Galectin-4 Antimicrobial Activity Primarily Occurs Through its C-Terminal Domain.

Although immune tolerance evolved to reduce reactivity with self, it creates a gap in the adaptive immune response against microbes that decorate themselves in self-like antigens. This is particularly apparent with carbohydrate-based blood group antigens, wherein microbes can envelope themselves in blood group structures similar to human cells. In this study, we demonstrate that the innate immune lectin, galectin-4 (Gal-4), exhibits strain-specific binding and killing behavior towards microbes that display blood group-like antigens. Examination of binding preferences using a combination of microarrays populated with ABO(H) glycans and a variety of microbial strains, including those that express blood group-like antigens, demonstrated that Gal-4 binds mammalian and microbial antigens that have features of blood group and mammalian-like structures. Although Gal-4 was thought to exist as a monomer that achieves functional bivalency through its two linked carbohydrate recognition domains, our data demonstrate that Gal-4 forms dimers and that differences in the intrinsic ability of each domain to dimerize likely influences binding affinity. While each Gal-4 domain exhibited blood group-binding activity, the C-terminal domain (Gal-4C) exhibited dimeric properties, while the N-terminal domain (Gal-4N) failed to similarly display dimeric activity. Gal-4C not only exhibited the ability to dimerize but also possessed higher affinity toward ABO(H) blood group antigens and microbes expressing glycans with blood group-like features. Furthermore, when compared to Gal-4N, Gal-4C exhibited more potent antimicrobial activity. Even in the context of the full-length protein, where Gal-4N is functionally bivalent by virtue of Gal-4C dimerization, Gal-4C continued to display higher antimicrobial activity. These results demonstrate that Gal-4 exists as a dimer and exhibits its antimicrobial activity primarily through its C-terminal domain. In doing so, these data provide important insight into key features of Gal-4 responsible for its innate immune activity against molecular mimicry.

Cytosolic galectin-4 enchains bacteria, restricts their motility, and promotes inflammasome activation in intestinal epithelial cells.

Galectin-4, a member of the galectin family of animal glycan-binding proteins (GBPs), is specifically expressed in gastrointestinal epithelial cells and is known to be able to bind microbes. However, its function in host-gut microbe interactions remains unknown. Here, we show that intracellular galectin-4 in intestinal epithelial cells (IECs) coats cytosolic Salmonella enterica serovar Worthington and induces the formation of bacterial chains and aggregates. Galectin-4 enchains bacteria during their growth by binding to the O-antigen of lipopolysaccharides. Furthermore, the binding of galectin-4 to bacterial surfaces restricts intracellular bacterial motility. Galectin-4 enhances caspase-1 activation and mature IL-18 production in infected IECs especially when autophagy is inhibited. Finally, orally administered S. enterica serovar Worthington, which is recognized by human galectin-4 but not mouse galectin-4, translocated from the intestines to mesenteric lymph nodes less effectively in human galectin-4-transgenic mice than in littermate controls. Our results suggest that galectin-4 plays an important role in host-gut microbe interactions and prevents the dissemination of pathogens. The results of the study revealed a novel mechanism of host-microbe interactions that involves the direct binding of cytosolic lectins to glycans on intracellular microbes.

Different roles of the heterodimer architecture of galectin-4 in selective recognition of oligosaccharides and lipopolysaccharides having ABH antigens.

The dimeric architecture of tandem-repeat type galectins, such as galectin-4 (Gal-4), modulates their biological activities, although the underlying molecular mechanisms have remained elusive. Emerging evidence show that tandem-repeat galectins play an important role in innate immunity by recognizing carbohydrate antigens present on the surface of certain pathogens, which very often mimic the structures of the human self-glycan antigens. Herein, we have analyzed the binding preferences of the C-domain of Gal-4 (Gal-4C) toward the ABH-carbohydrate histo-blood antigens with different core presentations and their recognition features have been rationalized by using a combined experimental approach including NMR, solid-phase and hemagglutination assays, and molecular modeling. The data show that Gal-4C prefers A over B antigens (two-fold in affinity), contrary to the N-domain (Gal-4N), although both domains share the same preference for the type-6 presentations. The behavior of the full-length Gal-4 (Gal-4FL) tandem-repeat form has been additionally scrutinized. Isothermal titration calorimetry and NMR data demonstrate that both domains within full-length Gal-4 bind to the histo-blood antigens independently of each other, with no communication between them. In this context, the heterodimeric architecture does not play any major role, apart from the complementary A and B antigen binding preferences. However, upon binding to a bacterial lipopolysaccharide containing a multivalent version of an H-antigen mimetic as O-antigen, the significance of the galectin architecture was revealed. Indeed, our data point to the linker peptide domain and the F-face of the C-domain as key elements that provide Gal-4 with the ability to cross-link multivalent ligands, beyond the glycan binding capacity of the dimer.

Exploring galectin interactions with human milk oligosaccharides and blood group antigens identifies BGA6 as a functional galectin-4 ligand.

Galectins (Gals), a family of multifunctional glycan-binding proteins, have been traditionally defined as ß-galactoside binding lectins. However, certain members of this family have shown selective affinity toward specific glycan structures including human milk oligosaccharides (HMOs) and blood group antigens. In this work, we explored the affinity of human galectins (particularly Gal-1, -3, -4, -7, and -12) toward a panel of oligosaccharides including HMOs and blood group antigens using a complementary approach based on both experimental and computational techniques. While prototype Gal-1 and Gal-7 exhibited differential affinity for type I versus type II Lac/LacNAc residues and recognized fucosylated neutral glycans, chimera-type Gal-3 showed high binding affinity toward poly-LacNAc structures including LNnH and LNnO. Notably, the tandem-repeat human Gal-12 showed preferential recognition of 3-fucosylated glycans, a unique feature among members of the galectin family. Finally, Gal-4 presented a distinctive glycan-binding activity characterized by preferential recognition of specific blood group antigens, also validated by saturation transfer difference nuclear magnetic resonance experiments. Particularly, we identified oligosaccharide blood group A antigen tetraose 6 (BGA6) as a biologically relevant Gal-4 ligand, which specifically inhibited interleukin-6 secretion induced by this lectin on human peripheral blood mononuclear cells. These findings highlight unique determinants underlying specific recognition of HMOs and blood group antigens by human galectins, emphasizing the biological relevance of Gal-4-BGA6 interactions, with critical implications in the development and regulation of inflammatory responses.

High expression of B3GALT5 suppresses the galectin-4-mediated peritoneal dissemination of poorly differentiated gastric cancer cells.

Peritoneal metastasis frequently accompanies metastatic and/or recurrent gastric cancer, leading to a poor prognosis owing to a lack of effective treatment. Hence, there is a pressing need to enhance our understanding of the mechanisms and molecules driving peritoneal metastasis. In a previous study, galectin-4 inhibition impeded peritoneal metastasis in a murine model. This study examined the glycan profiles of cell surface proteins and glycosphingolipids (GSLs) in cells with varying tumorigenic potentials to understand the intricate mechanisms underlying galectin-4-mediated regulation, particularly glycosylation. Detailed mass spectrometry analysis showed that galectin-4 knockout cells exhibit increased expression of lacto-series GSLs with ß1,3-linked galactose while showing no significant alterations in neolacto-series GSLs. We conducted real-time polymerase chain reaction (PCR) analysis to identify candidate glycosyltransferases that synthesize increased levels of GSLs. Subsequently, we introduced the candidate B3GALT5 gene and selected the clones with high expression levels. B3GALT5 gene-expressing clones showed GSL glycan profiles like those of knockout cells and significantly reduced tumorigenic ability in mouse models. These clones exhibited diminished proliferative capacity and showed reduced expression of galectin-4 and activated AKT. Moreover, co-localization of galectin-4 with flotillin-2 (a raft marker) decreased in B3GALT5-expressing cells, implicating GSLs in galectin-4 localization to lipid rafts. D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (a GSL synthase inhibitor) also affected galectin-4 localization in rafts, suggesting the involvement of GSL microdomains. We discovered that B3GALT5 plays a crucial role in regulating peritoneal metastasis of malignant gastric cancer cells by suppressing cell proliferation and modulating lipid rafts and galectin-4 via mechanisms that are yet to be elucidated.

Galectin network in osteoarthritis: galectin-4 programs a pathogenic signature of gene and effector expression in human chondrocytes in vitro.

Galectin-4 (Gal-4) is a member of the galectin family, which have been identified as galactose-binding proteins. Gal-4 possesses two tandem repeat carbohydrate recognition domains and acts as a cross-linking bridge in sulfatide-dependent glycoprotein routing. We herein document its upregulation in osteoarthritis (OA) in correlation with the extent of cartilage degradation in vivo. Primary human OA chondrocytes in vitro respond to carbohydrate-inhibitable Gal-4 binding with the upregulation of pro-degradative/-inflammatory proteins such as interleukin-1ß (IL-1ß) and matrix metalloproteinase-13 (MMP-13), as documented by RT-qPCR-based mRNA profiling and transcriptome data processing. Activation of p65 by phosphorylation of Ser536 within the NF-κB pathway and the effect of three p65 inhibitors on Gal-4 activity support downstream involvement of such signaling. In 3D (pellet) cultures, Gal-4 presence causes morphological and biochemical signs of degradation. Taken together, our findings strongly support the concept of galectins acting as a network in OA pathogenesis and suggest that blocking their activity in disease progression may become clinically relevant in the future.

Galectin-4 levels in hospitalized versus non-hospitalized subjects with obesity: the Malmö Preventive Project.

BACKGROUND: Obesity is strongly associated with the development of cardiovascular disease (CVD). However, the heterogenous nature of obesity in CVD-risk is still poorly understood. We aimed to explore novel CVD biomarkers and their possible association with presumed unhealthy obesity, defined as hospitalized subjects with obesity (HO). METHODS: Ninety-two proteins associated with CVD were analyzed in 517 (mean age 67 ± 6 years; 33.7% women) individuals with obesity (BMI ≥30 kg/m2) from the Malmö Preventive Project cohort, using a proximity extension array technique from the Olink CVD III panel. Individuals with at least one recorded hospitalization for somatic disease prior to study baseline were defined as HO phenotypes. Associations between proteins and HO (n = 407) versus non-hospitalized subjects with obesity (NHO, n = 110), were analyzed using multivariable binary logistic regression, adjusted for traditional risk factors. RESULTS: Of 92 analyzed unadjusted associations between biomarkers and HO, increased levels of two proteins were significant at a false discovery rate < 0.05: Galectin-4 (Gal-4) and insulin-like growth factor-binding protein 1 (IGFBP-1). When these two proteins were included in logistic regression analyses adjusted for age and sex, Gal-4 remained significant. Gal-4 was independently associated with the HO phenotype in multivariable logistic regression analysis (OR 1.72; CI95% 1.16-2.54). Post-hoc analysis revealed that this association was only present in the subpopulation with diabetes (OR 2.26; CI95% 1.25-4.07). However, an interaction analysis was performed, showing no significant interaction between Gal-4 and prevalent diabetes (p = 0.16). CONCLUSIONS: In middle-aged and older individuals with obesity, increased Gal-4 levels were associated with a higher probability of HO. This association was only significant in subjects with diabetes only, further implying a role for Gal-4 in diabetes and its complications.

Galectin 4 is a biomarker for early recurrence and death after surgical resection for pancreatic ductal adenocarcinoma.

BACKGROUND: Galectins are a group of carbohydrate-binding proteins that are involved in neoplastic development and progression. In a previous mass spectrometry-based study, we identified galectin 4 as a down-regulated protein in short-term survivors of pancreatic cancer. This study was performed to validate the prognostic value of galectin 4 in a larger cohort of pancreatic cancer patients undergoing surgical resection. METHODS: Galectin 4 expression was evaluated by tissue microarrays and immunohistochemistry in 140 patients with surgically resected pancreatic cancer. Kaplan-Meier and Cox proportional hazards modeling were used to explore the association between galectin 4 and survival. RESULTS: Galectin 4 staining expression was positive in 111 cases (79.3%). The expression of galectin 4 was significantly associated with tumor size (p = .008) and differentiation (p = .001). Galectin 4 expression was significantly correlated with disease recurrence within 1 year of surgery (adjusted HR 0.485, p = .027). There was also a significant association between galectin 4 and overall survival at 1 year (adjusted HR 0.482, p = .047) and at 3 years (adjusted HR 0.550, p = .025). CONCLUSION: Galectin 4 expression is a novel biomarker for early recurrence and mortality after surgical resection for pancreatic cancer.

Surface-bound galectin-4 regulates gene transcription and secretion of chemokines in human colorectal cancer cell lines.

One long-term complication of chronic intestinal inflammation is the development of colorectal cancer. However, the mechanisms linking inflammation to the colorectal tumorigenesis are poorly defined. Previously, we have demonstrated that galectin-4 is predominantly expressed in the luminal epithelia of the gastrointestinal tract, and its loss of expression plays a key role in the colorectal tumorigenesis. However, the mechanism by which galectin-4 regulates inflammation-induced tumorigenesis is unclear. Here, we show that galectin-4 secreted by the colorectal cancer cell lines was bound to the cell surface. Neutralization of surface-bound galectin-4 with anti-galectin-4 antibody resulted in increased cell proliferation with concomitant secretion of several chemokines into the extracellular medium. Neutralization of the surface-bound galectin-4 also resulted in the up-regulation of transcription of 29 genes, several of which are components of multiple inflammation signaling pathways. In an alternate experiment, binding of recombinant galectin-4 protein to cell surface of the galectin-4-negative colorectal cancer cells resulted in increased p27, and decreased cyclin D1 and c-Myc levels, leading to cell cycle arrest and apoptosis. Together, these data demonstrated that surface-bound galectin-4 is a dual function protein-down-regulating cell proliferation and chemokine secretion in galectin-4-expressing colorectal cancer cells on one hand and inducing apoptosis in galectin-4-negative colorectal cancer cells on the other hand.

Galectin-4 interacts with the drug transporter human concentrative nucleoside transporter 3 to regulate its function.

The intracellular N-terminal domain of the nucleoside and drug transporter human concentrative nucleoside transporter (hCNT)3 was used as bait in a glutathione S-transferase pull-down approach, to identify hCNT3 protein partners, using human colon homogenates as a prey source. Galectin (Gal)-4 was identified as a potential hCNT3 partner in the colon. The biochemical validation of the Gal-4-hCNT3 interaction was verified by targeted pull-down assays and coimmunoprecipitation experiments in HT-29 cells, which endogenously express hCNT3 and Gal-4. Furthermore, Gal-4 was shown to colocalize with hCNT3 in HT-29 cells. The biologic significance of this interaction was obtained from experiments in which Gal-4 was knocked down, showing that this protein is a regulator of hCNT3 trafficking and retention at the cell membrane, reducing its plasma membrane location by 70%. Conversely, the addition of Gal-4 increased hCNT3 location at the plasma membrane by 77%, thereby demonstrating that this lectin modulates hCNT3 function in colonic cells. The integrity of this partnership may be clinically relevant, because hCNT3 may be responsible for the translocation of thiopurines, such as 6-mercaptopurine, a front-line treatment in inflammatory bowel disease. The expression of Gal-4 and hCNT3 proteins is not impaired in inflamed colon from patients with Crohn's disease, thereby anticipating the integrity of this system for drug targeting.

Detection of Proteome Changes in Human Colon Cancer Induced by Cell Surface Binding of Growth-Inhibitory Human Galectin-4 Using Quantitative SILAC-Based Proteomics.

Endogenous lectins have the capacity to translate glycan-encoded information on the cell surface into effects on cell growth. As test cases to examine changes in protein presence associated with tumor growth inhibition, we applied SILAC-based proteomics on human colon carcinoma cells treated with galectin-4 (Gal-4). The five tested lines-LS 180, Vaco 432, Colo 205, CX 1, and HCT 116-responded with differentiation and reduced proliferation to Gal-4 binding. In proteomic analysis (mass spectral data deposited with PRIDE, PXD003489), 2654 proteins were quantified, of which 190 were down-regulated and 115 were up-regulated (>2-fold). 1D annotation analysis of the results indicated down-regulation of DNA replication-associated processes, while protein presence for secretory and transport functions appeared increased. The strongest induction was found for CALB2 (calretinin; ∼24-fold), TGM2 (protein-glutamine γ-glutamyltransferase 2; ∼11-fold), S100A3 (∼10-fold), and GSN (gelsolin; 9.5-fold), and the most pronounced decreases were seen for CDKN2A (tumor suppressor ARF; ∼6-fold), EPCAM (epithelial cell adhesion molecule; ∼6-fold), UBE2C (ubiquitin-conjugating enzyme E2 C; ∼5-fold), KIF2C (kinesin-like protein KIF2C; 5-fold), and LMNB1 (lamin-B1; ∼5-fold). The presence of the common proliferation marker Ki-67 was diminished about 4-fold. By tracing significant alterations of protein expression likely relevant for the observed phenotypic effects, the capacity of a galectin to affect the proteome of human colon cancer cells at multiple sites is revealed.

Galectin-4-mediated transcytosis of transferrin receptor.

Some native epithelia, for example, retinal pigment epithelium (RPE) and kidney proximal tubule (KPT), constitutively lack the basolateral sorting adaptor AP-1B; this results in many basolateral plasma membrane proteins being repositioned to the apical domain, where they perform essential functions for their host organs. We recently reported the underlying apical polarity reversal mechanism: in the absence of AP-1B-mediated basolateral sorting, basolateral proteins are shuttled to the apical plasma membrane through a transcytotic pathway mediated by the plus-end kinesin KIF16B. Here, we demonstrate that this apical transcytotic pathway requires apical sorting of basolateral proteins, which is mediated by apical signals and galectin-4. Using RPE and KPT cell lines, and AP-1B-knockdown MDCK cells, we show that mutation of the N-glycan linked to N727 in the basolateral marker transferrin receptor (TfR) or knockdown of galectin-4 inhibits TfR transcytosis to apical recycling endosomes and the apical plasma membrane, and promotes TfR lysosomal targeting and subsequent degradation. Our results report a new role of galectins in basolateral to apical epithelial transcytosis.

Recombinant expression, purification and preliminary biophysical and structural studies of C-terminal carbohydrate recognition domain from human galectin-4.

Galectin-4 (Gal4), a tandem-repeat type galectin, is expressed in healthy epithelium of the gastrointestinal tract. Altered levels of Gal4 expression are associated with different types of cancer, suggesting its usage as a diagnostic marker as well as target for drug development. The functional data available for this class of proteins suggest that the wide spectrum of cellular activities reported for Gal4 relies on distinct glycan specificity and structural characteristics of its two carbohydrate recognition domains. In the present work, two independent constructs for recombinant expression of the C-terminal domain of human galectin-4 (hGal4-CRD2) were developed. His6-tagged and untagged recombinant proteins were overexpressed in Escherichia coli, and purified by affinity chromatography followed by gel filtration. Correct folding and activity of hGal4-CRD2 were assessed by circular dichroism and fluorescence spectroscopies, respectively. Diffraction quality crystals were obtained by vapor-diffusion sitting drop setup and the crystal structure of CRD2 was solved by molecular replacement techniques at 1.78 Å resolution. Our work describes the development of important experimental tools that will allow further studies in order to correlate structure and binding properties of hGal4-CRD2 and human galectin-4 functional activities.

Assembly, organization and regulation of cell-surface receptors by lectin-glycan complexes.

Galectins are a family of ß-galactoside-binding lectins carrying at least one consensus sequence in the carbohydrate-recognition domain. Properties of glycosylated ligands, such as N- and O-glycan branching, LacNAc (N-acetyl-lactosamine) content and the balance of α2,3- and α2,6-linked sialic acid dramatically influence galectin binding to a preferential set of counter-receptors. The presentation of specific glycans in galectin-binding partners is also critical, as proper orientation and clustering of oligosaccharide ligands on multiple carbohydrate side chains increase the binding avidity of galectins for particular glycosylated receptors. When galectins are released from the cells, they typically concentrate on the cell surface and the local matrix, raising their local concentration. Thus galectins can form their own multimers in the extracellular milieu, which in turn cross-link glycoconjugates on the cell surface generating galectin-glycan complexes that modulate intracellular signalling pathways, thus regulating cellular processes such as apoptosis, proliferation, migration and angiogenesis. Subtle changes in receptor expression, rates of protein synthesis, activities of Golgi enzymes, metabolite concentrations supporting glycan biosynthesis, density of glycans, strength of protein-protein interactions at the plasma membrane and stoichiometry may modify galectin-glycan complexes. Although galectins are key contributors to the formation of these extended glycan complexes leading to promotion of receptor segregation/clustering, and inhibition of receptor internalization by surface retention, when these complexes are disrupted, some galectins, particularly galectin-3 and -4, showed the ability to drive clathrin-independent mechanisms of endocytosis. In the present review, we summarize the data available on the assembly, hierarchical organization and regulation of conspicuous galectin-glycan complexes, and their implications in health and disease.

Genome-scale analysis of DNA methylation in lung adenocarcinoma and integration with mRNA expression.

Lung cancer is the leading cause of cancer death worldwide, and adenocarcinoma is its most common histological subtype. Clinical and molecular evidence indicates that lung adenocarcinoma is a heterogeneous disease, which has important implications for treatment. Here we performed genome-scale DNA methylation profiling using the Illumina Infinium HumanMethylation27 platform on 59 matched lung adenocarcinoma/non-tumor lung pairs, with genome-scale verification on an independent set of tissues. We identified 766 genes showing altered DNA methylation between tumors and non-tumor lung. By integrating DNA methylation and mRNA expression data, we identified 164 hypermethylated genes showing concurrent down-regulation, and 57 hypomethylated genes showing increased expression. Integrated pathways analysis indicates that these genes are involved in cell differentiation, epithelial to mesenchymal transition, RAS and WNT signaling pathways, and cell cycle regulation, among others. Comparison of DNA methylation profiles between lung adenocarcinomas of current and never-smokers showed modest differences, identifying only LGALS4 as significantly hypermethylated and down-regulated in smokers. LGALS4, encoding a galactoside-binding protein involved in cell-cell and cell-matrix interactions, was recently shown to be a tumor suppressor in colorectal cancer. Unsupervised analysis of the DNA methylation data identified two tumor subgroups, one of which showed increased DNA methylation and was significantly associated with KRAS mutation and to a lesser extent, with smoking. Our analysis lays the groundwork for further molecular studies of lung adenocarcinoma by identifying novel epigenetically deregulated genes potentially involved in lung adenocarcinoma development/progression, and by describing an epigenetic subgroup of lung adenocarcinoma associated with characteristic molecular alterations.

Galectin-4 serves as a prognostic biomarker for the early recurrence / metastasis of hepatocellular carcinoma.

Galectin-4 is a multifunctional lectin found at both intracellular and extracellular sites. It could serve as a tumor suppressor intracellularly and promote tumor metastases extracellularly during colorectal cancer development. However, galectin-4 expression and its prognostic value for patients with hepatocellular carcinoma (HCC) have not been well investigated. Here we report that galectin-4 was significantly downregulated in early recurrent/metastatic HCC patients, when compared to non-recurrent/metastatic HCC patients. Low expression of gelectin-4 was well associated with larger tumor size, microvascular invasion, malignant differentiation, more advanced TNM stage, and poor prognosis. Cancer cell migration and invasion could be significantly reduced through overexpression of galectin-4, but upregulated by knocking down of galectin-4 in vitro. Moreover, the serum galectin-4 level could be significantly elevated solely by hepatitis B virus infection. Combined with clinicopathological features, the higher serologic level of galectin-4 was well associated with more aggressive characteristics of HCC. Taken together, galectin-4 expression closely associates with HCC progression and might have potential use as a prognostic biomarker for HCC patients.

Phosphorylation and externalization of galectin-4 is controlled by Src family kinases.

Galectin-4 is a cytosolic protein that lacks a signal sequence but is externalized and binds to 3-O-sulfated glycoconjugates extracellularly. The mechanism of subcellular localization and externalization of galectin-4 has not yet been determined. A preliminary experiment using pervanadate (PV) showed that galectin-4 is tyrosine-phosphorylated in cells and suggested that Src kinases are involved. Cell transfection with galectin-4 and active Src plasmids showed that galectin-4 can be tyrosine phosphorylated by members of the Src kinase family. The C-terminal peptide YVQI of galectin-4 was found to play an important role in its tyrosine phosphorylation, and the SH2 domains of Src and SHP2 were found to bind to this peptide. Immunofluorescence analysis showed that galectin-4 and phosphorylated proteins were intensely stained in the area of membrane protrusions of PV-treated or Src-activated cells. Furthermore, MUC1 derived from NUGC-4 cells was observed to bind to galectin-4, and externalization of the bound molecules from the cell to the medium increased in the hyperphosphorylated condition. Study of the transfection of the mutant galectin-4 which lacks the C-terminal peptide revealed that the phosphorylation status is important for externalization of galectin-4. These results suggest that externalization of galectin-4 can be regulated by signaling molecules and that it may function intracellularly as an adaptor protein serving to modulate the trafficking of glycoproteins.

Neuronal Galectin-4 is required for axon growth and for the organization of axonal membrane L1 delivery and clustering.

Axon membrane glycoproteins are essential for neuronal differentiation, although the mechanisms underlying their polarized sorting and organization are poorly understood. We describe here that galectin-4 (Gal-4), a lectin highly expressed in gastrointestinal tissues and involved in epithelial glycoprotein transport, is expressed by hippocampal and cortical neurons where it is sorted to discrete segments of the axonal membrane in a microtubule- and sulfatide-dependent manner. Gal-4 knockdown retards axon growth, an effect that can be rescued by recombinant Gal-4 addition. This Gal-4 reduction, as inhibition of sulfatide synthesis does, lowers the presence and clustered organization of axon growth-promoting molecule NCAM L1 at the axon membrane. Furthermore, we find that Gal-4 interacts with L1 by specifically binding to LacNAc branch ends of L1 N-glycans. Impairing the maturation of these N-glycans precludes Gal-4/L1 association resulting in a failure of L1 membrane cluster organization. In all, Gal-4 sorts to axon plasma membrane segments by binding to sulfatide-containing microtubule-associated carriers and being bivalent, it organizes the transport of L1, and likely other axonal glycoproteins, by attaching them to the carriers through their LacNAc termini. This mechanism would underlie L1 functional organization on the plasma membrane, required for proper axon growth.

Galectin-4 increases the ability of M2 macrophages to enhance antiviral CD4+ T-cell responses.

Galectin-4 (Gal-4) is a ß-galactoside-binding protein belonging to the galectin family. Although Gal-4 is known to be involved in several physiologic processes of the gastrointestinal tract, its immunomodulatory roles remain unclear. In this study, we investigated whether Gal-4 influences the function of M1 and M2 macrophages. Gal-4 treatment drove more robust changes in the gene expression of M2 macrophages compared to M1 macrophages. Antiviral immune response-related genes were significantly upregulated in Gal-4-treated M2 macrophages. Gal-4 significantly enhanced the immunostimulatory activity of M2 macrophages upon Toll-like receptor 7 stimulation or infection with lymphocytic choriomeningitis virus (LCMV). Moreover, the antibody production against LCMV infection and the antiviral CD4+ T-cell responses, but not the antiviral CD8+ T-cell responses, were greatly increased by Gal-4-treated M2 macrophages in vivo. The present results indicate that Gal-4 enhances the ability of M2 macrophages to promote antiviral CD4+ T-cell responses. Thus, Gal-4 could be used to boost antiviral immune responses.

Interleukin-30 subverts prostate cancer-endothelium crosstalk by fostering angiogenesis and activating immunoregulatory and oncogenic signaling pathways.

BACKGROUND: Cancer-endothelial interplay is crucial for tumor behavior, yet the molecular mechanisms involved are largely unknown. Interleukin(IL)-30, which is expressed as a membrane-anchored cytokine by human prostate cancer (PC) cells, promotes PC vascularization and progression, but the underlying mechanisms have yet to be fully explored. METHODS: PC-endothelial cell (EC) interactions were investigated, after coculture, by flow cytometry, transcriptional profiling, western blot, and ELISA assays. Proteome profiler phospho-kinase array unveiled the molecular pathways involved. The role of tumor-derived IL30 on the endothelium's capacity to generate autocrine circuits and vascular budding was determined following IL30 overexpression, by gene transfection, or its deletion by CRISPR/Cas9 genome editing. Clinical value of the experimental findings was determined through immunopathological study of experimental and patient-derived PC samples, and bioinformatics of gene expression profiles from PC patients. RESULTS: Contact with PC cells favors EC proliferation and production of angiogenic and angiocrine factors, which are boosted by PC expression of IL30, that feeds autocrine loops, mediated by IGF1, EDN1, ANG and CXCL10, and promotes vascular budding and inflammation, via phosphorylation of multiple signaling proteins, such as Src, Yes, STAT3, STAT6, RSK1/2, c-Jun, AKT and, primarily CREB, GSK-3α/ß, HSP60 and p53. Deletion of the IL30 gene in PC cells inhibits endothelial expression of IGF1, EDN1, ANG and CXCL10 and substantially impairs tumor angiogenesis. In its interaction with IL30-overexpressing PC cells the endothelium boosts their expression of a wide range of immunity regulatory genes, including CCL28, CCL4, CCL5, CCR2, CCR7, CXCR4, IL10, IL13, IL17A, FASLG, IDO1, KITLG, TNFA, TNFSF10 and PDCD1, and cancer driver genes, including BCL2, CCND2, EGR3, IL6, VEGFA, KLK3, PTGS1, LGALS4, GNRH1 and SHBG. Immunopathological analyses of PC xenografts and in silico investigation of 1116 PC cases, from the Prostate Cancer Transcriptome Atlas, confirmed the correlation between the expression of IL30 and that of both pro-inflammatory genes, NOS2, TNFA, CXCR5 and IL12B, and cancer driver genes, LGALS4, GNRH1 and SHBG, which was validated in a cohort of 80 PC patients. CONCLUSIONS: IL30 regulates the crosstalk between PC and EC and reshapes their transcriptional profiles, triggering angiogenic, immunoregulatory and oncogenic gene expression programs. These findings highlight the angiostatic and oncostatic efficacy of targeting IL30 to fight PC.