title: Interleukin-1β Processing Is Dependent on a Calcium-mediated Interaction with Calmodulin.
abstract: The secretion of IL-1β is a central event in the initiation of inflammation. Unlike most other cytokines, the secretion of IL-1β requires two signals: one signal to induce the intracellular up-regulation of pro-IL-1β and a second signal to drive secretion of the bioactive molecule. The release of pro-IL-1β is a complex process involving proteolytic cleavage by caspase-1. However, the exact mechanism of secretion is poorly understood. Here we sought to identify novel proteins involved in IL-1β secretion and intracellular processing to gain further insights into the mechanism of IL-1 release. A human proteome microarray containing 19,951 unique proteins was used to identify proteins that bind human recombinant pro-IL-1β. Probes with a signal-to-noise ratio of >3 were defined as biologically relevant. In these analyses, calmodulin was identified as a particularly strong hit, with a signal-to-noise ratio of ∼ 11. Using an ELISA-based protein-binding assay, the interaction of recombinant calmodulin with pro-IL-1β, but not mature IL-1β, was confirmed and shown to be calcium-dependent. Finally, using small molecule inhibitors, it was demonstrated that both calcium and calmodulin were required for nigericin-induced IL-1β secretion in THP-1 cells and primary human monocytes. Together, these data suggest that, following calcium influx into the cell, pro-IL-1β interacts with calmodulin and that this interaction is important for IL-1β processing and release.
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and joseph.ainscough@postgrad.manchester.ac.uk.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Ainscough
authors.affiliation: the Procter & Gamble Co., Cincinnati, Ohio 45253.
authors.forename: G Frank
authors.initials: GF
authors.lastname: Gerberick
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Ian
authors.initials: I
authors.lastname: Kimber
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Dearman
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D040081:Protein Array Analysis; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis; D040901:Proteomics
chemical_list: D002147:Calmodulin; C508585:IL1B protein, human; D053583:Interleukin-1beta; D011498:Protein Precursors; D002118:Calcium
keywords: IL-1; IL-1β; calcium; calmodulin (CaM); caspase 1 (CASP1); inflammasome