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J P Du

Publications and source records attributed to J P Du.

4 recordsLinked to original sources
PubMed2006

Overexpression of PrPC and its antiapoptosis function in gastric cancer.

Cellular prion protein (PrP(C)), a glycosylphosphatidylinositol-anchored membrane protein, was found in our lab to be widely expressed in gastric cancer cell lines. In order to evaluate its biological significance in human gastric cancer, we investigated its expression in a large series of gastric tissue samples (n = 124) by immuno histochemical staining with the monoclonal antibody 3F4. Compared with normal tissues, gastric adenocarcinoma showed increased PrP(C) expression, correlated with the histopathological differentiation (according to the WHO and Lauren classifications) and tumor progression (as documented by pTNM staging). To better understand the underlying mechanism, we introduced the PrP(C) and two pairs of RNAi into the poorly differentiated gastric cancer cell line AGS and found that PrP(C) suppressed ROS and slowed down apoptosis in transfected cells. Further study proved that the apoptosis-related protein Bcl-2 was upregulated whereas p53 and Bax were downregulated in the PrP(C)-transfected cells. A reverse effect was observed in PrP(C) siRNA-transfected cells. These results strongly suggested that PrP(C) might play a role as an effective antiapoptotic protein through Bcl-2-dependent apoptotic pathways in gastric cancer cells. Further study into the mechanism of these relationships might enrich the knowledge of PrP, better our understanding of the nature of gastric carcinoma, and further develop possible strategies to block or reverse the development of gastric carcinoma.

Adult↗
PubMed2002

Putative protein digestion in a sap-sucking homopteran plant pest (rice brown plant hopper; Nilaparvata lugens: Delphacidae)--identification of trypsin-like and cathepsin B-like proteases.

Sap-sucking phytophagous insect species of the order Hemiptera have been assumed not to carry out digestive proteolysis, but instead to rely on free amino acids in the phloem and xylem saps for their nutritional requirements. Extracts prepared from isolated guts of rice brown planthopper (Nilaparvata lugens), a homopteran crop pest, were shown to contain protease activity, with hydrolysis of both protein and synthetic peptide substrates being observed. Assays with specific inhibitors suggested that a trypsin-like serine protease was responsible for most of hydrolytic activity against synthetic substrates. A cDNA library was prepared from RNA extracted from N. lugens gut tissue, and screened for protease-encoding sequences. cDNAs for a cathepsin B-like protease and a trypsin-like protease were isolated and fully characterised; the latter exhibits a novel C-terminal region and an unusual activation mechanism, and represents a small gene family. Soya bean Kunitz trypsin inhibitor (SKTI) is an effective inhibitor of protein hydrolysis by N. lugens gut extracts in vitro, explaining why transgenic rice plants expressing this protein are partially resistant to the insect (Mol. Breed. 5 (1999) 1). It is suggested that digestive proteolysis may be widespread in sap-sucking homoptera, and can make a significant contribution to nutrition.

Amino Acid Sequence↗