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P21ras oncogene protein selectively increases low-voltage-activated Ca2+ current density in embryonic chick dorsal root ganglion neurons

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Wittinghofer,  Alfred
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Hahnel, C., Gottmann, K., Wittinghofer, A., & Lux, D. (1992). P21ras oncogene protein selectively increases low-voltage-activated Ca2+ current density in embryonic chick dorsal root ganglion neurons. European Journal of Neuroscience: European Neuroscience Association, 4(4), 361-368. doi:10.1111/j.1460-9568.1992.tb00883.x.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0019-AB8F-9
Abstract
p21ras protein resembles the alpha subunit of trimeric G-proteins, which regulate ion channel function. We now report a modulation of Ca2+ channels in vertebrate sensory neurons by p21ras in addition to its role in cell growth and differentiation. Quantitative microinjection of oncogenic p21-H-ras into embryonic chick dorsal root ganglion neurons was performed. After 4 h the current density of the low-voltage-activated (LVA; T-type) Ca2+ channels was increased. However, in contrast to trimeric G-proteins, which inhibit high-voltage-activated (HVA) Ca2+ channels in chick dorsal root ganglion neurons, p21ras did not significantly affect HVA Ca2+ currents. To study the time course of p21ras action, guanosine triphosphate-preloaded p21ras was added to the patch pipette. Full-length ras was effective only after a delay of 20 - 30 min. C-terminal modification by cellular enzymes is required to activate full-length ras, and can account for the observed delay. Unexpectedly, C-terminal-truncated p21ras, which was found to be inactive in biological assays, enhanced LVA Ca2+ currents within minutes. This suggests a G-protein-like modulation of the LVA Ca2+ channel by p21ras. In an early phase of neuronal differentiation, dorsal root ganglion neurons express only LVA Ca2+ currents. The regulatory role of p21ras on LVA channels may therefore be particularly important during differentiation.