Flagellin

Unconventional protein secretion represents an important process of the inflammatory response. The release of the pro-inflammatory cytokine interleukin (IL)-1beta which burst during pyroptosis as a consequence of gasdermin D plasma membrane pore formation, can also occur through other unconventional secretion pathways dependent on caspase-1 activation. However, how caspase-1 mediates cytokine release independently of gasdermin D remains poorly understood. Here we show that following caspase-1 activation by different inflammasomes, caspase-1 cleaves early endosome autoantigen 1 (EEA1) protein at Asp(127/132). Caspase-1 activation also results in the release of the endosomal EEA1 protein in a gasdermin D-independent manner. EEA1 knock-down results in adecreased release of caspase-1 and IL-1beta, but the pyroptotic release of other inflammasome components and lactate dehydrogenase was not affected. This study shows how caspase-1 control the release of EEA1 and IL-1beta in a pyroptotic-independent manner.