Single subunit type of ferritin from visceral mass of Saccostrea cucullata: cloning, expression and cisplatin-subunit analysis

Bioactive Molecules Delivery through Ferritin Nanoparticles: Sum Up of Current Loading Methods

Ferritin (Ft) is a protein with a peculiar three-dimensional architecture. It is characterized by a hollow cage structure and is responsible for iron storage and detoxification in almost all living organisms. It has attracted the interest of the scientific community thanks to its appealing features, such as its nano size, thermal and pH stability, ease of functionalization, and low cost for large-scale production. Together with high storage capacity, these properties qualify Ft as a promising nanocarrier for the development of delivery systems for numerous types of biologically active molecules. In this paper, we introduce the basic structural and functional aspects of the protein, and summarize the methods employed to load bioactive molecules within the ferritin nanocage.

A ferritin gene from Procambarus clarkii, molecular characterization and in response to heavy metal stress and lipopolysaccharide challenge

Ferritin plays important roles in iron storage, detoxification, and immune response. Here, a ferritin gene (PcFer) was identified in Procambarus clarkii, an economically important freshwater crayfish. Full-length PcFer cDNA was 1022-bp, including a 135-bp 5'-untranslated region (UTR) with a typical iron responsive element, a 374-bp 3'-UTR, and a 513-bp open reading frame encoding a polypeptide of 170 amino acids which contained the Ferritin domain. PcFer has ion binding sites, a ferrihydrite nucleation center, and an iron ion channel. PcFer is phylogenetically closely-related to Pacifastacus leniusculus and Eriocheir sinensis ferritins. Real-time quantitative reverse-transcription PCR analysis showed that PcFer was expressed in all tested P. clarkii tissues, and expressed most in hepatopancreas. After challenge with various heavy metals and lipopolysaccharide, respectively, the hepatopancreatic expression levels of PcFer were markedly upregulated. These results suggest that expression of PcFer might be involved in immune defense and protection of P. clarkii against heavy metal stress.

Time course of lead induced proteomic changes in gill of the Antarctic limpet Nacella Concinna (Gastropoda: Patellidae)

The effect of increasing levels of metals from anthropogenic sources on Antarctic invertebrates is poorly understood. Here we exposed limpets (Nacella concinna) to 0, 0.12 and 0.25 μg L− 1 lead for 12, 24, 48 and 168 h. We subsequently quantified the changes in protein abundance from gill, using 2D gel electrophoresis and mass spectrometry. We identified several antioxidant proteins, including the metal binding Mn-superoxide dismutase and ferritin, increasing abundances early on. Chaperones involved in the redox-dependent maturation of proteins in the endoplasmic reticulum (ER) showed higher abundance with lead at 48 h. Lead also increased the abundance of Zn-binding carbonic anhydrase at 12 h, suggesting a challenge to acid-base balance. Metabolic proteins increased abundance at 168 h, suggesting a greater ATP demand during prolonged exposure. Changes in abundance of the small G-protein cdc42, a signaling protein modifying cytoskeleton, increased early and subsequently reversed during prolonged exposure, possibly leading to the modification of thick filament structure and function. We hypothesize that the replacement of metals initially affected antioxidant proteins and increased the production of reactive oxygen species. This disrupted the redox-sensitive maturation of proteins in the ER and caused increased ATP demand later on, accompanied by changes in cytoskeleton.

SIGNIFICANCE

Proteomic analysis of gill tissue in Antarctic limpets exposed to different concentrations of lead (Pb) over a 168 h time period showed that proteomic changes vary with time. These changes included an increase in the demand of scavenging reactive oxygen species, acid-base balance and a challenge to protein homeostasis in the endoplasmic reticulum early on and subsequently an increase in energy metabolism, cellular signaling, and cytoskeletal modifications. Based on this time course, we hypothesize that the main mode of action of lead is a replacement of metal-cofactors of key enzymes involved in the scavenging of reactive oxygen species and the regulation of acid-base balance.

Ferritin from the Pacific abalone Haliotis discus hannai: Analysis of cDNA sequence, expression, and activity

Ferritin plays an important role in iron homeostasis due to its ability to bind and sequester large amounts of iron. In this study, the gene encoding a ferritin (HdhFer2) was cloned from Pacific abalone (Haliotis discus hannai). The full-length cDNA of HdhFer2 contains a 5'-UTR of 121 bp, an ORF of 516 bp, and a 3'-UTR of 252 bp with a polyadenylation signal sequence of AATAAA and a poly(A) tail. It also contains a 31 bp iron-responsive element (IRE) in the 5'-UTR position, which is conserved in many ferritins. HdhFer2 consists of 171 amino acid residues with a predicted molecular weight (MW) ∼19.8 kDa and a theoretical isoelectric point (PI) of 4.84. The deduced amino acid sequence of HdhFer2 contains two ferritin iron-binding region signatures (IBRSs). HdhFer2 mRNA was detected in a wide range of tissues and was dominantly expressed in the gill. Infection with the bacterial pathogen Vibrio anguillarum significantly upregulated HdhFer2 expression in a time-dependent manner. Recombinant HdhFer2 (rHdhFer2) purified from Escherichia coli was able to bind ferrous iron in a concentration-dependent manner. In summary, these results suggest that HdhFer2 is a crucial protein in the iron-withholding defense system, and plays an important role in the innate immune response of abalone.

Toxicological responses of the hard clam Meretrix meretrix exposed to excess dissolved iron or challenged by Vibrio parahaemolyticus

The responses of genes encoding defense components such as ferritin, the lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF), the inhibitor of nuclear factor-κB (IκB), metallothionein, and glutathione peroxidase were assessed at the transcriptional level in order to investigate the toxicological and immune mechanism of the hard clam Meretrix meretrix (HCMM) following challenge with iron or a bacterium (Vibrio parahaemolyticus). Fe dissolved in natural seawater led to an increase of Fe content in both the hepatopancreas and gill tissue of HCMM between 4 and 15 days of exposure. The ferritin gene responded both transcriptionally as indicated by real-time quantitative PCR and translationally as shown by western blotting results to iron exposure and both transcriptional and translational ferritin expression in the hepatopancreas had a positive correlation with the concentration of dissolved iron in seawater. Both iron and V. parahaemolyticus exposure triggered immune responses with similar trends in clam tissues. There was a significant post-challenge mRNA expression of LITAF and IκB at 3h, ferritin at 24h, and metallothionein and glutathione peroxidase at 48h. This behavior might be linked to their specific functions in physiological processes. These results suggested that similar signaling pathways were triggered during both iron and V. parahaemolyticus challenges. Here, we indicated that the ferritin of Meretrix meretrix was an intermediate in the pathway of iron homeostasis and in its innate immune defense mechanism.

Toxic effects of octylphenol on the expression of genes in liver identified by suppression subtractive hybridization of Rana chensinensis

Octylphenol (OP) is the degradative product of alkylphenol ethoxylates that are widely used to produce rubber, pesticides, and paints. It is chemically stable substance and demonstrates estrogenic effects, toxicity and carcinogenic effects in the environment. The toxin accumulates rapidly in the liver where it exerts most of its damage, but the molecular mechanisms behind its toxicity remain unclear. Due to limited information concerning the effect of OP on liver, this study investigates how OP causes hepatotoxicity in liver. Here, suppression subtractive hybridization was used to identify the alterations in gene transcription of the frog (Rana chensinensis) after exposure to OP. After hybridization and cloning, the subtractive cDNA libraries were obtained. At random, 207 positive clones were selected and sequenced from the subtractive libraries, which gave a total of 75 gene fragment sequences. The screening identified numerous genes involved in apoptosis, signal transduction, cytoskeletal remodeling, innate immunity, material and energy metabolism, translation and transcription which were extensively discussed. Two sequenced genes were analyzed further using real time quantitative PCR. The two genes from the library were found to be transcriptionally up-regulated. These results confirmed the successful construction of the subtractive cDNA library that was enriched for the genes that were differentially transcribed in the amphibian liver challenged with OP, and for the first time present the basic data on toxicity effect of OP on liver.

Molecular properties and immune defense of two ferritin subunits from freshwater pearl mussel, Hyriopsis schlegelii

Ferritin is a conserved iron-binding protein involved in cellular iron metabolism and host defense. In the present study, two distinct cDNAs for ferritins in the freshwater pearl mussel Hyriopsis schlegelii were identified (designated as HsFer-1 and HsFer-2) by SMART RACE approach and expressed sequence tag (EST) analysis. The full-length cDNAs of HsFer-1 and HsFer-2 were of 760 and 877 bp, respectively. Both of the two cDNAs contained an open reading frame (ORF) of 522 bp encoding for 174 amino acid residues. Sequence characterization and homology alignment indicated that HsFer-1 and HsFer-2 had higher similarity to H-type subunit of vertebrate ferritins than L-type subunit. Analysis of the HsFer-1 and HsFer-2 untranslated regions (UTR) showed that both of them had an iron response element (IRE) in the 5'-UTR, which was considered to be the binding site for iron regulatory protein (IRP). Quantitative real-time PCR (qPCR) assays were employed to examine the mRNA expression profiles. Under normal physiological conditions, the expression level of both HsFer-1 and HsFer-2 mRNA were the highest in hepatopancreas, moderate in gonad, axe foot, intestine, kidney, heart, gill, adductor muscle and mantle, the lowest in hemocytes. After stimulation with bacteria Aeromonas hydrophila, HsFer-1 mRNA experienced a different degree of increase in the tissues of hepatopancreas, gonad and hemocytes, the peak level was 2.47-fold, 9.59-fold and 1.37-fold, respectively. Comparatively, HsFer-2 showed up-regulation in gonad but down-regulation in hepatopancreas and hemocytes. Varying expression patterns indicate that two types of ferritins in H. schlegelii might play different roles in response to bacterial challenge. Further bacteriostatic analysis showed that both the purified recombinant ferritins inhibited the growth of A. hydrophila to a certain degree. Collectively, our results suggest that HsFer-1 and HsFer-2 are likely to be functional proteins involved in immune defense against bacterial infection.

A ferritin from Dendrorhynchus zhejiangensis with heavy metals detoxification activity

Ferritin, an iron homeostasis protein, has important functions in transition and storage of toxic metal ions. In this study, the full-length cDNA of ferritin was isolated from Dendrorhynchus zhejiangensis by cDNA library and RACE approaches. The higher similarity and conserved motifs for ferritin were also identified in worm counterparts, indicating that it belonged to a new member of ferritin family. The temporal expression of worm ferritin in haemocytes was analyzed by RT-PCR, and revealed the ferritin could be induced by Cd²⁺, Pb²⁺ and Fe²⁺. The heavy metal binding activity of recombinant ferritin was further elucidated by atomic force microscopy (AFM). It was observed that the ferritin protein could form a chain of beads with different size against three metals exposure, and the largest one with 35∼40 nm in height was identified in the Cd²⁺ challenge group. Our results indicated that worm ferritin was a promising candidate for heavy metals detoxification.

Cloning analysis of ferritin and the cisplatin-subunit for cancer cell apoptosis in Aplysia juliana hepatopancreas

Ferritin, an iron storage protein, plays a key role in iron metabolism in vivo. Here, we have cloned an inducible ferritin cDNA with 519 bp within the open reading frame fragment from the hepatopancreas of Aplysia juliana (AJ). The subunit sequence of the ferritin was predicted to be a polypeptide of 172 amino acids with a molecular mass of 19.8291kDa and an isoelectric point of 5.01. The cDNA sequence of hepatopancreas ferritin in AJ was constructed into a pET-32a system for expressing its relative protein efficiently in E. coli strain BL21, under isopropyl-β-d-thiogalactoside induction. The recombinant ferritin, which was further purified on a Ni-NTA resin column and digested with enterokinase, was detected as a single subunit of approximately 20 kDa mass using both SDS-PAGE and mass spectrometry. The secondary structure and phosphorylation sites of the deduced amino acids were predicted using both ExPASy proteomic tools and the NetPhos 2.0 server, and the subunit space structure of the recombinant AJ ferritin (rAjFer) was built using a molecular operating environment software system. The result of in-gel digestion and identification using MALDI-TOF MS/MS showed that the recombinant protein was AjFer. ICP-MS results indicated that the rAjFer subunit could directly bind to cisplatin[cis-Diaminedichloroplatinum(CDDP)], giving approximately 17.6 CDDP/ferritin subunits and forming a novel CDDP-subunit. This suggests that a nanometer CDDP core-ferritin was constructed, which could be developed as a new anti-cancer drug. The flow cytometry results indicated that CDDP-rAjFer could induce Hela cell apoptosis. Results of the real-time PCR and Western blotting showed that the expression of AjFer mRNA was up-regulated in AJ under Cd(2+) stress. The recombinant AjFer protein should prove to be useful for further study of the structure and function of ferritin in Aplysia.