Inhibition of Jingzhaotoxin-V on Kv4.3 channel / 生理学报

Kv4.3 channel is present in many mammalian tissues, predominantly in the heart and central nervous system. Its currents are transient, characterized by rapid activation and inactivation. In the hearts of most mammals, it is responsible for repolarization of the action potential of ventricular myocytes and is important in the regulation of the heart rate. Because of its central role in this important physiological process, Kv4.3 channel is a promising target for anti-arrhythmic drug development. Jingzhaotoxin-V (JZTX-V) is a novel peptide neurotoxin isolated from the venom of the spider Chilobrachys jingzhao. Whole-cell patch clamp recording showed that it partly blocked the transient outward potassium channels in dorsal root ganglion neurons of adult rats with an IC(50) value of 52.3 nmol/L. To investigate the effect of JZTX-V on Kv4.3 channel, JZTX-V was synthesized using the solid-phase chemical synthesis and separated by reverse phase high performance liquid chromatography (HPLC). The purity was tested by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MOLDI-TOF mass spectrometry). Two-electrode voltage-clamp technique was used to characterize the action of JZTX-V on Kv4.3 channels expressed in Xenopus laevis oocytes. As a result, JZTX-V displayed fast kinetics of inhibition and recovery from inactivation. Furthermore, it could inhibit Kv4.3 channel current in a time- and concentration-dependent manner with an IC(50) value of 425.1 nmol/L. The application of JZTX-V affected the activation and inactivation characteristics of Kv4.3 channel and caused a shift of the current-voltage relationship curve and the steady-state inactivation curve to depolarizing direction by approximately 29 mV and 10 mV, respectively. So we deduced that JZTX-V is a gating modifier toxin of Kv4.3 channel. Present findings should be helpful to develop JZTX-V into a molecular probe and drug candidate targeting to Kv4.3 channel in the myocardium.

Comparative proteome analysis of human lung squamous cell carcinoma / 中华肿瘤杂志

<p><b>OBJECTIVE</b>This study was designed to establish the two-dimensional electrophoresis profiles with high resolution and reproducibility from human lung squamous cell carcinoma tissue and paired tumor-adjacent normal bronchial epithelial tissue, and to identify differential expression of tumor-associated proteins by using proteome analysis.</p><p><b>METHODS</b>Comparative proteome analysis of human lung squamous carcinoma and paired normal bronchial mucosa adjacent to tumors from 20 cases were carried out. Total proteins of the carcinoma tissue and normal bronchial mucosa were separated by means of immobilized pH gradient-based two-dimensional gel electrophoresis (2-DE). The differentially expressed proteins were analyzed and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS).</p><p><b>RESULTS</b>(1) Seventy-six differentially expressed proteins were screened by analyzing the electrophoretic maps of the 20 carcinoma and control mucosa tissues. (2) Sixty-eight differential proteins were identified by peptide mass fingerprinting (PMF). Some proteins were products of oncogenes and others were involved in the regulation of cell cycle and signal transduction. (3) The expression of three proteins mdm2, c-Jun and EGFR, correlated with lung squamous carcinoma, were detected by immunohistochemical staining and Western blot analysis. The results showed that the expression of mdm2, c-Jun and EGFR were up-regulated in lung squamous carcinomas, whereas down-regulated in control normal mucosa. It was consistent with our proteome analysis results. Those results suggested that those proteins may play roles in the carcinogenesis of lung squamous carcinoma.</p><p><b>CONCLUSION</b>sixty-eight differentially expressed proteins were successfully characterized by comparative proteome analysis. Those results may provide scientific foundation for screening the molecular biomarkers which can be used in diagnosis and treatment of lung squamous carcinoma, as well as to improve patients' prognosis and provide a new clue for carcinogenesis research of lung squamous cell carcinoma.</p>

Solid-phase synthesis and biological characterization of S12A-HNTX-IV and R29A-HNTX-IV: two mutants of hainantoxin-IV / 生物工程学报

Hainantoxin-IV (HNTX-IV) purified from the venom of the spider Selenocosmia hainana is a potent antagonist that acts on tetrodotoxin-sensitive (TrX-S) sodium channels. It is a 35-residue polypeptide and includes three disulfide bridges. In order to investigate the structure-function relationship of HNTX-IV, two mutants (S12A-HNTX-IV and R29A-HNTX-IV) of HNTX-TV in which Ser12 and Arg29 were replaced by Ala respectively, were synthesized by solid-phase Fmoc chemistry, followed by oxidative refolding of purified peptides under the optimal conditions. The synthetic mutants were analyzed by MALDI-TOF mass spectrometry, nuclear magnetic resonance spectroscopy (NMR) and electrophysiological experiments for molecular weight, conformation and physiological activity, respectively. The results show that the mutants and native HNTX-IV (nHNTX-IV) have almost identical three-dimensional structures. The bioactivity level of S12A-HNTX-IV is also about the same as that of nHNTX-IV, suggesting that Ser12 does not play any important role for the bioactivity of this toxin. The bioactivity of R29A-HNTX-IV is reduced by at last 155 times, indicating that Arg29 is a key residue relative to the bioactivity of HNTX-IV. It is presumed that the decrease in activity of R29A-HNTX-IV is due to the changes of the property in the binding site rather than the change in the basic conformation of the molecule.

Expression and purification of recombinant huwentoxin-I in Pichia pastoris / 生物工程学报

HWTX-I is a peptide neurotoxin purified from the crude venom of the Chinese bird Spider Selenocosmia Huwena, which has analyesic activity. rHWTX-I expressed by P. pastoris and secreted to culture supernatant was first precipitated by (NH4)2SO4, then it was isolated and desalted by ultrofiltration following by ion exchange chromatography of CM column, after reverse phase HPLC of C18 column and vacuum drying, the pure HWTX-I protein was obtained which was proved to be recombinant HWTX-I by Tricine SDS-PAGE, MALDI-TOF mass spectrometry, amino acid composition analysis, the N-terminal amino acid sequence and its biological activity. The final yield of the purified HWTX-I was about 80 mg/L accounting for 23.6% of its total secretory proteins.