Gal-3BP in Viral Infections: An Emerging Role in Severe Acute Respiratory Syndrome Coronavirus 2.

Galectin-3 binding protein (Gal-3BP) is a multifunctional glycoprotein involved in cell-cell and cell-matrix interactions known to be upregulated in cancer and various viral infections, including HIV-1, HCV, and SARS-CoV-2, with a key role in regulating the antiviral immune response. Studies have identified a direct correlation between circulating levels of Gal-3BP and the severity of disease and/or disease progression for some viral infections, including SARS-CoV-2, suggesting a role of Gal-3BP in these processes. Due to Gal-3BP's complex biology, the molecular mechanisms underlying its role in viral diseases have been only partially clarified. Gal-3BP induces the expression of interferons (IFNs) and proinflammatory cytokines, including interleukin-6 (IL-6), mainly interacting with galectin-3, targeting the TNF receptor-associated factors (TRAF-6 and TRAF-3) complex, thus having a putative role in the modulation of TGF-ß signaling. In addition, an antiviral activity of Gal-3BP has been ascribed to a direct interaction of the protein with virus components. In this review, we explored the role of Gal-3BP in viral infections and the relationship between Gal-3BP upregulation and disease severity and progression, mainly focusing on SARS-CoV-2. Augmented knowledge of Gal-3BP's role in virus infections can be useful to evaluate its possible use as a prognostic biomarker and as a putative target to block or attenuate severe disease.

Galectin 3-binding protein suppresses amyloid-ß production by modulating ß-cleavage of amyloid precursor protein.

Alzheimer's disease (AD) is the most common type of dementia, and its pathogenesis is associated with accumulation of ß-amyloid (Aß) peptides. Aß is produced from amyloid precursor protein (APP) that is sequentially cleaved by ß- and γ-secretases. Therefore, APP processing has been a target in therapeutic strategies for managing AD; however, no effective treatment of AD patients is currently available. Here, to identify endogenous factors that modulate Aß production, we performed a gene microarray-based transcriptome analysis of neuronal cells derived from human induced pluripotent stem cells, because Aß production in these cells changes during neuronal differentiation. We found that expression of the glycophosphatidylinositol-specific phospholipase D1 (GPLD1) gene is associated with these changes in Aß production. GPLD1 overexpression in HEK293 cells increased the secretion of galectin 3-binding protein (GAL3BP), which suppressed Aß production in an AD model, neuroglioma H4 cells. Mechanistically, GAL3BP suppressed Aß production by directly interacting with APP and thereby inhibiting APP processing by ß-secretase. Furthermore, we show that cells take up extracellularly added GAL3BP via endocytosis and that GAL3BP is localized in close proximity to APP in endosomes where amyloidogenic APP processing takes place. Taken together, our results indicate that GAL3BP may be a suitable target of AD-modifying drugs in future therapeutic strategies for managing AD.

Prognostic biomarkers for immunotherapy with ipilimumab in metastatic melanoma.

New therapies, including the anti-cytotoxic T lymphocyte antigen (CTLA)-4 antibody, ipilimumab, is approved for metastatic melanoma. Prognostic biomarkers need to be identified, because the treatment has serious side effects. Serum samples were obtained before and during treatment from 56 patients with metastatic or unresectable malignant melanoma, receiving treatment with ipilimumab in a national Phase IV study (NCT0268196). Expression of a panel of 17 inflammatory-related markers reflecting different pathways including extracellular matrix remodeling and fibrosis, vascular inflammation and monocyte/macrophage activation were measured at baseline and the second and/or third course of treatment with ipilimumab. Six candidate proteins [endostatin, osteoprotegerin (OPG), C-reactive protein (CRP), pulmonary and activation-regulated chemokine (PARC), growth differentiation factor 15 (GDF15) and galectin-3 binding-protein (Gal3BP)] were persistently higher in non-survivors. In particular, high Gal3BP and endostatin levels were also independently associated with poor 2-year survival after adjusting for lactate dehydrogenase, M-stage and number of organs affected. A 1 standard deviation increase in endostatin gave 1·74 times [95% confidence interval (CI) = 1·10-2·78, P = 0·019] and for Gal3BP 1·52 times (95% CI = 1·01-2·29, P = 0·047) higher risk of death in the adjusted model. Endostatin and Gal3BP may represent prognostic biomarkers for patients on ipilimumab treatment in metastatic melanoma and should be further evaluated. Owing to the non-placebo design, we could only relate our findings to prognosis during ipilimumab treatment.

Increased Gal-3BP plasma levels in hospitalized patients infected with SARS-CoV-2.

Coronavirus disease 2019 (COVID-19) has quickly turned into a health, financial and societal problem globally. The complex pathogenesis of severe acute respiratory syndrome coronavirus centers on the unpredictable clinical progression of the disease, which may evolve abruptly and results in critical and life-threatening clinical complications. Effective laboratory biomarkers that can classify patients according to risk of progression to severe disease are essential for ensuring timely treatment. Gal-3BP is a human secreted protein with innate immune functions, which is upregulated in viral infections, promotes inflammation and has been shown to induce IL-6 expression. In this study, Gal-3BP plasma levels were measured retrospectively in a cohort of 84 hospitalized COVID-19 patients. These were classified as having either "non-severe" or "severe" disease. Compared to healthy controls, Gal-3BP plasma levels were markedly increased in COVID-19 patients (P < 0.0001). Moreover, the levels were higher in severe than in non-severe patients (P < 0.05). As expected, patients with severe disease had plasma levels of IL-6 higher than patients with non-severe disease (P < 0.01). In non-severe disease patients, Gal-3BP levels collected at a late stage (13.3 + 5.7 days after the first positive PCR result) were significantly lower than those collected at an early stage (4.2 + 2.9 days form the first positive PCR result). Larger prospective analyses are needed to strength our understanding of the prognostic utility of Gal-3BP in COVID-19 patients.

Polymeric immunoglobulin receptor and galectin-3-binding protein are raised in biliary atresia: Reveals a proteomic-based study.

To identify and evaluate differentially expressed plasma proteins in biliary atresia (BA), we performed plasma proteome profiling using liquid chromatography with tandem mass spectrometry (LC-MS/MS) in 20 patients with BA and 10 control children. Serological assays validated the most significant and highly upregulated proteins in a cohort of 45 patients and 15 controls. Bioinformatics tools were used for functional classification and protein-protein interactions of differentially expressed proteins (DEPs). Of 405 proteins detected in patients and 360 in controls, 242 proteins, each with ≥2 unique peptides (total of 3230 peptides), were common in both groups. Compared to controls, 90 proteins in patients were differentially expressed and were dysregulated. Twenty-five were significantly upregulated with polymeric immunoglobulin receptor (PIgR), galectin-3-binding protein (Gal-3BP), complement C2, the most prominent, and 15 had low expression. The bioinformatic analysis revealed functional interaction between DEPs and their role in an inflammatory immune response. Enzyme immunoassay for PIgR and Gal-3BP in patients' plasma showed their levels raised significantly (p = 0.0021 and p = 0.0369, respectively). The PIgR and Gal-3BP are novel proteins upregulated in BA and may be tested further for their utility as potential circulating disease biomarker(s). SIGNIFICANCE: The study shows that plasma PIgR and GAL-3BP levels are significantly raised in infants with BA within the first 3 months of life. If tested in a larger cohort, these proteins may be found to have their diagnostic potential and utility as disease biomarkers. The study also provides valuable information on the involvement of several DEPs in innate immune response, chronic inflammation, and fibrosis. This strengthens the hypothesis that the immune-mediated inflammatory processes are responsible for the progressive nature of BA.

Elevated plasma levels of galectin-3 binding protein are associated with post-stroke delirium - A pilot study.

To explore the role of systemic inflammation in post-stroke delirium, we investigated the level of two inflammatory mediators: high mobility group box 1 (HMGB1) and galectin-3 binding protein (Gal-3BP). Of 571 stroke patients, we compared plasma levels of HMGB1 and Gal-3BP in 79 delirious patients with 81 non-delirious patients matched for age and stroke severity. Delirious patients had higher Gal-3BP level (median: 1440 vs 1053 ng/mL, P < 0.01). An elevated level of Gal-3BP was associated with an increased risk of delirium. HMGB1 levels did not differ between groups. Our results suggest that pro-inflammatory monocytes and macrophages might be involved in delirium pathophysiology.

Plasma Galectin-3 and urine proteomics predict FEV1 improvement in omalizumab-treated patients with severe allergic asthma: Results from the PROXIMA sub-study.

BACKGROUND: Patients with severe allergic asthma (SAA) when treated with omalizumab may exhibit different extent of response. Identifying biomarkers that can predict the extent of treatment effectiveness in patients can be useful in personalizing omalizumab treatment. METHODS: Patients from the longitudinal phase of the PROXIMA study were selected for this ancillary study. After 12 months of omalizumab treatment, patients were categorized according to their response to treatment as: "clinical responder" (Asthma Control Questionnaire [ACQ] total score <1 at Month 12 and/or with a reduction in number of exacerbation versus the previous year); "functional responder" (an increment of ≥0.1 L in forced expiratory volume in 1 s [FEV1] at Month 12 versus baseline); and "super responder" (among clinical responders group, who also showed a functional response). Plasma galectin-3 (GAL-3) levels were quantified using a micro titer plate-based enzyme linked immunosorbent assay kit. RESULTS: The Majority of patients (86.36%) in sub-study population were identified as clinical responders. Of the total patients identified as clinical responders, 64.86% were identified as super responders. A statistically significant difference in the baseline plasma GAL-3 levels between responders and non-responders was observed only in the functional responders group (P = 0.0446). Patients with plasma GAL-3 level of ≥11 ng/mL had a greater probability of being a super responder (P = 0.0118) or a functional responder (P = 0.0032). CONCLUSION: Our findings support the use of plasma GAL-3 as a predictive marker to stratify responders and identify super responders and functional responders to omalizumab treatment in patients with severe allergic asthma using less invasive sample like plasma.

Gal-3BP Negatively Regulates NF-κB Signaling by Inhibiting the Activation of TAK1.

Galectin-3-binding protein (Gal-3BP) is a member of the family of scavenger receptor cysteine-rich (SRCR) domain-containing proteins, which are associated with the immune system. However, the functional roles and signaling mechanisms of Gal-3BP in host defense and the immune response remain largely unknown. Here, we identified cellular Gal-3BP as a negative regulator of NF-κB activation and proinflammatory cytokine production in lipopolysaccharide (LPS)-stimulated murine embryonic fibroblasts (MEFs). Furthermore, cellular Gal-3BP interacted with transforming growth factor ß-activated kinase 1 (TAK1), a crucial mediator of NF-κB activation in response to cellular stress. Gal-3BP inhibited the phosphorylation of TAK1, leading to suppression of its kinase activity and reduced protein stability. In vivo we found that Lgals3BP deficiency in mice enhanced LPS-induced proinflammatory cytokine release and rendered mice more sensitive to LPS-induced endotoxin shock. Overall, these results suggest that Gal-3BP is a novel suppressor of TAK1-dependent NF-κB activation that may have potential in the prevention and treatment of inflammatory diseases.