16-aa peptide from Human FLASH. Human control peptide sequence is 92% conserved in mouse FLASH.
Apoptosis or programmed cell death is a fundamental cellular process that is essential for normal tissue development and abnormal growth. Apoptosis is driven by two classes of specialized proteases known as caspases (Cysteine Aspartase). Several key factors are released from the mitochondria that regulate apoptosis. The first such factor (Cytochrome-C) to be described binds to a cytoplasmic scaffolding protein called Apaf-1 (Apoptosis Protease activating factor-1), a homolog of C. elegans Ced-4. Both Apaf-1 and Ced-4 are composed of an N-terminal Caspase Recrutiment domain (CARD) linked to a Nuceoltide-bidning domain (NBD), also known as NB-ARC or NOD domain. Ced-4 and Apaf-1 self-associate via the NBD and activate Casp-3 and -9. In response to certain apoptotic stimuli, Cytochrome-C is released from the mitochondria and binds to Apaf-1 to form a ternary complex with, and activate, the initiator pro-caspase-9. Active caspase-9 then turns on downstream effector caspases, initiating apoptosis. Recently, Additional members of Apaf-1 family, NOD1/CARD4 and NOD2 have been cloned and characterized.
FLASH or Caspase 8-associted protein 2/CASP8AP2 (mouse 1962-aa, ~ 220kD; human 1982-aa, chromosome 6) contains motif structurally related to CED4/Apaf1 and 2 tandem-repeated DED homologous domains. In adult mouse, highest expression was found in heart, brain, thymus, lung, testis, and spleen, and much lower expression in liver, kidney, and skeletal muscle. Flash binds caspase-8 and Fadd. It also specifically coimmunoprecipitated with activated Fas, suggesting that Casp8ap2 is part of the death-inducing signaling complex (DISC). Inhibition of FLASH expression abolishes TNF-induced NFKB activation in embryonic kidney cells. Expression or overexpression of FLASH activates NFKB through a central oligomerization domain, called the NFKB activation domain (NAD), in a TRAF2-NIK-IKKA-dependent pathway. FLASH coordinates downstream NFKB activity via a TRAF2-dependent pathway in TNF signaling.
