Conserved function of caspase-8 in apoptosis during bony fish evolution

Abstract

Caspase-8, a member of the caspase family, plays an important role in apoptotic signal transduction in mammals. Here we report the identification and characterization of the caspase-8 (casp8) gene in the zebrafish Danio rerio. The zebrafish casp8 gene has a genomic organization similar to mammalian casp8 genes, consisting of 10 exons. By chromosome mapping, we found that casp8 maps on linkage group 6 (LG6), a zebrafish chromosome segment orthologous to the long arm of human Chr. 2, which carries CASP8. In contrast, the zebrafish casp10-like gene and the cflar gene separately localize on LG9 and LG11, respectively, and these genes form a cluster with CASP8 on the human chromosome. This chromosomal segregation is unique to fish but not other vertebrates. Furthermore, we examined the function of zebrafish Casp8 protein in mammalian cells, and showed that it has pro-apoptotic activity when overexpressed. In addition, this molecule was capable of transmitting apoptotic signals mediated through not only Fas but also the TNF receptor in mouse Casp8-deficient cells. Expression analysis showed that casp8 is maternally expressed, and transcripts continue to be present throughout embryogenesis and into larval stages. These results show that zebrafish casp8 has a structure and function similar to mammalian CASP8 orthologs, and our study suggests that the role of caspase-8 in the apoptotic signal pathway has been conserved over at least 450 million years of vertebrate evolution.

Molecular Characterization of Caspase8 in Grass Carp (Ctenopharyngodon Idella)

“…In consideration of vital function of caspases, caspase8 gene has only been identified in a few fish species [10,14]. Based on computational genomic structural analyses, we isolated the putative caspase8 coding sequence from grass carp head kidney (Fig.…”

“…According to their structure analysis, caspase8 has an extended amino-terminal prodomain named death effector domain (DED) and a CASc domain (carboxyl-terminal catalytic domain), similar to caspase10 and different from other caspase homologs including caspase1 and csapase3. The caspases have been identified in various fish, including zebrafish [10,11], sea bass [12], rock bream [13], and striped murrel [14]. In this study, we isolated and identified the caspase8 from grass carp.…”

“…In vertebrates, most caspase homologs have been identified in mammal and teleost [8][9][10]. According to their structure analysis, caspase8 has an extended amino-terminal prodomain named death effector domain (DED) and a CASc domain (carboxyl-terminal catalytic domain), similar to caspase10 and different from other caspase homologs including caspase1 and csapase3.…”

Control of Programmed Cell Death During Zebrafish Embryonic Development

“…A clear ortholog of FADD, containing a DD and a death effector domain (DED), has been identified as well as an ortholog of Caspase 8, casp8a [31,35]. The latter possesses an N-terminal DED which allow association with FADD and a QACQG active-site motif that is characteristic of Caspases 8 and 10 in mammals.…”

“…Caspase 8a and FADD are both required for apoptosis induced by Apo2L/TRAIL orthologs in zebrafish embryos. Moreover, Caspase 8a is functionally conserved as it restores death receptor-induced apoptosis in mouse cells lacking endogenous Caspase 8 [35]. Two other genes related to casp8a exist (casp8l1 and casp8l2) but their possible involvement in the cell-extrinsic pathway is unclear.…”