Ligand-dependent transcriptional activities of four torafugu pufferfish Takifugu rubripes peroxisome proliferator-activated receptors.

Structural and functional properties were investigated for four peroxisome proliferator-activated receptors (PPARs), PPARalpha1, PPARalpha2, PPARbeta, and PPARgamma, from torafugu pufferfish Takifugu rubripes and determined for their transcriptional activity by the reporter assay using reporter plasmids containing three copies of the acyl-CoA oxidase PPAR response element. Although torafugu PPARs showed a high similarity in the primary structure to other vertebrate counterparts, torafugu PPARalpha2 and gamma contained additional sequences of 21 and 28 amino acids, respectively, as in the case of other teleost fish species when compared with African clawed frog counterparts. The transcriptional activity of torafugu PPARalpha1 was enhanced 4.5- and 11.5-fold by Wy-14643 and 5,8,11,14-eicosatetraynoic acid (ETYA) each at 10 microM, respectively, whereas that of PPARalpha2, 4.5- and 7.3-fold at the same concentration of the respective ligands, respectively. The activities of torafugu PPARalpha1 and alpha2 were also enhanced 5.6- and 6.3-fold by ETYA at 1 microM, respectively, but not by Wy-14643 at this concentration. Furthermore, the activities of the two torafugu PPARalphas were enhanced 4.3- and 7.6-fold by arachidonic acid, 4.4- and 5.2-fold by docosahexaenoic acid, and 6.7- and 8.0-fold by eicosapentaenoic acid each at 50 microM, respectively. On the other hand, the activities of torafugu PPARbeta and gamma were not changed by Wy-14643, ETYA, rosiglitazone, nor PUFAs. These results suggest that the activities of torafugu PPARbeta and gamma require undefined ligands. Alternatively, the molecular mechanisms involved in their activation are different from those of other vertebrates.

Identification of three isoforms for mitochondrial adenine nucleotide translocator in the pufferfish Takifugu rubripes.

Three adenine nucleotide translocator (ANT) genes were identified through in silico data mining of the Fugu genome database along with isolation of their corresponding cDNAs in vivo from the pufferfish (Takifugu rubripes). As a result of phylogenetic analysis, the ANT gene on scaffold_254 corresponded to mammalian ANT1, whereas both of those on scaffold_6 and scaffold_598 to mammalian ANT3. The ANT gene encoded by scaffold_6 was expressed ubiquitously in various tissues, whereas the ANT genes encoded by scaffold_254 and scaffold_598 were predominantly expressed in skeletal muscle and heart, respectively.

Characterization of the pufferfish Takifugu rubripes apolipoprotein multigene family.

We have characterized the apolipoprotein multigene family of the pufferfish Takifugu rubripes. The pufferfish mainly contains 28-kDa, 27-kDa, and 14-kDa apolipoproteins in its plasma and was designated apo-28 kDa, apo-27 kDa, and apo-14 kDa, respectively. N-terminal amino acid sequencing revealed that pufferfish apo-28 kDa and apo-27 kDa have an identical amino acid sequence except an additional propeptide in the former; and both are homologues of apoA-I from other animals. The sequence of pufferfish apo-14 kDa is homologous to that of eel apo-14 kDa previously reported, both being apparently specific to fish. In silico screening, using the publicly available Fugu genome database confirmed the pufferfish apoA-I and apo-14 kDa genes. The database further contained the genes encoding four types of apoA-IV, one apoC-II and two types of apoE. Thus, pufferfish contains nine genes encoding apolipoprotein multigene family. Two apoA-IV and one apoE genes were tandemly arrayed and located on one scaffold. Thus two sets of these genes formed two gene clusters. The apoC-II and apo-14 kDa genes are also located on a single scaffold. apoA-I and apo-14 kDa gene transcripts were mainly expressed in liver and less abundantly in brain. The transcripts of the former gene were also observed in intestine. In contrast, the transcripts encoding four apoA-IVs, one apoC-II, and two apoEs were mainly expressed in intestine. These structural details of pufferfish apolipoproteins and tissue distribution of their gene transcripts provide a novel evidence for better understanding of evolutionary relationships of apolipoprotein multigene family.