Chemical biology of glycoproteins: From chemical synthesis to biological impact

Assessment of genetically modified maize DP202216 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2019-159)

Genetically modified maize DP202216 was developed to confer tolerance to glufosinate-ammonium-containing herbicides and to provide an opportunity for yield enhancement under field conditions. These properties were achieved by introducing the mo-pat and zmm28 expression cassettes. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between maize DP202216 and its comparator needs further assessment, except for the levels of stearic acid (C18:0), which do not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the PAT and ZMM28 proteins as expressed in maize DP202216, and finds no evidence that the genetic modification would change the overall allergenicity of maize DP202216. In the context of this application, the consumption of food and feed from maize DP202216 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that maize DP202216 is as safe as the comparator and non-GM reference varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize DP202216 grains into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize DP202216. The GMO Panel concludes that maize DP202216 is as safe as its comparator and the tested non-GM reference varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize DP23211 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2019-163)

Genetically modified maize DP23211 was developed to confer control of certain coleopteran pests and tolerance to glufosinate-containing herbicide. These properties were achieved by introducing the pmi, mo-pat, ipd072Aa and DvSSJ1 expression cassettes. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between maize DP23211 and its conventional counterpart needs further assessment, except for those in levels of histidine, phenylalanine, magnesium, phosphorus and folic acid in grain, which do not raise safety and nutritional concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the IPD072Aa, PAT and PMI proteins and the DvSSJ1 dsRNA and derived siRNAs newly expressed in maize DP23211, and finds no evidence that the genetic modification impacts the overall safety of maize DP23211. In the context of this application, the consumption of food and feed from maize DP23211 does not represent a nutritional concern in humans and animals. Therefore, no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize DP23211 grains into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize DP23211. The GMO Panel concludes that maize DP23211 is as safe as its conventional counterpart and the tested non-GM reference varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize DP915635 for food and feed uses, under regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2020-172)

Genetically modified maize DP915635 was developed to confer tolerance to glufosinate herbicide and resistance to corn rootworm pests. These properties were achieved by introducing the ipd079Ea, mo-pat and pmi expression cassettes. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between maize DP915635 and its conventional counterpart needs further assessment, except for the levels of crude protein in forage, which does not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the IPD079Ea, PAT and PMI proteins expressed in maize DP915635. The GMO Panel finds no evidence that the genetic modification impacts the overall safety of maize DP915635. In the context of this application, the consumption of food and feed from maize DP915635 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that maize DP915635 is as safe as the conventional counterpart and non-GM maize varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize DP915635 grains into the environment, this would not raise environmental safety concerns. The post market environmental monitoring plan and reporting intervals are in line with the intended uses of maize DP915635. The GMO Panel concludes that maize DP915635 is as safe as its conventional counterpart and the tested non-GM maize varieties with respect to potential effects on human and animal health and the environment.

Engineered therapeutic proteins for sustained-release drug delivery systems

Proteins play a vital role in diverse biological processes in the human body, and protein therapeutics have been applied to treat different diseases such as cancers, genetic disorders, autoimmunity, and inflammation. Protein therapeutics have demonstrated their advantages, such as specific pharmaceutical effects, low toxicity, and strong solubility. However, several disadvantages arise in clinical applications, including short half-life, immunogenicity, and low permeation, leading to reduced drug effectiveness. The structure of protein therapeutics can be modified to increase molecular size, leading to prolonged stability and increased plasma half-life. Notably, the controlled-release delivery systems for the sustained release of protein drugs and preserving the stability of cargo proteins are envisioned as a potential approach to overcome these challenges. In this review, we summarize recent research progress related to structural modifications (PEGylation, glycosylation, poly amino acid modification, and molecular biology-based strategies) and promising long-term delivery systems, such as polymer-based systems (injectable gel/implants, microparticles, nanoparticles, micro/nanogels, functional polymers), lipid-based systems (liposomes, solid lipid nanoparticles, nanostructured lipid carriers), and inorganic nanoparticles exploited for protein therapeutics. STATEMENT OF SIGNIFICANCE: In this review, we highlight recent advances concerning modifying proteins directly to enhance their stability and functionality and discuss state-of-the-art methods for the delivery and controlled long-term release of active protein therapeutics to their target site. In terms of drug modifications, four widely used strategies, including PEGylation, poly amino acid modification, glycosylation, and genetic, are discussed. As for drug delivery systems, we emphasize recent progress relating to polymer-based systems, lipid-based systems developed, and inorganic nanoparticles for protein sustained-release delivery. This review points out the areas requiring focused research attention before the full potential of protein therapeutics for human health and disease can be realized.

Assessment of genetically modified cotton COT102 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-DE-2017-141)

Genetically modified cotton COT102 was developed to confer resistance against several lepidopteran species. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the differences in the agronomic-phenotypic and compositional characteristics between cotton COT102 and its non-GM comparator needs further assessment, except for levels of acid detergent fibre, which do not raise safety or nutritional concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the Vip3Aa19 and APH4 proteins as expressed in cotton COT102 and finds no evidence that the genetic modification would change the overall allergenicity of cotton COT102. In the context of this application, the consumption of food and feed from cotton COT102 does not represent a nutritional concern for humans and animals. The GMO Panel concludes that cotton COT102 is as safe as the non-GM comparator and non-GM cotton varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable cotton COT102 seeds into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of cotton COT102. The GMO Panel concludes that cotton COT102 is as safe as its non-GM comparator and the tested non-GM cotton varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize Bt11 × MIR162 × MIR604 × MON 89034 × 5307 × GA21 and 30 subcombinations, for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-DE-2018-149)

Genetically modified maize Bt11 × MIR162 × MIR604 × MON 89034 × 5307 × GA21 was developed by crossing to combine six single events: Bt11, MIR162, MIR604, MON 89034, 5307 and GA21, the GMO Panel previously assessed the 6 single maize events and 27 out of the 56 possible subcombinations and did not identify safety concerns. No new data on the single maize events or the assessed subcombinations were identified that could lead to modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in the six-event stack maize does not give rise to food and feed safety and nutritional concerns. The GMO Panel concludes that six-event stack maize, as described in this application, is as safe as the conventional counterpart and non-GM maize varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable six-event stack maize grains into the environment, this would not raise environmental safety concerns. The GMO Panel assessed the likelihood of interactions among the single events in 29 of the maize subcombinations not previously assessed and covered by the scope of this application and concludes that these are expected to be as safe as the single events, the previously assessed subcombinations and the six-event stack maize. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize Bt11 × MIR162 × MIR604 × MON 89034 × 5307 × GA21. The GMO Panel concludes that six-event stack maize and the 30 subcombinations covered by the scope of the application are as safe as its conventional counterpart and the tested non-GM maize varieties with respect to potential effects on human and animal health and the environment.

Recombinant protein expression: Challenges in production and folding related matters

Protein folding is a biophysical process by which proteins reach a specific three-dimensional structure. The amino acid sequence of a polypeptide chain contains all the information needed to determine the final three-dimensional structure of a protein. When producing a recombinant protein, several problems can occur, including proteolysis, incorrect folding, formation of inclusion bodies, or protein aggregation, whereby the protein loses its natural structure. To overcome such limitations, several strategies have been developed to address each specific issue. Identification of proper protein refolding conditions can be challenging, and to tackle this high throughput screening for different recombinant protein folding conditions can prove a sound solution. Different approaches have emerged to tackle refolding issues. One particular approach to address folding issues involves molecular chaperones, highly conserved proteins that contribute to proper folding by shielding folding proteins from other proteins that could hinder the process. Proper protein folding is one of the main prerequisites for post-translational modifications. Incorrect folding, if not dealt with, can lead to a buildup of protein misfoldings that damage cells and cause widespread abnormalities. Said post-translational modifications, widespread in eukaryotes, are critical for protein structure, function and biological activity. Incorrect post-translational protein modifications may lead to individual consequences or aggregation of therapeutic proteins. In this review article, we have tried to examine some key aspects of recombinant protein expression. Accordingly, the relevance of these proteins is highlighted, major problems related to the production of recombinant protein and to refolding issues are pinpointed and suggested solutions are presented. An overview of post-translational modification, their biological significance and methods of identification are also provided. Overall, the work is expected to illustrate challenges in recombinant protein expression.

Insights into the effect of protein glycosylation on carbohydrate substrate binding

The role of glycosylation in the binding of glycoproteins to carbohydrate substrates has not been well understood. The present study addresses this knowledge gap by elucidating the links between the glycosylation patterns of a model glycoprotein, a Family 1 carbohydrate-binding module (TrCBM1), and the thermodynamic and structural properties of its binding to different carbohydrate substrates using isothermal titration calorimetry and computational simulation. The variations in glycosylation patterns cause a gradual transition of the binding to soluble cellohexaose from an entropy-driven process to an enthalpy-driven one, a trend closely correlated with the glycan-induced shift of the predominant binding force from hydrophobic interactions to hydrogen bonding. However, when binding to a large surface of solid cellulose, glycans on TrCBM1 have a more dispersed distribution and thus have less adverse impact on the hydrophobic interaction forces, leading to overall improved binding. Unexpectedly, our simulation results also suggest an evolutionary role of O-mannosylation in transforming the substrate binding features of TrCBM1 from those of type A CBMs to those of type B CBMs. Taken together, these findings provide new fundamental insights into the molecular basis of the role of glycosylation in protein-carbohydrate interactions and are expected to better facilitate further studies in this area.

Assessment of genetically modified maize MON 87419 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2017-140)

Genetically modified maize MON 87419 was developed to confer tolerance to dicamba- and glufosinate-based herbicides. These properties were achieved by introducing the dmo and pat expression cassettes. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between maize MON 87419 and its conventional counterpart needed further assessment, except for the levels of arginine and protein in grains which did not raise safety and nutritional concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the dicamba mono-oxygenase (DMO) and phosphinothricin N-acetyltransferase (PAT) proteins as expressed in maize MON 87419. The GMO Panel finds no evidence that the genetic modification impacts the overall safety of maize MON 87419. In the context of this application, the consumption of food and feed from maize MON 87419 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that maize MON 87419 is as safe as the conventional counterpart and non-GM maize varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize MON 87419 grains into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize MON 87419. The GMO Panel concludes that maize MON 87419 is as safe as its conventional counterpart and the tested non-GM maize varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize GA21 × T25 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-DE-2016-137)

Genetically modified maize GA21 × T25 was developed by crossing to combine two single events: GA21 and T25. The GMO Panel previously assessed the two single maize events and did not identify safety concerns. No new data on the single maize events were identified that could lead to modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in maize GA21 × T25 does not give rise to food and feed safety and nutritional concerns. The GMO Panel concludes that maize GA21 × T25, as described in this application, is as safe as its conventional counterpart and the non-GM reference varieties tested, and no post-market monitoring of food and feed is considered necessary. In the case of accidental release of viable maize GA21 × T25 grains into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize GA21 × T25. Post-market monitoring of food and feed is not considered necessary. The GMO Panel concludes that maize GA21 × T25 is as safe as its conventional counterpart and the non-GM reference varieties tested, with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize DP4114 × MON 89034 × MON 87411 × DAS‐40278‐9 and subcombinations, for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA GMO‐NL‐2020‐171)

Genetically modified maize DP4114 × MON 89034 × MON 87411 × DAS‐40278‐9 was developed by crossing to combine four single events: DP4114, MON 89034, MON 87411 and DAS‐40278‐9. The GMO Panel previously assessed the four single maize events and two of the subcombinations and did not identify safety concerns. No new data on the single maize events or the assessed subcombinations were identified that could lead to modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in the four‐event stack maize does not give rise to food and feed safety and nutritional concerns. Therefore, no post‐market monitoring of food/feed is considered necessary. In the case of accidental release of viable four‐event stack maize grains into the environment, this would not raise environmental safety concerns. The GMO Panel assessed the likelihood of interactions among the single events in eight of the maize subcombinations not previously assessed and concludes that these are expected to be as safe as the single events, the previously assessed subcombinations and the four‐event stack maize. The post‐market environmental monitoring plan and reporting intervals are in line with the intended uses of maize DP4114 × MON 89034 × MON 87411 × DAS‐40278‐9. Post‐market monitoring of food/feed is not considered necessary. The GMO Panel concludes that the four‐event stack maize and its subcombinations are as safe as its non‐GM comparator and the tested non‐GM maize varieties with respect to potential effects on human and animal health and the environment.

Legionella pneumophila Infection of Human Macrophages Retains Golgi Structure but Reduces O-Glycans

Legionella pneumophila is an accidental pathogen that replicates intracellularly within the Legionella-containing vacuole (LCV) in macrophages. Within an hour of infection, L. pneumophila secretes effectors to manipulate Rab1 and intercept ER-derived vesicles to the LCV. The downstream consequences of interrupted ER trafficking on the Golgi of macrophages are not clear. We examined the Golgi structure and function in L. pneumophila-infected human U937 macrophages. Intriguingly, the size of the Golgi in infected macrophages remained similar to uninfected macrophages. Furthermore, TEM analysis also did not reveal any significant changes in the ultrastructure of the Golgi in L. pneumophila-infected cells. Drug-induced Golgi disruption impacted bacterial replication in human macrophages, suggesting that an intact organelle is important for bacteria growth. To probe for Golgi functionality after L. pneumophila infection, we assayed glycosylation levels using fluorescent lectins. Golgi O-glycosylation levels, visualized by the fluorescent cis-Golgi lectin, Helix pomatia agglutinin (HPA), significantly decreased over time as infection progressed, compared to control cells. N-glycosylation levels in the Golgi, as measured by L-PHA lectin staining, were not impacted by L. pneumophila infection. To understand the mechanism of reduced O-glycans in the Golgi we monitored UDP-GalNAc transporter levels in infected macrophages. The solute carrier family 35 membrane A2 (SLC35A2) protein levels were significantly reduced in L. pneumophila-infected U937 and HeLa cells and L. pneumophila growth in human macrophages benefitted from GalNAc supplementation. The pronounced reduction in Golgi HPA levels was dependent on the translocation apparatus DotA expression in bacteria and occurred in a ubiquitin-independent manner. Thus, L. pneumophila infection of human macrophages maintains and requires an intact host Golgi ultrastructure despite known interference of ER–Golgi trafficking. Finally, L. pneumophila infection blocks the formation of O-linked glycans and reduces SLC35A2 protein levels in infected human macrophages.

Assessment of genetically modified maize MON 89034 × 1507 × MIR162 × NK603 × DAS-40278-9 for food and feed uses, under regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2018-151)

Genetically modified maize MON 89034 × 1507 × MIR162 × NK603 × DAS‐40278‐9 was developed by crossing to combine five single events: MON 89034, 1507, MIR162, NK603 and DAS‐40278‐9. The GMO Panel previously assessed the five single maize events and 16 of the subcombinations and did not identify safety concerns. No new data on the single maize events or the assessed subcombinations were identified that could lead to the modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in the five‐event stack maize does not give rise to food and feed safety and nutritional concerns. The GMO Panel concludes that five‐event stack maize, as described in this application, is as safe as the non‐GM comparator and non‐GM maize varieties tested. In the case of accidental release of viable five‐event stack maize grains into the environment, this would not raise environmental safety concerns. The GMO Panel assessed the likelihood of interactions among the single events in nine of the maize subcombinations not previously assessed and concludes that these are expected to be as safe as the single events, the previously assessed subcombinations and the five‐event stack maize. The post‐market environmental monitoring plan and reporting intervals are in line with the intended uses of maize MON 89034 × 1507 × MIR162 × NK603 × DAS‐40278‐9. Post‐market monitoring of food/feed is not considered necessary. The GMO Panel concludes that the five‐event stack maize and its subcombinations are as safe as its non‐GM comparator and the tested non‐GM maize varieties with respect to potential effects on human and animal health and the environment.

Upregulation of protein N-glycosylation plays crucial roles in the response of Camellia sinensis leaves to fluoride

The tea plant (Camellia sinensis) is one of the three major beverage crops in the world with its leaves consumption as tea. However, it can hyperaccumulate fluoride with about 98% fluoride deposition in the leaves. Our previously studies found that cell wall proteins (CWPs) might play a central role in fluoride accumulation/detoxification in C. sinensis. CWP is known to be glycosylated, however the response of CWP N-glycosylation to fluoride remains unknown in C. sinensis. In this study, a comparative N-glycoproteomic analysis was performed through HILIC enrichment coupled with UPLC-MS/MS based on TMT-labeling approach in C. sinensis leaves. Totally, 237 N-glycoproteins containing 326 unique N-glycosites were identified. 73.4%, 18.6%, 6.3% and 1.7% of these proteins possess 1, 2, 3, and ≥4 modification site, respectively. 93.2% of these proteins were predicted to be localized in the secretory pathway and 78.9% of them were targeted to the cell wall and the plasma membrane. 133 differentially accumulated N-glycosites (DNGSs) on 100 N-glycoproteins (DNGPs) were detected and 85.0% of them exhibited upregulated expression after fluoride treatment. 78.0% DNGPs were extracellular DNGPs, which belonged to CWPs, and 53.0% of them were grouped into protein acting on cell wall polysaccharides, proteases and oxido-reductases, whereas the majority of the remaining DNGPs were mainly related to N-glycoprotein biosynthesis, trafficking and quality control. Our study shed new light on the N-glycoproteome study, and revealed that increased N-glycosylation abundance of CWPs might contribute to fluoride accumulation/detoxification in C. sinensis leave.

Assessment of genetically modified oilseed rape MON 94100 for food and feed uses, under regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2020-169)

Oilseed rape MON 94100 was developed to confer tolerance to dicamba herbicide. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between oilseed rape MON 94100 and its conventional counterpart needs further assessment, except for the levels of carbohydrates, calcium and ADF in seeds, which do not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the dicamba mono‐oxygenase (DMO) protein as expressed in oilseed rape MON 94100. The GMO Panel finds no evidence that the genetic modification impacts the overall safety of oilseed rape MON 94100. In the context of this application, the consumption of food and feed from oilseed rape MON 94100 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that oilseed rape MON 94100 is as safe as the conventional counterpart and non‐GM oilseed rape reference varieties tested, and no post‐market monitoring of food/feed is considered necessary. In the case of accidental release of viable oilseed rape MON 94100 seeds into the environment, this would not raise environmental safety concerns. The post‐market environmental monitoring plan and reporting intervals are in line with the intended uses of oilseed rape MON 94100. The GMO Panel concludes that oilseed rape MON 94100 is as safe as its conventional counterpart and the tested non‐GM oilseed rape reference varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified maize DP4114 × MON 810 × MIR604 × NK603 and subcombinations, for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA‐GMO‐NL‐2018‐150)

Maize DP4114 × MON 810 × MIR604 × NK603 (four‐event stack maize) was produced by conventional crossing to combine four single events: DP4114, MON 810, MIR604 and NK603. The GMO Panel previously assessed the four single maize events and one of the subcombinations and did not identify safety concerns. No new data on the single maize events or the assessed subcombination were identified that could lead to modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in the four‐event stack maize does not give rise to food and feed safety and nutritional concerns. The GMO Panel concludes that the four‐event stack maize, is as safe as the comparator and the selected non‐GM reference varieties. In the case of accidental release of viable grains of the four‐event stack maize into the environment, this would not raise environmental safety concerns. The GMO Panel assessed the likelihood of interactions among the single events in nine of the maize subcombinations not previously assessed and concludes that these are expected to be as safe as the single events, the previously assessed subcombination and the four‐event stack maize. Post‐market monitoring of food/feed is not considered necessary. The post‐market environmental monitoring plan and reporting intervals are in line with the intended uses of the four‐event stack maize. The GMO Panel concludes that the four‐event stack maize and its subcombinations are as safe as the non‐GM comparator and the selected non‐GM reference varieties with respect to potential effects on human and animal health and the environment.

Development of a Glycoform Library-based Strategy to Decipher the Role of Protein Glycosylation

Glycoproteins obtained from cell culture supernatants or lysates generally exist as mixtures of over 100 differently glycosylated protein forms (glycoforms). The study of glycosylation is significantly impeded because of the heterogeneous nature of glycoproteins. To overcome this challenge, we developed and optimized a glycoform library-based strategy to investigate the role of protein glycosylation. In this strategy, chemical synthesis was used to prepare individual homogeneous glycoforms and the role of glycosylation was determined by comparing a series of glycoforms with systematic differences in their glycosylation patterns.

Assessment of genetically modified maize NK603 × T25 × DAS-40278-9 and subcombinations, for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2019-164)

Maize NK603 × T25 × DAS-40278-9 (three-event stack maize) was produced by conventional crossing to combine three single events: NK603, T25 and DAS-40278-9. The GMO Panel previously assessed the three single maize events and two of the subcombinations and did not identify safety concerns. No new data on the single maize events or the two subcombinations were identified that could lead to modification of the original conclusions on their safety. The molecular characterisation, comparative analysis (agronomic, phenotypic and compositional characteristics) and the outcome of the toxicological, allergenicity and nutritional assessment indicate that the combination of the single maize events and of the newly expressed proteins in the three-event stack maize does not give rise to food and feed safety and nutritional concerns. The GMO Panel concludes that the three-event stack maize, as described in this application, is as safe as the non-GM comparator and the selected non-GM reference varieties. In the case of accidental release of viable grains of the three-event stack maize into the environment, this would not raise environmental safety concerns. The GMO Panel assessed the likelihood of interactions among the single events in one of the maize subcombinations not previously assessed and concludes that these are expected to be as safe as the single events, the previously assessed subcombinations and the three-event stack maize. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of the three-event stack maize. Post-market monitoring of food/feed is not considered necessary. The GMO Panel concludes that the three-event stack maize and its subcombinations are as safe as the non-GM comparator and the selected non-GM reference varieties with respect to potential effects on human and animal health and the environment.

Challenges and limitations in the studies of glycoproteins: A computational chemist's perspective

Experimenters face challenges and limitations while analyzing glycoproteins due to their high flexibility, stereochemistry, anisotropic effects, and hydration phenomena. Computational studies complement experiments and have been used in characterization of the structural properties of glycoproteins. However, recent investigations revealed that computational studies face significant challenges as well. Here, we introduce and discuss some of these challenges and weaknesses in the investigations of glycoproteins. We also present requirements of future developments in computational biochemistry and computational biology areas that could be necessary for providing more accurate structural property analyses of glycoproteins using computational tools. Further theoretical strategies that need to be and can be developed are discussed herein.

Pump-Free Microfluidic Device for the Electrochemical Detection of α1-Acid Glycoprotein

α₁-Acid glycoprotein (AGP) is a glycoprotein present in serum, which is associated with the modulation of the immune system in response to stress or injuries, and a biomarker for inflammatory diseases and cancers. Here, we propose a pump-free microfluidic device for the electrochemical determination of AGP. The microfluidic device utilizes capillary-driven flow and a passive mixing system to label the AGP with the Os (VI) complex (an electrochemical tag) inside the main channel, before delivering the products to the electrode surface. Furthermore, thanks to the resulting geometry, all the analytical steps can be carried out inside the device: labeling, washing, and detection by adsorptive transfer stripping square wave voltammetry. The microfluidic device exhibited a linear range from 500 to 2000 mg L^-1 (R² = 0.990) and adequate limit of detection (LOD = 231 mg L^-1). Commercial serum samples were analyzed to demonstrate the success of the method, yielding recoveries around 83%. Due to its simplicity, low sample consumption, low cost, short analysis time, disposability, and portability, the proposed method can serve as a point-of-care/need testing device for AGP.

Assessment of genetically modified cotton GHB811 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-ES-2018-154)

Cotton GHB811 was developed to confer tolerance to glyphosate and HPPD inhibitor herbicides. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between cotton GHB811 and its conventional counterpart needs further assessment, except for % lint, lint length and dihydrosterculic acid, which do not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the 2mEPSPS and HPPD W336 proteins as expressed in cotton GHB811 and finds no evidence that the genetic modification would change the overall allergenicity of cotton GHB811. In the context of this application, the consumption of food and feed from cotton GHB811 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that cotton GHB811 is as safe as the conventional counterpart and non-GM cotton reference varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable cotton GHB811 seeds into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of cotton GHB811. The GMO Panel concludes that cotton GHB811 is as safe as its conventional counterpart and the tested non-GM cotton reference varieties with respect to potential effects on human and animal health and the environment.

Assessment of genetically modified oilseed rape 73496 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2012-109)

Oilseed rape 73496 was developed to confer tolerance to the herbicidal active substance glyphosate through the expression of the glyphosate acetyltransferase protein GAT4621. The molecular characterisation data and bioinformatic analyses identify no issues requiring food/feed safety assessment. None of the identified differences between oilseed rape 73496 and its conventional counterpart in the agronomic/phenotypic endpoints tested needs further assessment. Differences identified in seed composition of oilseed rape 73496 as compared to its conventional counterpart raise no safety and nutritional concerns in the context of the scope of this application. No safety concerns are identified regarding toxicity and allergenicity of the GAT4621 protein as expressed in oilseed rape 73496. No evidence is found that the genetic modification would change the overall allergenicity of oilseed rape 73496. Based on the outcome of the comparative and nutritional assessments, the consumption of oilseed rape 73496 does not represent any nutritional concern, in the context of the scope of this application. The implementation of a post-market monitoring plan is recommended to confirm the predicted consumption data and to verify that the conditions of use are those considered during the pre-market risk assessment. In the case of accidental release of viable oilseed rape 73496 seeds into the environment, oilseed rape 73496 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of oilseed rape 73496. The GMO Panel concludes that oilseed rape 73496, as described in this application, is as safe as its conventional counterpart and the non-genetically modified oilseed rape reference varieties tested with respect to potential effects on human and animal health and the environment.

Synthesis of Glycodendrimers with Antiviral and Antibacterial Activity

Glycodendrimers are an important class of synthetic macromolecules that can be used to mimic many structural and functional features of cell-surface glycoconjugates. Their carbohydrate moieties perform key important functions in bacterial and viral infections, often regulated by carbohydrate-protein interactions. Several studies have shown that the molecular structure, valency and spatial organisation of carbohydrate epitopes in glycoconjugates are key factors in the specificity and avidity of carbohydrate-protein interactions. Choosing the right glycodendrimers almost always helps to interfere with such interactions and blocks bacterial or viral adhesion and entry into host cells as an effective strategy to inhibit bacterial or viral infections. Herein, the state of the art in the design and synthesis of glycodendrimers employed for the development of anti-adhesion therapy against bacterial and viral infections is described.

The Saccharomyces cerevisiae Ncw2 protein works on the chitin/β-glucan organisation of the cell wall

The NCW2 gene was recently described as encoding a GPI-bounded protein that assists in the re-modelling of the Saccharomyces cerevisiae cell wall (CW) and in the repair of damage caused by the polyhexamethylene biguanide (PHMB) polymer to the cell wall. Its absence produces a re-organization of the CW structure that result in resistance to lysis by glucanase. Hence, the present study aimed to extend the analysis of the Ncw2 protein (Ncw2p) to determine its physiological role in the yeast cell surface. The results showed that Ncw2p is transported to the cell surface upon O-mannosylation mediated by the Pmt1p-Pmt2p enzyme complex. It co-localises with the yeast bud scars, a region in cell surface formed by chitin deposition. Once there, Ncw2p enables correct chitin/β-glucan structuring during the exponential growth. The increase in molecular mass by hyper-mannosylation coincides with the increasing in chitin deposition, and leads to glucanase resistance. Treatment of the yeast cells with PHMB produced the same biological effects observed for the passage from exponential to stationary growth phase. This might be a possible mechanism of yeast protection against cationic biocides. In conclusion, we propose that Ncw2p takes part in the mechanism involved in the control of cell surface rigidity by aiding on the linkage between chitin and glucan layers in the modelling of the cell wall during cell growth.

Assessment of genetically modified soybean GMB151 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2018-153)

Soybean GMB151 was developed to confer tolerance to 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicides and resistance to nematodes. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between soybean GMB151 and its conventional counterpart needs further assessment, except for palmitic acid and heptadecenoic acid in seeds and carbohydrate and crude protein in forage, which does not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the HPPD-4 and Cry14Ab-1 proteins as expressed in soybean GMB151, and finds no evidence that the genetic modification would change the overall allergenicity of soybean GMB151. In the context of this application, the consumption of food and feed from soybean GMB151 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that soybean GMB151 is as safe as the conventional counterpart and non-GM soybean reference varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable soybean GMB151 seeds into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of soybean GMB151. The GMO Panel concludes that soybean GMB151 is as safe as its conventional counterpart and the tested non-GM soybean reference varieties with respect to potential effects on human and animal health and the environment.

Recent Advances in the Chemical Biology of N-Glycans

Asparagine-linked N-glycans on proteins have diverse structures, and their functions vary according to their structures. In recent years, it has become possible to obtain high quantities of N-glycans via isolation and chemical/enzymatic/chemoenzymatic synthesis. This has allowed for progress in the elucidation of N-glycan functions at the molecular level. Interaction analyses with lectins by glycan arrays or nuclear magnetic resonance (NMR) using various N-glycans have revealed the molecular basis for the recognition of complex structures of N-glycans. Preparation of proteins modified with homogeneous N-glycans revealed the influence of N-glycan modifications on protein functions. Furthermore, N-glycans have potential applications in drug development. This review discusses recent advances in the chemical biology of N-glycans.

Statement on in vitro protein digestibility tests in allergenicity and protein safety assessment of genetically modified plants

This statement supplements and updates the GMO Panel guidance document on allergenicity of genetically modified (GM) plants published in 2017. In that guidance document, the GMO Panel considered that additional investigations on in vitro protein digestibility were needed before providing any additional recommendations in the form of guidance to applicants. Thus, an interim phase was proposed to assess the utility of an enhanced in vitro digestion test, as compared to the classical pepsin resistance test. Historically, resistance to degradation by pepsin using the classical pepsin resistance test has been considered as additional information, in a weight-of-evidence approach, for the assessment of allergenicity and toxicity of newly expressed proteins in GM plants. However, more recent evidence does not support this test as a good predictor of allergenic potential for hazard. Furthermore, there is a need for more reliable systems to predict the fate of the proteins in the gastrointestinal tract and how they interact with the relevant human cells. Nevertheless, the classical pepsin resistance test can still provide some information on the physicochemical properties of novel proteins relating to their stability under acidic conditions. But other methods can be used to obtain data on protein's structural and/or functional integrity. It is acknowledged that the classical pepsin resistance test is embedded into international guidelines, e.g. Codex Alimentarius and Regulation (EU) No 503/2013. For future development, a deeper understanding of protein digestion in the gastrointestinal tract could enable the framing of more robust strategies for the safety assessment of proteins. Given the high complexity of the digestion and absorption process of dietary proteins, it is needed to clarify and identify the aspects that could be relevant to assess potential risks of allergenicity and toxicity of proteins. To this end, a series of research questions to be addressed are also formulated in this statement.

Deciphering protein post-translational modifications using chemical biology tools

Proteins carry out a wide variety of catalytic, regulatory, signalling and structural functions in living systems. Following their assembly on ribosomes and throughout their lifetimes, most eukaryotic proteins are modified by post-translational modifications; small functional groups and complex biomolecules are conjugated to amino acid side chains or termini, and the protein backbone is cleaved, spliced or cyclized, to name just a few examples. These modifications modulate protein activity, structure, location and interactions, and, thereby, control many core biological processes. Aberrant post-translational modifications are markers of cellular stress or malfunction and are implicated in several diseases. Therefore, gaining an understanding of which proteins are modified, at which sites and the resulting biological consequences is an important but complex challenge requiring interdisciplinary approaches. One of the key challenges is accessing precisely modified proteins to assign functional consequences to specific modifications. Chemical biologists have developed a versatile set of tools for accessing specifically modified proteins by applying robust chemistries to biological molecules and developing strategies for synthesizing and ligating proteins. This Review provides an overview of these tools, with selected recent examples of how they have been applied to decipher the roles of a variety of protein post-translational modifications. Relative advantages and disadvantages of each of the techniques are discussed, highlighting examples where they are used in combination and have the potential to address new frontiers in understanding complex biological processes.

Peptidyl ω-Asp Selenoesters Enable Efficient Synthesis of N-Linked Glycopeptides

Chemical synthesis is an attractive approach allows for the assembly of homogeneous complex N-linked glycopeptides and glycoproteins, but the limited coupling efficiency between glycans and peptides hampered the synthesis and research in the related field. Herein we developed an alternative glycosylation to construct N-linked glycopeptide via efficient selenoester-assisted aminolysis, which employs the peptidyl ω-asparagine selenoester and unprotected glycosylamine to perform rapid amide-bond ligation. This glycosylation strategy is highly compatible with the free carboxylic acids and hydroxyl groups of peptides and carbohydrates, and readily available for the assembly of structure-defined homogeneous N-linked glycopeptides, such as segments derived from glycoprotein EPO and IL-5.