Negative regulation of neuroblastoma cell growth by carbohydrate-dependent surface binding of galectin-1 and functional divergence from galectin-3.
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 carbohydrate-binding sites.
Kopitz
J
J
Institut für Pathochemie und Neurochemie and the Pathologisches Institut, Klinikum der Ruprecht-Karls-Universität, Im Neuenheimer Feld 220, D-69120 Heidelberg, Germany.
von Reitzenstein
C
C
André
S
S
Kaltner
H
H
Uhl
J
J
Ehemann
V
V
Cantz
M
M
Gabius
H J
HJ
D000943:Antigens, Differentiation / Q000378:metabolism*; D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D017931:DNA Primers; D037483:Galectin 1; D037502:Galectin 3; D006388:Hemagglutinins / Q000378:metabolism*; D006801:Humans; D009447:Neuroblastoma / Q000473:pathology*; D011485:Protein Binding; D014407:Tumor Cells, Cultured
D000943:Antigens, Differentiation; D017931:DNA Primers; D037483:Galectin 1; D037502:Galectin 3; D006388:Hemagglutinins