Anti-GM3 antibodies activate calcium inflow and inhibit platelet-derived growth factor beta receptors (PDGFβr) in T51B rat liver epithelial cells

Glycolipids expressed in the plasma membrane regulate a variety of cellular processes including intracellular calcium dynamics. We used flow cytometry to characterize the glycoconjugates on the plasma membrane of T51B liver epithelial cells. Antibodies against glycolipids found to be present were tested for their ability elevate intracellular calcium. An antibody against GM3 (DH2) nearly doubles intracellular calcium while an antibody against type II chains (1B2) increases calcium to nearly four times the baseline level, similar to levels obtained with epidermal growth factor (EGF). The antibodies stimulated calcium inflow but did not trigger calcium release from internal stores. In addition DH2 but not 1B2 inhibited platelet-derived growth factor beta receptor (PDGF-beta r) function. This is the first demonstration of activation of calcium inflow by agents that bind GM3 and type II chains. The ganglioside-mediated calcium inflow is likely to stimulate secretion by these liver cells.