Human neuronal voltage-dependent calcium channels: studies on subunit structure and role in channel assembly

Neuropharmacology. 1993 Nov;32(11):1089-102. doi: 10.1016/0028-3908(93)90004-m.


Voltage-dependent calcium (Ca2+) channels, expressed in the CNS, appear to be multimeric complexes comprised of at least alpha 1, alpha 2 and beta subunits. Previously, we cloned and expressed human neuronal alpha 1, alpha 2 and beta subunits to study recombinant channel complexes that display properties of those expressed in vivo. The alpha 1B-mediated channel subtype binds omega-conotoxin (CgTx) GVIA with high affinity and exhibits properties of N-type voltage-dependent Ca2+ channels. Here we describe several alpha 2 and beta splice variants and report results on the expression of omega-CgTx GVIA binding sites, assembly of the subunit complex and biophysical function of alpha 1B-mediated channel complexes containing some of these splice variants. We optimized recombinant expression in human embryonic kidney (HEK) 293 cells of alpha 1B alpha 2b beta 1 subunit complexes by controlling the expression levels of subunit mRNAs and monitored cell surface expression by binding of omega-CgTx GVIA to the alpha 1B subunit. Co-expression of either alpha 2b or beta 1 subunits with an alpha 1B subunit increased expression of binding sites while the most efficient expression was achieved when both alpha 2b and beta 1 subunits were co-expressed with an alpha 1B subunit. The presence of alpha 2b affects the affinity of omega-CgTx GVIA binding and barium (Ba2+) current magnitudes, although it does not appear to alter kinetic properties of the Ba2+ current. This is the first evidence of an alpha 2 subunit modulating the binding affinity of a cell-surface Ca2+ channel ligand. Our results demonstrate that alpha 1, alpha 2 and beta subunits together contribute to the efficient assembly and functional expression of voltage-dependent Ca2+ channel complexes.

MeSH terms

  • Amino Acid Sequence
  • Barium / metabolism
  • Base Sequence
  • Blotting, Northern
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism*
  • Cells, Cultured
  • Electrophysiology
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Neurons / metabolism*
  • Peptides / pharmacology
  • Polymerase Chain Reaction
  • RNA, Messenger / metabolism
  • omega-Conotoxin GVIA


  • Calcium Channel Blockers
  • Calcium Channels
  • Peptides
  • RNA, Messenger
  • Barium
  • omega-Conotoxin GVIA