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Acute hepatopancreatic necrosis disease (AHPND) is a severe, newly emergent penaeid shrimp disease caused by Vibrio parahaemolyticus that has already led to tremendous losses in the cultured shrimp industry. Until now, its disease-causing mechanism has remained unclear. Here we show that an AHPND-causing strain of V. parahaemolyticus contains a 70-kbp plasmid (pVA1) with a postsegregational killing system, and that the ability to cause disease is abolished by the natural absence or experimental deletion of the plasmid-encoded homologs of the Photorhabdus insect-related (Pir) toxins PirA and PirB. We determined the crystal structure of the V. parahaemolyticus PirA and PirB (PirAvp and PirBvp) proteins and found that the overall structural topology of PirAvp/PirBvp is very similar to that of the Bacillus Cry insecticidal toxin-like proteins, despite the low sequence identity (<10%). This structural similarity suggests that the putative PirABvp heterodimer might emulate the functional domains of the Cry protein, and in particular its pore-forming activity. The gene organization of pVA1 further suggested that pirABvp may be lost or acquired by horizontal gene transfer via transposition or homologous recombination.

Testicular orphan nuclear receptor 4 (TR4) is an orphan member of the nuclear receptor superfamily with diverse physiological functions. Using TR4 knockout (TR4 ؊/؊ ) mice to study its function in cardiovascular diseases, we found reduced cluster of differentiation (CD)36 expression with reduced foam cell formation in TR4 ؊/؊ mice. Mechanistic dissection suggests that TR4 induces CD36 protein and mRNA expression via a transcriptional regulation. Interestingly, we found this TR4-mediated CD36 transactivation can be further enhanced by polyunsaturated fatty acids (PUFAs), such as omega-3 and -6 fatty acids, and their metabolites such as 15-hydroxyeico-satetraonic acid (15-HETE) and 13-hydroxy octa-deca dieonic acid (13-HODE) and thiazolidinedione (TZD)-rosiglitazone. Both electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrate that TR4 binds to the TR4 response element located on the CD36 5 -promoter region for the induction of CD36 expression. Stably transfected TR4-siRNA or functional TR4 cDNA in the RAW264.7 macrophage cells resulted in either decreased or increased CD36 expression with decreased or increased foam cell formation. Restoring functional CD36 cDNA in the TR4 knockdown macrophage cells reversed the decreased foam cell formation. Together, these results reveal an important signaling pathway controlling CD36-mediated foam cell formation/cardiovascular diseases, and findings that TR4 transactivation can be activated via its ligands/activators, such as PUFA metabolites and TZD, may provide a platform to screen new drug(s) to battle the metabolism syndrome, diabetes, and cardiovascular diseases.A therosclerosis is a disease of both lipid disorder and chronic inflammation that results from interactions of modified lipoproteins, monocyte-derived macrophages, T cells, and cells from the vessel wall (1). Foam cell formation has a central role in the pathogenesis of atherosclerosis. Uptake of oxidized forms of low-density lipoproteins (oxLDL) induces macrophage maturation to form foam cells, which lead to the fatty streaks characteristic of early atherosclerosis. This uptake is mediated by specific macrophage scavenger receptors, including cluster of differentiation (CD)36 (2) and scavenger receptor A (SRA) (3), which recognize and internalize modified lipoproteins such as oxLDL. Among these 2 SRAs, CD36 accounts for a large proportion of oxLDL uptake by macrophages (4-7). Combined inhibition of SRA and CD36 blocks human and mouse foam cell formation in vitro, yet human subjects carrying CD36 mutation usually have a higher risk for atherosclerosis. CD36 roles in oxLDL-mediated foam cell formation in vitro are clear, but its roles in atherosclerosis in vivo are equivocal, which can be either atherogenic (6-8) or atheroprotective (9-11).Peroxisome proliferator-activated receptor (PPAR)␥ is one of the major CD36 upstream regulators in which PPAR␥/retinoid X receptor (RXR) can bind to DNA responsive elements on its 5Ј-promoter to modulate CD36 gene expression (12)....

The white spot syndrome virus DNA polymerase (DNA pol) gene (WSSV dnapol) has already been tentatively identified based on the presence of highly conserved motifs, but it shows low overall homology with other DNA pols and is also much larger (2351 amino acid residues vs 913-1244 aa). In the present study we perform a transcriptional analysis of the WSSV dnapol gene using the total RNA isolated from WSSV-infected shrimp at different times after infection. Northern blot analysis with a WSSV dnapol-specific riboprobe found a major transcript of 7.5 kb. 5'-RACE revealed that the major transcription start point is located 27 nucleotides downstream of the TATA box, at the nucleotide residue A within a CAGT motif, one of the initiator (Inr) motifs of arthropods. In a temporal expression analysis using differential RT-PCR, WSSV dnapol transcripts were detected at low levels at 2-4 h.p.i., increased at 6 h.p.i., and remained fairly constant thereafter. This is similar to the previously reported transcription patterns for genes encoding the key enzyme of nucleotide metabolism, ribonucleotide reductase. Phylogenetic analysis showed that the DNA pols from three different WSSV isolates form an extremely tight cluster. In addition, similar to an earlier phylogenetic analysis of WSSV protein kinase, the phylogenetic tree of viral DNA pols further supports the suggestion that WSSV is a distinct virus (likely at the family level) that does not belong to any of the virus families that are currently recognized.

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