Figure 3.

Effect of gangliosides on RTK activity. (A) Two EGFR monomers (1), in the presence of EGF, dimerize resulting in phosphorylation of tyrosine residues at their cytoplasmic portion (2). The interaction of the GlcNAc termini of the EGFR N-linked chains with ganglioside GM3 inhibits signaling (3), while interaction with GD3 reinforces it (4). (B) The MET receptor is comprised of a heavily glycosylated extracellular α chain (in blue) and a transmembrane β chain (in red), which undergoes phosphorylation of tyrosine residues of its cytoplasmic domain upon HGF binding (1 and 2). MET activation can be induced by interaction with disialogangliosides, such as GD3 and GD2, even in the absence of HGF (3). Sugar codes are as in the legend of Table 1.