Fucoganglioside α-fucosyl(α-galactosyl)-G_M1: a novel member of lipid membrane microdomain components involved in PC12 cell neuritogenesis

In order to search for novel components of lipid membrane microdomains involved in neural signalling pathways, mAbs (monoclonal antibodies) were raised against the detergent-insoluble membrane fraction of PC12 (pheochromocytoma) cells. Among the 22 hybrid clones, mAb PR#1 specifically detected a fucoganglioside Fuc(Gal)-G_M1 [α-fucosyl(α-galactosyl)-G_M1], a ganglioside homologous with G_M1a (II³NeuAc,GgOse₄Cer), as a novel member of microdomain components with biological functions. In the presence of mAb PR#1 in the culture medium, the outgrowth of neurites was induced in PC12 cells in a dose-dependent manner, with no effects on cell proliferation, suggesting that Fuc(Gal)-G_M1 is preferentially involved in PC12 cell neuritogenesis. Effects through Fuc(Gal)-G_M1 were different from those through G_M1a during differentiation, e.g. under PR#1 treatment on Fuc(Gal)-G_M1, round cell bodies with thinner cell processes were induced, whereas treatment with CTB (cholera toxin B subunit), a specific probe for G_M1a, produced flattened cell bodies with thicker pro-cesses. Molecular analysis demonstrated that the PR#1–Fuc(Gal)-G_M1 pathway was associated with Fyn and Yes of the Src family of kinases, although Src itself was not involved. No association was found with TrkA (tropomyosin receptor kinase A) and ERKs (extracellular-signal-regulated kinases), which are responsible for G_M1a-induced differentiation. From these findings, it is suggested that a fucoganglioside Fuc(Gal)-G_M1 provides a functional platform distinct from that of G_M1a for signal transduction in PC12 cell differentiation.