Molecular cloning and characterization of FADD from the manila clam Ruditapes philippinarum

Abstract

Fas-associated protein with death domain (FADD) is an essential element in cell death, and also implicates in cell cycle progression, inflammation and innate immunity. In the study, an FADD (designated as RpFADD) was identified and characterized from manila clam, Ruditapes philippinarum. Multiple alignments and phylogenetic analysis strongly suggested that RpFADD was a new member of the FADD family. The RpFADD transcripts were constitutively expressed in a wide range of tissues, and dominantly expressed in hemocytes. After challenged with Vibrio anguillarum or Micrococcus luteus, the expression level of RpFADD transcripts was significantly induced and reached the maximum level at 72 h and 48 h, respectively. Knockdown of RpFADD down-regulated the transcript levels of RpIKK, RpTAK1 and RpNF-κB with the exception of RpIκB. Moreover, RpFADD primarily localized in the cell cytoplasm, and its over-expression promoted the apoptosis of HeLa cells. These results revealed that RpFADD perhaps regulated the NF-κB signaling pathways positively, which provided a better understanding of RpFADD in innate immunity.