Glycosylation, galectins and cellular signaling

Proteomic analysis of Caenorhabditis elegans against Salmonella Typhi toxic proteins

Bacterial effector molecules are crucial infectious agents that can cause pathogenesis. In the present study, the pathogenesis of toxic Salmonella enterica serovar Typhi (S. Typhi) proteins on the model host Caenorhabditis elegans was investigated by exploring the host's regulatory proteins during infection through the quantitative proteomics approach. Extracted host proteins were analyzed using two-dimensional gel electrophoresis (2D-GE) and differentially regulated proteins were identified using MALDI TOF/TOF/MS analysis. Of the 150 regulated proteins identified, 95 were downregulated while 55 were upregulated. The interaction network of regulated proteins was predicted using the STRING tool. Most downregulated proteins were involved in muscle contraction, locomotion, energy hydrolysis, lipid synthesis, serine/threonine kinase activity, oxidoreductase activity, and protein unfolding. Upregulated proteins were involved in oxidative stress pathways. Hence, cellular stress generated by S. Typhi proteins in the model host was determined using lipid peroxidation as well as oxidant and antioxidant assays. In addition, candidate proteins identified via extract analysis were validated by western blotting, and the roles of several crucial molecules were analyzed in vivo using transgenic strains (myo-2 and col-19) and mutant (ogt-1) of C. elegans. To the best of our knowledge, this is the first study to report protein regulation in host C. elegans exposed to toxic S. Typhi proteins. It highlights the significance of p38 MAPK and JNK immune pathways.

Targeting Pyrimidine Metabolism in the Era of Precision Cancer Medicine

Metabolic rewiring is considered as a primary feature of cancer. Malignant cells reprogram metabolism pathway in response to various intrinsic and extrinsic drawback to fuel cell survival and growth. Among the complex metabolic pathways, pyrimidine biosynthesis is conserved in all living organism and is necessary to maintain cellular fundamental function (i.e. DNA and RNA biosynthesis). A wealth of evidence has demonstrated that dysfunction of pyrimidine metabolism is closely related to cancer progression and numerous drugs targeting pyrimidine metabolism have been approved for multiple types of cancer. However, the non-negligible side effects and limited efficacy warrants a better strategy for negating pyrimidine metabolism in cancer. In recent years, increased studies have evidenced the interplay of oncogenic signaling and pyrimidine synthesis in tumorigenesis. Here, we review the recent conceptual advances on pyrimidine metabolism, especially dihydroorotate dehydrogenase (DHODH), in the framework of precision oncology medicine and prospect how this would guide the development of new drug precisely targeting the pyrimidine metabolism in cancer.

Galectin-3: A factotum in carcinogenesis bestowing an archery for prevention

Cancer metastasis and therapy resistance are the foremost hurdles in oncology at the moment. This review aims to pinpoint the functional aspects of a unique multifaceted glycosylated molecule in both intracellular and extracellular compartments of a cell namely galectin-3 along with its metastatic potential in different types of cancer. All materials reviewed here were collected through the search engines PubMed, Scopus, and Google scholar. Among the 15 galectins identified, the chimeric gal-3 plays an indispensable role in the differentiation, transformation, and multi-step process of tumor metastasis. It has been implicated in the molecular mechanisms that allow the cancer cells to survive in the intravascular milieu and promote tumor cell extravasation, ultimately leading to metastasis. Gal-3 has also been found to have a pivotal role in immune surveillance and pro-angiogenesis and several studies have pointed out the importance of gal-3 in establishing a resistant phenotype, particularly through the epithelial-mesenchymal transition process. Additionally, some recent findings suggest the use of gal-3 inhibitors in overcoming therapeutic resistance. All these reports suggest that the deregulation of these specific lectins at the cellular level could inhibit cancer progression and metastasis. A more systematic study of glycosylation in clinical samples along with the development of selective gal-3 antagonists inhibiting the activity of these molecules at the cellular level offers an innovative strategy for primary cancer prevention.

Synthesis, Structure-Activity Relationships, and In Vivo Evaluation of Novel Tetrahydropyran-Based Thiodisaccharide Mimics as Galectin-3 Inhibitors

Galectin-3 is a member of a family of β-galactoside-binding proteins. A substantial body of literature reports that galectin-3 plays important roles in cancer, inflammation, and fibrosis. Small-molecule galectin-3 inhibitors, which are generally lactose or galactose-based derivatives, have the potential to be valuable disease-modifying agents. In our efforts to identify novel galectin-3 disaccharide mimics to improve drug-like properties, we found that one of the monosaccharide subunits can be replaced with a suitably functionalized tetrahydropyran ring. Optimization of the structure-activity relationships around the tetrahydropyran-based scaffold led to the discovery of potent galectin-3 inhibitors. Compounds 36, 40, and 45 were selected for further in vivo evaluation. The synthesis, structure-activity relationships, and in vivo evaluation of novel tetrahydropyran-based galectin-3 inhibitors are described.

Membrane protein regulators of melanoma pulmonary colonisation identified using a CRISPRa screen and spontaneous metastasis assay in mice

Metastasis is the spread of cancer cells to a secondary site within the body, and is the leading cause of death for cancer patients. The lung is a common site of metastasis for many cancer types, including melanoma. Identifying the genes involved in aiding metastasis of melanoma cells to the lungs is critical for the development of better treatments. As the accessibility of cell surface proteins makes them attractive therapeutic targets, we performed a CRISPR activation screen using a library of guide RNAs (gRNAs) targeting the transcription start sites of 2195 membrane protein-encoding genes, to identify genes whose upregulated expression aided pulmonary metastasis. Immunodeficient mice were subcutaneously injected in the flank with murine B16-F0 melanoma cells expressing dCas9 and the membrane protein library gRNAs, and their lungs collected after 14–21 days. Analysis was performed to identify the gRNAs that were enriched in the lungs relative to those present in the cells at the time of administration (day 0). We identified six genes whose increased expression promotes lung metastasis. These genes included several with well-characterized pro-metastatic roles (Fut7, Mgat5, and Pcdh7) that have not previously been linked to melanoma progression, genes linked to tumor progression but that have not previously been described as involved in metastasis (Olfr322 and Olfr441), as well as novel genes (Tmem116). Thus, we have identified genes that, when upregulated in melanoma cells, can aid successful metastasis and colonization of the lung, and therefore may represent novel therapeutic targets to inhibit pulmonary metastasis.

Galectin-3 N-terminal tail prolines modulate cell activity and glycan-mediated oligomerization/phase separation

Galectin-3 (Gal-3) has a long, aperiodic, and dynamic proline-rich N-terminal tail (NT). The functional role of the NT with its numerous prolines has remained enigmatic since its discovery. To provide some resolution to this puzzle, we individually mutated all 14 NT prolines over the first 68 residues and assessed their effects on various Gal-3-mediated functions. Our findings show that mutation of any single proline (especially P37A, P55A, P60A, P64A/H, and P67A) dramatically and differentially inhibits Gal-3-mediated cellular activities (i.e., cell migration, activation, endocytosis, and hemagglutination). For mechanistic insight, we investigated the role of prolines in mediating Gal-3 oligomerization, a fundamental process required for these cell activities. We showed that Gal-3 oligomerization triggered by binding to glycoproteins is a dynamic process analogous to liquid-liquid phase separation (LLPS). The composition of these heterooligomers is dependent on the concentration of Gal-3 as well as on the concentration and type of glycoprotein. LLPS-like Gal-3 oligomerization/condensation was also observed on the plasma membrane and disrupted endomembranes. Molecular- and cell-based assays indicate that glycan binding-triggered Gal-3 LLPS (or LLPS-like) is driven mainly by dynamic intermolecular interactions between the Gal-3 NT and the carbohydrate recognition domain (CRD) F-face, although NT-NT interactions appear to contribute to a lesser extent. Mutation of each proline within the NT differentially controls NT-CRD interactions, consequently affecting glycan binding, LLPS, and cellular activities. Our results unveil the role of proline polymorphisms (e.g., at P64) associated with many diseases and suggest that the function of glycosylated cell surface receptors is dynamically regulated by Gal-3.

The role of O-glycosylation in human disease

O-glycosylation is a highly frequent post-translation modification of proteins, with important functional implications in both physiological and disease contexts. The biosynthesis of O-glycans depends on several layers of regulation of the cellular glycosylation machinery, being organ-, tissue- and cell-specific. This review provides insights on the molecular mechanism underlying O-glycan biosynthesis and modification, and highlights illustrative examples of diseases that are triggered or modulated by aberrant cellular O-glycosylation. Particular relevance is given to genetic disorders of glycosylation, infectious diseases and cancer. Finally, we address the potential of O-glycans and their biosynthetic pathways as targets for novel therapeutic strategies.

A sweet spot for macrophages: Focusing on polarization

Macrophages are a type of functionally plastic cells that can create a pro-/anti-inflammatory microenvironment for organs by producing different kinds of cytokines, chemokines, and growth factors to regulate immunity and inflammatory responses. In addition, they can also be induced to adopt different phenotypes in response to extracellular and intracellular signals, a process defined as M1/M2 polarization. Growing evidence indicates that glycobiology is closely associated with this polarization process. In this research, we review studies of the roles of glycosylation, glucose metabolism, and key lectins in the regulation of macrophages function and polarization to provide a new perspective for immunotherapies for multiple diseases.

Targeted nanomedicine modalities for prostate cancer treatment

Prostate cancer (PC) is the second most common cause of death amongst men in the USA. Therapy of PC has been transformed in the past decade by introducing novel therapeutics, advanced functional imaging and diagnostic approaches, next generation sequencing, as well as improved application of existing therapies in localized PC. Treatment of PC at the different stages of the disease may include surgery, androgen deprivation therapy (ADT), chemotherapy and radiation therapy. However, although ADT has proven efficacious in PC treatment, its effectiveness may be temporary, as these tumors frequently develop molecular mechanisms of therapy resistance, which allow them to survive and proliferate even under conditions of testosterone deprivation, inhibition of androgen receptor signaling, or cytotoxic drug treatment. Importantly, ADT was found to induce key alterations which frequently result in the formation of metastatic tumors displaying a therapy refractory phenotype. Hence, to overcome these serious therapeutic impediments, novel PC cell-targeted therapeutic strategies are being developed. These include diverse platforms enabling specific enhanced antitumor drug uptake and increased intracellular accumulation. Studies have shown that these novel treatment modalities lead to enhanced antitumor activity and diminished systemic toxicity due to the use of selective targeting and decreased drug doses. The underlying mechanism of targeting and internalization is based upon the interaction between a selective ligand, conjugated to a drug-loaded nanoparticle or directly to an anti-cancer drug, and a specific plasma membrane biomarker, uniquely overexpressed on the surface of PC cells. Another targeted therapeutic approach is the delivery of unique anti-oncogenic signaling pathway-based therapeutic drugs, which are selectively cytotoxic to PC cells. The current paper reviews PC targeted modalities reported in the past 6 years, and discusses both the advantages and limitations of the various targeted treatment strategies.

The Dysregulated Galectin Network Activates NF-κB to Induce Disease Markers and Matrix Degeneration in 3D Pellet Cultures of Osteoarthritic Chondrocytes

This work aimed to study the dysregulated network of galectins in OA chondrocyte pellets, and to assess whether their recently discovered activity as molecular switches of functional biomarkers results in degradation of extracellular matrix in vitro. Scaffold-free 3D pellet cultures were established of human OA chondrocytes. Expression and secretion of galectin(Gal)-1, -3, and -8 were monitored relative to 2D cultures or clinical tissue sections by RT-qPCR, immunohistochemistry and ELISAs. Exposure of 2D and 3D cultures to an in vivo-like galectin mixture (Gal-1 and Gal-8: 5 µg/ml, Gal-3: 1 µg/ml) was followed by the assessment of pellet size, immunohistochemical matrix staining, and/or quantification of MMP-1, -3, and -13. Application of inhibitors of NF-κB activation probed into the potential of intervening with galectin-induced matrix degradation. Galectin profiling revealed maintained dysregulation of Gal-1, -3, and -8 in pellet cultures, resembling the OA situation in situ. The presence of the galectin mixture promoted marked reduction of pellet size and loss of collagen type II-rich extracellular matrix, accompanied by the upregulation of MMP-1, -3, and -13. Inhibition of p65-phosphorylation by caffeic acid phenethyl ester effectively alleviated the detrimental effects of galectins, resulting in downregulated MMP secretion, reduced matrix breakdown and augmented pellet size. This study suggests that the dysregulated galectin network in OA cartilage leads to extracellular matrix breakdown, and provides encouraging evidence of the feasible inhibition of galectin-triggered activities. OA chondrocyte pellets have the potential to serve as in vitro disease model for further studies on galectins in OA onset and progression.

Glycoengineering: scratching the surface

At the surface of many cells is a compendium of glycoconjugates that form an interface between the cell and its surroundings; the glycocalyx. The glycocalyx serves several functions that have captivated the interest of many groups. Given its privileged residence, this meshwork of sugar-rich biomolecules is poised to transmit signals across the cellular membrane, facilitating communication with the extracellular matrix and mediating important signalling cascades. As a product of the glycan biosynthetic machinery, the glycocalyx can serve as a partial mirror that reports on the cell's glycosylation status. The glycocalyx can also serve as an information-rich barrier, withholding the entry of pathogens into the underlying plasma membrane through glycan-rich molecular messages. In this review, we provide an overview of the different approaches devised to engineer glycans at the cell surface, highlighting considerations of each, as well as illuminating the grand challenges that face the next era of ‘glyco-engineers’. While we have learned much from these techniques, it is evident that much is left to be unearthed.

Role of glycosylation in TGF-β signaling and epithelial-to-mesenchymal transition in cancer

Glycosylation is a common posttranslational modification on membrane-associated and secreted proteins that is of pivotal importance for regulating cell functions. Aberrant glycosylation can lead to uncontrolled cell proliferation, cell-matrix interactions, migration and differentiation, and has been shown to be involved in cancer and other diseases. The epithelial-to-mesenchymal transition is a key step in the metastatic process by which cancer cells gain the ability to invade tissues and extravasate into the bloodstream. This cellular transformation process, which is associated by morphological change, loss of epithelial traits and gain of mesenchymal markers, is triggered by the secreted cytokine transforming growth factor-β (TGF-β). TGF-β bioactivity is carefully regulated, and its effects on cells are mediated by its receptors on the cell surface. In this review, we first provide a brief overview of major types of glycans, namely, N-glycans, O-glycans, glycosphingolipids and glycosaminoglycans that are involved in cancer progression. Thereafter, we summarize studies on how the glycosylation of TGF-β signaling components regulates TGF-β secretion, bioavailability and TGF-β receptor function. Then, we review glycosylation changes associated with TGF-β-induced epithelial-to-mesenchymal transition in cancer. Identifying and understanding the mechanisms by which glycosylation affects TGF-β signaling and downstream biological responses will facilitate the identification of glycans as biomarkers and enable novel therapeutic approaches.

Deciphering cell-cell interactions and communication from gene expression

Cell-cell interactions orchestrate organismal development, homeostasis and single-cell functions. When cells do not properly interact or improperly decode molecular messages, disease ensues. Thus, the identification and quantification of intercellular signalling pathways has become a common analysis performed across diverse disciplines. The expansion of protein-protein interaction databases and recent advances in RNA sequencing technologies have enabled routine analyses of intercellular signalling from gene expression measurements of bulk and single-cell data sets. In particular, ligand-receptor pairs can be used to infer intercellular communication from the coordinated expression of their cognate genes. In this Review, we highlight discoveries enabled by analyses of cell-cell interactions from transcriptomic data and review the methods and tools used in this context.

Tissue-specific control of galectin-1-driven circuits during inflammatory responses

The relevance of glycan-binding protein in immune tolerance and inflammation has been well established, mainly by studies of C-type lectins, siglecs and galectins both in experimental models and patient samples. Galectins, a family of evolutionarily conserved lectins, are characterized by sequence homology in the carbohydrate-recognition domain (CRD), atypical secretion via an ER-Golgi-independent pathway and the ability to recognize β-galactoside-containing saccharides. Galectin-1 (Gal-1), a prototype member of this family displays mainly anti-inflammatory and immunosuppressive activities, although, similar to many cytokines and growth factors, it may also trigger paradoxical pro-inflammatory effects under certain circumstances. These dual effects could be associated to tissue-, time- or context-dependent regulation of galectin expression and function, including particular pathophysiologic settings and/or environmental conditions influencing the structure of this lectin, as well as the availability of glycosylated ligands in immune cells during the course of inflammatory responses. Here, we discuss the tissue-specific role of Gal-1 as a master regulator of inflammatory responses across different pathophysiologic settings, highlighting its potential role as a therapeutic target. Further studies designed at analyzing the intrinsic and extrinsic pathways that control Gal-1 expression and function in different tissue microenvironments may contribute to design tailored therapeutic strategies aimed at positively or negatively modulate this glycan-binding protein in pathologic inflammatory conditions.

Interferon Receptor Trafficking and Signaling: Journey to the Cross Roads

Like most plasma membrane proteins, type I interferon (IFN) receptor (IFNAR) traffics from the outer surface to the inner compartments of the cell. Long considered as a passive means to simply control subunits availability at the plasma membrane, an array of new evidence establishes IFNAR endocytosis as an active contributor to the regulation of signal transduction triggered by IFN binding to IFNAR. During its complex journey initiated at the plasma membrane, the internalized IFNAR complex, i.e. IFNAR1 and IFNAR2 subunits, will experience post-translational modifications and recruit specific effectors. These finely tuned interactions will determine not only IFNAR subunits destiny (lysosomal degradation vs. plasma membrane recycling) but also the control of IFN-induced signal transduction. Finally, the IFNAR system perfectly illustrates the paradigm of the crosstalk between membrane trafficking and intracellular signaling. Investigating the complexity of IFN receptor intracellular routes is therefore necessary to reveal new insight into the role of IFNAR membrane dynamics in type I IFNs signaling selectivity and biological activity.

Integrated Glycoproteomics Identifies a Role of N-Glycosylation and Galectin-1 on Myogenesis and Muscle Development

Many cell surface and secreted proteins are modified by the covalent addition of glycans that play an important role in the development of multicellular organisms. These glycan modifications enable communication between cells and the extracellular matrix via interactions with specific glycan-binding lectins and the regulation of receptor-mediated signaling. Aberrant protein glycosylation has been associated with the development of several muscular diseases, suggesting essential glycan- and lectin-mediated functions in myogenesis and muscle development, but our molecular understanding of the precise glycans, catalytic enzymes, and lectins involved remains only partially understood. Here, we quantified dynamic remodeling of the membrane-associated proteome during a time-course of myogenesis in cell culture. We observed wide-spread changes in the abundance of several important lectins and enzymes facilitating glycan biosynthesis. Glycomics-based quantification of released N-linked glycans confirmed remodeling of the glycome consistent with the regulation of glycosyltransferases and glycosidases responsible for their formation including a previously unknown digalactose-to-sialic acid switch supporting a functional role of these glycoepitopes in myogenesis. Furthermore, dynamic quantitative glycoproteomic analysis with multiplexed stable isotope labeling and analysis of enriched glycopeptides with multiple fragmentation approaches identified glycoproteins modified by these regulated glycans including several integrins and growth factor receptors. Myogenesis was also associated with the regulation of several lectins, most notably the upregulation of galectin-1 (LGALS1). CRISPR/Cas9-mediated deletion of Lgals1 inhibited differentiation and myotube formation, suggesting an early functional role of galectin-1 in the myogenic program. Importantly, similar changes in N-glycosylation and the upregulation of galectin-1 during postnatal skeletal muscle development were observed in mice. Treatment of new-born mice with recombinant adeno-associated viruses to overexpress galectin-1 in the musculature resulted in enhanced muscle mass. Our data form a valuable resource to further understand the glycobiology of myogenesis and will aid the development of intervention strategies to promote healthy muscle development or regeneration.

Quantitative levels of serum N-glycans in type 1 diabetes and their association with kidney disease

We investigated associations of quantitative levels of N-glycans with hemoglobin A1c (HbA1c), renal function and renal function decline in type 1 diabetes. We measured 46 total N-glycan peaks (GPs) on 1565 serum samples from the Scottish Diabetes Research Network Type 1 Bioresource Study (SDRNT1BIO) and a pool of healthy donors. Quantitation of absolute abundance of each GP used 2AB-labeled mannose-3 as a standard. We studied cross-sectional associations of GPs and derived measures with HbA1c, albumin/creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR), and prospective associations with incident albuminuria and final eGFR. All GPs were 1.4 to 3.2 times more abundant in SDRTN1BIO than in the healthy samples. Absolute levels of all GPs were slightly higher with higher HbA1c, with strongest associations for triantennary trigalactosylated disialylated, triantennary trigalactosylated trisialylated structures with core or outer arm fucose, and tetraantennary tetragalactosylated trisialylated glycans. Most GPs showed increased abundance with worsening ACR. Lower eGFR was associated with higher absolute GP levels, most significantly with biantennary digalactosylated disialylated glycans with and without bisect, triantennary trigalactosylated trisialylated glycans with and without outer arm fucose, and core fucosylated biantennary monogalactosylated monosialylated glycans. Although several GPs were inversely associated prospectively with final eGFR, cross-validated multivariable models did not improve prediction beyond clinical covariates. Elevated HbA1c is associated with an altered N-glycan profile in type 1 diabetes. Although we could not establish GPs to be prognostic of future renal function decline independently of HbA1c, further studies to evaluate their impact in the pathogenesis of diabetic kidney disease are warranted.

Binding of a Soluble meso-Tetraarylporphyrin to Human Galectin-7 Induces Oligomerization and Modulates Its Pro-Apoptotic Activity

The selective targeting of protein-protein interactions remains a significant determinant for the proper modulation and regulation of cell apoptosis. Prototypic galectins such as human galectin-7 (GAL-7) are characterized by their ability to form homodimers that control the molecular fate of a cell by mediating subtle yet critical glycan-dependent interactions between pro- and anti-apoptotic molecular partners. Altering the structural architecture of GAL-7 can therefore result in resistance to apoptosis in various human cancer cells, further illustrating its importance in cell survival. In this study, we used a combination of biophysical and cellular assays to illustrate that binding of a water-soluble meso-tetraarylporphyrin molecule to GAL-7 induces protein oligomerization and modulation of GAL-7-induced apoptosis in human Jurkat T cells. Our results suggest that the integrity of the GAL-7 homodimer architecture is essential for its molecular function, in addition to providing an interesting porphyrin binding modulator for controlling apoptosis in mammalian cells.

Synthesis of selected unnatural sugar nucleotides for biotechnological applications

Sugar nucleotides are the principal building blocks for the synthesis of most complex carbohydrates and are crucial intermediates in carbohydrate metabolism. Uridine diphosphate (UDP) monosaccharides are among the most common sugar nucleotide donors and are transferred to glycosyl acceptors by glycosyltransferases or synthases in glycan biosynthetic pathways. These natural nucleotide donors have great biological importance, however, the synthesis and application of unnatural sugar nucleotides that are not available from in vivo biosynthesis are not well explored. In this review, we summarize the progress in the preparation of unnatural sugar nucleotides, in particular, the widely studied UDP-GlcNAc/GalNAc analogs. We focus on the "two-block" synthetic pathway that is initiated from monosaccharides, in which the first block is the synthesis of sugar-1-phosphate and the second block is the diphosphate bond formation. The biotechnological applications of these unnatural sugar nucleotides showing their physiological and pharmacological potential are discussed.

Leveraging glycomics data in glycoprotein 3D structure validation with Privateer

The heterogeneity, mobility and complexity of glycans in glycoproteins have been, and currently remain, significant challenges in structural biology. These aspects present unique problems to the two most prolific techniques: X-ray crystallography and cryo-electron microscopy. At the same time, advances in mass spectrometry have made it possible to get deeper insights on precisely the information that is most difficult to recover by structure solution methods: the full-length glycan composition, including linkage details for the glycosidic bonds. The developments have given rise to glycomics. Thankfully, several large scale glycomics initiatives have stored results in publicly available databases, some of which can be accessed through API interfaces. In the present work, we will describe how the Privateer carbohydrate structure validation software has been extended to harness results from glycomics projects, and its use to greatly improve the validation of 3D glycoprotein structures.

Galectins and their involvement in ocular disease and development

Galectins are carbohydrate binding proteins with high affinity to ß-galactoside containing glycoconjugates. Understanding of the functions of galectins has grown steadily over the past decade, as a result of substantial advancements in the field of glycobiology. Galectins have been shown to be versatile molecules that participate in a range of important biological systems, including inflammation, neovascularisation and fibrosis. These processes are of particular importance in ocular tissues, where a major theme of recent research has been to divert diseases away from pathways which result in loss of function into pathways of repair and regeneration. This review summarises our current understanding of galectins in the context important ocular diseases, followed by an update on current clinical studies and future directions.

Increased serum levels of galectin-9 in patients with chikungunya fever

Chikungunya fever (CHIKF) is an arboviral disease that has caused an epidemic burst of chronic inflammatory joint disease in Latin America in the last few years. Efforts are being spent in understanding the mechanisms by which it may cause such articular damage and in determining possible biomarkers of the disease. Galectins (GAL) are a family of animal lectins with an affinity for beta-galactosides. They have multiple functions including working as receptors in innate immunity and as a control for inflammatory responses in both innate and adaptive immunity. They regulate functions of immune cells, such as lymphocytes and macrophages, which have a main role in the chikungunya inflammatory process. Galectins are also involved in chronification of viral diseases, participate in the immunopathogenesis of chronic joint diseases such as rheumatoid arthritis, and have a role in inflammation in other arboviral diseases, such as dengue. Thus, we intended to determine the serum levels of galectin-1, -3, -4, -7, and -9 in patients with subacute and chronic articular manifestations of CHIKF and to evaluate their associations with clinical manifestations. We evaluated 44 patients with clinical manifestations of CHIKF and serological confirmation with IgM and/or IgG chikungunya virus (CHIKV) antibodies. Forty-nine age- and gender-matched healthy individuals served as controls. Anti-CHIKV IgM and IgG antibodies and galectins serum levels were measured by ELISA. We found higher levels of GAL-9 (patients median 2192 [1500-2631] pg/mL, controls median 46.88 [46.88-46.88] pg/mL, p < 0.0001) and lower levels of GAL-3 (patients median 235.5 [175.5-351.8] pg/mL, controls median 2236.0 [1256.0-2236.0] pg/mL, p < 0.0001) in patients than in controls. There was no statistical difference in levels of GAL-1, -4 and -7 between patients and control groups. There was no difference in GAL-9 serum levels between patients with subacute or chronic symptoms (median 2148 [1500-2722] pg/mL x 2212 [1844-2500] pg/mL, p = 0.3626). A significant association of GAL-9 with joint stiffness, both in its duration and intensity, was found. These results may reflect the participation of GAL-9 in the immunopathogenesis of the inflammatory process in chikungunya fever, as morning stiffness may reflect the systemic inflammatory process.

Elements of the Endomucin Extracellular Domain Essential for VEGF-Induced VEGFR2 Activity

Endomucin (EMCN) is the type I transmembrane glycoprotein, mucin-like component of the endothelial cell glycocalyx. We have previously shown that EMCN is necessary for vascular endothelial growth factor (VEGF)-induced VEGF receptor 2 (VEGFR2) internalization and downstream signaling. To explore the structural components of EMCN that are necessary for its function and the molecular mechanism of EMCN in VEGF-induced endothelial functions, we generated a series of mouse EMCN truncation mutants and examined their ability to rescue VEGF-induced endothelial functions in human primary endothelial cells (EC) in which endogenous EMCN had been knocked down using siRNA. Expression of the mouse full-length EMCN (FL EMCN) and the extracellular domain truncation mutants ∆21-81 EMCN and ∆21-121 EMCN, but not the shortest mutant ∆21-161 EMCN, successfully rescued the VEGF-induced EC migration, tube formation, and proliferation. ∆21-161 EMCN failed to interact with VEGFR2 and did not facilitate VEGFR2 internalization. Deletion of COSMC (C1GalT1C1) revealed that the abundant mucin-type O-glycans were not required for its VEGFR2-related functions. Mutation of the two N-glycosylation sites on ∆21-121 EMCN abolished its interaction with VEGFR2 and its function in VEGFR2 internalization. These results reveal ∆21-121 EMCN as the minimal extracellular domain sufficient for VEGFR2-mediated endothelial function and demonstrate an important role for N-glycosylation in VEGFR2 interaction, internalization, and angiogenic activity.

Galectins and Ovarian Cancer

Ovarian cancer is known for its aggressive pathological features, including the capacity to undergo epithelial to mesenchymal transition, promoting angiogenesis, metastatic potential, chemoresistance, inhibiting apoptosis, immunosuppression and promoting stem-like features. Galectins, a family of glycan-binding proteins defined by a conserved carbohydrate recognition domain, can modulate many of these processes, enabling them to contribute to the pathology of ovarian cancer. Our goal herein was to review specific galectin members identified in the context of ovarian cancer, with emphasis on their association with clinical and pathological features, implied functions, diagnostic or prognostic potential and strategies being developed to disrupt their negative actions.

Modeling the Effects of O-Sulfonation on the CID of Serine

We present the results of direct dynamics simulations and DFT calculations aimed at elucidating the effect of O-sulfonation on the collision-induced dissociation for serine. Toward this end, direct dynamics simulations of both serine and sulfoserine were performed at multiple collision energies and theoretical mass spectra obtained. Comparisons to experimental results are favorable for both systems. Peaks related to the sulfo group are identified and the reaction dynamics explored. In particular, three significant peaks (m/z 106, 88, and 81) seen in the theoretical mass spectrum directly related to the sulfo group are analyzed as well as major peaks shared by both systems. Our analysis shows that the m/z 106 peaks result from intramolecular rearrangements, intermolecular proton transfer among complexes composed of initial fragmentation products, and at high energy side-chain fragmentation. The m/z 88 peak was found to contain multiple constitutional isomers, including a previously unconsidered, low energy structure. It was also observed that the RM1 semiempirical method was not able to obtain all of the major peaks seen in experimens for sulfoserine. In contrast, PM6 did obtain all major experimental peaks.

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

3D Extracellular Matrix Mimics: Fundamental Concepts and Role of Materials Chemistry to Influence Stem Cell Fate

Synthetic 3D extracellular matrices (ECMs) find application in cell studies, regenerative medicine, and drug discovery. While cells cultured in a monolayer may exhibit unnatural behavior and develop very different phenotypes and genotypes than in vivo, great efforts in materials chemistry have been devoted to reproducing in vitro behavior in in vivo cell microenvironments. This requires fine-tuning the biochemical and structural actors in synthetic ECMs. This review will present the fundamentals of the ECM, cover the chemical and structural features of the scaffolds used to generate ECM mimics, discuss the nature of the signaling biomolecules required and exploited to generate bioresponsive cell microenvironments able to induce a specific cell fate, and highlight the synthetic strategies involved in creating functional 3D ECM mimics.

The emerging role of galectins in (re)myelination and its potential for developing new approaches to treat multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating and neurodegenerative disease of the central nervous system with unknown etiology. Currently approved disease-modifying treatment modalities are immunomodulatory or immunosuppressive. While the applied drugs reduce the frequency and severity of the attacks, their efficacy to regenerate myelin membranes and to halt disease progression is limited. To achieve such therapeutic aims, understanding biological mechanisms of remyelination and identifying factors that interfere with remyelination in MS can give respective directions. Such a perspective is given by the emerging functional profile of galectins. They form a family of tissue lectins, which are potent effectors in processes as diverse as adhesion, apoptosis, immune mediator release or migration. This review focuses on endogenous and exogenous roles of galectins in glial cells such as oligodendrocytes, astrocytes and microglia in the context of de- and (re)myelination and its dysregulation in MS. Evidence is arising for a cooperation among family members so that timed expression and/or secretion of galectins-1, -3 and -4 result in modifying developmental myelination, (neuro)inflammatory processes, de- and remyelination. Dissecting the mechanisms that underlie the distinct activities of galectins and identifying galectins as target or tool to modulate remyelination have the potential to contribute to the development of novel therapeutic strategies for MS.

Serum Galectin-3 Levels in Children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with underlying pathogenesis and etiological factors not fully understood. We assumed that galectin-3, which is also linked with inflammatory responses, may play an important role in the ethiopathogenesis of ADHD. In this study, we aimed to investigate whether serum galectin-3 levels are related to ADHD in childhood.

METHODS

The current study consisted of 35 treatment-naive children with ADHD and 35 control subjects. The severities of ADHD and conduct disorder symptoms were assessed via parent- and teacher-rated questionnaires. The severity of anxiety and depression symptoms of the children were determined by the self-report scale. Venous blood samples were collected and serum galectin-3 levels were measured.

RESULTS

The ADHD group had significantly higher serum Galectin-3 levels than the control group. To control confounding factors, including age, sex, and BMI percentile, one-way analysis of covariance (ANCOVA) test was also performed. Analyses revealed a significantly higher serum log- Galectin-3 levels in children with ADHD compared to controls. No association was found between the mean serum galectin-3 levels and sociodemographic characteristics and clinical test scores, except the oppositional defiant behavior scores.

CONCLUSION

Our research supports the hypothesis that serum levels of galectin-3 might be related to ADHD.

Nglyc: A Random Forest Method for Prediction of N-Glycosylation Sites in Eukaryotic Protein Sequence

Background:

N-Glycosylation is one of the most important post-translational mechanisms in eukaryotes. N-glycosylation predominantly occurs in N-X-[S/T] sequon where X is any amino acid other than proline. However, not all N-X-[S/T] sequons in proteins are glycosylated. Therefore, accurate prediction of N-glycosylation sites is essential to understand Nglycosylation mechanism.

Objective:

In this article, our motivation is to develop a computational method to predict Nglycosylation sites in eukaryotic protein sequences.

Methods:

In this article, we report a random forest method, Nglyc, to predict N-glycosylation site from protein sequence, using 315 sequence features. The method was trained using a dataset of 600 N-glycosylation sites and 600 non-glycosylation sites and tested on the dataset containing 295 Nglycosylation sites and 253 non-glycosylation sites. Nglyc prediction was compared with NetNGlyc, EnsembleGly and GPP methods. Further, the performance of Nglyc was evaluated using human and mouse N-glycosylation sites.

Results:

Nglyc method achieved an overall training accuracy of 0.8033 with all 315 features. Performance comparison with NetNGlyc, EnsembleGly and GPP methods shows that Nglyc performs better than the other methods with high sensitivity and specificity rate.

Conclusion:

Our method achieved an overall accuracy of 0.8248 with 0.8305 sensitivity and 0.8182 specificity. Comparison study shows that our method performs better than the other methods. Applicability and success of our method was further evaluated using human and mouse N-glycosylation sites. Nglyc method is freely available at https://github.com/bioinformaticsML/ Ngly.

Potential Interaction between Galectin-2 and MUC5AC in Mouse Gastric Mucus

Galectins are a group of animal lectins characterized by their specificity for β-galactosides. Of these, galectin-2 (Gal-2) is predominantly expressed in the gastrointestinal tract. In the current study, we used a mouse gastric mucous fraction to investigate whether Gal-2 is secreted from epithelial cells and identify its potential ligands in gastric mucus. Gal-2 was detected in the mouse gastric mucous fraction and could be eluted from it by the addition of lactose. Affinity chromatography using recombinant mouse galectin-2 (mGal-2)-immobilized adsorbent and subsequent LC-MS/MS identified MUC5AC, one of the major gastric mucin glycoproteins, as a potential ligand of mGal-2. Furthermore, MUC5AC was detected in the mouse gastric mucous fraction by Western blotting, and recombinant mGal-2 was adsorbed to this fraction in a carbohydrate-dependent manner. These results suggested that Gal-2 and MUC5AC in mouse gastric mucus interact in a β-galactoside-dependent manner, resulting in a stronger barrier structure protecting the mucosal surface.

CDG and immune response: From bedside to bench and back

Glycosylation is an essential biological process that adds structural and functional diversity to cells and molecules, participating in physiological processes such as immunity. The immune response is driven and modulated by protein-attached glycans that mediate cell-cell interactions, pathogen recognition and cell activation. Therefore, abnormal glycosylation can be associated with deranged immune responses. Within human diseases presenting immunological defects are congenital disorders of glycosylation (CDG), a family of around 130 rare and complex genetic diseases. In this review, we have identified 23 CDG with immunological involvement, characterized by an increased propensity to-often life-threatening-infection. Inflammatory and autoimmune complications were found in 7 CDG types. CDG natural history(ies) and the mechanisms behind the immunological anomalies are still poorly understood. However, in some cases, alterations in pathogen recognition and intracellular signaling (eg, TGF-β1, NFAT, and NF-κB) have been suggested. Targeted therapies to restore immune defects are only available for PGM3-CDG and SLC35C1-CDG. Fostering research on glycoimmunology may elucidate the involved pathophysiological mechanisms and open new therapeutic avenues, thus improving CDG patients' quality of life.

Molecular, transcriptional and functional delineation of Galectin-8 from black rockfish (Sebastes schlegelii) and its potential immunological role

Galectins are β-galactoside-binding lectins, which are involved in pattern recognition, cell adhesion, and stimulation of the host innate immune responses against microbial pathogens. In spite of several functional studies on different galectins isolated from vertebrates and invertebrates, this is the first report to present functional studies for galectin-8 from the marine teleost tissues. In the present study, we characterized galectin-8 homolog from black rockfish (Sebastes schlegelii), in molecular and functional aspects. Rockfish galectin-8 (SsGal8) was found to consist of a 969 bp long open reading frame (ORF), encoding a protein of 322 amino acids and the predicted molecular weight was 35.82 kDa. In silico analysis of SsGal8 revealed the presence of two carbohydrate binding domains (CRDs), at both N and C-termini and a linker peptide of 40 amino acids, in between the two domains. As expected, the phylogenetic tree categorized SsGal8 as a tandem-repeat galectin, and ultimately positioned it in the sub-clade of fish galectin-8. rSsGal8 was able to strongly agglutinate fish erythrocytes and the inhibition of agglutination was successfully exhibited by lactose and d-galactose. Bacterial agglutination assay resulted in agglutination of both Gram (+) and Gram (-) bacteria, including Escherichia coli, Vibrio harveyi, Vibrio parahaemolyticus, Streptococcus parauberis, Lactococcus garvieae, Streptococcus iniae and Vibrio tapetis. The tissue distribution analysis based on qPCR assays, revealed a ubiquitous tissue expression of SsGal8 for the examined rockfish tissues, with the most pronounced expression in blood, followed by brain, intestine, head kidney and kidney. Furthermore, the mRNA transcription level of SsGal8 was significantly up-regulated in spleen, liver and head kidney, upon immune challenges with Streptococcus iniae, LPS and poly I:C, in a time dependent manner. Taken together, these findings strongly suggest the contribution of SsGal8 in regulating innate immune responses to protect the rockfish from bacterial infections.

N-acetylglucosaminyltransferase I promotes glioma cell proliferation and migration through increasing the stability of the glucose transporter GLUT1

Abnormal alteration of N-glycosylation structure contributes to glioma progression. N-acetylglucosaminyltransferase I (MGAT1) plays an essential role in the conversion of processed high-mannose cores into complex or hybrid N-linked oligosaccharide structures. The function of MGAT1 in glioma development remains largely unknown. Here, we found that the expression of MGAT1 is higher in glioblastoma compared to normal brain tissues. Inhibition of EGFR signalling pathway or serum starvation reduces MGAT1 expression. Knockdown of MGAT1 inhibits glioma cell proliferation and migration. Furthermore, MGAT1 promotes complex N-glycosylation of glucose transporter 1 (Glut1) and increases Glut1 protein levels. In summary, our findings indicate that MGAT1 is highly expressed in glioblastoma and promotes glioma cells at least partly through upregulation of Glut1 protein.

Emerging structural insights into glycosyltransferase-mediated synthesis of glycans

Glycans linked to proteins and lipids play key roles in biology; thus, accurate replication of cellular glycans is crucial for maintaining function following cell division. The fact that glycans are not copied from genomic templates suggests that fidelity is provided by the catalytic templates of glycosyltransferases that accurately add sugars to specific locations on growing oligosaccharides. To form new glycosidic bonds, glycosyltransferases bind acceptor substrates and orient a specific hydroxyl group, frequently one of many, for attack of the donor sugar anomeric carbon. Several recent crystal structures of glycosyltransferases with bound acceptor substrates reveal that these enzymes have common core structures that function as scaffolds upon which variable loops are inserted to confer substrate specificity and correctly orient the nucleophilic hydroxyl group. The varied approaches for acceptor binding site assembly suggest an ongoing evolution of these loop regions provides templates for assembly of the diverse glycan structures observed in biology.

Systematic and site-specific analysis of N-glycoproteins on the cell surface by integrating bioorthogonal chemistry and MS-based proteomics

Glycoproteins on the cell surface are essential for various cellular activities including cell-cell communication and cell-matrix interaction. Alterations of glycosylation are correlated with many diseases such as cancer and infectious diseases. However, it is greatly challenging to systematically and site-specially analyze glycoproteins only located on cell surface because of the heterogeneity of glycans, the low abundance of many surface glycoproteins and the requirement of effective methods to separate surface glycoproteins. In this chapter, we briefly review existing mass spectrometry (MS)-based methods for global analysis of surface glycoproteins. Then we discuss an effective method integrating metabolic labeling, click and enzymatic reactions, and MS-based proteomics to comprehensively and site-specifically investigate cell surface N-glycoproteins. A detailed protocol for this method is also included. In combination with quantitative proteomics, we applied this method to quantify cell surface N-glycoproteins and study the relationship between cell invasiveness and N-sialoglycoproteins on the cell surface. Considering the importance of surface glycoproteins, this method can be extensively applied to advance glycoscience, which leads to a better understanding of the molecular mechanisms of human diseases, and the discovery of surface glycoproteins as biomarkers for disease detection.

How altering the modular architecture affects aspects of lectin activity: case study on human galectin-1

Discoveries on involvement of glycan-protein recognition in many (patho)physiological processes are directing attention to exploring the significance of a fundamental structural aspect of sugar receptors beyond glycan specificity, i.e., occurrence of distinct types of modular architecture. In order to trace clues for defining design-functionality relationships in human lectins, a lectin's structural unit has been used as source material for engineering custom-made variants of the wild-type protein. Their availability facilitates comparative analysis toward the stated aim. With adhesion/growth-regulatory human galectin-1 as example, the strategy of evaluating how changes of its design (here, from the homodimer of non-covalently associated domains to (i) linker-connected di- and tetramers and (ii) a galectin-3-like protein) affect activity is illustrated by using three assay systems of increasing degree of glycan complexity. Whereas calorimetry with two cognate disaccharides and array testing with 647 (glyco)compounds disclosed no major changes, galectin histochemical staining profiles of tissue sections that present natural glycome complexity revealed differences between wild-type and linker-connected homo-oligomers as well as between the galectin-3-like variant and wild-type galectin-3 for cell-type positivity, level of intensity at the same site and susceptibility for inhibition by a bivalent glycocompound. These results underscore the strength of the documented approach. Moreover, they give direction to proceed to (i) extending its application to other members of this lectin family, especially galectin-3 and (ii) then analyzing impact of architectural alterations on cell surface lattice formation and ensuing biosignaling systematically, considering the variants' potential for translational medicine.

Roles for Golgi Glycans in Oogenesis and Spermatogenesis

Glycosylation of proteins by N- and O-glycans or glycosaminoglycans (GAGs) mostly begins in the endoplasmic reticulum and is further orchestrated in the Golgi compartment via the action of >100 glycosyltransferases that reside in this complex organelle. The synthesis of glycolipids occurs in the Golgi, also by resident glycosyltransferases. A defect in the glycosylation machinery may impair the functions of glycoproteins and other glycosylated molecules, and lead to a congenital disorder of glycosylation (CDG). Spermatogenesis in the male and oogenesis in the female are tightly regulated differentiation events leading to the production of functional gametes. Insights into roles for glycans in gamete production have been obtained from mutant mice following deletion or inactivation of genes that encode a glycosylation activity. In this review, we will summarize the effects of altering the synthesis of N-glycans, O-glycans, proteoglycans, glycophosphatidylinositol (GPI) anchored proteins, and glycolipids during gametogenesis in the mouse. Glycosylation genes whose deletion causes embryonic lethality have been investigated following conditional deletion using various Cre recombinase transgenes with a cell-type specific promoter. The potential effects of mutations in corresponding glycosylation genes of humans will be discussed in relation to consequences to fertility and potential for use in contraception.

Selective inhibition of N-linked glycosylation impairs receptor tyrosine kinase processing

Global inhibition of N-linked glycosylation broadly reduces glycan occupancy on glycoproteins, but identifying how this inhibition functionally impacts specific glycoproteins is challenging. This limits our understanding of pathogenesis in the congenital disorders of glycosylation (CDG). We used selective exo-enzymatic labeling of cells deficient in the two catalytic subunits of oligosaccharyltransferase - STT3A and STT3B - to monitor the presence and glycosylation status of cell surface glycoproteins. We show reduced abundance of two canonical tyrosine receptor kinases - the insulin receptor and insulin-like growth factor 1 receptor (IGF-1R) - at the cell surface in STT3A-null cells, due to decreased N-linked glycan site occupancy and proteolytic processing in combination with increased endoplasmic reticulum localization. Providing cDNA for Golgi-resident proprotein convertase subtilisin/kexin type 5a (PCSK5a) and furin cDNA to wild-type and mutant cells produced under-glycosylated forms of PCSK5a, but not furin, in cells lacking STT3A. Reduced glycosylation of PCSK5a in STT3A-null cells or cells treated with the oligosaccharyltransferase inhibitor NGI-1 corresponded with failure to rescue receptor processing, implying that alterations in the glycosylation of this convertase have functional consequences. Collectively, our findings show that STT3A-dependent inhibition of N-linked glycosylation on receptor tyrosine kinases and their convertases combines to impair receptor processing and surface localization. These results provide new insight into CDG pathogenesis and highlight how the surface abundance of some glycoproteins can be dually impacted by abnormal glycosylation.

Global Proteomic Response of Caenorhabditis elegans Against PemKSa Toxin

Bacterial exotoxins are major causative agents that infect by promoting cell and tissue damages through disabling the invading host immune system. However, the mode of action by which toxins modulate host immune system and lead cell death is still not completely understood. The nematode, Caenorhabditis elegans has been used as an attractive model host for toxicological studies. In this regard, the present study was undertaken to assess the impact of Staphylococcus aureus toxin (PemK) on the host C. elegans through global proteomics approach. Our proteomic data obtained through LC-MS/MS, subsequent bioinformatics and biochemical analyses revealed that in response to PemKSa a total of 601 proteins of C. elegans were differentially regulated in response to PemKSa. The identified proteins were found to mainly participate in ATP generation, protein synthesis, lipid synthesis, cytoskeleton, heat shock proteins, innate immune defense, stress response, neuron degeneration, and muscle assembly. Current findings suggested that involvement of several regulatory proteins that appear to play a role in various molecular functions in combating PemKSa toxin-mediated microbial pathogenicity and/or host C. elegans immunity modulation. The results provided a preliminary view of the physiological and molecular response of a host toward a toxin and provided insight into highly complex host-toxin interactions.

The role of galectin-3 in modulation of anxiety state level in mice

Galectin-3 (Gal-3), a member of lectin family that binds to oligosaccharides, is involved in several biological processes, including maturation and function of nervous system. It had been reported that Gal-3 regulates oligodendrocytes differentiation and that Gal-3/Toll-like receptor-4 (TLR4) axis is involved in neuroinflammation. As both, central nervous system (CNS) maturation and neuroinflammation may affect behavior, the principle aim of this study was to examine the effects of Gal-3 gene deletion on behavior. Here we provide the evidence that Gal-3 deficiency shows clear anxiogenic effect in mature untreated animals (basal conditions). This was accompanied with lower interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) relative gene expression and hippocampal content, with no effect on TLR4 expression. Gal-3 deficiency was also accompanied with lower brain-derived neurotrophic factor (BDNF) relative gene expression and immunoreactivity in hippocampus (predominantly in CA1 region). Besides, the Gal-3 gene deletion resulted in attenuation of the hippocampal relative gene expression of GABA-A receptor subunits 2 and 5 (GABA-AR2S and GABA-AR5S), On the other hand, Gal-3 deficiency attenuates LPS-induced neuroinflammation. The anxiogenic effect of acute neuroinflammation was accompanied with increased hippocampal IL-6, TNF-α and TLR4 gene expression, as well as decreased gene and immunohistochemical BDNF expression in hippocampus, with significant decline in GABA-AR2S in wild type (WT) mice in comparison to basal conditions. Gal-3 gene deletion prevented the increase in IL-6, the decline in BDNF gene expression and immunoreactivity, and reduction in hippocampal GABA-AR2S, and therefore attenuated the anxiogenic effect of neuroinflammation. In summary, our data demonstrate that apparently opposite effects of Gal-3 deficiency on anxiety levels (anxiogenic effect under basal conditions and anxiolytic action during neuroinflammation) seem to be related to the shift in IL-6, TNF-α and hippocampal BDNF.

Polymer Nanoplatforms at Work in Prostate Cancer Therapy

Prostate cancer (PCa) is the most common male urogenital malignancy worldwide. Surgery, endocrine therapy, radiotherapy, and chemotherapy are the main clinical management options for PCa. However, these three therapies each have limitations. For example, surgery is not suitable for the advanced PCa patients with extensive metastases, and radiotherapy causes serious side effects. Primary endocrine therapy promotes the progression of hormone‐sensitive PCa into the castration‐resistant prostate cancer. Therefore, considering these drawbacks, chemotherapy has become an effective and extensive treatment for PCa. Among the modern therapeutic strategies against advanced PCa, polymer‐nanocarrier‐incorporated formulations have gradually emerged due to their well‐controlled release profiles and improved tumor targeting abilities. The drug delivery systems based on polymer nanoplatforms passively target tumors via the enhanced permeability and retention effect. Simultaneously, stimuli‐responsive polymer nanoplatforms unload cargoes in response to certain stimuli in the tumor area. Furthermore, the active targeting ligand‐conjugated polymer nanoformulations against PCa‐specific markers have also achieved great success in PCa therapies. Herein, the advanced polymer nanoplatforms for PCa therapy are reviewed, while the future development of polymer nanoplatforms for PCa therapy is also predicted.

Enzymatic Tagging of Glycoproteins on the Cell Surface for Their Global and Site-Specific Analysis with Mass Spectrometry

The cell surface is normally covered with sugars that are bound to lipids or proteins. Surface glycoproteins play critically important roles in many cellular events, including cell-cell communications, cell-matrix interactions, and response to environmental cues. Aberrant protein glycosylation on the cell surface is often a hallmark of human diseases such as cancer and infectious diseases. Global analysis of surface glycoproteins will result in a better understanding of glycoprotein functions and the molecular mechanisms of diseases and the discovery of surface glycoproteins as biomarkers and drug targets. Here, an enzyme is exploited to tag surface glycoproteins, generating a chemical handle for their selective enrichment prior to mass spectrometric (MS) analysis. The enzymatic reaction is very efficient, and the reaction conditions are mild, which are well-suited for surface glycoprotein tagging. For biologically triplicate experiments, on average 953 N-glycosylation sites on 393 surface glycoproteins per experiment were identified in MCF7 cells. Integrating chemical and enzymatic reactions with MS-based proteomics, the current method is highly effective to globally and site-specifically analyze glycoproteins only located on the cell surface. Considering the importance of surface glycoproteins, this method is expected to have extensive applications to advance glycoscience.

Human trophoblast requires galectin-3 for cell migration and invasion

Invasive extravillous cytotrophoblast of the human placenta expresses galectins-1, -3, and -8 in vivo and in vitro. This study aimed to investigate the potential role of galectin-3 in cell migration and invasion, using recombinant human galectin-3 (rhgalectin-3), small molecule galectin inhibitor I₄₇, and galectin-3 silencing. HTR-8/SVneo cell migration was stimulated by rhgalectin-3 and reduced by I₄₇, which could be neutralised by rhgalectin-3. Inhibitor specificity and selectivity for the galectins expressed in extravillous trophoblast were validated in solid phase assays using recombinant galectin-1, -3, -8, confirming selectivity for galectin-3. HTR-8/SVneo cell migration and invasion, and invasion by isolated trophoblast cells in primary culture were significantly reduced in the presence of I_47, which could be restored by rhgalectin-3. Upon HTR-8/SVneo cell treatment with galectin-3 siRNA both LGALS3 and galectin-3 protein were dramatically decreased. Silencing of galectin-3 induced significant reduction in cell migration and invasion, which was restored by rhgalectin-3. The influence on known mediators of cell invasion, MMP2 and -9, and integrins α₁, α₅, and β₁ was followed in silenced cells, showing lower levels of MMPs and a large reduction in integrin subunit β₁. These results show that galectin-3 acts as a pro-invasive autocrine/paracrine factor in trophoblast in vitro.

Modification of the glycosylation of extracellular vesicles alters their biodistribution in mice

Extracellular vesicles (EVs) are considered sophisticated vehicles for cell-to-cell communication, thanks to the possibility of handling a variable cargo in a shell with multiple types of decoders. Surface glycosylation of EVs is a method that could be used to control their interaction with different cells and, consequently, the biodistribution of the vesicles in the body. Herein, we produced EVs derived from mouse liver proliferative cells, and we treated them with neuraminidase, an enzyme that digests the terminal sialic acid residues from glycoproteins. Afterwards, we labeled the EVs directly with [124I]Na and injected them in mice intravenously or into the hock. The amount of radioactivity in major organs was measured at different time points after administration both in vivo using positron emission tomography and ex vivo (after animal sacrifice) using dissection and gamma counting. The results showed that intravenous injection leads to the rapid accumulation of EVs in the liver. Moreover, after some hours the distribution led to the presence of EVs in different organs including the brain. Glycosidase treatment induced an accumulation in the lungs, compared with the intact EVs. Furthermore, when the EVs were injected through the hock, the neuraminidase-treated vesicles distributed better at the axillary lymph nodes than the untreated EVs. This result shows that modification of the glycosylated complexes on the EV surface can affect the distribution of these vesicles, and specifically removing the sialic acid residues allows more EVs to reach and accumulate at the lungs.

Alternative splicing of Ikaros regulates the FUT4/LeX-α5β1 integrin-FAK axis in acute lymphoblastic leukemia

Unveiling the mechanism of the relapse of acute lymphoblastic leukemia (ALL) is the key to improve the prognosis of ALL and remains a huge challenge. Glycan-based interactions play a vital role in immune surveillance, cell-cell adhesion and cell-matrix interaction, contributing to treatment failure in tumor. However, the glycan essential for leukemia development and its upstream regulatory mechanism by oncogenic drivers were rarely reported. Here, we demonstrated that Le^X, a well-characterized cancer-related glycan epitope, strengthened the cell-matrix interaction via glycosylating α5β1 integrin under the control of the driver oncogenic Ikaros isoform (IK6) in ALL. By analyzing the expression profile of Ikaros and the level of FUT4/Le^X in clinical samples, we found that FUT4/Le^X was positively correlated with dysfunctional Ikaros isoforms. IK1 (Full length Ikaros) regulates the level of FUT4 as a transcription repressor, while IK6 abolished the wild-type Ikaros mediated transcriptional repression and resulted in higher level of FUT4 expression. Moreover, we demonstrated that FUT4 could activate α5β1-mediated sequential signal transduction and accelerate adhesion and invasion between integrin α5β1 in leukemia cells and fibronectin in extracellular matrix (ECM) via increasing glycosylation. Together, our study provides a new insight into the mechanisms by which Ikaros mutation induced ALL cells invasion and a potential strategy for drug-resistance ALL by blocking Le^X in combination with common chemotherapy.

Deficiency of the mitochondrial sulfide regulator ETHE1 disturbs cell growth, glutathione level and causes proteome alterations outside mitochondria

The mitochondrial enzyme ETHE1 is a persulfide dioxygenase essential for cellular sulfide detoxification, and its deficiency causes the severe and complex inherited metabolic disorder ethylmalonic encephalopathy (EE). In spite of well-described clinical symptoms of the disease, detailed cellular and molecular characterization is still ambiguous. Cellular redox regulation has been described to be influenced in ETHE1 deficient cells, and to clarify this further we applied image cytometry and detected decreased levels of reduced glutathione (GSH) in cultivated EE patient fibroblast cells. Cell growth initiation of the EE patient cells was impaired, whereas cell cycle regulation was not. Furthermore, Seahorse metabolic analyzes revealed decreased extracellular acidification, i. e. decreased lactate formation from glycolysis, in the EE patient cells. TMT-based large-scale proteomics was subsequently performed to broadly elucidate cellular consequences of the ETHE1 deficiency. More than 130 proteins were differentially regulated, of which the majority were non-mitochondrial. The proteomics data revealed a link between ETHE1-deficiency and down-regulation of several ribosomal proteins and LIM domain proteins important for cellular maintenance, and up-regulation of cell surface glycoproteins. Furthermore, several proteins of endoplasmic reticulum (ER) were perturbed including proteins influencing disulfide bond formation (e.g. protein disulfide isomerases and peroxiredoxin 4) and calcium-regulated proteins. The results indicate that decreased level of reduced GSH and alterations in proteins of ribosomes, ER and of cell adhesion lie behind the disrupted cell growth of the EE patient cells.

LGALS3 Promotes Treatment Resistance in Glioblastoma and Is Associated with Tumor Risk and Prognosis

BACKGROUND

LGALS3 promotes tumor progression in diverse cancers. However, the involvement of LGALS3 in glioblastoma has not yet been broadly illuminated.

METHODS

Microarray was performed to detect the gene expression profiles of radioresistance in T98G cells and identified a universally upregulated gene, LGALS3. The impact of LGALS3 on the survival of glioblastoma cells facing ionizing irradiation or temozolomide was investigated by the Cell Counting Kit-8 (CCK-8). A total of 120 glioblastoma cases were collected to analyze the relationship between LGALS3 expression and patient prognosis. Another 961 patients with glioma and 1,351 healthy controls were recruited to study the association of SNPs across the LGALS3 gene with glioblastoma susceptibility. The functional SNP sites were also studied in cellular experiments.

RESULTS

An effective protection of LGALS3 from ionizing irradiation or temozolomide-induced cell death in T98G and U251 cells was found. In addition, high expression of LGALS3 could work as an independent risk factor for survival of patients with glioblastoma. Two SNP sites (rs4644 and rs4652) across the LGALS3 gene were associated with increased risk for glioblastoma, and the C allele of rs4652 and the A allele of rs4644 could enhance glioblastoma resistance to radio-chemotherapy, but not cell proliferation.

CONCLUSIONS

Our results suggest that LGALS3 is an important biomarker influencing glioblastoma risk and prognosis and a potential target for treating the malignancy, especially ones with resistance against the standard therapy.

IMPACT

LGALS3 promotes glioblastoma cells' resistance to ionizing irradiation and temozolomide and predicts poor prognosis. Targeting LGALS3 may limit the therapeutic resistance in glioblastoma and increase patient survival.