Taurine-induced neuronal differentiation: the influence of calcium and the ganglioside GM1.
Taurine-induced differentiation was examined in the murine neuroblastoma Neuro-2a cell line in the presence or absence of the monosialoganglioside GM1 and under conditions in which Ca2+ levels were manipulated. Taurine (4 mM), GM1 (200 micrograms/ml), or taurine with GM1 were applied to culture media that contained either various concentrations of Ca2+ or the Ca2+ ionophore A23187. Taurine or GM1 and taurine with GM1 increased the number of cells emitting neurites above that found for controls. A significant interaction was found between treatment (taurine, GM1 or taurine + GM1) and the manipulations of Ca2+ levels, affecting the number of neurites and producing changes on the neuritic and perikaryal surfaces. Treatment with both taurine and taurine + GM1 and the various concentrations of Ca2+ resulted in a significant increase in neurite elongation. The Ca2+ ionophore A23187 in the presence of taurine or taurine + GM1 caused neurites to grow longer than observed in media containing Ca2+, either in a low concentration (about 125 microM) or at 1-2 mM. Taurine-treated cultures in the presence of extracellular Ca2+ or A23187 were characterized by surfaces with numerous microvillar, spine-like projections. This effect was enhanced with GM1 and was less pronounced in the medium containing low levels of Ca2+. Transmission electron microscopy of the taurine-stimulated neurons revealed an excessive number of clear-core vesicles (40-200 nm in diameter) in perikarya, neurites and neuritic varicosities and growth cones. In addition, numerous aggregates of intermediate filaments were seen. They were most abundant in the taurine + GM1 treated cultures. The taurine + A23187 cultures also exhibited numerous microtubules within the elongated processes. The different neuritic patterns induced by taurine under conditions in which Ca2+ levels were manipulated and/or when cells were exposed to exogenous GM1 suggest that taurine's actions depend in part on Ca2+ flux.
Spoerri
P E
PE
Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, KY 40292.
Caple
C G
CG
Roisen
F J
FJ
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D005677:G(M1) Ganglioside / Q000494:pharmacology*; D008854:Microscopy, Electron; D009474:Neurons / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D015388:Organelles / Q000648:ultrastructure; D013654:Taurine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D013654:Taurine; D005677:G(M1) Ganglioside; D000001:Calcimycin; D002118:Calcium