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Galectin-3 Induces a Pro-degradative/inflammatory Gene Signature in Human Chondrocytes, Teaming Up with Galectin-1 in Osteoarthritis Pathogenesis

ABSTRACT: Inflammatory chemo- and cytokines and matrix-degrading proteases underlie the progression of osteoarthritis (OA). Aiming to define upstream regulators for these disease markers, we pursued initial evidence for an upregulation of members of the adhesion/growth-regulatory galectin family. Immunohistochemical localization of galectin-3 (Gal-3) in sections of human cartilage with increasing levels of degeneration revealed a linear correlation reaching a chondrocyte positivity of 60%. Presence in situ was cytoplasmic, in OA chondrocyte cultures the lectin was secreted and binding of Gal-3 yielded lactose-inhibitable surface staining. Exposure of cells to the lectin led to enhanced gene expression and secretion of functional disease markers. Genome-wide transcriptomic analysis broadened this insight to reveal a pro-degradative/inflammatory gene signature under the control of NF-κB. Fittingly, targeting this route of activation by inhibitors impaired the unfavourable response to Gal-3 binding, as also seen by shortening the lectin’s collagen-like repeat region. Gal-3’s activation profile overlaps with that of homodimeric galectin-1 (Gal-1) and also has distinctive (supplementing) features. Tested at subsaturating concentrations in a mixture, we found cooperation between the two galectins, apparently able to team up as driving forces in OA pathogenesis. In summary, our results suggest that a network of endogenous lectins acts as upstream master regulator in OA.

ORGANISM(S): Homo sapiens

PROVIDER: GSE85254 | GEO | 2017/02/09

SECONDARY ACCESSION(S): PRJNA337951

REPOSITORIES: GEO

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Project description:Identification of interactors is a major attempt in cell biology. Not only protein-protein but also protein-carbohydrate interactions are of high relevance for signal transduction in biological systems. Here we aim to identify novel interacting binding partners for the β-galactoside-binding proteins Galectin-1 (Gal-1) and Galectin-3 (Gal-3) in context of the eye disease proliferative vitreoretinopathy (PVR). PVR is one of the most common failures after retinal detachment surgeries and is characterized by the migration, adhesion and epithelial-to-mesenchymal transition (EMT) of retinal pigment epithelial cells (RPE) and the subsequent formation of sub- and epiretinal fibrocellular membranes. Gal-1 and Gal-3 bind in a dose- and carbohydrate-dependent manner to mesenchymal RPE cells and inhibit cellular processes like attachment and spreading. Yet knowledge about glycan-dependent interactors of Gal-1 and Gal-3 on RPE cells is very limited, although this is a prerequisite to unravel the influence of galectins on distinct cellular processes in RPE cells. In this approach, we identified by galectin pull-down experiments and quantitative proteomic screening 131 Galectin-3 and 15 Galectin-1 interactors. They mainly play a role in multiple binding processes and are mostly membrane proteins. Here we focused on two novel identified interactors of Gal-1 and Gal-3 in the context of PVR: the low-density lipoprotein receptor LRP1 and the platelet-derived growth factor receptor beta PDGFRB. We observed crosslinking and lattice formation of exogenous Gal-1 and Gal-3 with LRP1/PDGFRB and ITGB1 on the cell surface of human RPE cells. Weaker binding of Gal-1 and Gal-3 on these interactors and no lattice formation on the cell surface was seen, when complex-type-N-glycosylation was inhibited by treatment of the cells with Kifunensine. In conclusion, the identified specific glycoprotein ligands for Gal-1 and Gal-3 give us new insights in the highly specific binding of galectins to dedifferentiated RPE cells and the resulting prevention of PVR-associated cellular events.

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Galectin-3 Induces a Pro-degradative/inflammatory Gene Signature in Human Chondrocytes, Teaming Up with Galectin-1 in Osteoarthritis Pathogenesis

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