synthetic analogues of mycoplasmal lipopeptides, we investigated activation of the transcription factor NF-kappaB in the C3H/HeJ mouse-derived DMBM-3 cell line. The lipopeptides activated NF-kappaB at below nanomolar concentrations. Activation in the murine system occurred distinctly earlier than TNF-alpha liberation, excluding autocrine stimulation by TNF-alpha. As determined from a supershift experiment, the active NF-kappaB complex consisted of the heterodimer p50/p65(RelA). The relevance of these findings for the inflammatory response to mycoplasmas and for mycoplasma-mediated effects on HIV-infected macrophages is discussed.
