The delivery of bioactive macromolecular substances into cells provides an efficient approach to changing cellular conditions, and is thus of enormously potential therapeutic significance. It has also been an extremely difficult approach due the the impediment and protective nature of cell membrance until the protein transduction domain's (PTD's) capability to ferry macromolecule across cell membrance was discovered. PTD's efficient transductive function has rendered an exciting promise to the clinical treatment of diseases, therapeutic proteins drug development, and basic medical and applied research. The technology has been successfully applied to deliver a variety of substances into cells or tissue organs, and its superior application values have been explicitly demonstrated.
Cell Membrane Permeability ; physiology ; Drug Delivery Systems ; methods ; Genetic Therapy ; Humans ; Protein Sorting Signals ; Protein Transport ; physiology

Objective To investigate the effect of the fusion of leader peptide on the structure of human manganese superoxide dismutase (SOD2) and anti-cisplatin (DDP)-induced renal injury. Methods The effect of mitochondrion targeting sequence (MTS) on the structure and activity of SOD2 was analyzed by structure prediction and superoxide dismutase (SOD) specific-activity determination. The DDP injury model of Kunming (KM) mice was established, and amifostine (AMFT) was set as a positive control. Indicators such as kidney index, renal function, kidney antioxidant capacity, and appearance and pathology changes of mice kidney were used to evaluate the effect of MTS-SOD2 against DDP-induced kidney injury. Results The MTS leader peptide seemed to change the secondary and tertiary structures of SOD2 to some extent, but it also increased the specific activity of the MTS-SOD2 protein. Pre-administration of a medium dose of MTS-SOD2 (0.84 mg/kg) before the use of DDP significantly reduced the level of renal malondialdehyde and increased the SOD activity and total antioxidant capacity (T-AOC) in the kidney, thereby reducing the renal pathological damage and consequently maintaining renal function. The overall protective effect of MTS-SOD2 was comparable to or even better than that of 200 mg/kg AMFT. Conclusion The MTS leader peptide enhances the activity of SOD2 and confers it with an excellent anti-DDP-induced renal-injury effect because of its transmembrane function.

Antioxidant enzymes fused with cell-penetrating peptides could enter cells and protect cells from irradiation damage. However, the unselective transmembrane ability of cell-penetrating peptide may also bring antioxidant enzymes into tumor cells, thus protecting tumor cells and consequently reducing the efficacy of radiotherapy. There are active matrix metalloproteinase (MMP)-2 or MMP-9 in most tumor cellular microenvironments. Therefore, a fusion protein containing an MMP-2/9 cleavable substrate peptide X, a cell-penetrating peptide R9, a glutathione S-transferase (GST), and a human Cu, Zn superoxide dismutase (SOD1), was designed and named GST-SOD1-X-R9. In the tumor microenvironment, GST-SOD1-X-R9 would lose its cell-penetrating peptide and could not enter tumor cells due to the cleavage of substrate X by active MMP-2/9, thereby achieving selected entering normal cells. The complete nucleotide sequence of SOD1-X-R9 was synthesized and inserted into the prokaryotic expression vector pGEX-4T-1. The pGEX4T-1-SOD1-X-R9 recombinant plasmid was obtained, and soluble expression of the fusion protein was achieved. GST-SOD1-X-R9 was purified by ammonium sulfate precipitation and GST affinity chromatography. The molecular weight of the fusion protein was approximately 47 kDa, consistent with the theoretical value. The SOD and GST activities were 2 954 U/mg and 328 U/mg, respectively. Stability test suggested that almost no change in either SOD activity or GST activity of GST-SOD1-X-R9 was observed under physiological conditions. The fusion protein could be partially digested by collagenase Ⅳ in solution. Subsequently, the effect of MMP-2/9 activity on transmembrane ability of the fusion protein was tested using 2D and 3D cultured HepG2 cells. Little extracellular MMP-2 activity of HepG2 cells was observed under 2D culture condition. While under the 3D culture model, the size and the MMP-2 activity of the HepG2 tumor spheroid increased daily. GST-SOD1-R9 proteins showed the same transmembrane efficiency in 2D cultured HepG2 cells, but the transmembrane efficiency of GST-SOD1-X-R9 in 3D cultured HepG2 spheres was reduced remarkably. This study provided a basis for further investigating the selectively protective effect of GST-SOD1-X-R9 against oxidative damage in normal cells.
Ammonium Sulfate ; Antioxidants ; Cell-Penetrating Peptides/pharmacology* ; Endopeptidases ; Glutathione Transferase/metabolism* ; Humans ; Matrix Metalloproteinase 2/genetics* ; Matrix Metalloproteinase 9/genetics* ; Recombinant Fusion Proteins ; Recombinant Proteins ; Superoxide Dismutase/metabolism* ; Superoxide Dismutase-1

The fusion of cell permeable peptide TAT and bifunctional antioxidant enzymes, GST (Glutathione sulfur transferase)-TAT-SOD1 (Cu, Zn superoxide dismutase), is an intracellular superoxide scavenger. Compared with SOD1-TAT, GST-TAT-SOD1 has better protective effect on oxidative damage but less transduction efficiency. A novel cell permeable bifunctional antioxidant enzymes with the fusion of GST, SOD1 and polyarginine R9 was constructed for higher transduction efficiency. The full nucleotide sequence of SOD1-R9 was synthesized and inserted into the prokaryotic expression vector pGEX-4T-1 with the GST tag. After the successful construction of the prokaryotic expression vectors of GST-SOD1-R9, the recombinant vector was then transformed into Escherichia coli BL21 (DE3) and the GST-SOD1-R9 fusion protein was produced with the induction of IPTG. The soluble expression of GST-SOD1-R9 fusion protein was combining with the induction temperature and time. The best soluble expression was obtained with the induction temperature of 25 ℃ and the induction time of 11 h. The fusion protein was purified through the combination of 80% ammonium sulfate precipitation and affinity chromatography using glutathione agarose, and verified by SDS-PAGE and special enzymatic activity. The thermal and pH stability of GST-SOD1-R9 fusion protein were analyzed and the SOD and GST activity of fusion protein were proved to be well maintained under physiological conditions. Finally, the transduction efficiency of GST-SOD1-R9 fusion protein was proved to be better than GST-TAT-SOD1 fusion protein (P<0.05). These works establish a foundation for further study of the protective effect of GST-SOD1-R9 fusion protein against oxidative damage.

Superoxide dismutase (SOD) family is necessary to protect cells from the toxicity of reactive oxygen species produced during normal metabolism. Among SODs, manganese-containing superoxide dismutase (Mn-SOD, SOD2) is the most important one. The DNA fragment containing the full nucleotide of full-length human SOD2 was synthesized and inserted into the prokaryotic expression vector pGEX-4T-1 with tag GST. DNA construct was then transformed into Escherichia coli BL21 (DE3) and expression was induced with IPTG at 25 ℃. The recombinant fusion protein GST-SOD2 (46 kDa) was purified from the bacterial lysate by GST resin column affinity chromatography. GST tag was cleaved with thrombin, and a crude SOD2 recombinant protein (25 kDa) was obtained and further purified by heparin affinity chromatography. Activities of the two SOD2 proteins were 1 788 and 2 000 U/mg, respectively. Both SOD2 proteins were stable under physiological condition and cell-penetrating (P<0.05). Our findings open the possibility to study the structure and effects of two full-length recombinant SOD2 proteins.

Two proteins of similar molecular weight (named as ASPR-C-1 and ASPR-C-2) from the crude drug of Angelica sinensis were purified and characterized by 80% ammonium sulfate precipitation, Sephadex G-50 gel filtration chromatography, and DEAE-Sepharose anion exchange chromatography. The molecular weight of ASPR-C-1 and ASPR-C-2 on SDS-PAGE was 17.33 kDa and 17.18 kDa, respectively. They were mainly monomeric in solution, but partially formed dimers and they were glycoproteins with glycosyl content of 2.6% and 8.2%, respectively. Both ASPR-C-1 and ASPR-C-2 were identified to be members of pathogenesis-related 10 family of proteins by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and have ribonuclease activities with the specific activity of 73.60 U/mg and 146.76 U/mg, respectively. The optimum pH of the two isoforms was similar, at about 5.6, while their optimum temperatures were different. The optimum temperature of ASPR-C-1 was 50 ℃, and that of ASPR-C-2 was 60 ℃. Both isoforms presented highest thermal stability at 60 ℃. However, ASPR-C-2 was more thermotolerant than ASPR-C-1. The latter was rapidly inactivated and retained only about 20% residual activity while the former still maintained about 80% of its original activity at a higher treatment temperature (80 to 100 ℃). In addition, Fe²⁺ had an activating effect on the ribonuclease activities of two isoforms while Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Ag⁺, Cu²⁺, EDTA (Elhylene diamine tetraacetic acid), dithiothreitol and sodium dodecylsulphate showed different degrees of inhibition of the enzyme activities. Our findings provide a foundation for further research on the biological function of PR-10 protein from Angelica sinensis.
Angelica sinensis ; Chromatography, Gel ; Chromatography, Ion Exchange ; Electrophoresis, Polyacrylamide Gel ; Enzyme Stability ; Hydrogen-Ion Concentration ; Kinetics ; Molecular Weight ; Protein Isoforms ; Temperature