At cell surface microdomains, glycosyl epitopes, carried either by glycosphingolipids, N-or O-linked oligosaccharides, are recognized by carbohydrate-binding proteins or complementary carbohydrates. In both cases, the carbohydrate epitopes may be clustered with specific signal transducers, tetraspanins, adhesion receptors or growth factor receptors. Through this framework, carbohydrates can mediate cell signaling leading to changes in cellular phenotype. Microdomains involved in carbohydrate-dependent cell adhesion inducing cell activation, motility, and growth are termed "glycosynapse". In this review a historical synopsis of glycosphingolipids-enriched microdomains study leading to the concept of glycosynapse is presented. Examples of glycosynapse as signaling unit controlling the tumor cell phenotype are discussed in three contexts:(i) Cell-to-cell adhesion mediated by glycosphingolipids-to-glycosphingolipids interaction between interfacing glycosynaptic domains, through head-to-head (trans) carbohydrate-to-carbohydrate interaction.(ii) Functional role of GM3 complexed with tetraspanin CD9, and interaction of such complex with integrins, or with fibroblast growth factor receptor, to control tumor cell phenotype and its reversion to normal cell phenotype.(iii) Inhibition of integrin-dependent Met kinase activity by GM2/tetraspanin CD82 complex in glycosynaptic microdomain.Data present here suggest that the organizational status of glycosynapse strongly affects cellular phenotype influencing tumor cell malignancy.

The novel coronavirus SARS-CoV-2 causes COVID-19, a highly pathogenic viral infection threatening millions. The majority of the individuals infected are asymptomatic or mildly symptomatic showing typical clinical signs of common cold. However, approximately 20% of the patients can progress to acute respiratory distress syndrome (ARDS), evolving to death in about 5% of cases. Recently, angiotensin-converting enzyme 2 (ACE2) has been shown to be a functional receptor for virus entry into host target cells. The upregulation of ACE2 in patients with comorbidities may represent a propensity for increased viral load and spreading of infection to extrapulmonary tissues. This systemic infection is associated with higher neutrophil to lymphocyte ratio in infected tissues and high levels of pro-inflammatory cytokines leading to an extensive microthrombus formation with multiorgan failure. Herein we investigated whether SARS-CoV-2 can stimulate extracellular neutrophils traps (NETs) in a process called NETosis. We demonstrated for the first time that SARS-CoV-2 in fact is able to activate NETosis in human neutrophils. Our findings indicated that this process is associated with increased levels of intracellular Reactive Oxygen Species (ROS) in neutrophils. The ROS-NET pathway plays a role in thrombosis formation and our study suggest the importance of this target for therapy approaches against disease.

Glycosphingolipids (GSLs) at the cell surface membrane are associated or complexed with signal transducers (Src family kinases and small G-proteins), tetraspanins, growth factor receptors, and integrins. Such organizational framework, defining GSL-modulated or -dependent cell adhesion, motility, and growth, is termed "glycosynapse" (Hakomori, S., and Handa, K.

Cancer cells depend on altered metabolism and nutrient uptake to generate and keep the malignant phenotype. The hexosamine biosynthetic pathway is a branch of glucose metabolism that produces UDP-GlcNAc and its derivatives, UDP-GalNAc and CMP-Neu5Ac and donor substrates used in the production of glycoproteins and glycolipids. Growing evidence demonstrates that alteration of the pool of activated substrates might lead to different glycosylation and cell signaling. It is already well established that aberrant glycosylation can modulate tumor growth and malignant transformation in different cancer types. Therefore, biosynthetic machinery involved in the assembly of aberrant glycans are becoming prominent targets for anti-tumor drugs. This review describes three classes of glycosylation, O-GlcNAcylation, N-linked, and mucin type O-linked glycosylation, involved in tumor progression, their biosynthesis and highlights the available inhibitors as potential anti-tumor drugs.

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Deregulated cellular metabolism is a hallmark of tumors. Cancer cells increase glucose and glutamine flux to provide energy needs and macromolecular synthesis demands. Several studies have been focused on the importance of glycolysis and pentose phosphate pathway. However, a neglected but very important branch of glucose metabolism is the hexosamine biosynthesis pathway (HBP). The HBP is a branch of the glucose metabolic pathway that consumes ϳ2-5% of the total glucose, generating UDP-GlcNAc as the end product. UDP-GlcNAc is the donor substrate used in multiple glycosylation reactions. Thus, HBP links the altered metabolism with aberrant glycosylation providing a mechanism for cancer cells to sense and respond to microenvironment changes. Here, we investigate the changes of glucose metabolism during epithelial mesenchymal transition (EMT) and the role of O-GlcNAcylation in this process. We show that A549 cells increase glucose uptake during EMT, but instead of increasing the glycolysis and pentose phosphate pathway, the glucose is shunted through the HBP. The activation of HBP induces an aberrant cell surface glycosylation and O-GlcNAcylation. The cell surface glycans display an increase of sialylation ␣2-6, poly-LacNAc, and fucosylation, all known epitopes found in different tumor models. In addition, modulation of O-GlcNAc levels was demonstrated to be important during the EMT process. Taken together, our results indicate that EMT is an applicable model to study metabolic and glycophenotype changes during carcinogenesis, suggesting that cell glycosylation senses metabolic changes and modulates cell plasticity.Altered metabolism represents the first known difference between cancer cells and normal cells (1). The Warburg effect consists of an increase of glucose uptake for producing energy by a high rate of glycolysis followed by lactic acid fermentation even under high oxygen tension ("aerobic glycolysis"). Understanding the metabolism of tumors remains a topic of intense study with important therapeutic potential (2, 3). Several advances in cancer metabolism research over past years have enhanced our understanding of how aerobic glycolysis and other metabolic shifts support the anabolic demands of high growth rate (4). Traditionally, the study of glucose metabolism usually focused on the use of glucose for energy needs. However, cancer cells use glucose in anabolic pathways that provide precursors for the synthesis of lipids, proteins, glycans, and DNA to satisfy the demands of growth and proliferation. Several studies have been focused on the importance of the pentose phosphate pathway (PPP), 3 to generate NADPH that ensures the antioxidant defenses of the cell and to generate the nucleotides in high demand or the use of intermediates of the glycolytic pathway to generate molecules such as lipids or amino acids (5). However, a neglected but integral branch of glucose metabolism is the hexosamine biosynthesis pathway (HBP).Approximately 2-5% of glucose influx is directed to the HBP by the rate-limiting enzyme ...

Hyperglycemia is a common feature of diabetes mellitus, considered as a risk factor for cancer. However, its direct effects in cancer cell behavior are relatively unexplored. Herein we show that high glucose concentration induces aberrant glycosylation, increased cell proliferation, invasion and tumor progression of colon cancer. By modulating the activity of the rate-limiting enzyme, glutamine-fructose-6-phosphate amidotransferase (GFAT), we demonstrate that hexosamine biosynthetic pathway (HBP) is involved in those processes. Biopsies from patients with colon carcinoma show increased levels of GFAT and consequently aberrant glycans’ expression suggesting an increase of HBP flow in human colon cancer. All together, our results open the possibility that HBP links hyperglycemia, aberrant glycosylation and tumor malignancy, and suggest this pathway as a potential therapeutic target for colorectal cancer.

Ganglioside GM2 complexed with tetraspanin CD82 in glycosynaptic microdomain of HCV29 and other epithelial cells inhibits hepatocyte growth factor-induced cMet tyrosine kinase. In addition, adhesion of HCV29 cells to extracellular matrix proteins also activates cMet kinase through ''cross-talk '' of integrins with cMet, leading to inhibition of cell motility and growth. Present studies indicate that cell motility and growth are greatly influenced by expression of GM2, GM3, or GM2/GM3 complexes, which affect cMet kinase activity of various types of cells, based on the following series of observations: (i) Cells expressing CD82, cultured with GM2 and GM3 cocoated on silica nanospheres, displayed stronger and more consistent motility inhibition than those cultured with GM2 or GM3 alone or with other glycosphingolipids. (ii) GM2-GM3, in the presence of Ca 2؉ form a heterodimer, as evidenced by electrospray ionization (ESI) mass spectrometry and by specific reactivity with mAb 8E11, directed to GM2/GM3 dimer structure. (iii) Cells expressing cMet and CD82 were characterized by enhanced motility associated with HGF-induced cMet activation. Both cMet and motility were strongly inhibited by culturing cells with GM2/GM3 dimer coated on nanospheres. (iv) Adhesion of HCV29 or YTS-1/CD82 cells to laminin-5-coated plate activated cMet kinase in the absence of HGF, whereas GM2/GM3 dimer inhibited adhesioninduced cMet kinase activity and inhibited cell motility. (v) Inhibited cell motility as in i, iii, and iv was restored to normal level by addition of mAb 8E11, which blocks interaction of GM2/GM3 dimer with CD82. Signaling through Src and MAP kinases is activated or inhibited in close association with cMet kinase, in response to GM2/GM3 dimer interaction with CD82. Thus, a previously uncharacterized GM2/GM3 heterodimer complexed with CD82 inhibits cell motility through CD82-cMet or integrin-cMet pathway.glycosphingolipid ͉ growth factor receptor ͉ ldlD cells ͉ tyrosine kinase G lycosphingolipids (GSLs), including gangliosides, interact with specific membrane proteins, such as growth factor receptors, integrins, tetraspanins (TSPs), and nonreceptor cytoplasmic kinases (e.g., Src family kinases and small G proteins), to form glycosynaptic microdomains controlling GSL-dependent or -modulated cell adhesion, growth, and motility (for review, see refs. 1-3).Our previous studies indicate the following: (i) Ganglioside the GM3/TSP CD9 complex interacts with integrin ␣3␤1 or ␣5␤1 and inhibits motility of CD9-expressing tumor cells (4, 5). (ii) The GM3/CD9/CD81 complex inhibits tyrosine kinase associated with fibroblast growth factor receptor (FGFR) (6) and blocks functional interaction of integrins with FGFR (7). (iii) Enhancement of GM3 or CD9 level in bladder cancer cell line YTS-1 causes reversion to normal phenotype, whereby Src kinase activity is strongly inhibited (8).In contrast to these previous studies, focused on GM3-CD9 interaction that inhibits tumor cell motility, our recent studies (9) addressed the functional role of t...