Browsing by Author "Quach, Jeanie"

Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Entamoeba histolytica-Induced Caspase-4 Activation Regulates IL-1β Secretion Through Caspase-1
    (2018-04-27) Quach, Jeanie; Chadee, Kris C.; McCafferty, Donna-Marie; Yates, Robin Michael
    Entamoeba histolytica (Eh) is the causative agent of amebiasis, one of the top four parasitic causes of mortality worldwide. In 90% of infected individuals, Eh harmlessly colonizes the large intestine and results in a non-invasive and asymptomatic infection. In the remaining 10% of infected individuals, the parasite breaches the intestinal barrier causing amebic colitis and in rare cases, it can cause extra-intestinal lesions, mainly liver abscesses. During invasion, Eh encounter macrophages in the lamina propria and this intricate host-parasite interaction is critical in eliciting a tissue damaging raging pro-inflammatory response. When Eh binds macrophages via the Gal-lectin, surface EhCP-A5 ligates α5β1 integrin to activate caspase-1 in a complex known as the NLRP3 inflammasome. In this study, we investigated the parasite requirements underlying macrophage caspase-4 and -1 activation and the role caspase-4 play in augmenting pro-inflammatory cytokine responses. Surprisingly, caspase-4 activation was similar to caspase-1 requiring live Eh attachment via the Gal-lectin, EhCP-A5 and cellular stresses such as K+ efflux and ROS. However, unlike caspase-1, caspase-4 activation was independent of ASC and NLRP3. Using CRISPR/Cas9 gene editing of caspase-4 and caspase-1 in human macrophages, we determined that caspase-1 and bioactive IL-1β release was highly dependent on caspase-4 activation in response to Eh. Formaldehyde cross-linking to stabilize protein-protein interactions in transfected COS-7 cells stimulated with Eh revealed that caspase-4 specifically interacted with caspase-1 in a protein complex that enhanced the cleavage of caspase-1 CARD domains to augment IL-1β release. The mouse ortholog caspase-11, displayed similar requirements for its activation, however, it was not involved in regulating caspase-1 activation in the same way as caspase-4. These findings reveal a novel role for human caspase-4 as a critical sensor molecule to amplify downstream pro-inflammatory responses when macrophage encounters live Eh.