g(m1)-ganglioside and lanthanum-chloride

Treatment of three neuroblastoma cell types in culture with neuraminidase resulted in enhanced neurite outgrowth. These included the mouse Neuro-2A and rat B104 and B50 lines. The morphological changes depended on the presence of exogenous Ca2+ and were accompanied by modest but statistically significant increases in 45Ca2+ influx. Neuraminidase-stimulated neuritogenesis was blocked by the B subunit of cholera toxin (cholera B) and anti-GM1 antibody, a finding suggesting the effect was due to an increased amount of GM1 on the cell surface. Cholera B also blocked the increase in 45Ca2+ influx. The mouse N1A-103 line, previously characterized as "neurite minus," did not respond to neuraminidase with either neurite outgrowth or enhanced Ca2+ influx. These results point to an influence of GM1 on neuritogenesis in cells with differentiation potential and suggest a mechanism involving modulation of Ca2+ flux.

Topics: Animals; Antibodies; Axons; Calcium; Calcium Radioisotopes; Cholera Toxin; G(M1) Ganglioside; Lanthanum; Mice; Neuraminidase; Neuroblastoma; Peptide Fragments; Rats; Tumor Cells, Cultured

Cultures of mouse Neuro-2a neuroblastoma cells treated with 3-6 mM extracellular Ca2+ exhibited enhanced neurite extension characterized by increased neurite numbers and lengths. The ganglioside GM1 potentiated the effect of extracellular Ca2+ by increasing further the number and length of the neurites formed in response to exogenous Ca2+. Maximal neuritic numbers were achieved with 4 mM Ca2+ while the longest neurites were observed in medium containing 4-6 mM Ca2+. Stimulation of the Ca2+ influx with the ionophore A23187 or the amino acid taurine also enhanced neurite formation and GM1 potentiated these actions. Transmission electron microscopy revealed numerous microtubules and neurofilaments in neurites and microfilaments with the spine-like processes along fine neuritic branches and in the filopodia of growth cones. Neuritic varicosities and growth cones contained a variety of vesicles. All of these structures were increased in the presence of GM1 and were increased further by extracellular Ca2+ or A23187. The ability of GM1 to enhance neuritogenesis was diminished by EGTA or Ruthenium red. Similarly, the effect of GM1 was diminished or abolished by Ca2+ channel blockers such as CdCl2 or LaCl3. X-ray microprobe analysis revealed that GM1 alone enhanced intracellular levels of total ionic and membrane bound Ca2+, perhaps accounting for the increased neuritogenesis observed under conditions in which Ca2+ was manipulated. The present study suggest that the neuritogenic action of GM1 is Ca2+ dependent.

Topics: Animals; Axons; Cadmium; Cadmium Chloride; Calcimycin; Calcium; Cell Differentiation; Cell Line; Egtazic Acid; G(M1) Ganglioside; Intermediate Filaments; Lanthanum; Mice; Microtubules; Neuroblastoma; Neurons; Ruthenium Red; Taurine