p21ras Oncogene Protein Selectively Increases Low-voltage-activated Ca2+ Current Density in Embryonic Chick Dorsal...

Area of Science:

• Neuroscience
• Molecular Biology
• Cellular Physiology

Background:

• p21ras protein shares similarities with alpha subunits of G-proteins, known regulators of ion channel function.
• G-proteins modulate ion channel activity, including high-voltage-activated (HVA) calcium channels in sensory neurons.

Purpose of the Study:

• To investigate the role of p21ras in modulating calcium (Ca2+) channel function in vertebrate sensory neurons.
• To compare the effects of p21ras on Ca2+ channels with those of trimeric G-proteins.

Main Methods:

• Quantitative microinjection of oncogenic p21-H-ras into embryonic chick dorsal root ganglion neurons.
• Patch-clamp electrophysiology to measure Ca2+ channel current density.
• Application of full-length and C-terminal-truncated p21ras to assess time course and mechanism of action.

Main Results:

• p21ras significantly increased the current density of low-voltage-activated (LVA; T-type) Ca2+ channels after 4 hours.
• p21ras did not significantly affect HVA Ca2+ currents, unlike trimeric G-proteins.
• Full-length ras required a 20-30 minute delay for effect, suggesting post-translational modification, while truncated ras acted rapidly.

Conclusions:

• p21ras directly modulates LVA Ca2+ channels in sensory neurons, independent of its known roles in cell growth.
• The rapid action of truncated p21ras suggests a G-protein-like modulation mechanism for LVA channels.
• p21ras regulation of LVA channels may be crucial during the early stages of neuronal differentiation.