| Abstract | The death domain (DD) is a conserved region of about 80 residues found on death receptors, and which is required for death signalling, as well as a variety of non-apoptotic functions [ 11828422, 12655292]. Proteins containing this domain include the low affinity neurotrophin receptor p73, Fas, FADD (Fas-associated death domain protein), TNF-1 (tumour necrosis factor receptor-1), Pelle protein kinase, and the Tube adaptor protein [15226512].
The induction of apoptosis also relies on the presence of a second domain, called the death effector domain. The death effector domain (DED) occurs in proteins that regulate programmed cell death, including both pro- and anti-apoptotic proteins; many of these proteins are also involved in controlling cellular activation and proliferation pathways [12719729]. Proteins containing this domain include FADD (DED N-terminal, DD C-terminal), PEA-15 (phosphoproteins enriched in astrocytes 15kDa), caspases and FLIP.
The induction of apoptosis results in the activation of caspases, a family of aspartyl-specific cysteine proteases that are the main executioners of apoptosis. For example, the DED of FADD recruits two DED-containing caspases, caspase-8 and caspase-10, to form the death-inducing signal complex, which initiates apoptosis. Proteins containing the caspase recruitment domain (CARD) are involved in the recruitment and activation of caspases during apoptosis [12101092]. Other CARD proteins participate in NF-kappaB signalling pathways associated with innate or adaptive immune responses. Proteins containing CARD include Raidd, APAF-1 (apoptotic protease activating factor 1), procaspase 9 and iceberg (inhibitor of interleukin-1-beta generation).
The DD shows strong structural similarity to both DED and CARD. They all display a 6-helical closed bundle fold, with greek key topology and an internal psuedo two-fold symmetry. However, despite their overall similarity in topology, each domain forms specialised interactions, typically only with members of its own subfamily, for example DED with DED. |
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