Protein N-glycosylation Research Articles

Relevance of Class I α-Mannosidases to Cassava Postharvest Physiological Deterioration.

Class I α-mannosidases (MNSs) play important roles in protein N-glycosylation. However, no data are currently available about MNSs in cassava (Manihot esculenta), of which the functions are therefore not known, particularly in relevance to postharvest physiological deterioration (PPD). A total of seven genes were identified from the cassava genome in the present study. Two (MeMNS2 and MeMNS6) of the seven genes may be pseudogenes, as indicated by sequence alignment and exon–intron organizations. Five MNSs could be classified into three subfamilies. Tissue-specific expression analysis revealed that MNS genes have distinct expression patterns in different tissues between sugar cassava and cultivated cassava varieties, indicating their functional diversity. A PPD response and defense model was proposed based on the transcription data of MNSs and genes involved in reactive oxygen species, signal transduction, and cell wall remodeling. The findings help in the understanding of PPD responses in cassava.

Environmental factors influence the Haloferax volcanii S-layer protein structure.

S-layers commonly cover archaeal cell envelopes and are composed of proteins that self-assemble into a paracrystalline surface structure. Despite their detection in almost all archaea, there are few reports investigating the structural properties of these proteins, with no reports exploring this topic for halophilic S-layers. The objective of the present study was to investigate the secondary and tertiary organization of the Haloferax volcanii S-layer protein. Such investigations were performed using circular dichroism, fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. The protein secondary structure is centered on β-sheets and is affected by environmental pH, with higher disorder in more alkaline conditions. The pH can also affect the protein’s tertiary structure, with higher tryptophan side-chain exposure to the medium under the same conditions. The concentrations of Na, Mg and Ca ions in the environment also affect the protein structures, with small changes in α-helix and β-sheet content, as well as changes in tryptophan side chain exposure. These changes in turn influence the protein’s functional properties, with cell envelope preparations revealing striking differences when in different salt conditions. Thermal denaturation assays revealed that the protein is stable. It has been reported that the S-layer protein N-glycosylation process is affected by external factors and the present study indicates for the first time changes in the protein structure.

Parallel reaction monitoring with multiplex immunoprecipitation of N-glycoproteins in human serum for detection of hepatocellular carcinoma.

The N-glycosylation of proteins is one of the most important post-translational modifications relevant to various biological functions. The identification and quantification of N-glycoproteins in liquid chromatography-mass spectrometry (LC-MS) is challenging because of their low analytical sensitivity and selectivity. This is due to their microheterogeneity and the difficulty of synthesizing N-glycopeptides as an internal standard. Parallel reaction monitoring (PRM) is widely used in targeted LC-MS. The key advantage of LC-PRM is that it can identify N-glycopeptides using tandem mass spectrometry (MS/MS) fragmentation, even without an internal standard. We investigated the feasibility of analyzing N-glycoproteins using multiplex immunoprecipitation to improve sensitivity and selectivity. We targeted N-glycoproteins [α-fetoprotein (AFP), vitronectin (VTN), and α-1-antichymotrypsin (AACT)] that are abnormally glycosylated in hepatocellular carcinoma (HCC). Their tryptic N-glycopeptides were selected to determine the percentages of fucosylated N-glycopeptides using Y ions, which include glycopeptide fragments with amino acid sequences. Finally, we confirmed that the area under the receiver operating characteristic curve (AUC = 0.944) for the combination of AFP and VTN increased more so than for a single glycopeptide (AUC = 0.889 for AFP and 0.792 for VTN) with respect to discriminating between HCC and cirrhosis serum. This study shows that an LC-PRM method using multiplex N-glycoproteins immunoprecipitated from serum could be applied to develop and verify cancer biomarkers. Graphical abstract.

The OST-complex as target for RNAi-based pest control in Nilaparvata lugens.

RNAi-based pest control strategies are emerging as environment friendly and species-specific alternatives for the use of conventional pesticides. Because N-glycosylation is important for many biological processes, such as growth and development, the early steps of protein N-glycosylation are promising targets for an RNAi-based pest control strategy. Through injection of dsRNAs, the expression of the catalytic subunits of the oligosaccharyl transferase complex was efficiently silenced in nymphs of the notorious rice pest insect Nilaparvata lugens. Silencing of both STT3 isoforms resulted in a high mortality of the N. lugens nymphs. However, our data reveals the occurrence of a functional redundancy between the two isoforms when silencing only one of the isoforms. These observations confirm the potential to use the early genes in the N-glycosylation pathway as targets for an RNAi-based pest control strategy. In addition, the existence of a functional redundancy between the two STT3 isoforms presents a factor which one must take into account when designing RNAi-based approaches.

Characterizing the selectivity of ER α-glucosidase inhibitors.

The endoplasmic reticulum (ER) contains both α-glucosidases and α-mannosidases which process the N-linked oligosaccharides of newly synthesized glycoproteins and thereby facilitate polypeptide folding and glycoprotein quality control. By acting as structural mimetics, iminosugars can selectively inhibit these ER localized α-glycosidases, preventing N-glycan trimming and providing a molecular basis for their therapeutic applications. In this study, we investigate the effects of a panel of nine iminosugars on the actions of ER luminal α-glucosidase I and α-glucosidase II. Using ER microsomes to recapitulate authentic protein N-glycosylation and oligosaccharide processing, we identify five iminosugars that selectively inhibit N-glycan trimming. Comparison of their inhibitory activities in ER microsomes against their effects on purified ER α-glucosidase II, suggests that 3,7a-diepi-alexine acts as a selective inhibitor of ER α-glucosidase I. The other active iminosugars all inhibit α-glucosidase II and, having identified 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) as the most effective of these compounds, we use in silico modeling to understand the molecular basis for this enhanced activity. Taken together, our work identifies the C-3 substituted pyrrolizidines casuarine and 3,7a-diepi-alexine as promising “second-generation” iminosugar inhibitors.

Quantitative Analyses Reveal Novel Roles for N-Glycosylation in a Major Enteric Bacterial Pathogen.

In eukaryotes, glycosylation plays a role in proteome stability, protein quality control, and modulating protein function; however, similar studies in bacteria are lacking. Here, we investigate the roles of general protein glycosylation systems in bacteria using the enteropathogen Campylobacter jejuni as a well-defined example. By using a quantitative proteomic strategy, we were able to monitor changes in the C. jejuni proteome when glycosylation is disrupted. We demonstrate that in C. jejuni, N-glycosylation is essential to maintain proteome stability and protein quality control. These findings guided us to investigate the role of N-glycosylation in modulating bacterial cellular activities. In glycosylation-deficient C. jejuni, the multidrug efflux pump and electron transport pathways were significantly impaired. We demonstrate that in vivo, fully glycosylation-deficient C. jejuni bacteria were unable to colonize its natural avian host. These results provide the first evidence of a link between proteome stability and complex functions via a bacterial general glycosylation system.IMPORTANCE Advances in genomics and mass spectrometry have revealed several types of glycosylation systems in bacteria. However, why bacterial proteins are modified remains poorly defined. Here, we investigated the role of general N-linked glycosylation in a major food poisoning bacterium, Campylobacter jejuni The aim of this study is to delineate the direct and indirect effects caused by disrupting this posttranslational modification. To achieve this, we employed a quantitative proteomic strategy to monitor alterations in the C. jejuni proteome. Our quantitative proteomic results linked general protein N-glycosylation to maintaining proteome stability. Functional analyses revealed novel roles for bacterial N-glycosylation in modulating multidrug efflux pump, enhancing nitrate reduction activity, and promoting host-microbe interaction. This work provides insights on the importance of general glycosylation in proteins in maintaining bacterial physiology, thus expanding our knowledge of the emergence of posttranslational modification in bacteria.

New insights into the ORF2 capsid protein, a key player of the hepatitis E virus lifecycle

Hepatitis E Virus (HEV) genome encodes three proteins including the ORF2 capsid protein. Recently, we demonstrated that HEV produces three different forms of ORF2: (i) the ORF2i form (infectious ORF2) which is the component of infectious particles, (ii) the secreted ORF2g (glycosylated ORF2) and ORF2c (cleaved ORF2) forms that are not associated with infectious particles, but are the major antigens in HEV-infected patient sera. The ORF2 protein sequence contains three highly conserved potential N-glycosylation sites (N1, N2 and N3). The status and biological relevance of ORF2 N-glycosylation in HEV lifecycle remain to be elucidated. Here, we generated and extensively characterized a series of ORF2 mutants in which the three N-glycosylation sites were mutated individually or in combination. We demonstrated that the ORF2g/c protein is N-glycosylated on N1 and N3 sites but not on the N2 site. We showed that N-glycosylation of ORF2 protein does not play any role in replication and assembly of infectious HEV particles. We found that glycosylated ORF2g/c forms are very stable proteins which are targeted by patient antibodies. We also demonstrated that the ORF2i protein is translocated into the nucleus of infected cells. Hence, our study led to new insights into the molecular mechanisms of ORF2 expression.

Serum protein N-glycosylation changes in multiple myeloma

BackgroundMultiple myeloma is characterized by clonal proliferation of malignant plasma cells in the bone marrow that produce monoclonal immunoglobulins. N-glycosylation changes of these monoclonal immunoglobulins have been reported in multiple myeloma, but previous studies only detected limited serum N-glycan features. MethodsHere, a more detailed study of the human serum N-glycome of 91 multiple myeloma patients and 51 controls was performed. We additionally analyzed sequential samples from patients (n = 7) which were obtained at different time points during disease development as well as 16 paired blood serum and bone marrow plasma samples. N-glycans were enzymatically released and measured by mass spectrometry after linkage specific derivatization of sialic acids. ResultsA decrease in both α2,3- and α2,6-sialylation, galactosylation and an increase in fucosylation within complex-type N-glycans were found in multiple myeloma patients compared to controls, as well as a decrease in difucosylation of diantennary glycans. The observed glycosylation changes were present in all ISS stages, including the “low-risk” ISS I. In individual patients, difucosylation of diantennary glycans decreased with development of the disease. Protein N-glycosylation features from blood and bone marrow showed strong correlation. Moreover, associations of monoclonal immunoglobulin (M-protein) and albumin levels with glycan traits were discovered in multiple myeloma patients. Conclusions & general significanceIn conclusion, serum protein N-glycosylation analysis could successfully distinguish multiple myeloma from healthy controls. Further studies are needed to assess the potential roles of glycan trait changes and the associations of glycans with clinical parameters in multiple myeloma early detection and prognosis.

N-glycoproteins exhibit a positive expression level-evolutionary rate correlation.

The different proteins of any proteome evolve at enormously different rates. One of the primary factors influencing rates of protein evolution is expression level, with highly expressed proteins tending to evolve at slow rates. This phenomenon, known as the expression level-evolutionary rate (E-R) anticorrelation, has been attributed to the abundance-dependent deleterious effects of misfolding or misinteraction. We have recently shown that secreted proteins either lack an E-R anticorrelation or exhibit a significantly reduced E-R anticorrelation. This effect may be due to the strict quality control to which secreted proteins are subject in the endoplasmic reticulum (which is expected to reduce the rate of misfolding and its deleterious effects) or to their extracellular location (expected to reduce the rate of misinteraction and its deleterious effects). Among secreted proteins, N-glycosylated ones are under particularly strong quality control. Here, we investigate how N-linked glycosylation affects the E-R anticorrelation. Strikingly, we observe a positive E-R correlation among N-glycosylated proteins. That is, N-glycoproteins that are highly expressed evolve at faster rates than lowly expressed N-glycoproteins, in contrast to what is observed among intracellular proteins.

Targeting STT3A-oligosaccharyltransferase with NGI-1 causes herpes simplex virus 1 dysfunction.

Herpes simplex virus 1 (HSV-1) is a contagious neurotropic herpesvirus responsible for oral lesions and herpesviral encephalitis. The HSV-1 envelope contains N-glycosylated proteins involved in infection and that are candidate drug targets. NGI-1 is a small-molecule inhibitor of oligosaccharyltransferase (OST) complexes STT3A-OST and STT3B-OST, which catalyze cotranslational and post-translational N-glycosylation, respectively. Because host OSTs attach HSV-1 glycans, NGI-1 might have anti-HSV-1 activity. We evaluated HSV-1 function using NGI-1 and human embryonic kidney 293 knockout lines for OST isoform-specific catalytic and accessory subunits. N-glycosylation of 2 representative envelope proteins (gC and gD) was primarily dependent upon STT3A-OST, but to a large extent replaceable by STT3B-OST. Knockouts impairing STT3A- or STT3B-OST activity, by themselves, did not appreciably affect HSV-1 function (plaque-forming units, normalized to viral particles measured by unglycosylated capsid protein VP5 content). However, with cells lacking STT3B-OST activity (missing the catalytic subunit STT3B or the oxidoreductase subunits magnesium transporter 1/tumor suppressor candidate 3) and thus solely dependent upon STT3A-OST for N-glycosylation, NGI-1 treatment resulted in HSV-1 having cell type-dependent dysfunction (affecting infectivity with Vero cells much more than with the 293 lines). Ablation of post-translational N-glycosylation can therefore make HSV-1 infectivity, and possibly masking of immunogenic peptide epitopes by glycans, highly sensitive to pharmacological inhibition of cotranslational N-glycosylation.-Lu, H., Cherepanova, N. A., Gilmore, R., Contessa, J. N., Lehrman, M. A. Targeting STT3A-oligosaccharyltransferase with NGI-1 causes herpes simplex virus 1 dysfunction.

Deficiency of AtGFAT1 activity impairs growth, pollen germination and tolerance to tunicamycin in Arabidopsis.

The hexosamine biosynthetic pathway (HBP) plays essential roles in growth and development in plants. However, insight into the biological function of glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), mediating the first regulatory step of the HBP, remains unclear in plants. Here, we report the molecular characterization of Arabidopsis AtGFAT1 gene. AtGFAT1 was highly expressed in mature pollen grains, but its expression was not detectable in the rest of the organs. Pollen grains bearing the gfat1-2 knockout allele displayed defects in a polar deposition of pectin and callose in the pollen cell wall, leading to no genetic transmission of the gfat1-2 allele through the male gametophyte. AtGFAT1 overexpression increased glucosamine (GlcN) content and enhanced resistance to tunicamycin (Tm) treatment, while RNAi-mediated suppression reduced GlcN content and resistance to Tm treatment. However, the decrease in Tm resistance by RNAi suppression of AtGFAT1 was recovered by a GlcN supplement. The exogenous GlcN supplement also rescued gfat1-2/gaft1-2 mutant plants, which were otherwise not viable. The gfat1-2/gfat1-2 plants stopped growing at the germination stage on GlcN-free medium, but GlcN supplement allowed wild-type growth of gfat1-2/gfat1-2 plants. In addition, reactive oxygen species production, cell death and a decrease in protein N-glycosylation were observed in gfat1-2/gaft1-2 mutant plants grown on GlcN-free medium, whereas these aberrant defects were not detectable on GlcN-sufficient medium. Taken together, these results show that the reduction of protein N-glycosylation was at least partially responsible for many aberrant phenotypes in growth and development as well as the response to Tm treatment caused by AtGFAT1 deficiency in Arabidopsis.

Smac mimetic suppresses tunicamycin-induced apoptosis via resolution of ER stress

Since Inhibitor of Apoptosis (IAP) proteins have been implicated in cellular adaptation to endoplasmic reticulum (ER) stress, we investigated the regulation of ER stress-induced apoptosis by small-molecule second mitochondria-derived activator of caspase (Smac) mimetics that antagonize IAP proteins. Here, we discover that Smac mimetic suppresses tunicamycin (TM)-induced apoptosis via resolution of the unfolded protein response (UPR) and ER stress. Smac mimetics such as BV6 selectively inhibit apoptosis triggered by pharmacological or genetic inhibition of protein N-glycosylation using TM or knockdown of DPAGT1, the enzyme that catalyzes the first step of protein N-glycosylation. In contrast, BV6 does not rescue cell death induced by other typical ER stressors (i.e., thapsigargin (TG), dithiothreitol, brefeldin A, bortezomib, or 2-deoxyglucose). The protection from TM-triggered apoptosis is found for structurally different Smac mimetics and for genetic knockdown of cellular IAP (cIAP) proteins in several cancer types, underlining the broader relevance. Interestingly, lectin microarray profiling reveals that BV6 counteracts TM-imposed inhibition of protein glycosylation. BV6 consistently abolishes TM-stimulated accumulation of ER stress markers such as glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) and reduces protein kinase RNA-like ER kinase (PERK) phosphorylation and X box-binding protein 1 (XBP1) splicing upon TM treatment. BV6-stimulated activation of nuclear factor-κB (NF-κB) contributes to the resolution of ER stress, since NF-κB inhibition by overexpression of dominant-negative IκBα superrepressor counteracts the suppression of TM-stimulated transcriptional activation of CHOP and GRP78 by BV6. Thus, our study is the first to show that Smac mimetic protects from TM-triggered apoptosis by resolving the UPR and ER stress. This provides new insights into the regulation of cellular stress responses by Smac mimetics.

Proteomic Landscape of Aldosterone-Producing Adenoma.

Primary aldosteronism is a disease of excessive production of adrenal steroid hormones and the most common cause of endocrine hypertension. Primary aldosteronism results mainly from bilateral adrenal hyperplasia or unilateral aldosterone-producing adenoma (APA). Primary aldosteronism cause at the molecular level is incompletely understood and a targeted treatment preventing excessive adrenal steroid production is not available. Here, we perform deep quantitative proteomic and phosphoproteomic profiling of 6 pairs of APA and adjacent nontumoral adrenal cortex. We show that increased steroidogenesis in APA is accompanied by upregulation of steroidogenic enzymes (HSD3B2, CYP21A2, CYP11B2) and of proteins involved in cholesterol uptake (LSR). We demonstrate that HSD3B2 is phosphorylated at Ser95 or 96 and identify a novel phosphorylation site, Ser489, in CYP21A2, suggesting that steroidogenic enzymes are regulated by phosphorylation. Our analysis also reveals altered ECM (extracellular matrix) composition in APA that affects ECM-cell surface interactions and actin cytoskeleton rearrangements. We show that RHOC, a GTPase controlling actin organization in response to extracellular stimuli, is upregulated in APA and promotes expression of the aldosterone synthase gene CYP11B2. Our data also indicate deregulation of protein N-glycosylation and GABAergic signaling in APAs. Finally, we find that mTORC1 (mammalian target of rapamycin complex 1) signaling is the major pathway deregulated in APA. Our study provides a rich resource for future research on the molecular mechanisms of primary aldosteronism.

Uncovering Eukaryotic Glycosylation Mechanism by Cryo-EM

Glycosylation is the most dominant modification of eukaryotic secretory and membrane-bound proteins. It mainly occur in endoplasmic reticulum (ER) and Golgi. Glycosylation plays important role in many essential biological processes, such as intercellular recognition, protein folding and stability, protein-protein or protein-ligand interactions, and many enzyme activities. We investigated the structural mechanism of eukaryotic glycosylation in ER using cryo-EM. One example is the oligosaccharyltransferase complex, OST, which is the key enzyme in N-glycosylation. We report a 3.5-Å resolution cryo-EM structure of the Saccharomyces cerevisiae OST, revealing the assembly of its eight subunits. We found that seven phospholipids mediate many of the inter-subunit interactions, and an Stt3 N-glycan mediates interactions with Wbp1 and Swp1 in the lumen. Ost3 was found to mediate the OST-Sec61 translocon interface. Our studies provide novel insights into co-translational protein N-glycosylation and some other functions of glycosylation in eukaryotic cell.

The structure of mammalian β-mannosidase provides insight into β-mannosidosis and nystagmus.

β-Mannosidase is a lysosomal enzyme from the glycosyl hydrolase family 2 that cleaves the single β(1-4)-linked mannose at the nonreducing end of N-glycosylated proteins, and plays an important role in the polysaccharide degradation pathway. Mutations in the MANBA gene, which encodes the β-mannosidase, can lead to the lysosomal storage disease β-mannosidosis, as well as nystagmus, an eye condition characterized by involuntary eye movements. Here, we present the first structures of a mammalian β-mannosidase in both the apo- and mannose-bound forms. The structure is similar to previously determined β-mannosidase structures with regard to domain organization and fold, however, there are important differences that underlie substrate specificity between species. Additionally, in contrast to most other ligand-bound β-mannosidases from bacterial and fungal sources where bound sugars were in a boat-like conformation, we find the mannose in the chair conformation. Evaluation of known disease mutations in the MANBA gene provides insight into their impact on disease phenotypes. Together, these results will be important for the design of therapeutics for treating diseases caused by β-mannosidase deficiency. DATABASE: Structural data are available in the Protein Data Bank under the accession numbers 6DDT and 6DDU.

Glucosidase Inhibition to Study Calnexin-assisted Glycoprotein Folding in Cells.

Calnexin is a chaperone protein that plays a critical role in glycoprotein folding in the endoplasmic reticulum (ER). The function of calnexin depends on its binding to monoglucosylated oligosaccharides on nascent glycoproteins, whereas the generation of monoglucosylated oligosaccharides depends on the activity of α-glucosidases I and II, which trim off terminal glucose residues sequentially from triglucosylated N-glycans. This biochemical mechanism can be exploited to study calnexin-assisted folding and subsequent ER exiting of glycoproteins in cells. In our investigation of the intracellular trafficking of N-glycosylated serine proteases, we used an inhibitor of α-glucosidases I and II to block the trimming of triglucosylated oligosaccharides, thereby inhibiting calnexin-assisted glycoprotein folding. The study helped us to discover a key role of calnexin in the folding, ER exiting, and extracellular expression of N-glycosylated serine proteases such as corin, enteropeptidase, and prothrombin. A similar approach of glucosidase inhibition can be used to study the calnexin/calreticulin-dependent folding and intracellular trafficking of other N-glycosylated proteins.

Prostate Protein N-Glycosylation Profiling by Means of DNA Sequencer-Assisted Fluorophore-Assisted Carbohydrate Electrophoresis.

DNA sequencer-assisted fluorophore-assisted carbohydrate electrophoresis allows for accurate profiling of the asparagine-linked (N-) glycosylation patterns, a posttranslational modification present on many soluble and membrane proteins. This technique has been extensively tested to identify N-glycosylation patterns associated with serum proteins. Here we describe the use of DNA sequencer-assisted fluorophore-assisted carbohydrate electrophoresis to identify the N-glycosylation patterns of prostate proteins in urine.

Site-Specific N-Glycosylation on the AAV8 Capsid Protein.

Adeno associated virus (AAV) is a versatile gene delivery tool, which has been approved as a human gene therapy vector for combating genetic diseases. AAV capsid proteins are the major components that determine the tissue specificity, immunogenicity and in vivo transduction performance of the vector. In this study, the AAV8 capsid glycosylation profile was systemically analyzed by peptide mass fingerprinting utilizing high-resolution mass spectrometry to determine the presence of capsid glycosylation. We identified N-glycosylation on the amino acid N499 of the capsid protein. We characterized the overall sugar profile for vector produced in 293 cells. Multiple N-glycosylated host-cell proteins (HCPs) copurified with AAV8 vectors and were identified by analyzing LC-MS data utilizing a human database and proteome discoverer search engine. The N-glycosylation analysis by MALDI-TOF MS, highlighted the probability of AAV8 interaction with terminal galactosylated N-glycans within the HCPs.

UDP-N-acetylglucosamine-dolichyl-phosphate N-acetylglucosaminephosphotransferase is indispensable for oogenesis, oocyte-to-embryo transition, and larval development of the nematode Caenorhabditis elegans.

N-linked glycosylation of proteins is the most common post-translational modification of proteins. The enzyme UDP-N-acetylglucosamine-dolichyl-phosphate N-acetylglucosaminephosphotransferase (DPAGT1) catalyses the first step of N-glycosylation, and DPAGT1 knockout is embryonic lethal in mice. In this study, we identified the sole orthologue (algn-7) of the human DPAGT1 in the nematode C. elegans. The gene activity was disrupted by RNAi and deletion mutagenesis, which resulted in larval lethality, defects in oogenesis and oocyte-to-embryo transition. Endomitotic oocytes, abnormal fusion of pronuclei, abnormal AB cell rotation, disruption of permeation barriers of eggs, and abnormal expression of chitin and chitin synthase in oocytes and eggs were the typical phenotypes observed. The results indicate that N-glycosylation is indispensable for these processes. We further screened an N-glycosylated protein database of C. elegans, and identified 456 germline-expressed genes coding N-glycosylated proteins. By examining RNAi phenotypes, we identified five germline-expressed genes showing similar phenotypes to the algn-7 (RNAi) animals. They were ribo-1, stt-3, ptc-1, ptc-2, and vha-19. We identified known congenital disorders of glycosylation (CDG) genes (ribo-1 and stt-3) and a recently found CDG gene (vha-19). The results show that phenotype analyses using the nematode could be a powerful tool to detect new CDG candidate genes and their associated gene networks.

Molecular epidemiology of the hemagglutinin gene of prevalent influenza virus A/H1N1/pdm09 among patient in Iran

In 2015, the influenza virus A/H1N1/pdm09 strain outbreak became prevalent throughout the different provinces of Iran. There are relatively limited complete genetic sequences available for this virus from Asian countries. Diagnosis and virological surveillance of influenza is essential for detecting novel genetic variants causing epidemic potential. This study describes the genetic properties of HA genome of influenza A/H1N1 pdm09 viruses circulating in Iran during the 2015/2016 season. In order to investigate the genetic pattern of influenza A/H1N1 pdm09, a total of 1758 nasopharyngeal swabs were screened by real-time RT-PCR. Of those, 510 cases were found to be positive for A/H1N1/pdm09 virus. Evolution of the approximately 100 positive specimens with high virus load was conducted via genomic phylogeny. Phylogenetic analysis of the HA genes of the A/H1N1pdm09 viruses revealed the circulation of clade 6B1, characterized by amino acid substitutions S84N, S162N and I216T, where position 162 became glycosylated. The N-glycosylation of HA protein is post or co-translational modification that affect the evolution of influenza viruses. For influenza A(H1N1) pdm09 viruses, we found more mutations in the antigenic sites than in the stem region. The results of this study confirmed the necessity of constant regular antigenic and molecular surveillance of circulating seasonal influenza viruses.