ABSTRACT
Galectins are soluble glycan-binding proteins that interact with a wide range of glycoproteins and glycolipids and modulate a broad spectrum of physiological and pathological processes. The expression and subcellular localization of different galectins vary among tissues and cell types and change during processes of tissue repair, fibrosis and cancer where epithelial cells loss differentiation while acquiring migratory mesenchymal phenotypes. The epithelial-mesenchymal transition (EMT) that occurs in the context of these processes can include modifications of glycosylation patterns of glycolipids and glycoproteins affecting their interactions with galectins. Moreover, overexpression of certain galectins has been involved in the development and different outcomes of EMT. This review focuses on the roles and mechanisms of Galectin-1 (Gal-1), Gal-3, Gal-4, Gal-7 and Gal-8, which have been involved in physiologic and pathogenic EMT contexts.
Subject(s)
Galectins , Neoplasms , Humans , Galectins/genetics , Galectins/metabolism , Fibrosis , Glycoproteins , Epithelial-Mesenchymal Transition , GlycolipidsABSTRACT
Galectins, which correspond to a group of proteins capable of recognizing and reversibly binding to ß-galactoside carbohydrates, have been the subject of innovation and development of technological products. Galectins play biological roles, such as cell proliferation and apoptosis, and some studies showed differences in the concentrations of galectins dispersed in serum of patients with cancer. For this reason, different studies have evaluated the biotechnological potential of these proteins as biomarkers for the prognosis and/or diagnosis of physiological disorders. Thus, this review discusses recent technological advancements in targeting galectins for the treatment of cancer and using galectins for cancer prognosis and diagnosis. Data mining was performed using the search descriptors "Galectin 9* and cancer*" and the ESPACENET and Cortellis Drug Discovery Intelligence (CDDI) databases. PRISMA guidelines were followed as a basis for literature review which aimed to conduct a systematic study of galectin-9 patents related to cancer prognosis, diagnosis and treatment. Results showed the importance of galectin-9 protein patents in furthering biomedical advancements in the global fight against cancer.
Subject(s)
Galectins , Neoplasms , Humans , Galectins/metabolism , Neoplasms/diagnosis , Neoplasms/drug therapy , CarbohydratesABSTRACT
Galectins, a family of evolutionarily conserved glycan-binding proteins, play key roles in diverse biological processes including tissue repair, adipogenesis, immune cell homeostasis, angiogenesis, and pathogen recognition. Dysregulation of galectins and their ligands has been observed in a wide range of pathologic conditions including cancer, autoimmune inflammation, infection, fibrosis, and metabolic disorders. Through protein-glycan or protein-protein interactions, these endogenous lectins can shape the initiation, perpetuation, and resolution of these processes, suggesting their potential roles in disease monitoring and treatment. However, despite considerable progress, a full understanding of the biology and therapeutic potential of galectins has not been reached due to their diversity, multiplicity of cell targets, and receptor promiscuity. In this article, we discuss the multiple galectin-binding partners present in different cell types, focusing on their contributions to selected physiologic and pathologic settings. Understanding the molecular bases of galectin-ligand interactions, particularly their glycan-dependency, the biochemical nature of selected receptors, and underlying signaling events, might contribute to designing rational therapeutic strategies to control a broad range of pathologic conditions.
Subject(s)
Galectins , Neoplasms , Humans , Galectins/metabolism , Polysaccharides/metabolism , Signal Transduction , Inflammation , LigandsABSTRACT
Galectins are a family of endogenous glycan-binding proteins that have crucial roles in a broad range of physiological and pathological processes. As a group, these proteins use both extracellular and intracellular mechanisms as well as glycan-dependent and independent pathways to reprogramme the fate and function of numerous cell types. Given their multifunctional roles in both tissue fibrosis and cancer, galectins have been identified as potential therapeutic targets for these disorders. Here, we focus on the therapeutic relevance of galectins, particularly galectin 1 (GAL1), GAL3 and GAL9 to tumour progression and fibrotic diseases. We consider an array of galectin-targeted strategies, including small-molecule carbohydrate inhibitors, natural polysaccharides and their derivatives, peptides, peptidomimetics and biological agents (notably, neutralizing monoclonal antibodies and truncated galectins) and discuss their mechanisms of action, selectivity and therapeutic potential in preclinical models of fibrosis and cancer. We also review the results of clinical trials that aim to evaluate the efficacy of galectin inhibitors in patients with idiopathic pulmonary fibrosis, nonalcoholic steatohepatitis and cancer. The rapid pace of glycobiology research, combined with the acute need for drugs to alleviate fibrotic inflammation and overcome resistance to anticancer therapies, will accelerate the translation of anti-galectin therapeutics into clinical practice.
Subject(s)
Galectins , Neoplasms , Humans , Galectins/metabolism , Neoplasms/drug therapy , Antibodies, Monoclonal , Polysaccharides/metabolism , FibrosisABSTRACT
Galectins are a family of proteins with an affinity for ß-galactosides that have roles in neuroprotection and neuroinflammation. Several studies indicate that patients with neurodegenerative diseases have alterations in the concentration of galectins in their blood and brain. However, the results of the studies are contradictory; hence, a meta-analysis is performed to clarify whether patients with neurodegenerative diseases have elevated galectin levels compared to healthy individuals. Related publications are obtained from the databases: PubMed, Central-Conchrane, Web of Science database, OVID-EMBASE, Scope, and EBSCO host until February 2022. A pooled standard mean difference (SMD) with a 95% confidence interval (CI) is calculated by fixed-effect or random-effect model analysis. In total, 17 articles are included in the meta-analysis with a total of 905 patients. Patients with neurodegenerative diseases present a higher level of galectin expression compared to healthy individuals (MDS = 0.70, 95% CI 0.28-1.13, p = 0.001). In the subgroup analysis by galectin type, a higher galectin-3 expression is observed in patients with neurodegenerative diseases. Patients with Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALD), and Parkinson's disease (PD) expressed higher levels of galectin-3. Patients with multiple sclerosis (MS) have higher levels of galectin-9. In conclusion, our meta-analysis shows that patients with neurovegetative diseases have higher galectin levels compared to healthy individuals. Galectin levels are associated with the type of disease, sample, detection technique, and region of origin of the patients.
Subject(s)
Alzheimer Disease , Amyotrophic Lateral Sclerosis , Neurodegenerative Diseases , Galectin 3 , Galectins/metabolism , HumansABSTRACT
Neurodegeneration is a pathological condition that is associated with the loss of neuronal function and structure. In neurodegenerative diseases, mounting evidence indicates that neuroinflammation is a common factor that contributes to neuronal damage and neurodegeneration. Neuroinflammation is characterized by the activation of microglia, the neuroimmune cells of the central nervous system (CNS), which have been implicated as active contributors to neuronal damage. Glycan structure modification is defining the outcome of neuroinflammation and neuronal regeneration; moreover, the expression of galectins, a group of lectins that specifically recognize ß-galactosides, has been proposed as a key factor in neuronal regeneration and modulation of the inflammatory response. Of the different galectins identified, galectin-1 stimulates the secretion of neurotrophic factors in astrocytes and promotes neuronal regeneration, whereas galectin-3 induces the proliferation of microglial cells and modulates cell apoptosis. Galectin-8 emerged as a neuroprotective factor, which, in addition to its immunosuppressive function, could generate a neuroprotective environment in the brain. This review describes the role of galectins in the activation and modulation of astrocytes and microglia and their anti- and proinflammatory functions within the context of neuroinflammation. Furthermore, it discusses the potential use of galectins as a therapeutic target for the inflammatory response and remodeling in damaged tissues in the central nervous system.
Subject(s)
Neurodegenerative Diseases , Astrocytes/metabolism , Astrocytes/pathology , Galectins/metabolism , Humans , Microglia/metabolism , Microglia/pathology , Neurodegenerative Diseases/pathology , Neuroinflammatory DiseasesABSTRACT
Reactive oxygen species (ROS) have been extensively studied in biology in the past years. This class of molecules can be derived from endogenous sources (e.g., phagocytic cells as neutrophils, eosinophils, monocytes, macrophages, and organelles as mitochondria and peroxisomes) and participate in physiological and pathological conditions. The beneficial and harmful effects of ROS depend on redox regulation, which establishes the balance between their production and the activity of antioxidant systems to prevent oxidative stress in vivo. Neutrophils are the immune effectors most well depicted with an intense oxidative burst in response to tissue inflammation. Several proteins and members of the galectin family are involved in this fine modulation of ROS production by neutrophils. Interestingly, studies have indicated that Galectin-1 (Gal-1) can up- or downregulate ROS production by neutrophils even when exposed to N-formyl-Met-Leu-Phe (fMLP) or Phorbol Myristate Acetate (PMA), both of which are potent neutrophil stimulants that trigger high levels of ROS production. Similarly, Galectin-3 (Gal-3) induces ROS in neutrophils from a sterile or nonsterile inflammatory environment, possibly creating a negative loop that could control ROS production. Besides, superoxide production is also induced by Galectin-8 (Gal-8) and Galectin-9 (Gal-9) in neutrophils but in a different manner. We describe herein the luminol and lucigenin-dependent chemiluminescence technique by using a luminometer as a method of assessment to measure ROS production by human neutrophils isolated and exposed to purified human recombinant Gal-1. The protocol described herein could be applied for the investigation of the role of other galectins in the modulation of ROS production by neutrophils.
Subject(s)
Galectins , Neutrophils , Reactive Oxygen Species , Galectins/genetics , Galectins/metabolism , Galectins/pharmacology , Humans , Neutrophils/drug effects , Neutrophils/metabolism , Reactive Oxygen Species/analysis , Reactive Oxygen Species/metabolism , Respiratory Burst , Tetradecanoylphorbol Acetate/pharmacologyABSTRACT
Development of an aberrant vascular network is a hallmark of the multistep pathological process of tumor growth and metastasis. In response to hypoxia, several pro-angiogenic factors are synthesized to support vascularization programs required for cancer progression. Emerging data indicate the involvement of glycans and glycan-binding proteins as critical regulators of vascular circuits in health and disease. Galectins may be regulated by hypoxic conditions and control angiogenesis in different physiopathological settings. These ß-galactoside-binding proteins may promote sprouting angiogenesis by interacting with different glycosylated receptors and triggering distinct signaling pathways. Understanding the role of galectins in tumor neovascularization will contribute to the design of novel anti-angiogenic therapies aimed at complementing current anti-cancer modalities and overcoming resistance to these treatments. Here we describe selected strategies and methods used to study the role of hypoxia-regulated galectins in the regulation of blood vessel formation.
Subject(s)
Galectins , Hypoxia , Neoplasms , Neovascularization, Pathologic , Galectins/metabolism , Humans , Hypoxia/physiopathology , Neoplasms/blood supply , Neovascularization, Pathologic/physiopathology , Signal TransductionABSTRACT
Galectins are a family of proteins with affinity for ß-galactosides and their expression correlates with overall survival (OS) in several cancers. However, in breast cancer their prognostic potential is unclear. In this study we performed a meta-analysis to clarify the prognostic value of galectin expression in breast cancer and to identify sources of heterogeneity. For this purpose, we performed a search of related publications in PubMed, Central-Conchrane, Web of Science database, OVID-EMBASE, Scope and EBSCOhost until November 2021.Thirteen articles were included with a total of 2700 patients. High galectin expression was found not to correlate with OS in breast cancer (HR = 1.11, 95% CI 0.93-1.31). In the case of galectin-3, correlation with OS was observed when performing subgroup analysis by cellular localization (HR = 0.59, 95% CI 0.36-0.94 for cytoplasmic and HR = 1.82, 95% CI 1.00-3.29 for cytoplasmic plus nuclear). Galectin-7 correlates with DFS/PFS/DSS (HR = 2.43; 95% CI 1.36-4.31). Finally, galectin-3 correlates with some clinicopathological features such as lymph node metastasis, estrogen receptor expression and age. In conclusion, galectin-3 correlates with OS in breast cancer when cellular localization is considered while galectin-7 correlates with DFS/PFS/DSS. The cellular localization of galectins should be as fundamental aspect to be determined in future studies.
Subject(s)
Breast Neoplasms , Breast Neoplasms/pathology , Female , Galectin 3/metabolism , Galectins/metabolism , Humans , Prognosis , Receptors, EstrogenABSTRACT
Galectin-9 (Gal-9) is a beta-galactoside-binding protein with a variety of biological functions related to immune response. However, in allergic diseases, its mechanism of action is not fully understood. This study evaluates the expression pattern of Gal-9 in patients with atopic dermatitis (AD), in ovalbumin (OVA)-induced experimental atopic dermatitis (AD) in mice, as well as its effect on human keratinocytes. The skin of OVA-immunized BALB/c mice was challenged with drops containing OVA on days 11, 14-18, and 21-24. HaCaT cells were cultured in the following experimental conditions: control (growth medium only) or stimulated with TNF-α/IFN-γ, or IL-4, or IL-17 with or without Gal-9 treatment. AD was characterized by increased levels of Gal-9 in mouse and human skin, especially in the epidermis, and with a marked influx of Gal-9 positive eosinophils and mast cells compared to the control group. Gal-9 showed an immunomodulatory effect on keratinocytes by decreasing the release of IL-6 by IL-4-stimulated keratinocytes or increasing the IL-6 and RANTES levels by IL-17- or TNF-α/IFN-γ-stimulated cells, respectively. Under IL-17, Gal-9 treatment also altered the proliferation rate of cells. Overall, increased levels of Gal-9 in AD skin contribute to the control of inflammatory response and the proliferative process of keratinocytes, suggesting this lectin as a relevant therapeutic target.
Subject(s)
Dermatitis, Atopic/metabolism , Dermatitis, Atopic/pathology , Galectins/metabolism , Keratinocytes/metabolism , Keratinocytes/pathology , Animals , Cell Movement , Cell Proliferation , Cytokines/metabolism , Disease Models, Animal , Humans , Inflammation/pathology , Male , Mice, Inbred BALB C , Skin/pathology , Up-Regulation/geneticsABSTRACT
The relevance of glycan-binding proteins 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, atypical secretion via an endoplasmic reticulum-Golgi-independent pathway and by the ability to recognize ß-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 delineate tailored therapeutic strategies aimed at positively or negatively modulating this glycan-binding protein in pathologic inflammatory conditions.
Subject(s)
Galectin 1 , Galectins , Carbohydrates , Galectin 1/genetics , Galectins/metabolism , Humans , Inflammation/metabolism , Polysaccharides/metabolismABSTRACT
Despite recent advances in diagnosis and treatment, glioblastoma (GBM) represents the most common and aggressive brain tumor in the adult population, urging identification of new rational therapeutic targets. Galectins, a family of glycan-binding proteins, are highly expressed in the tumor microenvironment (TME) and delineate prognosis and clinical outcome in patients with GBM. These endogenous lectins play key roles in different hallmarks of cancer by modulating tumor cell proliferation, oncogenic signaling, migration, vascularization and immunity. Additionally, they have emerged as mediators of resistance to different anticancer treatments, including chemotherapy, radiotherapy, immunotherapy, and antiangiogenic therapy. Particularly in GBM, galectins control tumor cell transformation and proliferation, reprogram tumor cell migration and invasion, promote vascularization, modulate cell death pathways, and shape the tumor-immune landscape by targeting myeloid, natural killer (NK), and CD8+ T cell compartments. Here, we discuss the role of galectins, particularly galectin-1, -3, -8, and -9, as emerging glyco-checkpoints that control different mechanisms associated with GBM progression, and discuss possible therapeutic opportunities based on inhibition of galectin-driven circuits, either alone or in combination with other treatment modalities.
Subject(s)
Galectins/metabolism , Glioblastoma/drug therapy , Glioblastoma/metabolism , Molecular Targeted Therapy , Polysaccharides/metabolism , Animals , Disease Progression , Drug Resistance, Neoplasm , Glioblastoma/immunology , HumansABSTRACT
Pancreatic ductal adenocarcinoma is one of the most aggressive tumors with a microenvironment marked by hypoxia and starvation. Galectin-3 has been evaluated in solid tumors and seems to present both pro/anti-tumor effects. So, this study aims to characterize the expression of Galectin-3 from pancreatic tumor cells and analyze its influence for cell survive and motility in mimetic microenvironment. For this, cell cycle and cell death were accessed through flow cytometry. Characterization of inside and outside Galectin-3 was performed through Real-Time Quantitative Reverse Transcription PCR (qRT-PCR), immunofluorescence, Western blot, and ELISA. Consequences of Galectin-3 extracellular inhibition were investigated using cell death and scratch assays. PANC-1 showed increased Galectin-3 mRNA expression when cultivated in hypoxia for 24 and 48 h. After 24 h in simultaneously hypoxic/deprived incubation, PANC-1 shows increased Galectin-3 protein and secreted levels. For Mia PaCa-2, cultivation in deprivation was determinant for the increasing in Galectin-3 mRNA expression. When cultivated in simultaneously hypoxic/deprived condition, Mia PaCa-2 also presented increasing for the Galectin-3 secreted levels. Treatment of PANC-1 cells with lactose increased the death rate when cells were incubated simultaneously hypoxic/deprived condition. Therefore, it is possible to conclude that the microenvironmental conditions modulate the Galectin-3 expression on the transcriptional and translational levels for pancreatic cancer cells.
Subject(s)
Blood Proteins/metabolism , Galectins/metabolism , Nutrients/metabolism , Pancreatic Neoplasms/metabolism , Blood Proteins/genetics , Blood Proteins/isolation & purification , Cell Cycle , Cell Death , Cell Hypoxia , Galectins/genetics , Galectins/isolation & purification , Humans , Pancreatic Neoplasms/pathology , Tumor Cells, Cultured , Tumor MicroenvironmentABSTRACT
The water-soluble fractions of pectin extracted from the pulp of ripe papayas have already been found to exert positive effects on cancer cell cultures. However, the mechanisms that lead to these beneficial effects and the pectin characteristics that exert these effects are still not well understood. Characteristics such as molecular size, monosaccharide composition and structural conformation are known as polysaccharide factors that can cause alterations in cellular response. During fruit ripening, a major polysaccharide solubilization, depolymerization, and chemical modification occur. The aims of this work are to fractionate the pectin extracted from the pulp of papayas at two stages of ripening (fourth and ninth day after harvesting) into uronic and neutral fractions and to test them for the inhibition of human recombinant galectin-3 and the inhibition of colon cancer cell growth. The structures of the fractions were chemically characterized, and the uronic fraction extracted from the fourth day after harvesting presented the best biological effects across different concentrations in both galectin-3 inhibition and viability assays. The results obtained may help to establish a relationship between the chemical structures of papaya pectins and the positive in vitro biological effects, such as inhibiting cancer cell growth.
Subject(s)
Blood Proteins/metabolism , Carica/physiology , Colonic Neoplasms/metabolism , Galectins/metabolism , Pectins/pharmacology , Uronic Acids/chemistry , Carica/chemistry , Cell Proliferation/drug effects , Cell Survival/drug effects , Cell Wall/chemistry , Colonic Neoplasms/drug therapy , Down-Regulation/drug effects , Gene Expression Regulation, Neoplastic/drug effects , HCT116 Cells , HT29 Cells , Humans , Pectins/chemistry , Polysaccharides/analysisABSTRACT
Communication between individuals via molecules, termed chemosignaling, is widespread among animal and plant species. However, we lack knowledge on the specific functions of the substances involved for most systems. The femoral gland is an organ that secretes a waxy substance involved in chemical communication in lizards. Although the lipids and volatile substances secreted by the femoral glands have been investigated in several biochemical studies, the protein composition and functions of secretions remain completely unknown. Applying a proteomic approach, we provide the first attempt to comprehensively characterize the protein composition of femoral gland secretions from the Galápagos marine iguana. Using samples from several organs, the marine iguana proteome was assembled by next-generation sequencing and MS, resulting in 7513 proteins. Of these, 4305 proteins were present in the femoral gland, including keratins, small serum proteins, and fatty acid-binding proteins. Surprisingly, no proteins with discernible roles in partner recognition or inter-species communication could be identified. However, we did find several proteins with direct associations to the innate immune system, including lysozyme C, antileukoproteinase (ALP), pulmonary surfactant protein (SFTPD), and galectin (LGALS1) suggesting that the femoral glands function as an important barrier to infection. Furthermore, we report several novel anti-microbial peptides from the femoral glands that show similar action against Escherichia coli and Bacillus subtilis such as oncocin, a peptide known for its effectiveness against Gram-negative pathogens. This proteomics data set is a valuable resource for future functional protein analysis and demonstrates that femoral gland secretions also perform functions of the innate immune system.
Subject(s)
Anti-Infective Agents/metabolism , Anti-Infective Agents/pharmacology , Iguanas/metabolism , Immune System/metabolism , Immunity, Innate , Proteome/metabolism , Transcriptome , Animals , Apoproteins/genetics , Apoproteins/metabolism , Bacillus subtilis/drug effects , Brain/metabolism , Chemotactic Factors/genetics , Chemotactic Factors/metabolism , Ecuador , Endopeptidases/genetics , Endopeptidases/metabolism , Escherichia coli/drug effects , Galectins/genetics , Galectins/metabolism , Heart/physiology , High-Throughput Nucleotide Sequencing , Humans , Iguanas/genetics , Iguanas/immunology , Immunity, Innate/genetics , Lung/metabolism , Muramidase/genetics , Muramidase/metabolism , Muscles/metabolism , Myocardium/metabolism , Organ Specificity , Proteome/genetics , Proteome/immunology , Proteomics , Pulmonary Surfactant-Associated Proteins/genetics , Pulmonary Surfactant-Associated Proteins/metabolism , Skin/metabolism , Tandem Mass Spectrometry , Transcriptome/geneticsABSTRACT
Galectin-8 (Gal-8) is a tandem-repeat type galectin with affinity for ß-galactosides, bearing two carbohydrate recognition domains (CRD) connected by a linker peptide. The N- and C-terminal domains (Gal-8N and Gal-8C) share 35% homology, and their glycan ligand specificity is notably dissimilar: while Gal-8N shows strong affinity for α(2-3)-sialylated oligosaccharides, Gal-8C has higher affinity for non-sialylated oligosaccharides, including poly-N-acetyllactosamine and/ or A and B blood group structures. Particularly relevant for understanding the biological role of this lectin, full-length Gal-8 can bind cell surface glycoconjugates with broader affinity than the isolated Gal-8N and Gal-8C domains, a trait also described for other tandem-repeat galectins. Herein, we aim to discuss the potential use of separate CRDs in modelling tandem-repeat galectin-8 and its biological functions. For this purpose, we will cover several aspects of the structure-function relationship of this protein including crystallographic structures, glycan specificity, cell function and biological roles, with the ultimate goal of understanding the potential role of each CRD in predicting full-length Gal-8 involvement in relevant biological processes.
Subject(s)
Carbohydrate Metabolism , Galectins/metabolism , Amino Acid Sequence , Crystallography, X-Ray , Galectins/chemistry , Humans , Ligands , Protein Conformation , Sequence Homology, Amino AcidABSTRACT
Galectins are small proteins with pleiotropic functions, which depend on both their lectin (glycan recognition) and non-lectin (recognition of other biomolecules besides glycans) interactions. Currently, 15 members of this family have been described in mammals, each with its structural and ligand recognition particularities. The galectin/ligand interaction translates into a plethora of biological functions that are particular for each cell/tissue type. In this sense, the cells of the immune system are highly sensitive to the action of these small and essential proteins. While galectins play central roles in tumor progression, they are also excellent negative regulators (checkpoints) of the immune cell functions, participating in the creation of a microenvironment that promotes tumor escape. This review aims to give an updated view on how galectins control the tumor's immune attack depending on the tumor microenvironment, because determining which galectins are essential and the role they play will help to develop future clinical trials and benefit patients with incurable cancer.
Subject(s)
Clinical Trials as Topic , Galectins/metabolism , Immune System/metabolism , Neoplasms/metabolism , Animals , Humans , Immune Checkpoint Inhibitors/pharmacology , Immune Checkpoint Inhibitors/therapeutic use , Immune System/drug effects , Neoplasms/diagnosis , PrognosisABSTRACT
A predominant protein of human eosinophils is galectin-10 (Gal-10), also known as Charcot-Leyden crystal protein (CLC-P) because of its remarkable ability to form Charcot-Leyden crystals (CLCs), which are frequently found in tissues from patients with eosinophilic disorders. CLC-P/Gal-10 is highly expressed in human eosinophils and considered a biomarker of eosinophil involvement in inflammation. However, the intracellular sites where large pools of CLC-P/Gal-10 constitutively reside are still unclear, and whether this protein is derived or not from eosinophil granules remains to be established. Here, we applied pre-embedding immunonanogold transmission electron microscopy combined with strategies for optimal antigen and cell preservation and quantitative imaging analysis to investigate, for the first time, the intracellular localization of CLC-P/Gal-10 at high resolution in resting and activated human eosinophils. We demonstrated that CLC-P/Gal-10 is mostly stored in the peripheral cytoplasm of human eosinophils, being accumulated within an area of â¼250 nm wide underneath the plasma membrane and not within specific (secretory) granules, a pattern also observed by immunofluorescence. High-resolution analysis of single cells revealed that CLC-P/Gal-10 interacts with the plasma membrane with immunoreactive microdomains of high CLC-P/Gal-10 density being found in â¼60% of the membrane area. Eosinophil stimulation with CCL11 or TNF-α, which are known inducers of eosinophil secretion, did not change the peripheral localization of CLC-P/Gal-10 as observed by both immunofluorescence and immuno-EM (electron microscopy). Thus, in contrast to other preformed eosinophil proteins, CLC-P/Gal-10 neither is stored within secretory granules nor exported through classical degranulation mechanisms (piecemeal degranulation and compound exocytosis).
Subject(s)
Eosinophils/metabolism , Galectins/metabolism , Secretory Vesicles/metabolism , Cell Degranulation , Eosinophils/physiology , Humans , Hypersensitivity/enzymology , Hypersensitivity/pathology , Secretory Vesicles/ultrastructureABSTRACT
Upon overnutrition, adipocytes activate a homeostatic program to adjust anabolic pressure. An inflammatory response enables adipose tissue (AT) expansion with concomitant enlargement of its capillary network, and reduces energy storage by increasing insulin resistance. Galectin-12 (Gal-12), an endogenous lectin preferentially expressed in AT, plays a key role in adipocyte differentiation, lipolysis, and glucose homeostasis. Here, we reveal biochemical and biophysical determinants of Gal-12 structure, including its preferential recognition of 3-fucosylated structures, a unique feature among members of the galectin family. Furthermore, we identify a previously unanticipated role for this lectin in the regulation of angiogenesis within AT. Gal-12 showed preferential localization within the inner side of lipid droplets, and its expression was upregulated under hypoxic conditions. Through glycosylation-dependent binding to endothelial cells, Gal-12 promoted in vitro angiogenesis. Moreover, analysis of in vivo AT vasculature showed reduced vascular networks in Gal-12-deficient (Lgals12-/-) compared to wild-type mice, supporting a role for this lectin in AT angiogenesis. In conclusion, this study unveils biochemical, topological, and functional features of a hypoxia-regulated galectin in AT, which modulates endothelial cell function through recognition of 3-fucosylated glycans. Thus, glycosylation-dependent programs may control AT homeostasis by modulating endothelial cell biology with critical implications in metabolic disorders and inflammation.
Subject(s)
Adipocytes/metabolism , Endothelial Cells/metabolism , Galectins/metabolism , Neovascularization, Pathologic/metabolism , Adipose Tissue/metabolism , Animals , Cell Physiological Phenomena/physiology , Insulin Resistance/physiology , Lipid Droplets/metabolism , Lipolysis/physiology , Mice, Knockout , Polysaccharides/metabolismABSTRACT
Lectins are proteins or glycoproteins of non-immunological origin capable of reversibly and specifically binding to glycoconjugates. They exist in free form or associated with cells and are widely distributed in nature, being found in plants, microorganisms, and animals. Due to their characteristics and mainly due to the possibility of reversible binding to glycoconjugates, lectins have stood out as important tools in research involving Neurobiology. These proteins have the ability to modulate molecular targets in the central nervous system (CNS) which may be involved with neuroplasticity, neurobehavioral effects, and neuroprotection. The present report integrates existing information on the activity of animal and plant lectins in different areas of Neuroscience, presenting perspectives to direct new research on lectin function in the CNS, providing alternatives for understanding neurological diseases such as mental disorders, neurodegenerative, and neuro-oncological diseases, and for the development of new drugs, diagnoses and therapies in the field of Neuroscience.