During bacterial invasion, protein complexes called inflammasomes are activated. This in turn activates caspase enzymes, which cleave gasdermin D in two, releasing an active fragment known as gasdermin-D-NT. The fragments (shown as red ovals) perforate the membranes of the bacteria (in green) that are infecting cells, killing them, and also group together to form pores that punch holes in the membrane of the infected cell. This causes pyroptosis: The cell explodes open, releasing bacteria together with cytokines that sound an immune alarm. Outside the cell, gasdermin-D-NT fragments can also kill bacteria directly.
Xing Liu, PhD, Boston Children's Hospital and Youdong Pan, PhD, Brigham & Women's Hospital