Figure 3. Representation of the plasma membrane-associated sialidase Neu3 overexpression effects in human fibroblasts. The Neu3 overexpression in these cells determined several cell signals that caused up-regulation of enzymes, such as the plasma membrane-associated ß-galactosidase and ß-glucosidase and the intracellular GM3 synthase. The ß-galactosidase and ß-glucosidase activities produced ceramide from ganglioside GM3 in the plasma membrane. The high concentration of ceramide acts on two important cells mechanisms: reduction of cell proliferation and induction of apoptosis. The increased GM3 synthase expression maintains a constant concentration of GM3.