Research ArticleEVOLUTION

Characterization of the Extrinsic Apoptotic Pathway in the Basal Chordate Amphioxus

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Science Signaling  14 Sep 2010:
Vol. 3, Issue 139, pp. ra66
DOI: 10.1126/scisignal.2000906

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Ahead of Its Time

Extrinsic apoptosis is mediated by cell surface death receptor (DR) proteins, which are members of the tumor necrosis factor receptor (TNFR) superfamily, and is thought to be restricted to vertebrates. TNFR family members, such as the Fas receptor, contain death domains (DDs) through which they interact with DD-containing adaptor proteins, such as Fas-associated DD (FADD), to activate initiator caspases and trigger apoptosis. Noting that the genome of the basal chordate amphioxus Branchiostoma belcheri tsingtauense (Bbt) contains genes that encode DRs and DD-containing adaptors, Yuan et al. investigated whether extrinsic apoptotic signaling occurred in this archetypal vertebrate. They analyzed two amphioxus DD-containing proteins, BbtFADDs 1 and 2, and a previously uncharacterized DR-containing protein, BbtDR1, which triggered responses ranging from apoptosis to gene activation depending on the adaptors with which it interacted. Together, these data suggest that apoptosis mediated through DRs was established at the emergence of the chordates, at least 550 million years ago.

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