Negative Regulation of Neuroblastoma Cell Growth by Carbohydrate-dependent Surface Binding of Galectin-1 and Functional Divergence from Galectin-3

Abstract

The cell density-dependent growth inhibition of human SK-N-MC neuroblastoma cells is initiated by increased ganglioside sialidase activity leading to elevated cell surface presentation of ganglioside GM1, a ligand of galectin-1. We herein show that the extent of the cell surface expression of the galectin coincides with marked increases of the sialidase activity. Reverse transcriptase-polymerase chain reaction analysis excludes a regulation at the transcriptional level. Exposure of cells to purified galectin-1 reveals its carbohydrate-dependent activity to reduce cell proliferation. Assays to detect DNA fragmentation biochemically and cytometrically and to block caspases render it unlikely that galectin-1 acts as a classical proapoptotic factor on these cells. Because the chimeric galectin-3 shares binding sites and binding parameters with galectin-1 for these cells, we tested whether this galectin will elicit the same response as the homodimeric cross-linking galectin-1. Evidently, galectin-3 fails to affect cell growth by itself but interferes with galectin-1 upon coincubation. Its proteolytically truncated variant, the C-terminal lectin domain with impaired capacity to form aggregates when surface bound, has only weak binding properties. Thus, the way in which the galectin-1 interacts topologically with an apparently common set of ligands relative to galectin-3 is crucial for eliciting post-binding events. We conclude that galectin-1 is a probable effector in the sialidase-dependent growth control in this system. Moreover, the experiments with galectin-3 reveal functional divergence, most probably based on different topologies of presentation of homologous carbohydratebinding sites.

Galectin-1 Upregulates CXCR4 to Promote Tumor Progression and Poor Outcome in Kidney Cancer

“…6 Extracellular Gal-1 has inhibitory effects on the proliferation of neuroblastoma and lymphoma cells. 25,26 In contrast, suppression of Gal-1 in glioma cells arrests cell growth, implying that endogenous Gal-1 has a growth-promoting role. 27 Furthermore, the silencing of Gal-1 significantly reduces metastatic potential in murine breast and colon cancer cells.…”

Conformational flexibility of N-glycans in solution studied by REMD simulations

“…There are many cases where the same glycan acts as a ligand for different lectins. A typical example is provided by the common pentasaccharide moiety of ganglioside GM1 being a target both for cross-linking by galectin-1 to inhibit the growth of human SK-N-MC neurobastoma cells (Kopitz et al 2001) and for the AB 5 toxin of Vibrio cholera (Siebert et al 2003). The different conformations of tetrasaccharide sialyl Lewis x bound to E-selectin seen in different NMR-based analyses serve as another example of the "bunch-of-keys" model (Harris et al 1999).…”

Galectin-1 Interacts with the α5β1 Fibronectin Receptor to Restrict Carcinoma Cell Growth via Induction of p21 and p27

“…Purification and Labeling of Galectins-Galectins-1, -3, and -5 (human homodimeric prototype Gal-1, murine chimera-type galectin-3, and rat monomeric prototype galectin-5) were purified after recombinant production by affinity chromatography on Sepharose 4B to which lactose had been covalently attached via divinyl sulfone activation, and biotinylation was performed under activity-preserving conditions as described (4,22,23). All galectins were routinely checked for purity by one-and two-dimensional gel electrophoresis under reducing and denaturing conditions, gel filtration, and nanoelectrospray ionization mass spectrometry as well as for activity by hemagglutination and solid phase assays as described (24 -26).…”