Human caspase-4 and caspase-5 regulate the one-step non-canonical inflammasome activation in monocytes

Elena Viganò, Catherine Emma Diamond, Roberto Spreafico, Akhila Balachander, Radoslaw M. Sobota, Alessandra Mortellaro*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

269 Citations (Scopus)


Monocytes promote the early host response to infection releasing key pro-inflammatory cytokines, such as IL-1β. The biologically inactive IL-1β precursor is processed to active form by inflammasomes, multi-protein complexes activating caspase-1. Human monocytes exhibit an unconventional one-step pathway of inflammasome activation in response to lipopolysaccharide (LPS) alone. Although this lineage-restricted mechanism is likely to contribute to the pathology of endotoxin shock, signalling pathways regulating this mechanism are currently unknown. Here we report that caspase-4 and caspase-5 mediate IL-1α and IL-1β release from human monocytes after LPS stimulation. Although caspase-4 remains uncleaved, caspase-5 undergoes rapid processing upon LPS treatment. We also identify an additional caspase-5 cleavage product in LPS-stimulated monocytes, which correlates with IL-1 secretion. This one-step pathway requires Syk activity and Ca 2+ flux instigated by CD14/TLR4-mediated LPS internalization. Identification of caspase-4/5 as the key determinants of one-step inflammasome activation in human monocytes provides potential targets for therapeutic intervention in endotoxin shock.

Original languageEnglish
Article number8761
JournalNature Communications
Publication statusPublished - 28 Oct 2015
Externally publishedYes


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