Vitellocyte-specific expression of phospholipid hydroperoxide glutathione peroxidases in Clonorchis sinensis.
Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a major antioxidant enzyme and may protect against lipid hydroperoxidation in biomembranes. We isolated full-length cDNA sequences encoding four different PHGPxs from a causative agent of cholangiocarcinoma, Clonorchis sinensis (CsGPx1, CsGPx2, CsGPx3 and CsGPx4). These sequences contained an in-frame TGA codon for selenocysteine (Sec) and a concurrent Sec insertion sequence in their 3'-untranslated regions. The open reading frames were composed of six exons in the chromosomal segments of CsGPx1 (7705bp), CsGPx2 (5871bp) and CsGPx3 (3867bp) and five exons in CsGPx4 (5655bp). The positions of these introns were tightly conserved between the trematode and vertebrate PHGPx genes. Oxidative stimulation of viable worms with H(2)O(2) or paraquat resulted in 1.5- to 2-fold induction of the GPx activity. The CsGPx proteins were specifically localised in vitellocytes within vitelline follicles and premature eggs in the proximal uterus. In the eggs, glutathione, an electron donor for GPx, was co-localised with the CsGPx proteins, while thioredoxin, which is preferred by peroxiredoxin, was principally detected in the extracellular space between the embryonic cell mass and an eggshell. Our data may suggest a concerted or a specialised function between a thioredoxin-dependent enzyme(s) and GPx in protecting against H(2)O(2)-derived damage during maturation of the embryo and formation of the eggshell, in these catalase-lacking trematode parasites. The uniquely conserved genomic organisation and Sec-dependency amongst trematode and vertebrate PHGPx homologues will also provide insight into the evolutionary episode and functional/biochemical diversification of GPx proteins.
Cai
Guo-Bin
GB
Department of Molecular Parasitology, Sungkyunkwan University School of Medicine, Center for Molecular Medicine, Samsung Biomedical Research Institute, Suwon, Gyeonggi-do 440-746, Republic of Korea.
Bae
Young-An
YA
Kim
Seon-Hee
SH
Sohn
Woon-Mok
WM
Lee
Yoon-Song
YS
Jiang
Ming-Sen
MS
Kim
Tong-Soo
TS
Kong
Yoon
Y
D000818:Animals; D003004:Clonorchis sinensis / Q000201:enzymology* / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D005091:Exons / Q000235:genetics; D015870:Gene Expression; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D016877:Oxidants / Q000494:pharmacology; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017279:Selenocysteine / Q000235:genetics / Q000378:metabolism
D018076:DNA, Complementary; D004527:Egg Proteins; D016877:Oxidants; D012333:RNA, Messenger; D017279:Selenocysteine; D006861:Hydrogen Peroxide; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D005979:Glutathione Peroxidase