IL-1β in humans and mice does not encode a typical signal peptide and, as a result, newly synthesized pro-IL-1β accumulates within the cytoplasm of activated monocytes and macrophages . Conversion of the inactive pro-IL-1β to its mature form requires the proteolytic action of IL-1β-converting enzyme (ICE), also termed caspase-1 . Secretion of mature IL-1β from LPS-activated monocytes/macrophages is not a constitutive process. These cells must encounter a secondary stimulus that specifically activates the posttranslational processing events . Moreover, owing to its pro-inflammatory nature, IL-1β is regarded as a tumor-promoting cytokine. In fact, enhanced tumor metastasis and angiogenesis has been observed under the influence of IL-1β . IL-1β is able to facilitate tumor progression in murine models of lung cancer. In addition, upregulation of metastasis and tumor angiogenesis by IL-1β has been associated with increased activity of matrix metalloproteinases and expression of the pro-angiogenic molecule hepatocyte growth factor .
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Function:
Interleukin (IL)-1β is a cytokine with a key role in the pathophysiology of local and systemic inflammation. IL-1β induces cytokine, chemokine, proinflammatory molecule secretion, and adhesion molecule expression in diverse cells.
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Cellular Localization:
Cytoplasm, cytosol . Secreted . Lysosome . Secreted, extracellular exosome . The precursor is cytosolic (PubMed:15192144). In response to inflammasome-activating signals, such as ATP for NLRP3 inflammasome or bacterial flagellin for NLRC4 inflammasome, cleaved and secreted (PubMed:24201029, PubMed:33377178, PubMed:33883744). Mature form is secreted and released in the extracellular milieu by passing through the gasdermin-D (GSDMD) pore (PubMed:33883744). In contrast, the precursor form is not released, due to the presence of an acidic region that is proteolytically removed by CASP1 during maturation (PubMed:33883744). The secretion is dependent on protein unfolding and facilitated by the cargo receptor TMED10 (PubMed:32272059). .
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Tissue Expression:
Expressed in activated monocytes/macrophages (at protein level).