| Voltage-gated calcium channels are an essential family of transmembrane proteins that allow calcium influx and depolarization of the membrane potential. Consistent with the diversity of calcium channel isoforms and subunit distribution, these channels mediate a variety of cellular processes including neurotransmitter release, sensory perception, spontaneous firing activity, gene transcription, and excitation-contraction coupling. The objective of this work was to delineate similarities and differences in calcium channel activity and regulation across a range of calcium channel subtypes. I compared calcium channel splicing and biophysical properties, interaction with external cations, block by a series of hydrophobic compounds, and regulation by a member of the G protein-coupled receptor family. In the course of these experiments, I have discovered novel loss of function splice isoforms of T-type Cav3.1, evidence for an external cation binding site on L-type Cav1.2 and P/Q-type Cav2.1 channels, and state dependent block of Cav2 family channels by hydrophobic aliphatic monoamine compounds. These data also revealed the existence of a functional channel-receptor signalling complex between N-type Cav2.2 channels and the opioid-receptor like (ORL1) receptor that mediated an agonist independent channel regulation. Several of these data have important implications in designing therapeutics for the treatment of pain. Overall, these data found that calcium channel functional properties associated with conserved transmembrane domains were consistent across many channel isoforms, while channel traits linked to intra- or extracellular regions of the protein became divergent. |
