Antimicrobial peptide Pc-pis: A new cancer cell killer.

The antimicrobial peptide (AMP) Pc-pis, a member of Piscidin family from fish with cationic amphipathic structure, has potent, broad-spectrum antimicrobial activity against bacteria, fungi and parasite, and lower hemolytic activity. Here, we reported that Pc-pis had antitumor activity. Pc-pis killed tumor cells including HeLa cells. Previously, it is reported that AMPs bind to the membrane of bacteria to generate the pores to lyse the target cells, and similarly, the cancer cell incorporate phosphatidyl-serine on the outer leaflet of plasma membrane so that amphipathic AMPs can bind to the membrane to kill it. Our data supported that notion because suitable size osmo-protectant PEG4000 prevented HeLa cells from death induced by Pc-pis. Additionally, Fusion protein GFP-Pc-pis accumulated mainly at the nuclear membranes of HeLa cells and positive net charge in modified Pc-pis intensified but negative net charges eliminated this effect. Thus, positively charged residues were important for its affinity to the membrane. Our work will lay the groundwork of the development of Pc-pis antitumor activity.

[Preparation and subcellular localization of antibody against RIP3].

AIM: To determine the localization of RIP3 in NIH3T3 cell line and explore its roles in the signal transduction pathway of TNF-alpha-induced caspase-independent cell death. METHODS: RIP3 gene was cloned from NIH3T3 cell line by RT-PCR and the amino acid 287-486 sequence of RIP3 was overexpressed in E.coli strain BL21. The protein was purified by electrodialysis to immune rabbits. Nine weeks later, the serum of the rabbits was harvested and anti-RIP3 polyclonal antibodies was purified and its specificity was detected by Western blot. Immunofluorescence was used to determine the subcellular localization of RIP3 in NIH3T3 cell line and the effects of TNF-alpha and z-VAD.fmk on RIP3 for its localization changing. RESULTS: A high concentration of rabbit polyclonal antibody against RIP3 with good immunological characteristics was obtained. RIP3 was successfully detected by Western blot with anti-RIP3 antibody in 293T cells transfected with pcDNA3-flag-RIP3 and in mouse NIH3T3 cell line. The results of immunofluorescent staining displayed that RIP3 localized in cytoplasm in untreated NIH3T3 cells. Treatment with TNF-alpha or z-VAD. fmk alone didn't change its distribution. However in the cells induced by z-VAD.fmk and TNF-alpha, RIP3 was detected in both cytoplasm and nucleolus. CONCLUSION: The polyclonal antibody against RIP3 with high concentration and specificity was successfully obtained. In NIH3T3 cell line, RIP3 localized in cytoplasm, which was subject to change induced by z-VAD.fmk and TNF-alpha, suggesting that RIP3 plays an important role in TNF-alpha induced caspase-independent cell death signal transduction pathway.