Cloning and Sequencing of a Gene Encoding Aminopeptidase N in the Midgut of Helicoverpa armigera(Hubner)

A cDNA encoding aminopeptidase N was cloned by degenerated PCR combined with RACE technique in this paper. The full-length of APN-Harm is 3 043 bp. Open reading frame is 2 856 bp in length, encoding 951 amino acid residues. Its predicted molecular weight and isoelectric point are 108. 3 kDa and 5.29, respectively. This deduced amino acid sequence shares some common structural features with aminopeptidase N from several moth species, including the consensus zinc-binding motif HEXXHX18E and the GAMEN motif common to gluzincin aminopeptidases. The first 20 amino acid residues at N-termini is hydrophobic transmembrane helix. The sequence of APN-Harm was deposited in GenBank and the accession number is AY181026.

Knockout of three aminopeptidase N genes does not affect susceptibility of Helicoverpa armigera larvae to Bacillus thuringiensis Cry1A and Cry2A toxins

Bacillus thuringiensis(Bt)insecticidal toxins have been globally utilized for control of agricultural insects through spraying or transgenic crops.Binding of Bt toxins to special receptors on midgut epithelial cells of target insects is a key step in the mode of action.Previous studies suggested aminopeptidase N1(APN1)as a receptor or putative receptor in several lepidopteran insects including Helicoverpa armigera through evidence from RNA interefence‐based gene silencing approaches.In the current study we tested the role of APNs in the mode of action of Bt toxins using clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR‐associated protein 9‐mediated gene knockout.Three APN genes(HaAPN1,HaAPN2 and HaAPN5)were individually knocked out in a susceptible strain(SCD)of H.armigera to establish three homozygous knockout strains.Qualitative in vitro binding studies indicated binding of Cry1Ac or Cry2Ab to midgut brush border membrane vesicles was not obviously affected by APN knockout.Bioassay results showed that none of the three knockouts had significant changes in susceptibility to Cry1A or Cry2A toxins when compared with the SCD strain.This suggests that the three HaAPN genes we tested may not be critical in the mode of action of Cry1A or Cry2A toxins in H.armigera.

Anti-tumor targeted drug delivery systems mediated by aminopeptidase N/CD13

Aminopeptidase N(APN)/CD13 is a transmembrane glycoprotein,which is overexpressed on tumor neovascular endothelial cells and most tumor cells,where it plays an important role in tumor angiogenesis.Peptides containing the Asn-Gly-Arg(NGR)motif can specifically recognize APN/CD13 allowing them to act as tumor-homing peptides for the targeted delivery of anti-tumor drugs to tumor neovascular endothelial cells and tumor cells.This article reviews the literature and recent developments related to APN/CD13,its role in tumor growth and some antitumor drug delivery systems containing NGR peptides designed to target APN/CD13.

Real-time identification of gut microbiota with aminopeptidase N using an activable NIR fluorescent probe

A NIR fluorescent probe(DDAA) derived from fluorophore DDAO with alanine as the recognition group was developed for sensing aminopeptidase N(APN) in gut microbiota.Using DDAA as the real-time guidance tool for the fluorescence imaging of intestinal microorganism,target bacteria and saccharomycete possessing active APN were identified successfully from human feces.

Gene cloning and expression of aminopeptidase N and cadherin from midgut of the rice stem borer, Chilo suppressalis

The rice stem borer, Chilo suppressalis Walker is one of the most important insect pests on rice in Asia, north Africa and southern Europe. Transgenic Bt rice has been developed in the laboratory with good resistance to this pest and other Lepidopteran insects, which will provide a possible alternative tool for this pest control. The full-length cDNAs encoding an aminopeptidase N （CsAPN） and a cadherin （CsCad） were cloned from C. suppressalis. CsAPN showed common features of, and high identities to, other insect APNs in its deduced amino acid sequence. Although a full-length cDNA encoding cadherin-like protein has been reported in GenBank, the newly isolated cadherin here （CsCad） showed some differences in its amino acid sequence, especially at the 7th cadherin repeat region （CR7）, which indicated the newly isolated CsCad might be another allele. CsAPN and CsCad were successfully expressed in insect Tn cells, and the blot analysis showed these two proteins could bind Bt toxin CrylAb. The results will provide valuable information for the studies of toxin mode of action and the possible toxin resistance mechanisms in this pest.

A bestatin-based fluorescent probe for aminopeptidase N cell imaging

Aminopeptidase N （APN） is an important drug target and biomarker for various tumors. The current work characterizes a novel APN-targeted fluorescent probe （Bes-Green, 2） that manifests comparable inhibitory activity with Bestatin. This probe has capacity of tightly binding to the APN for imaging endogenous APN in living human ovarian clear cell carcinoma cells （ES-2） and has potential application in biological study of cellular APN.

Arrhythmogenic properties of dismantling cadherin-mediated adhesion in murine hearts

Objective： To evaluate the arrhythmogenic effects of dismantling cadherin-mediated adhesion by recombinant mouse aminopeptidase N （rmAPN） in murine hearts. Methods： rmAPN was incubated with cultured neonatal rat cardiomyocytes as well as being infused in adult mice. The cell-cell connections were immunolabelled and observed by laser confocal microscopy. Disruption of the N-terminal of N-cadherin （N-cad） was detected by western blot and quantitative immunofluorescence. The risk of inducible ventricular tachyarrhythmia was evaluated in mice by an electrophysiological study. Results： Disrupted cell-cell contact was observed in cultured neonatal rat cardiomyocytes in response to 30-40 ng/μL rmAPN. Loss of the N-terminal in N-cad and altered distribution of connexin 43 （Cx43） were observed in hearts from rmAPN-infused mice. In addition, a reduction of phosphorylated Cx43 was also detected concomitant with redistribution of Cx43. Electrophysiological studies of rmAPN-infused mice showed prolonged QRS duration and increased inducibility of ventricular tachycardias. Conclusion： Disruption of N-cad by rmAPN contributes to gap junction remodeling and may elicit arrhythmogenic effects. The disorder of adherent junctions by proteolytic enzymes may play an important role in arrhythmogenic mechanisms in correlated diseases.

A preliminary study on the interaction between Asn-Gly-Arg(NGR)-modified multifunctional nanoparticles and vascular epithelial cells

Previously developed Asn-Gly-Arg(NGR) peptide-modified multifunctional poly(ethyleneimine)–poly(ethylene glycol)(PEI–PEG)-based nanoparticles(TPIC) have been considered to be promising carriers for the co-delivery of DNA and doxorubicin(DOX). As a continued effort, the aim of the present study was to further evaluate the interaction between TPIC and human umbilical vein endothelial cells(HUVEC) to better understand the cellular entry mechanism. In the present investigation,experiments relevant to co-localization, endocytosis inhibitors and factors influencing the internalization were performed. Without any treatment, there was no co-localization between aminopeptidase N/CD13(APN/CD13) and caveolin 1(CAV1). However, co-localization between CD13 and CAV1 was observed when cells were incubated with an anti-CD13 antibody or TPIC. As compared with antibody treatment,TPIC accelerated the speed and enhanced the degree of co-localization. TPIC entered HUVEC not only together with CD13 but also together with CAV1. However, this internalization was not dependent on the enzyme activity of CD13 but could be inhibited by methyl-β-eyclodextfin(MβCD), further identifying the involvement of caveolae-mediated endocytosis(CvME). This conclusion was also verified by endocytosis inhibitor experiments.

棉铃虫中肠氨肽酶APN4与Cry1Ac、Cry2Aa结合能力的比较

【目的】Bt杀虫蛋白(Bacillus thuringiensis)具有高度的靶标特异性,已经被广泛用于农业害虫防治。Bt杀虫蛋白要发挥杀虫活性,必须首先与其受体蛋白结合,氨肽酶N(Aminopeptidase N)是一类重要的Bt受体蛋白。因此,分析该受体与Bt杀虫蛋白的结合能力,可为进一步明确不同Bt的分子作用机制、Bt的抗性治理以及新Bt的开发应用等提供借鉴。【方法】本文利用Ligand blot和Elisa方法比较了棉铃虫Helicoverpa armigera中肠APN4(Aminopeptidase N4,APN4)与Cry1Ac、Cry2Aa的结合能力。【结果】原核表达的APN4片段与活化的Cry1Ac、Cry2Aa都可以结合,解离常数(Kd)分别是48.59 nmol/L和21.73 nmol/L。【结论】APN4片段与Cry1Ac、Cry2Aa的结合能力在数量级上不存在显著性差异。

Genome-wide identification and comparative analysis of Cry toxin receptor families in 7 insect species with a focus on Spodoptera litura

Cadherin,aminopeptidase N(APN)and alkaline phosphatase(ALP)have been characterized as Cry receptors.In this study,comparative genomic analysis of the 3 receptor families was performed in 7 insects.ALPs and APNs are divided into three and eight clades in phylogenetic trees,respectively.ALPs in clade 3 and APNs in clade 1 contain multiple paralogs within each species and most paralogs are located closely in chromosomes.Drosophila melanogaster has expanded APNs in clade 5 and were lowly expressed in midgut.Cadherins are divided into 16 clades;they may diverge before holometabolous insect speciation except for BtR and Cad89D-like clades.Eight insects from different orders containing BtR orthologs are sensitive to Cryl A or Cry3A,while five species without BtR are insensitive to both toxins.Most APNs in clade 1,several ALPs in clade 3,BtR and Cad89D-like genes were highly or moderately expressed in larval midgut of Spodoptera litura and the other six species,and several members in these clades have been identi-•fied as Cry receptors.Expressions of putative 5.litura Cry receptors in the midgut after exposing to Bt toxins were also analyzed.

Anti-tumor efficiency of NGR-modified PEG-PLGA micelles containing paclitaxel:in vitro and in vivo

In the present study, we prepared novel NGR-modified PEG-PLGA polymeric micelles containing paclitaxel （NGR- PM-PTX） in order to evaluate their potential targeting to aminopeptidase N receptors expressed on tumor endothelial cells and the tumor cell surface and its anti-tumor activity in vitro and in vivo. NGR-PM-PTX was prepared by thin-film hydration method. The in vitro targeting characteristics of NGR-modified PM on HUVEC （human umbilical vein endothelial cells）, HT1080 （human fibrosarcoma cells） and MCF-7 （human breast adenocarcinoma cells） were then investigated. The anti-tumor activity of NGR-PM-PTX was evaluated in HT1080 tumor-bearing mice in vivo. The targeting activity of the NGR-modified PM was demonstrated by flow cytometry and confocal microscopy in vitro. NGR-PM-PTX also produced marked anti-tumor activity to HTI080 tumor-beating mice in vivo.

cNGR-based synergistic-targeted NIR fluorescent probe for tracing and bioimaging of pancreatic ductal adenocarcinoma

Identification of fluorescent biomarkers with peptide ligand-directed receptors for diagnosis or theranostic of pancreatic ductal adenocarcinoma (PDAC) is still challenging. As potential prognostic/predictive bioimaging targets, both aminopeptidase N(APN, known as CD13) and Caveolin-1 are found as upregulation on the cell membrane surface of PDAC, in which APN is the principal receptor of the cyclic peptide cNGR (Asn-Gly-Arg, NGR) and Caveolin-1 can synergistically mediate endocytosis in this receptor-targeted process. Herein, we conjugate cNGR to dicyanomethylene-4H-pyran (DCM) chromophore to develop a synergistic-targeted near-infrared (NIR) fluorescent probe DCM-cNGR with strongly intrinsic NIR fluorescence, stable optical performance, low cytotoxicity, and rapid accumulation in PANC-1 cells with the synergistic overexpressed APN receptor-targeted and Caveolin-1-mediated endocytosis. As demonstrated, DCM-cNGR can realize noninvasive NIR imaging for targeting PANC-1 tumor in vivo after intravenous injection into PANC-1 xenograft tumor of nude mice, making a great promise to improve the precision diagnosis and therapy of pancreatic cancer with real time tracing and bioimaging of PDAC in vitro and in vivo.