Molecular Characterization and Antibacterial Activity Analysis of Two Novel Penaeidin Isoforms from Pacific White Shrimp, Litopenaeus vannamei

Anticancer Mechanisms and Potential Anticancer Applications of Antimicrobial Peptides and Their Nano Agents

Traditional chemotherapy is one of the main methods of cancer treatment, which is largely limited by severe side effects and frequent development of multi-drug resistance by cancer cells. Antimicrobial peptides (AMPs) with high efficiency and low toxicity, as one of the most promising new drugs to replace chemoradiotherapy, have become a current research hotspot, attracting the attention of worldwide researchers. AMPs are natural-source small peptides from the innate immune system, and certain AMPs can selectively kill a broad spectrum of cancer cells while exhibiting less damage to normal cells. Although it involves intracellular mechanisms, AMPs exert their anti-cancer effects mainly through membrane destruction effect; thus, AMPs also hold unique advantages in fighting drug-resistant cancer cells. However, the poor stability and hemolytic toxicity of peptides limit their clinical application. Fortunately, functionalized nanoparticles have many possibilities in overcoming the shortcomings of AMPs, which provides a huge prospect for better application of AMPs. In this paper, we briefly introduce the characteristics and different sources of AMPs, review and summarize the mechanisms of action and the research status of AMPs used as an anticancer therapy, and finally focus on the further use of AMPs nano agents in the anti-cancer direction.

Co-expression of four penaeidins in transgenic rice seeds: an alternative strategy for substitute antibiotic agricultural products

The co-expression of multiple antimicrobial peptides (AMPs) in genetically modified (GM) crops can give plants a broader antibacterial spectrum and lower the pathogen risk of drug resistance. Therefore, four penaeidins (shrimp-derived AMPs) were fused and encoded in an artificial gene (PEN1234), driven by the seed-specific promoter Pzein, with the aim of co-expression in seeds of transgenic rice. The resistant rice plants, acquired via Agrobacterium-mediated transformation and glufosinate screening, were identified by PCR and the modified disk-diffusion method, and eight GM lines with high AMP content in the seeds were obtained. Among them, the PenOs017 line had the largest penaeidin content, at approximately 251-300 μg/g in seeds and 15-47 μg/g in roots and leaves. The AMPs in the seeds kept their antibacterial properties even after the seed had been boiled in hot water and could significantly inhibit the growth of methicillin-resistant Staphylococcus aureus, and AMPs in the leaves could effectively inhibit Xanthomonas oryzae pv. Oryzae. The results indicate that PenOs017 seeds containing AMPs are an ideal raw-material candidate for antibiotic-free food and feed, and may require fewer petrochemical fungicides or bactericides for disease control during cultivation than conventional rice.

The Antimicrobial Potential and Aquaculture Wastewater Treatment Ability of Penaeidins 3a Transgenic Duckweed

With the development of aquaculture, wastewater treatment and diseases have been paid more and more attention. The question of how to improve the immunity of aquatic species, as well as treat aquaculture wastewater, has become an urgent problem. In this study, duckweed with a high protein content (37.4%) (Lemna turionifera 5511) has been employed as a feedstock for aquatic wastewater treatment and the production of antimicrobial peptides. Penaeidins 3a (Pen3a), from Litopenaeus vannamei, were expressed under the control of CaMV-35S promoter in duckweed. Bacteriostatic testing using the Pen3a duckweed extract showed its antibacterial activity against Escherichia coli and Staphylococcus aureus. Transcriptome analysis of wild type (WT) duckweed and Pen3a duckweed showed different results, and the protein metabolic process was the most up-regulated by differential expression genes (DEGs). In Pen3a transgenic duckweed, the expression of sphingolipid metabolism and phagocytosis process-related genes have been significantly up-regulated. Quantitative proteomics suggested a remarkable difference in protein enrichment in the metabolic pathway. Pen3a duckweed decreased the bacterial number, and effectively inhibited the growth of Nitrospirae. Additionally, Pen3a duckweed displayed better growth in the lake. The study showed the nutritional and antibacterial value of duckweed as an animal feed ingredient.

Molecular characterization and expression analysis of dopa decarboxylase involved in the antibacterial innate immunity of the freshwater crayfish, Procambarus clarkii

Dopa decarboxylase (DDC) is responsible for the synthesis of dopamine, which acts as an important modulator in the nervous systems of vertebrates and invertebrates. Recent studies have indicated that DDC also plays crucial roles in the insect innate immune system. However, the functions of DDC in immunomodulation in crustaceans have not been thoroughly elucidated to date. In this study, a new full-length cDNA of the DDC protein was identified from red swamp crayfish, Procambarus clarkii (named Pc-ddc). The ORF of Pc-ddc encoded 474 amino acids, which possessed a 377-amino-acid domain. Pc-ddc was expressed at a relatively high level in the hemocytes and gills of crayfish. This protein was expressed at a relatively low level in the hepatopancreas and intestine. The expression level of Pc-ddc was clearly upregulated in hemocytes, hepatopancreas, gills, and intestine tissues after challenge with S. aureus or E. ictaluri. The results of the enzyme catalysis assay showed that the enzyme catalysis activity of rPc-DDC was 35 ± 2.8 ng h^-1 mg^-1 (n = 3). In addition, the results of the mimetic crayfish hemocytes encapsulation assay showed that the encapsulation rate of beads coated with rPc-DDC was clearly increased. The results of the bacterial binding assay showed that rPc-DDC strongly binds to S. aureus and E. ictaluri. Finally, when Pc-ddc was knocked down, the number of surviving crayfish clearly decreased after S. aureus or E. ictaluri was injected. All of these results indicate that Pc-DDC is an important immunomodulating enzyme in the neuroendocrine-immune (NEI) system of crayfish.

Comparative transcriptome and potential antiviral signaling pathways analysis of the gills in the red swamp crayfish, Procambarus clarkii infected with White Spot Syndrome Virus (WSSV)

Red swamp crayfish is an important model organism for research of the invertebrate innate immunity mechanism. Its excellent disease resistance against bacteria, fungi, and viruses is well-known. However, the antiviral mechanisms of crayfish remain unclear. In this study, we obtained high-quality sequence reads from normal and white spot syndrome virus (WSSV)-challenged crayfish gills. For group normal (GN), 39,390,280 high-quality clean reads were randomly assembled to produce 172,591 contigs; whereas, 34,011,488 high-quality clean reads were randomly assembled to produce 182,176 contigs for group WSSV-challenged (GW). After GO annotations analysis, a total of 35,539 (90.01%), 14,931 (37.82%), 28,221 (71.48%), 25,290 (64.05%), 15,595 (39.50%), and 13,848 (35.07%) unigenes had significant matches with sequences in the Nr, Nt, Swiss-Prot, KEGG, COG and GO databases, respectively. Through the comparative analysis between GN and GW, 12,868 genes were identified as differentially up-regulated DEGs, and 9,194 genes were identified as differentially down-regulated DEGs. Ultimately, these DEGs were mapped into different signaling pathways, including three important signaling pathways related to innate immunity responses. These results could provide new insights into crayfish antiviral immunity mechanism.

BAX, a novel cell pro-apoptotic protein, involved in hemocytes early antiviral immune response in fresh water crayfish, Procambarus clarkii

Apoptosis plays an important role in various biological processes and acts as a host defending mechanism by which infected cells are eliminated to restrict the virus propagation scale. Bax is a crucial pro-apoptotic protein, which mediates the release of cytochrome c from mitochondrion to cytosol in mammalian. However, its role in invertebrate is still obscure. Here, a novel pro-apoptotic protein gene was identified from hemocytes of red swamp crayfish. There was a Bcl-2 domain in the C-terminus of Pc-Bax, which possessed 497 amino acids residues. And an important transmembrane region existed in the C-terminus of Pc-Bax, which implied that Pc-Bax located in mitochondrial membrane. Besides, Pc-Bax was expressed at a relative high level in hemocytes, and a relative low expression levels in hepatopancreas, gills, and intestine. In hemocytes, Pc-Bax transcript was rapidly up-regulated from 12 h to 36 h after WSSV infection. And there was the same trend for Pc-Bax protein expression level in hemocytes after WSSV infection. Results of qRT-PCR testing for VP28 gene showed WSSV replication was obviously enhanced after Pc-Bax knockdown. Meantime, hemocytes apoptosis was suppressed in Pc-Bax knockdown crayfish after WSSV injection, compared with the dsGFP injection group and normal group. Taken together, these results revealed that crayfish hemocytes apoptosis scale was enhanced to suppress WSSV replication by up-regulating Bax protein expression level after WSSV infection.

Cloning, identification and functional analysis of a β-catenin homologue from Pacific white shrimp, Litopenaeus vannamei

Wnt signaling is known to control multiple of cellular processes such as cell differentiation, communication, apoptosis and proliferation, and is also reported to play a role during microbial infection. β-catenin is a key regulator of the Wnt signaling cascade. In the present study, we cloned and identified a β-catenin homologue from Litopenaeus vannamei termed Lvβ-catenin. The full-length of Lvβ-catenin transcript was 2797 bp in length within a 2451 bp open reading frame (ORF) that encoded a protein of 816 amino acids. Lvβ-catenin protein was comprised of several characteristic domains such as an N-terminal region of GSK-β consensus phosphorylation site and Coed coil section, a central region of 12 continuous Armadillo/β-Catenin-like repeat (ARM) domains and a C-terminal region. Real-time PCR showed Lvβ-catenin expression was responsive to Vibrio parahaemolyticus and white spot syndrome virus (WSSV) infection. Dual-reporter analysis showed that over-expression of Lvβ-catenin could induce activation of the promoter activities of several antimicrobial peptides (AMPs) such as shrimp PEN4, suggesting that Lvβ-catenin could play a role in regulating the production of AMPs. Knockdown of Lvβ-catenin enhanced the sensitivity of shrimps to V. parahaemolyticus and WSSV challenge, suggesting Lvβ-catenin could play a positive role against bacterial and viral pathogens. In summary, the results presented in this study provided some insights into the function of Wnt/β-catenin of shrimp in regulating AMPs and the host defense against invading pathogens.

In-depth comparative transcriptome analysis of intestines of red swamp crayfish, Procambarus clarkii, infected with WSSV

Crayfish has become one of the most important farmed aquatic species in China due to its excellent disease resistance against bacteria and viruses. However, the antiviral mechanism of crayfish is still not very clear. In the present study, many high-quality sequence reads from crayfish intestine were obtained using Illumina-based transcriptome sequencing. For the normal group (GN), 44,600,142 high-quality clean reads were randomly assembled to produce 125,394 contigs. For the WSSV-challenged group (GW), 47,790,746 high-quality clean reads were randomly assembled to produce 148,983 contigs. After GO annotation, 39,482 unigenes were annotated into three ontologies: biological processes, cellular components, and molecular functions. In addition, 15,959 unigenes were mapped to 25 different COG categories. Moreover, 7,000 DEGs were screened out after a comparative analysis between the GN and GW samples, which were mapped into 250 KEGG pathways. Among these pathways, 36 were obviously changed (P-values < 0.05) and 28 pathways were extremely significantly changed (P-values < 0.01). Finally, five key DEGs involved in the JAK-STAT signaling pathway were chosen for qRT-PCR. The results showed that these five DEGs were obviously up-regulated at 36 h post WSSV infection in crayfish intestine. These results provide new insight into crayfish antiviral immunity mechanisms.