A novel acidic serine protease, ASPNJ inhibits proliferation, induces apoptosis and enhances chemo-susceptibility of acute promyelocytic leukemia cell

Cytotoxicity of alkaline serine protease (ASPNJ) on Jurkat cells and its correlation with changes in the expression of membrane-associated proteins

We aim to study the inhibitory effect of alkaline serine protease (ASPNJ) on lymphocytic leukemia Jurkat cells and its related mechanism through examining the expression of membrane proteins or membrane-associated proteins. MTT assay and trypan blue staining were used to detect the inhibitory effect of ASPNJ on the proliferation and growth of Jurkat cells. Wright-Giemsa staining was used to observe the effect of ASPNJ on the morphology of Jurkat cells. The effect of ASPNJ on Jurkat cell apoptosis was detected by flow cytometry. Two-dimensional electrophoresis-mass spectrometry (2-DE-MS) was used to detect and identify the differentially expressed proteins of Jurkat cells treated with ASPNJ (4 μg/mL, 3 h), of which three were selected and verified by Western blot. ASPNJ significantly inhibited the proliferation of leukemia cells (Raji, U937, and Jurkat), caused obvious morphological changes, and induced apoptosis of Jurkat cells. ASPNJ also increased the sensitivity of Jurkat cells to vincristine (VCR). Seven differentially expressed proteins were obtained through 2DE-MS, of which Peroxiredoxin-6 (PRDX6), Calcium-binding protein (CHP1), and 40S ribosomal protein SA (RPSA) were validated. ASPNJ can cause significant toxic effects on Jurkat cells and enhance the effects of VCR. The mechanism of action of ASPNJ on Jurkat cells may be related to differentially expressed proteins such as PRDX6. This study provides a new experimental basis and direction for antileukemia research.

Preparation of Nereid oligopeptide and investigation of the mechanism underlying the induction of apoptosis in human lung cancer H1299 cells

In the present study, oligopeptides from Nereid (Perinereis aibuhitensis) were prepared via enzymatic hydrolysis, and the mechanism underlying the induction of apoptosis in H1299 cells was investigated. According to the analysis of the inhibition rate on proliferation, alkaline protease demonstrated the best enzymatic efficiency. The optimal conditions for hydrolysis were as follows: 50°C and pH 10 for 6 h; a material-to-liquid ratio of 1:1 (g/ml); and addition of 400 U/g enzyme. The hydrolysates were purified using ultrafiltration, anion chromatography, gel filtration chromatography, and high-performance liquid chromatography. The Nereid oligopeptide (NOP), with a molecular weight of 841 kDa and an amino acid sequence of glutamine-isoleucine-asparagine-glutamine-histidine-leucine, was obtained. NOP inhibited the proliferation of H1299 cells in a time- and dose-dependent manner. Morphological changes and apoptosis were also induced by NOP in H1299 cells. The western blot analysis revealed that the B-cell lymphoma 2/Bcl-2 associated X (Bcl-2/Bax) ratio was reduced by 24.7% in the NOP treatment group compared with the control group. The relative expression levels of cleaved caspase-9 (cleaved-CASP9) and cleaved caspase-3 (cleaved-CASP3) in the NOP treatment group were 2.55- and 1.71-fold higher than those measured in the control group, respectively. These results suggested that NOP exerts antitumor effects by influencing the proliferation and apoptosis of H1299 cells.

Rapid Degradation of SARS-CoV-2 Spike S Protein by A Specific Serine Protease

The S protein of SARS-CoV-2 is a crucial structural and functional component for virus entry. Due to the constant mutation of the virus, there are very limited ways to prevent and control COVID-19. This experiment used a macroscopic SDS-PAGE method and proved that the S protein of wild-type SARS-CoV-2 virus, especially the S1 subunit, is very sensitive to alkaline serine protease with acidic pI (ASPNJ), NJ represents Neanthes japonica (Izuka) from which ASP is purified). ASPNJ cleaves proteins when the carbonyl group of the peptide bond is contributed by arginine or lysine. ASPNJ can degrade the S protein very quickly and effectively in vitro with relative selectivity. It can be inferred that the S, S1 and RBD of SARS-CoV-2 variants can also be easily degraded by ASPNJ. This rapid and strong degradation of the S protein by ASPNJ may become a potential new treatment strategy.

Serine Protease from Nereis virens Inhibits H1299 Lung Cancer Cell Proliferation via the PI3K/AKT/mTOR Pathway

This study explores the in vitro anti-proliferative mechanism between Nereis Active Protease (NAP) and human lung cancer H1299 cells. Colony formation and migration of cells were significantly lowered, following NAP treatment. Flow cytometry results suggested that NAP-induced growth inhibition of H1299 cells is linked to apoptosis, and that NAP can arrest the cells at the G0/G1 phase. The ERK/MAPK and PI3K/AKT/mTOR pathways were selected for their RNA transcripts, and their roles in the anti-proliferative mechanism of NAP were studied using Western blots. Our results suggested that NAP led to the downregulation of p-ERK (Thr 202/Tyr 204), p-AKT (Ser 473), p-PI3K (p85), and p-mTOR (Ser 2448), suggesting that NAP-induced H1299 cell apoptosis occurs via the PI3K/AKT/mTOR pathway. Furthermore, specific inhibitors LY294002 and PD98059 were used to inhibit these two pathways. The effect of NAP on the downregulation of p-ERK and p-AKT was enhanced by the LY294002 (a PI3K inhibitor), while the inhibitor PD98059 had no obvious effect. Overall, the results suggested that NAP exhibits antiproliferative activity by inducing apoptosis, through the inhibition of the PI3K/AKT/mTOR pathway.

A Purified Serine Protease from Nereis virens and Its Impaction of Apoptosis on Human Lung Cancer Cells

Nereis active protease (NAP) is a novel fibrinolytic active serine protease from the polychaete Nereis virens. In this study, NAP was purified from Nereis virens and the effects of NAP on human lung cancer cells were investigated. Our results indicated that NAP inhibited the proliferation and induced apoptosis of H1299 cells in a time- and dose-dependent manner. The loss of mitochondrial membrane potential, the activation of Bax and cleaved-caspase 3/9, the release of cytochrome C, and the suppression of Bcl-2 and poly-ADP ribose polymerase were observed in NAP-treated H1299 cells by flow cytometry and Western blotting. Moreover, the expression levels of Bax and Bcl-2 mRNA were determined by real-time quantitative polymerase chain reaction and the Bax/Bcl-2 expression ratio was increased in the NAP-treated cell lines. The results indicated that NAP-induced apoptosis may be related to mitochondria mediated apoptosis and occurs through caspase-dependent pathways. Then, the effects of NAP on tumor growth in animal models were observed, where 5 or 10 mg/kg of NAP noticeably reduced tumor volume and weight and increased apoptosis as determined by Western blotting when compared to the negative control group. Therefore, our findings suggest that NAP could be a hopeful anticancer medicine for its propensity to inhibit growth and induce of apoptosis in human lung cancer cells.

Molecular cloning, expression, and anti-tumor activity of a novel serine protease from Arenicola cristata

Arenicola cristata, a marine annelid, is a well-known and prized traditional Chinese medicine. However, the serine protease gene of A. cristata has not been cloned yet. In this study, a novel protease of A. cristata was cloned, sequenced, and expressed in Escherichia coli, and the functions of this recombinant protease were also investigated. The whole complementary DNA (cDNA) of this novel protease was of 980 bp in length and consisted of an open reading frame of 861 bp encoding 286 aa. Sequence analysis of the deduced amino acid sequence revealed that the protease belongs to the serine protease family. The active enzyme of the proposed A. cristata protease is composed of a signal peptide, a propeptide, and a mature polypeptide. The molecular weight of the recombinant mature protein was ~26 kDa after over-expression in E. coli. The recombinant protein significantly inhibited cell growth and induced cell apoptosis of esophageal squamous cell carcinoma (ESCC) in vitro, and reduced tumorigenicity in vivo. Furthermore, administration of the recombinant protein led to the activation of caspase-9 as well as down-regulation of Mcl-1 and Bcl-2. Taken together, our findings indicated that the recombinant serine protease of A. cristata could inhibit ESCC cell growth by mitochondrial apoptotic pathway and might act as a potential pharmacological agent for ESCC therapy.