Recent studies, including ours, on bioactive
gangliosides revealed that certain
gangliosides have an interesting ability to modulate a variety of cell functions. For instance, we demonstrated that a
tetrasialoganglioside, GQ1b, promotes neurite outgrowth when added in nanomolar concentrations to cells from two human
neuroblastoma cell lines. Also, phosphorylation of several
cell surface proteins was observed on addition of
ATP. Several lines of evidence indicated that this phosphorylation is probably catalysed by a novel cell surface membrane-bound
protein kinase which is specifically activated by a particular
ganglioside (Gg). Because of its location on the cell surface we proposed calling this type of
kinase(s) ecto-Gg
kinase. A procedure to inhibit the phosphorylation of the
cell surface protein resulted in suppression of the GQ1b-dependent promotion of neuritogenesis, strongly suggesting that these two cellular events are intricately coupled. Other evidence also indicated that the GQ1b-dependent neuritogenesis is mediated through a receptor-coupled process of the cell surface membrane. Thus, it is likely that this represents a new type of biosignal transduction that is mediated through cell surface
carbohydrate recognition (ecto biosignal transduction system).