Oligomerized CARD16 promotes caspase-1 assembly and IL-1 β processing

Publication date: 2015 Source:FEBS Open Bio, Volume 5 Author(s): Tadayoshi Karasawa, Akira Kawashima, Fumitake Usui, Hiroaki Kimura, Koumei Shirasuna, Yoshiyuki Inoue, Takanori Komada, Motoi Kobayashi, Yoshiko Mizushina, Junji Sagara, Masafumi Takahashi Increasing evidence indicates that caspase recruitment domain (CARD)-mediated caspase-1 (CASP1) assembly is an essential process for its activation and subsequent interleukin (IL)-1β release, leading to the initiation of inflammation. Both CARD16 and CARD17 were previously reported as inhibitory homologs of CASP1; however, their molecular function remains unclear. Here, we identified that oligomerization activity allows CARD16 to function as a CASP1 activator. We investigated the molecular characteristics of CARD16 and CARD17 in transiently transfected HeLa cells. Although both CARD16 and CARD17 interacted with CASP1CARD, only CARD16 formed a homo-oligomer. Oligomerized CARD16 formed a filament-like structure with CASP1CARD and a speck with apoptosis-associated speck-like protein containing a CARD. A filament-like structure formed by CARD16 promoted CASP1 filament assembly and IL-1β release. In contrast, CARD17 did not form a homo-oligomer or filaments and inhibited CASP1-dependent IL-1β release. Mutated CARD16D27G, mimicking the CARD17 amino acid sequence, formed a homo-oligomer but failed to form a filament-like structure. Consequently, CARD16D27G weakly promoted CASP1 filament assembly and subse...
Source: FEBS Open Bio - Category: Molecular Biology Source Type: research