Clonorchiasis, caused by the infection of Clonorchis sinensis ( C. sinensis), is a kind of neglected tropical disease, but it is highly related to cholangiocarcinoma and hepatocellular carcinoma (HCC). It has been well known that the excretory/secretory products of C. sinensis ( CsESPs) play key roles in clonorchiasis associated carcinoma. From genome and transcriptome of C. sinensis, we identified one component of CsESPs, severin ( Csseverin), which had three putative gelsolin domains. Its homologues are supposed to play a vital role in apoptosis resistance of tumour cell.
There was significant similarity in tertiary structures between human gelsolin and Csseverin by bioinformatics analysis. We identified that Csseverin expressed at life stage of adult worm, metacercaria and egg by the method of quantitative real-time PCR and western blotting. Csseverin distributed in vitellarium and intrauterine eggs of adult worm and tegument of metacercaria by immunofluorence assay. We obtained recombinant Csseverin (r Csseverin) and confirmed that r Csseverin could bind with calciumion in circular dichroism spectrum analysis. It was demonstrated that r Csseverin was of the capability of actin binding by gel overlay assay and immunocytochemistry. Both Annexin V/PI assay and mitochondrial membrane potential assay of human hepatocarcinoma cell line PLC showed apoptosis resistance after incubation with different concentrations of r Csseverin. Morphological analysis, apoptosis-associated changes of mitochondrial membrane potential and Annexin V/PI apoptosis assay showed that co-incubation of PLC cells with r Csseverin in vitro led to an inhibition of apoptosis induced by serum-starved for 24 h.
Collectively, the molecular properties of Csseverin, a molecule of CsESPs, were characterized in our study. r Csseverin could cause obvious apoptotic inhibition in human HCC cell line. Csseverin might exacerbate the process of HCC patients combined with C. sinensis infection.
Clonorchis sinensis ( C. sinensis) has afflicted more than 35 million people in world and approximately 15 million in China, creating a socio-economic burden in epidemic regions. The infection of C. sinensis is highly related to cholangiocarcinoma and hepatocellular carcinoma (HCC). It has been documented that excretory/secretory products of C. sinensis ( CsESPs) involved in the pathogenesis of HCC. Csseverin, expressed at life stage of egg, metacercaria and adult worm, was a component of CsESPs. In the current study, we characterized the properties of Csseverin such as sequence signature, actin and calciumion binding activity. In addition, we demonstrated that Csseverin could cause apoptotic inhibition in spontaneously apoptotic human HCC cell line PLC cells by using morphological analysis, detection of the apoptosis-associated change of mitochondrial membrane potential (MMP) as well as Annexin V/PI apoptosis assay. Our study provided an exploratory sight view of mechanism involved in progress of carcinoma associated with the infection of C. sinensis and Csseverin might exacerbate the process of C. sinensis infected HCC patients.