The first evidence of biological activity for free Hypusine, an enigmatic amino acid discovered in the '70s

Hypusine amino acid [N^ε-(4-amino-2-hydroxybutyl)-lysine] was first isolated in 1971 from bovine brain extracts. Hypusine originates from a post-translational modification at the eukaryotic translation initiation factor 5A (eIF5A), a protein produced by archaebacteria and eukaryotes. The eIF5A protein is the only one described containing the hypusine residue, which is essential for its activity. Hypusine as a free amino acid is a consequence of proteolytic degradation of eIF5A. Herein, we showed, for the first time, evidence of biological activity for the free hypusine. C6 rat glioma cells were treated with hypusine, and different cellular parameters were evaluated. Hypusine treatment significantly reduced C6 cell proliferation and potently suppressed their clonogenic capacity without leading to apoptosis. Hypusine also decreased the Eif5A transcript content and the global protein synthesis profile that may occur due to negative feedback in response to high hypusine concentration, controlling the content of newly synthesized eIF5A, which can affect the translation process. Besides, hypusine treatment also altered cellular metabolism by changing the pathways for energy production, reducing cellular respiration coupled with oxidative phosphorylation, and increasing the anaerobic metabolism. These observed results and the relationship between eIF5A and tumor processes led us to test the combination of hypusine with the chemotherapeutic drug temozolomide. Combining temozolomide with hypusine reduced the MTT conversion to the same levels as those observed using double temozolomide dosage alone, demonstrating a synergetic action between the compounds. Thus, since 1971, this is the first study showing evidence of biological activity for hypusine not associated with being an essential component of the eiF5A protein. Finding out the molecular targets of hypusine are the following efforts to completely characterize its biological activity.

Titanium-protein nanocomposites as new biomaterials produced by high-pressure torsion

The development of new biomaterials with outstanding mechanical properties and high biocompatibility has been a significant challenge in the last decades. Nanocrystalline metals have provided new opportunities in producing high-strength biomaterials, but the biocompatibility of these nanometals needs to be improved. In this study, we introduce metal-protein nanocomposites as high-strength biomaterials with superior biocompatibility. Small proportions of bovine serum albumin (2 and 5 vol%), an abundant protein in the mammalian body, are added to titanium, and two nanocomposites are synthesized using a severe plastic deformation process of high-pressure torsion. These new biomaterials show not only a high hardness similar to nanocrystalline pure titanium but also exhibit better biocompatibility (including cellular metabolic activity, cell cycle parameters and DNA fragmentation profile) compared to nano-titanium. These results introduce a pathway to design new biocompatible composites by employing compounds from the human body.

Characterization of pomegranate peel extracts obtained using different solvents and their effects on cell cycle and apoptosis in leukemia cells

Pomegranate (Punica granatum L.) has been used in traditional herbal medicine by several cultures as an anti-inflammatory, antioxidant, antihyperglycemic, and for treatment and prevention of cancer and other diseases. Different parts of the fruit, extraction methods, and solvents can define the chemical profile of the obtained extracts and their biological activities. This study aimed to characterize the chemical profile of peel extracts collected using different extraction solvents and their biological effects on the cell cycle and apoptosis of THP-1 leukemic cells. Aqueous extract presented the highest content of punicalagins (α pun = 562.26 ± 47.14 mg/L and β pun = 1,251.13 ± 22.21 mg/L) and the lowest content of ellagic acid (66.38 ± 0.21 mg/L), and it promoted a significant impairment of the cell cycle S phase. In fact, punicalagin-enriched fraction, but not an ellagic acid-enriched fraction, caused an S phase cell cycle arrest. All extracts increased the number of apoptotic cells. Punicalagin-enriched fraction increased the percentage of cells with fragmented DNA, which was intensified by ellagic acid combination. The treatment combining punicalagin and ellagic acid fractions increased the apoptotic cleaved PARP1 protein and reduced the activation of the growth-related mTOR pathway. Thus, these results evidence that solvent choice is critical for the phenolic compounds profile of pomegranate peel extracts and their biological activities.

Transcriptome analysis in Parhyale hawaiensis reveal sex-specific responses to AgNP and AgCl exposure

Analysis of the transcriptome of organisms exposed to toxicants offers new insights for ecotoxicology, but further research is needed to enhance interpretation of results and effectively incorporate them into useful environmental risk assessments. Factors that must be clarified to improve use of transcriptomics include assessment of the effect of organism sex within the context of toxicant exposure. Amphipods are well recognized as model organisms for toxicity evaluation because of their sensitivity and amenability to laboratory conditions. To investigate whether response to metals in crustaceans differs according to sex we analyzed the amphipod Parhyale hawaiensis after exposure to AgCl and Ag nanoparticles (AgNP) via contaminated food. Gene specific analysis and whole genome transcriptional profile of male and female organisms were performed by both RT-qPCR and RNA-seq. We observed that expression of transcripts of genes glutathione transferase (GST) did not differ among AgCl and AgNP treatments. Significant differences between males and females were observed after exposure to AgCl and AgNP. Males presented twice the number of differentially expressed genes in comparison to females, and more differentially expressed were observed after exposure to AgNP than AgCl treatments in both sexes. The genes that had the greatest change in expression relative to control were those genes related to peptidase and catalytic activity and chitin and carbohydrate metabolic processes. Our study is the first to demonstrate sex specific differences in the transcriptomes of amphipods upon exposure to toxicants and emphasizes the importance of considering gender in ecotoxicology.

Insulin action on protein synthesis and its association with eIF5A expression and hypusination

The hormone insulin plays a central role in the metabolism of carbohydrates, lipids, and proteins. In relation to protein metabolism, insulin stimulates amino acid uptake and activates protein synthesis in responsive cells by modulation of signal transduction pathways, such as associated to Akt/PkB, mTOR, S6Ks, 4E-BP1, and several translation initiation/elongation factors. In this context, there is no information on direct cellular treatment with insulin and effects on eukaryotic translation initiation factor 5A (eIF5A) regulation. The eIF5A protein contains an exclusive amino acid residue denominated hypusine, which is essential for its activity and synthesized by posttranslational modification of a specific lysine residue using spermidine as substrate. The eIF5A protein is involved in cellular proliferation and differentiation processes, as observed for satellite cells derived from rat muscles, revealing that eIF5A has an important role in muscle regeneration. The aim of this study was to determine whether eIF5A expression and hypusination are influenced by direct treatment of insulin on L6 myoblast cells. We observed that insulin increased the content of eIF5A transcripts. This effect occurred in cells treated or depleted of fetal bovine serum, revealing a positive insulin effect independent of other serum components. In addition, it was observed that hypusination follows the maintenance of eIF5A protein content in the serum depleted cells and treated with insulin. These results demonstrate that eIF5A is modulated by insulin, contributing the protein synthesis machinery control, as observed by puromycin incorporation in nascent proteins.

Alternative Start Codon Connects eIF5A to Mitochondria

Eukaryotic translation initiation factor 5A (eIF5A), a protein containing the amino acid residue hypusine required for its activity, is involved in a number of physiological and pathological cellular processes. In humans, several EIF5A1 transcript variants encode the canonical eIF5A1 isoform B, whereas the hitherto uncharacterized variant A is expected to code for a hypothetical eIF5A1 isoform, referred to as isoform A, which has an additional N-terminal extension. Herein, we validate the existence of eIF5A1 isoform A and its production from transcript variant A. In fact, variant A was shown to encode both eIF5A1 isoforms A and B. Mutagenic assays revealed different efficiencies in the start codons present in variant A, contributing to the production of isoform B at higher levels than isoform A. Immunoblotting and mass spectrometric analyses showed that isoform A can undergo hypusination and acetylation at specific lysine residues, as observed for isoform B. Examination of the N-terminal extension suggested that it might confer mitochondrial targeting. Correspondingly, we found that isoform A, but not isoform B, co-purified with mitochondria when the proteins were overproduced. These findings suggest that eIF5A1 isoform A has a role in mitochondrial function. J. Cell. Physiol. 231: 2682-2689, 2016. © 2016 Wiley Periodicals, Inc.

A Brazilian social bee must cultivate fungus to survive

The nests of social insects provide suitable microenvironments for many microorganisms as they offer stable environmental conditions and a rich source of food [1-4]. Microorganisms in turn may provide several benefits to their hosts, such as nutrients and protection against pathogens [1, 4-6]. Several examples of symbiosis between social insects and microorganisms have been found in ants and termites. These symbioses have driven the evolution of complex behaviors and nest structures associated with the culturing of the symbiotic microorganisms [5, 7, 8]. However, while much is known about these relationships in many species of ants and termites, symbiotic relationships between microorganisms and social bees have been poorly explored [3, 4, 9, 10]. Here, we report the first case of an obligatory relationship between the Brazilian stingless bee Scaptotrigona depilis and a fungus of the genus Monascus (Ascomycotina). Fungal mycelia growing on the provisioned food inside the brood cell are eaten by the larva. Larvae reared in vitro on sterilized larval food supplemented with fungal mycelia had a much higher survival rate (76%) compared to larvae reared under identical conditions but without fungal mycelia (8% survival). The fungus was found to originate from the material from which the brood cells are made. Since the bees recycle and transport this material between nests, fungus would be transferred to newly built cells and also to newly founded nests. This is the first report of a fungus cultivation mutualism in a social bee.

Chlamydophila pneumonia and increased TLR4 gene expression in leukocytes are associated with acute myocardial infarction

We investigated the relationship of the positivity for Chlamydophila pneumoniae (Cpn) and Mycoplasma pneumonia (Mpn), inflammatory and metabolic markers, and mRNA expression and polymorphisms of the TLR2, TLR4, IL-6 and TNFA genes with acute myocardial infarction (AMI). Two hundred and eighteen individuals (98 AMI and 120 non-AMI) were selected at two Clinical Centers. Blood samples were drawn to extract DNA and RNA and to measure laboratory variables including anti-Cpn IgM and IgG. Cpn and Mpn genomic DNA as well as TLR2, TLR4, IL-6 and TNFA mRNA expression were evaluated by quantitative real-time PCR (qPCR). Gene polymorphisms were detected by PCR-HRM. AMI patients had higher positivity for Cpn-DNA (17.3%) than non-AMI group (6.7%, p=0.018). In addition, Cpn-DNA positivity was an independent predictor of risk for AMI (OR: 2.56, CI: 1.08 - 6.04, p=0.031). Positivity for anti-Cpn IgG and Mpn-DNA was similar between AMI and non-AMI (> 0.05). TLR4 mRNA expression was higher in AMI than non-AMI individuals (p=0.005). CD14 -260C> T, TNFA -308A> G, TLR2 c.2258G> A, TLR4 c.896A> G and TLR4 c.1196> T variants were not associated with increased risk for AMI (p> 0.05). In the AMI group, individuals carrying CD14 -260CC genotype had higher hsCRP levels than CT/TT carriers (p=0.041). These results are suggestive that Cpn-DNA positivity and increased TLR4 mRNA expression in blood leukocytes may be associated with AMI and could be useful markers to evaluate the severity and progression of the atherosclerotic disease in AMI patients.

MSX1 gene polymorphisms in non-syndromic cleft lip and/or palate

OBJECTIVE

The aim of this study was to investigate the contribution of 6 polymorphic variants of the MSX1 gene in non-syndromic cleft lip and/or palate (NSCL/P).

METHODS

Three hundred and fifty-eight individuals (158 NSCL/P cases and 200 controls) were genotyped by TaqMan allelic discrimination using predesigned SNP assays. Statistical analyses were conducted using the software spss 15.0 and the r statistical suite. Haplotype block structure and haplotype frequencies were determined using the Haploview. A P-value of 0.05 and confidence interval of 95% were used for all of statistical tests.

RESULTS

The patients with non-syndromic cleft lip and/or palate were characterized by similar distribution of MSX1 genotypes and allele in comparison to subjects without oral clefts (P > 0.05). Two haplotype blocks were constructed with polymorphisms of MSX1 gene and haplotypes formed showed a similar frequency in patients with and without oral clefts.

CONCLUSIONS

The present study provides no evidence that MSX1 polymorphisms (rs3775261, rs1042484, rs12532, rs6446693, rs4464513 and rs1907998) play a major role in NSCL/P.

Potential contribution of translational factors to triiodo-L-thyronine-induced insulin synthesis by pancreatic beta cells

BACKGROUND

Thyroid hormones (THs) are known to regulate protein synthesis by acting at the transcriptional level and inducing the expression of many genes. However, little is known about their role in protein expression at the post-transcriptional level, even though studies have shown enhancement of protein synthesis associated with mTOR/p70S6K activation after triiodo-L-thyronine (T3) administration. On the other hand, the effects of TH on translation initiation and polypeptidic chain elongation factors, being essential for activating protein synthesis, have been poorly explored. Therefore, considering that preliminary studies from our laboratory have demonstrated an increase in insulin content in INS-1E cells in response to T3 treatment, the aim of the present study was to investigate if proteins of translational nature might be involved in this effect.

METHODS

INS-1E cells were maintained in the presence or absence of T3 (10(-6) or 10(-8) M) for 12 hours. Thereafter, insulin concentration in the culture medium was determined by radioimmunoassay, and the cells were processed for Western blot detection of insulin, eukaryotic initiation factor 2 (eIF2), p-eIF2, eIF5A, EF1A, eIF4E binding protein (4E-BP), p-4E-BP, p70S6K, and p-p70S6K.

RESULTS

It was found that, in parallel with increased insulin generation, T3 induced p70S6K phosphorylation and the expression of the translational factors eIF2, eIF5A, and eukaryotic elongation factor 1 alpha (eEF1A). In contrast, total and phosphorylated 4E-BP, as well as total p70S6K and p-eIF2 content, remained unchanged after T3 treatment.

CONCLUSIONS

Considering that (i) p70S6K induces S6 phosphorylation of the 40S ribosomal subunit, an essential condition for protein synthesis; (ii) eIF2 is essential for the initiation of messenger RNA translation process; and (iii) eIF5A and eEF1A play a central role in the elongation of the polypeptidic chain during the transcripts decoding, the data presented here lead us to suppose that a part of T3-induced insulin expression in INS-1E cells depends on the protein synthesis activation at the post-transcriptional level, as these proteins of the translational machinery were shown to be regulated by T3.

A genome-wide screen for Neurospora crassa transcription factors regulating glycogen metabolism

Transcription factors play a key role in transcription regulation as they recognize and directly bind to defined sites in promoter regions of target genes, and thus modulate differential expression. The overall process is extremely dynamic, as they have to move through the nucleus and transiently bind to chromatin in order to regulate gene transcription. To identify transcription factors that affect glycogen accumulation in Neurospora crassa, we performed a systematic screen of a deletion strains set generated by the Neurospora Knockout Project and available at the Fungal Genetics Stock Center. In a wild-type strain of N. crassa, glycogen content reaches a maximal level at the end of the exponential growth phase, but upon heat stress the glycogen content rapidly drops. The gene encoding glycogen synthase (gsn) is transcriptionally down-regulated when the mycelium is exposed to the same stress condition. We identified 17 deleted strains having glycogen accumulation profiles different from that of the wild-type strain under both normal growth and heat stress conditions. Most of the transcription factors identified were annotated as hypothetical protein, however some of them, such as the PacC, XlnR, and NIT2 proteins, were biochemically well-characterized either in N. crassa or in other fungi. The identification of some of the transcription factors was coincident with the presence of DNA-binding motifs specific for the transcription factors in the gsn 5'-flanking region, and some of these DNA-binding motifs were demonstrated to be functional by Electrophoretic Mobility Shift Assay (EMSA) experiments. Strains knocked-out in these transcription factors presented impairment in the regulation of gsn expression, suggesting that the transcription factors regulate glycogen accumulation by directly regulating gsn gene expression. Five selected mutant strains showed defects in cell cycle progression, and two transcription factors were light-regulated. The results indicate that there are connections linking different cellular processes, such as metabolism control, biological clock, and cell cycle progression.

T3 acutely increases GH mRNA translation rate and GH secretion in hypothyroid rats

Cytoskeleton controls the stability of transcripts, by mechanisms that involve mRNAs and eEF1A attachment to it. Besides, it plays a key role in protein synthesis and secretion, which seems to be impaired in somatotrophs of hypothyroid rats, whose cytoskeleton is disarranged. This study investigated the: eEF1A and GH mRNA binding to cytoskeleton plus GH mRNA translation rate and GH secretion, in sham-operated and thyroidectomized rats treated with T3 or saline, and killed 30min thereafter. Thyroidectomy reduced: (a) pituitary F-actin content, and eEF1A plus GH mRNA binding to it; (b) GH mRNA recruitment to polysome; and (c) liver IGF-I mRNA expression, indicating that GH mRNA stability and translation rate, as well as GH secretion were impaired. T3 acutely reversed all these changes, which points toward a nongenomic action of T3 on cytoskeleton rearrangement, which might contribute to the increase on GH mRNA translation rate and GH secretion.