Apoptosis DAP-kinase Regions That Regulate Cell Death

The death-associated protein kinase (DAP-kinase) promotes apoptotic signaling by Interferon , Fas, and Tumor Necrosis Factor α (TNF-α). Raveh et al. overexpressed random DAP-kinase fragments in cells to determine whether specific regions of the protein could prevent apoptosis. Four fragments that blocked apoptosis included: (i) an ankyrin repeat region, (ii) the linker region, (iii) the death domain central core, and (iv) the COOH-terminal 17 residues. Each fragment inhibited TNF-α-directed apoptosis in cells possessing DAP-kinase, but not in DAP-kinase deficient cells, indicating that fragment-dependent inhibition occurs through a dominant negative effect on DAP-kinase. To determine whether the COOH-terminal fragment regulated DAP-kinase catalytic activity, a COOH-terminal DAP-kinase deletion mutant, tail, was overexpressed in cells. Although tail possessed kinase activity similar to wild-type DAP-kinase, the ability of tail to effect apoptosis was greatly increased, equaling apoptosis mediated by a constitutively active DAP-kinase mutant. Thus, the COOH-terminus could be involved in negative regulation of DAP-kinase through an intramolecular mechanism that tightly regulates DAP-kinase interaction with downstream effectors.

Raveh, T., Berissi, H., Eisenstein, M., Spivak, T., and Kimchi, A. (2000) A functional genetic screen identifies regions at the C-terminal tail and death-domain of death-associated protein kinase that are critical for its proapoptotic activity. Proc. Natl. Acad. Sci. U.S.A. 97: 1572-1577. [Abstract] [Full Text]