The gene of an archaeal α-l-fucosidase is expressed by translational frameshifting

The standard rules of genetic translational decoding are altered in specific genes by different events that are globally termed recoding. In Archaea recoding has been unequivocally determined so far only for termination codon readthrough events. We study here the mechanism of expression of a gene encoding for a α-l-fucosidase from the archaeon Sulfolobus solfataricus (fucA1), which is split in two open reading frames separated by a −1 frameshifting. The expression in Escherichia coli of the wild-type split gene led to the production by frameshifting of full-length polypeptides with an efficiency of 5%. Mutations in the regulatory site where the shift takes place demonstrate that the expression in vivo occurs in a programmed way. Further, we identify a full-length product of fucA1 in S.solfataricus extracts, which translate this gene in vitro by following programmed −1 frameshifting. This is the first experimental demonstration that this kind of recoding is present in Archaea

The role of copper(II) in the aggregation of human amylin

Amylin is the 37-residue peptide hormone produced by the islet β-cells in the pancreas and the formation of amylin aggregates is strongly associated with β-cells degeneration in type 2 diabetes, as demonstrated by more than 95% of patients exhibiting amylin amyloid upon autopsy. It is widely recognized that metal ions such as copper(II) have been implicated in the aggregation process of amyloidogenic peptides such as Aβ and α-synuclein and there is evidence that also amylin self-assembly is largely affected by copper(II). For this reason, in this work, the role of copper(II) in the aggregation of amylin has been investigated by several different experimental approaches. Mass spectrometric investigations show that copper(II) induces significant changes in the amylin structure which decrease the protein fibrillogenesis as observed by ThT measurements. Accordingly, solid-state NMR experiments together with computational analysis carried out on a model amylin fragment confirmed the non fibrillogenic nature of the copper(II) induced aggregated structure. Finally, the presence of copper(II) is also shown to have a major influence on amylin proneness to be degraded by proteases and cytotoxicity studies on different cell cultures are reported

Spectroscopic investigation of auranofin binding to zinc finger HIV-2 nucleocapsid peptides

The nucleocapsidic protein (NC) of orthoretroviruses has been considered as a promising target for antiretroviral drugs. Compounds, including zinc ejectors and metal derivatives capable to substitute the zinc ion in the nucleocapsidic zinc fingers, have been described. Auranofin, a gold(I) drug used for the treatment of rheumatoid arthritis, restricts the viral reservoir in the monkey AIDS model and induces containment of viral load following anti-retroviral therapy suspension. Here is reported a study of the interactions of auranofin with two synthetic CCHC-type peptides corresponding to the C-terminal zinc finger of the HIV-2 NC protein from two different isolates, using spectroscopic techniques and mass spectrometry. Both apopeptides interact very slowly with auranofin forming an Au-peptide complex. In contrast, as shown by mass spectrometry, the zinc-bound peptides interact on a shorter time-scale by forming an Et3P-Au-peptide complex and an Au-peptide complex. The two peptides show kinetic differences in the formation of zinc complexes, in Zn2+ binding constants as well in Zn2+ displacement by Au+

Identification of major Toxoneuron nigriceps venom proteins using an integrated transcriptomic/proteomic approach

Endoparasitoids in the order Hymenoptera are natural enemies of several herbivorous insect pest species. During oviposition they inject a mixture of factors, which include venom, into the host, ensuring the successful parasitism and the development of their progeny. Although these parasitoid factors are known to be responsible for host manipulation, such as immune system suppression, little is known about both identity and function of the majority of their venom components. To identify the major proteins of Toxoneuron nigriceps (Hymenoptera: Braconidae) venom, we used an integrated transcriptomic and proteomic approach. The tandem-mass spectrometric (LC-MS/MS) data combined with T. nigriceps venom gland transcriptome used as a reference database resulted in the identification of a total of thirty one different proteins. While some of the identified proteins have been described in venom from several parasitoids, others were identified for the first time. Among the identified proteins, hydrolases constituted the most abundant family followed by transferases, oxidoreductases, ligases, lyases and isomerases. The hydrolases identified in the T. nigriceps venom glands included proteases, peptidases and glycosidases, reported as common components of venom from several parasitoid species. Taken together, the identified proteins included factors that could potentially inhibit the host immune system, manipulate host physiological processes and host development, as well as provide nutrients to the parasitoid progeny, degrading host tissues by specific hydrolytic enzymes. The venom decoding provides us with information about the identity of candidate venom factors which could contribute to the success of parasitism, together with other maternal and embryonic factors

Peptidoglycan and muropeptides from pathogens <em>Agrobacterium</em> and <em>Xanthomonas</em> elicit plant innate immunity:structure and activity

Peptidoglycan (PGN) is a unique and essential structural part of the bacterial cell wall. PGNs from two contrasting Gram-negative plant pathogenic bacteria elicited components characteristic of the innate immune system in Arabidopsis thaliana, such as transcription of the defense gene PR1, oxidative burst, medium alkalinization, and formation of callose. Highly purified muropeptides from PGNs were more effective elicitors of early defense responses than native PGN. Therefore, PGN and its constituents represent a Microbe-Associated Molecular Pattern (MAMP) in plant-bacterial interactions. PGN and muropeptides from aggressive Xanthomonas campestris pv. campestris were significantly more active than those from Agrobacterium tumefaciens, which must maintain host cell viability during infection. The structure of muropeptide components and the distinctive differences are described. Differing defense-eliciting abilities appear to depend on subtle structural differences in either carbohydrate or peptide groups

XXV CONGRESSO NAZIONALE ITALIANO DI ENTOMOLOGIA

Identificazione delle principali componenti del veleno di Toxoneuron nigriceps integrando un approccio trascrittomico e proteomico. Toxoneuron nigriceps (V.) (Hymenoptera: Braconidae) è un endoparassitoide di stadi larvali di Heliothis virescens (F.) (Lepidoptera: Noctuidae). Al momento dell’ovideposizione, la femmina inietta nel corpo dell'ospite il veleno e il fluido del calice ovarico, un secreto denso contenente proteine ovariche e un polydnavirus del genere bracovirus (TnBV). Queste secrezioni materne, insieme a fattori embrionali, i teratociti, cellule derivanti dalla dissociazione della serosa, sono responsabili delle principali alterazioni fisiologiche osservate a carico dell’ospite, al fine di garantire un ambiente adeguato per lo sviluppo del parassitoide. Uno dei fattori chiave coinvolti nella regolazione dell’ospite, da parte del parassitoide, sembrerebbe essere il veleno. Ad oggi il ruolo del veleno di T. nigriceps risulta poco conosciuto, sebbene le informazioni preliminari indichino un coinvolgimento nella soppressione della risposta immunitaria. Le principali componenti del veleno di T. nigriceps sono state identificate mediante un approccio combinato di trascrittomica e proteomica. Il trascrittoma delle ghiandole del veleno è stato realizzato de novo mediante RNAseq e risulta costituito da 17742 contigs. Le sequenze sono state analizzate con il software Blast2GO fornendo un quadro completo delle putative proteine presenti nel veleno e le relative informazioni sulle funzioni molecolari, sui processi biologici e sui putativi compartimenti cellulari. L’analisi proteomica è stata condotta sulle componenti del veleno, mediante separazione per elettroforesi bidimensionale, escissione e digestione triptica degli spots e successiva analisi di spettrometria di massa tandem (HPLC-MS/MS). Il software MASCOT, ha consentito di incrociare le peak-list sperimentali con i dati di trascrittomica, permettendo di identificare numerose putative proteine presenti nel veleno di T. nigriceps. L’identificazione molecolare e la successiva caratterizzazione di queste molecole saranno essenziali per comprendere il ruolo svolto da ciascun componente nell’induzione e nella regolazione della sindrome patologica osservata negli ospiti parassitizzati, contribuendo a chiarire l'azione e l’interazione di tutti i fattori parassitari sia di origine materna che embrionale

A signalling cascade involving receptor-activated phospholipase A2, glycerophosphoinositol 4-phosphate, Shp1 and Src in the activation of cell motility

Background: Shp1, a tyrosine-phosphatase-1 containing the Src-homology 2 (SH2) domain, is involved in inflammatory and immune reactions, where it regulates diverse signalling pathways, usually by limiting cell responses through dephosphorylation of target molecules. Moreover, Shp1 regulates actin dynamics. One Shp1 target is Src, which controls many cellular functions including actin dynamics. Src has been previously shown to be activated by a signalling cascade initiated by the cytosolic-phospholipase A2 (cPLA2) metabolite glycerophosphoinositol 4-phosphate (GroPIns4P), which enhances actin polymerisation and motility. While the signalling cascade downstream Src has been fully defined, the mechanism by which GroPIns4P activates Src remains unknown. Methods: Affinity chromatography, mass spectrometry and co-immunoprecipitation studies were employed to identify the GroPIns4P-interactors; among these Shp1 was selected for further analysis. The specific Shp1 residues interacting with GroPIns4P were revealed by NMR and validated by site-directed mutagenesis and biophysical methods such as circular dichroism, isothermal calorimetry, fluorescence spectroscopy, surface plasmon resonance and computational modelling. Morphological and motility assays were performed in NIH3T3 fibroblasts. Results: We find that Shp1 is the direct cellular target of GroPIns4P. GroPIns4P directly binds to the Shp1-SH2 domain region (with the crucial residues being Ser 118, Arg 138 and Ser 140) and thereby promotes the association between Shp1 and Src, and the dephosphorylation of the Src-inhibitory phosphotyrosine in position 530, resulting in Src activation. As a consequence, fibroblast cells exposed to GroPIns4P show significantly enhanced wound healing capability, indicating that GroPIns4P has a stimulatory role to activate fibroblast migration. GroPIns4P is produced by cPLA2 upon stimulation by diverse receptors, including the EGF receptor. Indeed, endogenously-produced GroPIns4P was shown to mediate the EGF-induced cell motility. Conclusions: This study identifies a so-far undescribed mechanism of Shp1/Src modulation that promotes cell motility and that is dependent on the cPLA2 metabolite GroPIns4P. We show that GroPIns4P is required for EGF-induced fibroblast migration and that it is part of a cPLA2/GroPIns4P/Shp1/Src cascade that might have broad implications for studies of immune-inflammatory response and cancer. [Figure not available: see fulltext.

α-Thalassemia Associated with Hb Instability: A Tale of Two Features. The Case of Hb Rogliano or α1 Cod 108(G15)Thr→Asn and Hb Policoro or α2 Cod 124(H7)Ser→Pro.

<div><p>We identified two new variants in the third exon of the α-globin gene in families from southern Italy: the Hb Rogliano, α1 cod108 ACC>AAC or α1[α108(G15)Thr→Asn] and the Hb Policoro, α2 cod124 TCC>CCC or α2[α124(H7)Ser→Pro]. The carriers showed mild α-thalassemia phenotype and abnormal hemoglobin stability features. These mutations occurred in the G and H helices of the α-globin both involved in the specific recognition of AHSP and β1 chain. Molecular characterization of mRNA, globin chain analyses and molecular modelling studies were carried out to highlight the mechanisms causing the α-thalassemia phenotype. The results demonstrated that the α-thalassemia defect associated with the two Hb variants originated by different defects. Hb Rogliano showed an intrinsic instability of the tetramer due to anomalous intra- and inter-chain interactions suggesting that the variant chain is normally synthesized and complexed with AHSP but rapidly degraded because it is unable to form the α1β1 dimers. On the contrary in the case of Hb Policoro two different molecular mechanisms were shown: the reduction of the variant mRNA level by an unclear mechanism and the protein instability due to impairment of AHSP interaction. These data highlighted that multiple approaches, including mRNA quantification, are needed to properly identify the mechanisms leading to the α-thalassemia defect. Elucidation of the specific mechanism leads to the definition of a given phenotype providing important guidance for the diagnosis of unstable variants.</p></div