Promotes caspase-mediated apoptosis. This proapoptotic activity is mediated predominantly through the activation of caspase-9. May be a component of the inflammasome, a protein complex which also includes NALP2, CARD8 and CASP1 and whose function would be the activation of proinflammatory caspases. Tissue specificity: Widely expressed at low levels. Detected in peripheral blood leukocytes, lung, small intestine, spleen, thymus, colon and at lower levels in placenta, liver and kidney. Very l