The interaction of trichosanthin with supported phospholipid membranes studied by surface plasmon resonance

Backbone and side-chain chemical shift assignments for the ribosome-inactivating protein trichobakin (TBK)

Trichobakin (TBK) is a type-I ribosome-inactivating protein (RIP-I), acting as an extremely potent inhibitor of protein synthesis in the cell-free translation system of rabbit reticulocyte lysate (IC₅₀: 3.5 pM). In this respect, TBK surpasses the well-studied highly homologous RIP-I trichosanthin (IC₅₀: 20-27 pM), therefore creation of recombinant toxins based on it is of great interest. TBK needs to penetrate into cytosol through the cell membrane and specifically bind to α-sarcin/ricin loop of 28S ribosome RNA to perform the function of specific RNA depurination. At the moment, there is no detailed structural-dynamic information in solution about diverse states RIP-I can adopt at different stages on the way to protein synthesis inhibition. In this work, we report a near-complete assignment of ¹H, ¹³C, and ¹⁵N TBK (27.3 kDa) resonances and analysis of the secondary structure based on the experimental chemical shifts data. This work will serve as a basis for further investigations of the structure, dynamics and interactions of the TBK with its molecular partners using NMR techniques.

Ribosome-inactivating proteins (RIPs) and their important health promoting property

Ribosome-inactivating proteins (RIPs), widely present in plants, certain fungi and bacteria, can inhibit protein synthesis by removing one or more specific adenine residues from the large subunit of ribosomal RNAs (rRNAs).

Anti-tumor action of trichosanthin, a type 1 ribosome-inactivating protein, employed in traditional Chinese medicine: a mini review

Trichosanthin (TCS) as a midterm abortifacient medicine has been used clinically in traditional Chinese medicine for centuries. Additionally, TCS manifests a host of pharmacological properties, for instance, anti-HIV and anti-tumor activities. TCS has been reported to inhibit cell growth of a diversity of cancers, including cervical cancer, choriocarcinoma, and leukemia/lymphoma, etc. This article purported to review the various anti-tumor activities of TCS and the mechanism of apoptosis it induced in these tumor cells. These research progresses provide an insight into cancer research and treatment as well as disclose new pharmacological properties of the ancient but popular Chinese medicine.

Investigation of interaction of human platelet membrane components with anticoagulant drugs Abciximab and Eptifibatide

Abciximab (Abci) and eptifibatide (Epti) are antiaggregate drugs which may reduce thrombotic complications in acute coronary syndromes. The aim of this work was the investigation of the interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and Abci or Epti, and the influence of these drugs on the phospholipid ratio in the platelet membrane. The interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and antiaggregate drugs were investigated using the Surface Plasmon Resonance Imaging technique (SPRI). Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) were first immobilized onto the gold chip surface. The phospholipid ratio in the platelet membrane was determined by the HPLC. Only PI, PS, PE and PC were determined. Human platelets treated 'in vitro' with Abci or Epti exhibit changes in the phospholipid ratio in the platelet membrane. The ratio of PS decreases and PC rises. The SPRI distinctly shows interactions between phospholipids and glycoprotein GPIIb/IIIa, and between the phospholipid-glycoprotein GPIIb/IIIa complex and Abci or Epti. The interaction between phospholipids and glycoprotein GPIIb/IIIa is growing in the sequence: PI<<SM<PE<PC<PS. The interaction between phospholipid-glycoprotein GPIIb/IIIa complex and Abci/Epti is growing in the sequence: PS<PI<PC<PE<SM. SPRI was proved to be excellent tool for observation of such interactions.

The anti-viral protein of trichosanthin penetrates into human immunodeficiency virus type 1

Trichosanthin (TCS) is a type I ribosome-inactivating protein with potent inhibitory activity against human immunodeficiency virus type 1, and has been clinically applied in acquired immunodeficiency syndrome (AIDS) therapy. Previous studies revealed that TCS recognized human immunodeficiency virus type 1 (HIV-1) particles. Here, we investigated the physical relationship between TCS and HIV-1 particles, and demonstrated that TCS penetrates into viral particles, where it is protected from various protease digestion. The penetration of TCS exerts no obvious effect on viral integrity. FYY140-142, D176, and K177 were identified as key amino acid residues for the membranetranslocation process. Moreover, TCS penetrated into HIV-1 virions showed potent anti-viral activity. Overall, the observations suggest that the penetration of TCS into HIV-1 particles may be important for eliminating the virus.

Trichosanthes kirilowii tuber extract induces G2/M phase arrest via inhibition of tubulin polymerization in HepG2 cells

Trichosanthes kirilowii tuber is one of most popular herbal plant of East Asia, which has been prescribed for patients with diabetes, rigorous coughing, breast abscesses, and cancer-related symptoms.

AIM OF THE STUDY

To investigated the anticancer properties of the methanol extract of Trichosanthes kirilowii tuber (TKE), focusing on cell cycle arrest and microtubule instability in HepG2 cells.

MATERIALS AND METHODS

Cell growth and death were checked using a CCK-8 assay and a LDH release assay respectively. Cell cycle was analyzed by FACS after PI staining. Immunofluorescence, Western blot, real-time PCR for tubulin were performed.

RESULTS

TKE treatment inhibited cell growth at around 25 microg/mL of IC50 in a CCK-8 assay and a LDH release assay, but did not result in cell death. We found that TKE induced cell cycle arrest at the G2/M phase in a time-dependent manner. However, an immunofluorescence assessment of beta-tubulin revealed a dramatically reduced amount of polymerized tubulin after TKE treatment. Furthermore, TKE treatment radically decreased the polymerized portion of soluble tubulin in a dose-dependent manner, as did colchicine; the effects, however, were opposite to those of paclitaxel in comparative analysis of polymerized to soluble tubulin. We also found that TKE treatment moderately affected alpha-tubulin protein production, but not that of beta-tubulin and its gene expression using a Western assay and real-time PCR.

CONCLUSIONS

Anticancer mechanisms of TKE linked to the inhibition of tubulin polymerization, through which it exerts cell cycle arrest at the G2/M phase in the HepG2 cell line.

Two Novel Proteins Bind Specifically to Trichosanthin on Choriocarcinoma Cell Membrane

Trichosanthin is the active protein component in the Chinese herb Trichosanthes kirilowi, which has distinct pharmacological properties. The cytotoxicity of trichosanthin was demonstrated by its selective inhibition of various choriocarcinoma cells. When Jar cells were treated with trichosanthin, the influx of calcium into the cells was observed by confocal laser scanning microscopy. When the distribution of trichosanthin-binding proteins on Jar cells was studied, two classes of binding sites for trichosanthin were shown by radioligand binding assay. Furthermore, the cytoplasmic membrane of Jar cells was biotinylated and the trichosanthin-binding proteins were isolated with trichosanthin-coupled Sepharose beads. Two protein bands with molecular masses of about 50 kDa and 60 kDa were revealed, further characterization of which should shed light on the mechanism of the selective cytotoxicity of trichosanthin to Jar cells.

Specific interaction between Smad1 and CHIP: a surface plasmon resonance study

The TGF-beta superfamily signaling pathway regulates many important biological processes, including cell growth, differentiation and embryonic pattern formation. Smad1, a member of this signaling pathway that functions downstream of serine/threonine kinase receptors, has ability to interact with carboxyl terminus of Hsc70-interacting protein (CHIP), which is an E3 ubiquitin ligase in other cases. It has been reported that Smurf1, a member of the Hect family E3 ubiquitin ligases, can target Smad1 to 26S proteasome for degradation. In this paper, we studied the interaction of Smad1 and CHIP by combination of surface plasmon resonance and supported monolayer approach. The specific binding of Smad1 to CHIP indicates that the degradation of Smad1 may also be mediated by CHIP, and CHIP may play an essential role in the TGF-beta signaling pathway.

Recent advances in trichosanthin, a ribosome-inactivating protein with multiple pharmacological properties

Trichosanthin (TCS), a ribosome-inactivating protein extracted from the root tuber of Chinese medicinal herb Trichosanthes kirilowii Maximowicz, has multiple pharmacological properties including abortifacient, anti-tumor and anti-HIV. It is traditionally used to induce abortion but its antigenicity and short plasma half-life have limited the repeated clinical administration. In this review, work to locating antigenic sites and prolonging plasma half-life are discussed. Studies on structure-function relationship and mechanism of cell entry are also covered. Recently, TCS has been found to induce apoptosis, enhance the action of chemokines and inhibit HIV-1 integrase. These findings give new insights on the pharmacological properties of TCS and other members of ribosome-inactivating proteins.

Truncated hemoglobin o of Mycobacterium tuberculosis: the oligomeric state change and the interaction with membrane components

Being an obligate aerobe, the Mycobacterium tuberculosis cells would have to evolve a mechanism to collect and deliver the hardly available O(2) to survive in granulomas and to maintain the low level of respiration during latency. The M. tuberculosis truncated hemoglobin o (trHbO), when heterologously expressed in Escherichia coli cells, was found to significantly enhance the cellular respiration and cell growth. This study was undertaken in an attempt to understand the molecular details for trHbO to promote the cellular respiration, focusing on the ways through which trHbO is recruited to the cell membrane and O(2) molecules are delivered. Our data demonstrate that the trHbO protein is able to promote the growth of E. coli cells in a fashion that depends on the presence of the respiratory chain terminal oxidase cytochrome o complex (or Cyo complex). The trHbO protein appears to interact with the Cyo B subunit of the Cyo complex directly, likely in a dynamic manner. The trHbO is also able to bind membrane lipids in a non-specific way, during the process electrostatic and hydrophobic interactions both likely exist. Besides, binding with membrane induces the dissociation of trHbO from dimers to monomers. In light of these observations, a hypothesis was made to explain how trHbO might serve as an O(2) collector and/or reservoir for M. tuberculosis cells under O(2)-limiting or lacking conditions.

Inositol hexakisphosphate (InsP6) can weaken the Ca(2+)-dependent membrane binding of C2AB domain of synaptotagmin I

The synaptic vesicle protein synaptotagmin I has been proposed to serve as a Ca(2+) sensor for rapid exocytosis. In the present work, two fragments of the large cytoplasmic domain of synaptotagmin I, C2A and C2AB, were compared by combining surface plasmon resonance with circular dichroism and fluorescence techniques. C2AB and C2A had almost identical membrane binding constants, indicating that C2A is the predominate domain to bind to negatively charged phospholipids. After reacting with inositol hexakisphosphate (InsP6) a conformational change of C2AB was detected in the presence of liposome. The InsP6 binding notably weakened the Ca(2+)-dependent C2AB-membrane interaction, which suggests that InsP6 may act as a modulator of neurotransmitter release by altering the state of synaptotagmin-phospholipid interaction.