Human caspase-4 mediates noncanonical inflammasome activation against gram-negative bacterial pathogens.
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Casson CN, Yu J, Reyes VM, Taschuk FO, Yadav A, Copenhaver AM, Nguyen HT, Collman RG, Shin S
Human caspase-4 mediates noncanonical inflammasome activation against gram-negative bacterial pathogens.
Proc Natl Acad Sci U S A. 2015 May 26;112(21):6688-93. doi: 10.1073/pnas.1421699112. Epub 2015 May 11.
- PubMed ID
- 25964352 [ View in PubMed]
- Abstract
Inflammasomes are critical for host defense against bacterial pathogens. In murine macrophages infected by gram-negative bacteria, the canonical inflammasome activates caspase-1 to mediate pyroptotic cell death and release of IL-1 family cytokines. Additionally, a noncanonical inflammasome controlled by caspase-11 induces cell death and IL-1 release. However, humans do not encode caspase-11. Instead, humans encode two putative orthologs: caspase-4 and caspase-5. Whether either ortholog functions similar to caspase-11 is poorly defined. Therefore, we sought to define the inflammatory caspases in primary human macrophages that regulate inflammasome responses to gram-negative bacteria. We find that human macrophages activate inflammasomes specifically in response to diverse gram-negative bacterial pathogens that introduce bacterial products into the host cytosol using specialized secretion systems. In primary human macrophages, IL-1beta secretion requires the caspase-1 inflammasome, whereas IL-1alpha release and cell death are caspase-1-independent. Instead, caspase-4 mediates IL-1alpha release and cell death. Our findings implicate human caspase-4 as a critical regulator of noncanonical inflammasome activation that initiates defense against bacterial pathogens in primary human macrophages.