Disease-associated mutations in CIAS1 induce cathepsin B-dependent rapid cell death of human THP-1 monocytic cells

Mutations in the cold-induced autoinflammatory syndrome 1 (CIAS1) gene are associated with a spectrum of autoinflammatory diseases, including familial cold autoinflammatory syndrome, Muckle-Wells syndrome, and chronic infantile neurologic, cutaneous, articular syndrome, also known as neonatal-onset multisystem inflammatory disease. CIAS1 encodes cryopyrin, a protein that localizes to the cytosol and functions as pattern recognition receptor. Cryopyrin also participates in nuclear factor-kappa B regulation and caspase-1-mediated maturation of interleukin 1 R. In this study, we showed that disease-associated mutations in CIAS1 induced rapid cell death of THP-1 monocytic cells. The features of cell death, including 7-AAD staining, the presence of cellular edema, and early membrane damage resulting in lactate dehydrogenase (LDH) release, indicated that it was more likely to be necrosis than apoptosis, and was effectively blocked with the cathepsin B-specific inhibitor CA-074-Me. CA-074-Me also suppressed induced by disease-associated mutation lysosomal leakage and mitochondrial damage. In addition, R837, a recently identified activator of cryopyrin-associated inflammasomes, induced cell death in wild type CIAS1-transfected THP-1 cells. These results indicated that monocytes undergo rapid cell death in a cathepsin B-dependent manner upon activation of cryopyrin, which is also a specific phenomenon induced by disease-associated mutation of CIAS1.