Enhanced green fluorescence protein tracks trichosanthin in human choriocarcinoma cells as a feasible and stable reporter.

Trichosanthin (TCS) is a ribosome-inactivating protein (RIP) which can inhibit the growth of human choriocarcinoma (JAR) cells. There are no clear mechanisms to discover the interaction pathway and cytotoxicity of TCS in JAR cells. In this paper, we showed the distribution and transport of endogenously expressed TCS in JAR cells. Enhanced Green Fluorescence Protein (EGFP), fused with TCS, was applied as a reporter to track the behavior of TCS in JAR cells. Firstly, we investigated the expression stability of EGFP and physiological effects on JAR cells. A stable cell line expressing EGFP was created, which could reproduce and express EGFP even if transplanted into nude mice. Based on the proved stability and feasibility of EGFP in cultured cells and in vivo, the fusion gene of EGFP and TCS was constructed and transfected into JAR cells by liposome. The fluorescence microscopy showed that TCS-EGFP fusion gene was expressed in JAR cells in 24 to 48 hours and the fluorescence spread in cytoplasm mainly and in nucleus partially, which could trace the distribution and transport of TCS-EGFP in JAR cells. Most of fluorescent cells died after 48 hours for the cytotoxicity of expressed TCS-EGFP. These results first reported a stable expression and tracing method by EGFP in JAR cells, and provided theoretical basis to apply TCS in cancer therapy.

Identification of gibberellin acid-responsive proteins in rice leaf sheath using proteomics.

The phytohormone gibberellin acid (GA) controls many aspects of plant development. In this study, we identified proteins that are differentially expressed between the rice (Oryza sativa L.) GA-deficient cultivar, Aijiaonante, and its parental line, Nante. Proteins were extracted from rice leaf sheath and examined by 2DGE. Among more than 1200 protein spots reproducibly detected on each gel, 29 were found to be highly up-regulated by GAs in Nante, and 6 were down-regulated by GAs in Aijiaonante. These 35 proteins were identified by MALDI-TOF MS and were classified into three groups based on their putative function in metabolism, stress/defense processes and signal transduction. These data suggest that metabolic pathways are the main target of regulation by GAs during rice development. Our results provide new information about the involvement of GAs in rice development.

Overproduction of OsSLRL2 alters the development of transgenic Arabidopsis plants.

SLR1 (SLENDER RICE 1) was thought to be the sole DELLA protein in rice considering the constitutive GA response phenotype of slr1 mutants. There were two other SLR1 homologous SLRL1 and SLRL2 (SLR1 like 1 and 2) which did not have DELLA domain but still shared high level similarity to the C-terminal region of SLR1 found after searching the whole rice genome. SLRL2 specially expressed in the embryo of immature rice seeds and the expression of SLRL2 was increased when treated with GA(3). The SLRL2 over-expressed transgenic Arabidopsis plants were semi-dwarfed, late flowering, and insensitive to GA. Moreover, the expression of AtGA20ox1 and AtGA3ox1 was increased and the expression of AtGA2ox1 decreased, indicating SLRL2 was a repressor of GA signaling. We suggested SLRL2 might function to overcome too strong GA responses and maintained a basic repression. Furthermore, a different form of DELLA family in monocots against dicots was discussed.

Y55 and D78 are crucial amino acid residues of a new IgE epitope on trichosanthin.

Trichosanthin (TCS) possesses many biological and pharmaceutical activities, but its strong immunogenicity limits its clinical application. To reduce the immunogenicity of TCS, we modified the reported method for the prediction of antigenic site and identified two crucial amino acid residues (Y55 and D78) for a new epitope. We mutated these two residues into glycine and serine, respectively, and obtained three mutants, Y55G, D78S, and Y55G/D78S. These mutants induced less amount of Ig and IgG antibodies in C57BL/6J mice than wild-type TCS (wTCS) (p<0.01) and almost lost the ability to induce IgE antibody production. The mutants stimulated fewer TCS-specific B cells in C57BL/6J mice than wTCS (p<0.01). Compared with wTCS, Y55G, D78S, and Y55G/D78S lost 26.9%, 17.9%, and 98.7% specific binding ability to anti-TCS monoclonal antibody TCS4E9, respectively. These mutants still retained RNA N-glycosidase activity. In conclusion, Y55 and D78 are two crucial amino acid residues of a new IgE epitope on TCS, and their mutation reduces the immunogenicity of TCS, but still retained the enzymatic activity.

Trichomislin, a novel ribosome-inactivating protein, induces apoptosis that involves mitochondria and caspase-3.

Trichomislin, a novel ribosome-inactivating protein, was cloned from the genome of Trichosanthes kirilowii Maxim. The gene was recombined to prokaryotic expression vector and the protein was purified by cation-exchange chromatography. The secondary structure of trichomislin was measured by circular-dichroism analysis and the ratios of alpha-helices and beta-sheets were calculated. Trichomislin could inhibit the synthesis of protein in rabbit reticulocyte lysate systems and its reaction mechanism was to inactivate ribosome as an rRNA N-glycosidase. Antitumor analyses indicated trichomislin induced the apoptosis and inhibited the growth of choriocarcinoma cells. Further investigation showed that trichomislin could bind to and enter choriocarcinoma cells, and then increase the caspase-3 activity in a time-dependent manner. At the same time, the concentration of cytochrome c in cytosol increased while that in mitochondria decreased. These results suggested that trichomislin induced apoptosis by releasing cytochrome c from mitochondria which then triggered the caspase family member activation.

[Callus induction and regeneration from mature seeds of indica rice minghui 63 and anti-fungal assay of transgenic rice plants].

A large number of callus from mature seeds of indica rice minghui 63 were obtained through pre-induction on medium with 2 mg/L 2,4-D but without inorganic and organic components for 9 days. Trichosanthin gene was transferred into indica rice minghui 63 by using agrobacterium with the help of bombardment and the transgenic plants were obtained by inducing regeneration. Southern and Western blot analysis showed that the trichosanthin gene had been transferred into genome of minghui 63 and expressed in rice plants. The anti-fungal assay suggested that transgenic rice plants enhanced resistance to infection of Pyricularia oryzae.

Capillary electrophoresis and circular dichroism study of trichosanthin and its mutants.

The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumor and anti-human-immunodeficiency-virus (anti-HIV). In this study, circular dichroism (CD) and capillary electrophoresis were used for the first time to study TCS and its two TCS mutants of Y55G TCS (tyrosine 55 converted to glycine) and FYY140-142GSA TCS (tripeptide phenylalanine-tyrosine-tyrosine 140-142 converted to glycine-serine-alanine). The results indicated that the substitution of amino acids changed the secondary structures and the hydrophobility of TCS. Moreover, both Y55G TCS and FYY140-142GSA TCS demonstrated attenuated cytotoxicity and reactive oxygen species (ROS) production in human choriocarcinoma cells (JAR cells) as compared to natural TCS and wild-type TCS. Our results demonstrated the cytotoxicity of TCS on JAR cells and TCS-induced production of ROS might be TCS-conformational related, suggesting that CD and capillary electrophoresis study might throw new insight into the anti-tumor and anti-HIV mechanism of TCS.