Discovery of a lectin domain that regulates enzyme activity in mouse N-acetylglucosaminyltransferase-IVa (MGAT4A)

N-Glycosylation is a common post-translational modification, and the number of GlcNAc branches in N-glycans impacts glycoprotein functions. N-Acetylglucosaminyltransferase-IVa (GnT-IVa, also designated as MGAT4A) forms a β1-4 GlcNAc branch on the α1-3 mannose arm in N-glycans. Downregulation or loss of GnT-IVa causes diabetic phenotypes by dysregulating glucose transporter-2 in pancreatic β-cells. Despite the physiological importance of GnT-IVa, its structure and catalytic mechanism are poorly understood. Here, we identify the lectin domain in mouse GnT-IVa’s C-terminal region. The crystal structure of the lectin domain shows structural similarity to a bacterial GlcNAc-binding lectin. Comprehensive glycan binding assay using 157 glycans and solution NMR reveal that the GnT-IVa lectin domain selectively interacts with the product N-glycans having a β1-4 GlcNAc branch. Point mutation of the residue critical to sugar recognition impairs the enzymatic activity, suggesting that the lectin domain is a regulatory subunit for efficient catalytic reaction. Our findings provide insights into how branching structures of N-glycans are biosynthesized

Diabetic Cardiomyopathy: An Immunometabolic Perspective.

The heart possesses a remarkable inherent capability to adapt itself to a wide array of genetic and extrinsic factors to maintain contractile function. Failure to sustain its compensatory responses results in cardiac dysfunction, leading to cardiomyopathy. Diabetic cardiomyopathy (DCM) is characterized by left ventricular hypertrophy and reduced diastolic function, with or without concurrent systolic dysfunction in the absence of hypertension and coronary artery disease. Changes in substrate metabolism, oxidative stress, endoplasmic reticulum stress, formation of extracellular matrix proteins, and advanced glycation end products constitute the early stage in DCM. These early events are followed by steatosis (accumulation of lipid droplets) in cardiomyocytes, which is followed by apoptosis, changes in immune responses with a consequent increase in fibrosis, remodeling of cardiomyocytes, and the resultant decrease in cardiac function. The heart is an omnivore, metabolically flexible, and consumes the highest amount of ATP in the body. Altered myocardial substrate and energy metabolism initiate the development of DCM. Diabetic hearts shift away from the utilization of glucose, rely almost completely on fatty acids (FAs) as the energy source, and become metabolically inflexible. Oxidation of FAs is metabolically inefficient as it consumes more energy. In addition to metabolic inflexibility and energy inefficiency, the diabetic heart suffers from impaired calcium handling with consequent alteration of relaxation-contraction dynamics leading to diastolic and systolic dysfunction. Sarcoplasmic reticulum (SR) plays a key role in excitation-contraction coupling as Ca(2+) is transported into the SR by the SERCA2a (sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a) during cardiac relaxation. Diabetic cardiomyocytes display decreased SERCA2a activity and leaky Ca(2+) release channel resulting in reduced SR calcium load. The diabetic heart also suffers from marked downregulation of novel cardioprotective microRNAs (miRNAs) discovered recently. Since immune responses and substrate energy metabolism are critically altered in diabetes, the present review will focus on immunometabolism and miRNAs

Evaluation of Selected Classical Force Fields for Alchemical Binding Free Energy Calculations of Protein-Carbohydrate Complexes

Protein–carbohydrate recognition is crucial in many vital biological processes including host–pathogen recognition, cell-signaling, and catalysis. Accordingly, computational prediction of protein–carbohydrate binding free energies is of enormous interest for drug design. However, the accuracy of current force fields (FFs) for predicting binding free energies of protein–carbohydrate complexes is not well understood owing to technical challenges such as the highly polar nature of the complexes, anomerization, and conformational flexibility of carbohydrates. The present study evaluated the performance of alchemical predictions of binding free energies with the GAFF1.7/AM1-BCC and GLYCAM06j force fields for modeling protein–carbohydrate complexes. Mean unsigned errors of 1.1 ± 0.06 (GLYCAM06j) and 2.6 ± 0.08 (GAFF1.7/AM1-BCC) kcal·mol^–1 are achieved for a large data set of monosaccharide ligands for <i>Ralstonia solanacearum</i> lectin (RSL). The level of accuracy provided by GLYCAM06j is sufficient to discriminate potent, moderate, and weak binders, a goal that has been difficult to achieve through other scoring approaches. Accordingly, the protocols presented here could find useful applications in carbohydrate-based drug and vaccine developments

Validated determination of NRG1 Ig-like domain structure by mass spectrometry coupled with computational modeling

High resolution hydroxyl radical protein footprinting (HR-HRPF) is a mass spectrometry-based method that measures the solvent exposure of multiple amino acids in a single experiment, offering constraints for experimentally informed computational modeling. HR-HRPF-based modeling has previously been used to accurately model the structure of proteins of known structure, but the technique has never been used to determine the structure of a protein of unknown structure. Here, we present the use of HR-HRPF-based modeling to determine the structure of the Ig-like domain of NRG1, a protein with no close homolog of known structure. Independent determination of the protein structure by both HR-HRPF-based modeling and heteronuclear NMR was carried out, with results compared only after both processes were complete. The HR-HRPF-based model was highly similar to the lowest energy NMR model, with a backbone RMSD of 1.6 Å. To our knowledge, this is the first use of HR-HRPF-based modeling to determine a previously uncharacterized protein structure

Bio-chemical amelioration effects on physico-chemical dynamics of sodic soils under rice (Oryza sativa) –wheat (Triticum aestivum) cropping system

The effect of dhaincha (Sesbania aculeata) as first crop on physico-chemical dynamics and productivity of “B” class sodic soils was assessed on farmer’s field under rice-wheat cropping system to generate the knowledge of sodic soil management for increasing the soil and crop productivity for sustainable crop production in sodic soil environment. The experiment was laid out in randomized block design at ten sites having six treatment combinations of different doses of gypsum and green manuring with sesbania under two cropping sequences, i e sesbania-rice (Oryza sativa L.) -wheat (Triticum aestivum L.) and rice-wheat. Cultivation of sesbania with gypsum significantly decreased the surface soil pH from 9.3 to 8.6 and increased the hydraulic conductivity from 0.3 × 10-3 to 3.7 × 10-3 cm/hr and buildup of soil organic matter by increasing organic carbon content from 0.20 % to 0.22 % through growing of sesbania. Sesbania green manure also increased the available water content in the soil system, which enhanced soil moisture availability for longer period. As a result, rice crop yield increased by 16.2 % in sesbania-rice- wheat cropping system in comparison to rice–wheat cropping sequence because of synergistic effect of sesbania with gypsum. Consequently, residual effect of sesbania green manuring alone and in combination with gypsum significantly enhanced the wheat grain yield by 42.5 % and 72.5 % and 80% in T4, T5 and T6 treatments respectively during first year in sesbania–rice-wheat cropping sequence as compared to control. In consecutive second year, rice and wheat grain yields further enhanced by 8.1 % and 2.71% respectively, under sesbania –rice -wheat than that of rice –wheat cropping sequence. Under sesbania- rice- wheat and rice-wheat-sesbania cropping sequence, rice and wheat grain yield were similar. Hence, inclusion of Sesbania aculeata as green manure either before or after rice-wheat cropping sequence is equally better to improve the soil physical dynamics and crop productivity of ‘B’ class sodic soils in Indo-Gangetic region of Uttar Pradesh

Bisecting GlcNAc Is a General Suppressor of Terminal Modification of N-glycan

Glycoproteins are decorated with complex glycans for protein functions. However, regulation mechanisms of complex glycan biosynthesis are largely unclear. Here we found that bisecting GlcNAc, a branching sugar residue in N-glycan, suppresses the biosynthesis of various types of terminal epitopes in N-glycans, including fucose, sialic acid and human natural killer-1. Expression of these epitopes in N-glycan was elevated in mice lacking the biosynthetic enzyme of bisecting GlcNAc, GnT-III, and was conversely suppressed by GnT-III overexpression in cells. Many glycosyltransferases for N-glycan terminals were revealed to prefer a nonbisected N-glycan as a substrate to its bisected counterpart, whereas no up-regulation of their mRNAs was found. This indicates that the elevated expression of the terminal N-glycan epitopes in GnT-III-deficient mice is attributed to the substrate specificity of the biosynthetic enzymes. Molecular dynamics simulations further confirmed that nonbisected glycans were preferentially accepted by those glycosyltransferases. These findings unveil a new regulation mechanism of protein N-glycosylation.This work was supported by Grant-in-Aid for Scientific Research (C) to Y.K. [17K07356], Leading Initiative for Excellent Young Researchers (LEADER) project to Y.K. from the Japan Society for the Promotion of Science (JSPS), by Takeda Science Foundation, and by Mochida Memorial Foundation for Medical and Pharmaceutical Research

Study of Marine Natural Products as Anti-SARS-CoV-2 Agents Using Molecular Modeling

Corresponding author (BioMolecular Sciences): Priyanka Samanta, [email protected]://egrove.olemiss.edu/pharm_annual_posters_2022/1018/thumbnail.jp

Biallelic variants in LIG3 cause a novel mitochondrial neurogastrointestinal encephalomyopathy

none67si: Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy. DNA from these patients was subjected to whole exome sequencing. In all patients, compound heterozygous variants in a new disease gene, LIG3, were identified. All variants were predicted to have a damaging effect on the protein. The LIG3 gene encodes the only mitochondrial DNA (mtDNA) ligase and therefore plays a pivotal role in mtDNA repair and replication. In vitro assays in patient-derived cells showed a decrease in LIG3 protein levels and ligase activity. We demonstrated that the LIG3 gene defects affect mtDNA maintenance, leading to mtDNA depletion without the accumulation of multiple deletions as observed in other mitochondrial disorders. This mitochondrial dysfunction is likely to cause the phenotypes observed in these patients. The most prominent and consistent clinical signs were severe gut dysmotility and neurological abnormalities, including leukoencephalopathy, epilepsy, migraine, stroke-like episodes, and neurogenic bladder. A decrease in the number of myenteric neurons, and increased fibrosis and elastin levels were the most prominent changes in the gut. Cytochrome c oxidase (COX) deficient fibres in skeletal muscle were also observed. Disruption of lig3 in zebrafish reproduced the brain alterations and impaired gut transit in vivo. In conclusion, we identified variants in the LIG3 gene that result in a mitochondrial disease characterized by predominant gut dysmotility, encephalopathy, and neuromuscular abnormalities.This work was supported by Telethon Grant GGP15171 to E.B. and R.D.G. and by a donation from Kobe city to the Department of General Pediatrics, Kobe University Graduate School of Medicine (K550003302). S.C. was supported by a Dutch Cancer Foundation grant (KWF11011). V.C. and A.M. were supported by the Italian Ministry of Health (“Ricerca Corrente” funding). R.D.G. is the recipient of grants from University of Ferrara (FAR and FIR funds).openBonora, Elena; Chakrabarty, Sanjiban; Kellaris, Georgios; Tsutsumi, Makiko; Bianco, Francesca; Bergamini, Christian; Ullah, Farid; Isidori, Federica; Liparulo, Irene; Diquigiovanni, Chiara; Masin, Luca; Rizzardi, Nicola; Cratere, Mariapia Giuditta; Boschetti, Elisa; Papa, Valentina; Maresca, Alessandra; Cenacchi, Giovanna; Casadio, Rita; Martelli, Pierluigi; Matera, Ivana; Ceccherini, Isabella; Fato, Romana; Raiola, Giuseppe; Arrigo, Serena; Signa, Sara; Sementa, Angela Rita; Severino, Mariasavina; Striano, Pasquale; Fiorillo, Chiara; Goto, Tsuyoshi; Uchino, Shumpei; Oyazato, Yoshinobu; Nakamura, Hisayoshi; Mishra, Sushil K; Yeh, Yu-Sheng; Kato, Takema; Nozu, Kandai; Tanboon, Jantima; Morioka, Ichiro; Nishino, Ichizo; Toda, Tatsushi; Goto, Yu-Ichi; Ohtake, Akira; Kosaki, Kenjiro; Yamaguchi, Yoshiki; Nonaka, Ikuya; Iijima, Kazumoto; Mimaki, Masakazu; Kurahashi, Hiroki; Raams, Anja; MacInnes, Alyson; Alders, Mariel; Engelen, Marc; Linthorst, Gabor; de Koning, Tom; den Dunnen, Wilfred; Dijkstra, Gerard; van Spaendonck, Karin; van Gent, Dik C; Aronica, Eleonora M; Picco, Paolo; Carelli, Valerio; Seri, Marco; Katsanis, Nicholas; Duijkers, Floor A M; Taniguchi-Ikeda, Mariko; De Giorgio, RobertoBonora, Elena; Chakrabarty, Sanjiban; Kellaris, Georgios; Tsutsumi, Makiko; Bianco, Francesca; Bergamini, Christian; Ullah, Farid; Isidori, Federica; Liparulo, Irene; Diquigiovanni, Chiara; Masin, Luca; Rizzardi, Nicola; Cratere, Mariapia Giuditta; Boschetti, Elisa; Papa, Valentina; Maresca, Alessandra; Cenacchi, Giovanna; Casadio, Rita; Martelli, Pierluigi; Matera, Ivana; Ceccherini, Isabella; Fato, Romana; Raiola, Giuseppe; Arrigo, Serena; Signa, Sara; Sementa, Angela Rita; Severino, Mariasavina; Striano, Pasquale; Fiorillo, Chiara; Goto, Tsuyoshi; Uchino, Shumpei; Oyazato, Yoshinobu; Nakamura, Hisayoshi; Mishra, Sushil K; Yeh, Yu-Sheng; Kato, Takema; Nozu, Kandai; Tanboon, Jantima; Morioka, Ichiro; Nishino, Ichizo; Toda, Tatsushi; Goto, Yu-Ichi; Ohtake, Akira; Kosaki, Kenjiro; Yamaguchi, Yoshiki; Nonaka, Ikuya; Iijima, Kazumoto; Mimaki, Masakazu; Kurahashi, Hiroki; Raams, Anja; MacInnes, Alyson; Alders, Mariel; Engelen, Marc; Linthorst, Gabor; de Koning, Tom; den Dunnen, Wilfred; Dijkstra, Gerard; van Spaendonck, Karin; van Gent, Dik C; Aronica, Eleonora M; Picco, Paolo; Carelli, Valerio; Seri, Marco; Katsanis, Nicholas; Duijkers, Floor A M; Taniguchi-Ikeda, Mariko; De Giorgio, Robert

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe