Regulation of voltage-dependent calcium channels in rat sensory neurones involves a Ras-mitogen-activated protein kinase pathway

J Physiol. 2000 Sep 15;527 Pt 3(Pt 3):433-44. doi: 10.1111/j.1469-7793.2000.00433.x.


The small G-protein Ras, a critical component in the signalling pathways regulating cell growth, is involved in the tonic upregulation of voltage-dependent calcium channels (VDCCs) in rat sensory neurones. To investigate which downstream effector(s) of Ras is involved in this process, a series of Ras mutant cDNAs were co-expressed with green fluorescent protein (GFP) in primary cultured rat dorsal root ganglion neurones (DRGs). Constitutively active V12Ras (glycine 12 to valine) markedly increased basal calcium current density by 41 % compared with control cells (GFP alone). In contrast, a farnesylation-defective mutant, V12S186Ras (cysteine 186 to serine; activates no downstream effectors), significantly reduced calcium current density by 47 %. Ras effector region mutants V12C40 (tyrosine 40 to cysteine; activates the p110 alpha-subunit of phosphatidylinositol 3-kinase) and V12G37 (glutamic acid 37 to glycine; activates Ral guanine nucleotide dissociation stimulator) had no significant effect on VDCC current. However, V12S35Ras (threonine 35 to serine; activates Raf-1 and the mitogen-activated protein kinase (MAPK) pathway) markedly increased basal calcium current density by 67 %, suggesting that Raf-1 activation is sufficient for Ras enhancement of calcium current in these cells. Raf-1 activates MEK (MAPK kinase) in the MAPK pathway, and the MEK inhibitor U0126 reduced calcium current by 45 % after 10-15 min, whereas the inactive analogue U0124 had no effect. This rapid time course for MEK inhibition suggests direct modulation of VDCCs via the Ras-MAPK pathway rather than gene expression-mediated effects. The relative proportions of omega-conotoxin GVIA- and nicardipine-sensitive N- ( approximately 40 %) and L- ( approximately 40 %) type currents were unaffected by either V12S35Ras expression or U0126 pre-treatment, suggesting that all components of calcium current in DRGs, are enhanced via this pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Butadienes / pharmacology
  • Calcium Channels, N-Type / drug effects*
  • Calcium Channels, N-Type / genetics
  • Cells, Cultured
  • Chromones / pharmacology
  • Electrophysiology
  • Enzyme Inhibitors
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / drug effects
  • Ganglia, Spinal / metabolism
  • Membrane Potentials / physiology
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism*
  • Morpholines / pharmacology
  • Neurons, Afferent / drug effects*
  • Neurons, Afferent / metabolism
  • Nitriles / pharmacology
  • Patch-Clamp Techniques
  • Phosphoinositide-3 Kinase Inhibitors
  • Plasmids / genetics
  • Rats
  • Up-Regulation
  • ras Proteins / genetics
  • ras Proteins / metabolism*


  • Butadienes
  • Calcium Channels, N-Type
  • Chromones
  • Enzyme Inhibitors
  • Morpholines
  • Nitriles
  • Phosphoinositide-3 Kinase Inhibitors
  • U 0126
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Mitogen-Activated Protein Kinases
  • ras Proteins