title: Interleukin 1 beta propeptide is detected intracellularly and extracellularly when human monocytes are stimulated with LPS in vitro.
abstract: Human interleukin 1 beta (IL-1 beta) is synthesized as an inactive precursor that is cleaved by IL-1 converting enzyme (ICE) between Asp116 and Ala117 to form COOH-terminal mature IL-1 beta and NH2-terminal IL-1 beta propeptide. Little is known about the fate of the NH2-terminal cleavage product. In this study, human recombinant (hr)IL-1 beta propeptide (amino acids 2-116) was produced and used to prepare specific antibodies which do not recognize mature human IL-1 beta. These anti-propeptide antibodies were used for immunoprecipitation of biosynthetically labeled proteins from lipopolysaccharide-stimulated human monocytes. Analysis of immunoprecipitates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed that these antibodies recognize precursor IL-1 beta and two unique proteins: one migrating at 17.5 kD and one at 14 kD. The larger of these two proteins has a migration nearly identical to that of the recombinant IL-1 beta propeptide, and most likely represents naturally derived propeptide. The protein migrating at 14 kD may result from a second cleavage by ICE, between Asp27 and Gly28. These proteins accumulate intracellularly and extracellularly during pulse-chase experiments, and therefore represent stable products of precursor IL-1 beta cleavage.
authors.affiliation: Department of Pediatrics, University of Tennessee, Memphis.
authors.forename: G C
authors.initials: GC
authors.lastname: Higgins
authors.forename: J L
authors.initials: JL
authors.lastname: Foster
authors.forename: A E
authors.initials: AE
authors.lastname: Postlethwaite
mesh_terms: D000918:Antibody Specificity; D001483:Base Sequence; D001667:Binding, Competitive; D015153:Blotting, Western; D002846:Chromatography, Affinity; D004247:DNA; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D007375:Interleukin-1; D008070:Lipopolysaccharides; D011498:Protein Precursors; D011994:Recombinant Proteins; D004247:DNA