Fig. 4

Galectins modulate cellular activities of FGF4. A The effect of FGF4-Fc (5 ng/mL), galectins (5 µg/mL) and a mixture of FGF4-Fc (5 ng/mL)/ galectin (5 µg/mL) on NIH3T3 cell proliferation assessed with the Presto Blue Cell Viability Reagent. Mean values +/-SD from at least three independent experiments are shown. Statistical analyses were performed with Student’s t-test (*p < 0.05; **p < 0.005 and ***p < 0.001). B Effects of FGF4-Fc (108 ng/mL), galectins (50 µg/mL) and a mixture of FGF4-Fc (108 ng/mL) / galectin (50 µg/mL) on glucose uptake by adipocytes. Mean values +/-SD from at least three independent experiments are shown. Statistical analyses were performed with Student’s t-test (*p < 0.05; **p < 0.005 and ***p < 0.001). C A hypothetical model of the modulation of FGF4 signaling by galectins. Simultaneous binding of multivalent galectins to the N-glycans of FGF4 and to yet unidentified extracellular matrix (ECM) components attracts FGF4 to the cell surface, thereby forming a reservoir of growth factor in the vicinity of plasma membrane-embedded FGFRs. Galectin-facilitated cell binding is reflected in altered FGF4/FGFR signaling and endocytosis, which ultimately shapes cell division without affecting metabolic activity of cells. The diversity of galectins’ effects on FGF4 is likely determined by different binding partners of particular galectins in the ECM