In the Spafford lab, we examine four domain voltage-gated cation channels:
More information on this subject can be found in the Evolution of Ion Channels research topic in Frontiers in Physiology.
1. Cav3 T-type channels:
“Sodium with your T” (Salvador Dalíesque)
“T”-type channels are categorized amongst the calcium channels, but invertebrate ones, like in the pond snail, Lymnaea stagnalis can masquerade as sodium channels, by gene splicing of a unique veil of extracellular turret residues upstream of the selectivity filter in Domain II coded by Exon 12.
Adriano Senatore, Wendy Guan, Adrienne N. Boone and J. David Spafford, (2014) “T-type Channels Become Highly Permeable to Sodium Ions Using an Alternate Extracellular Turret Region (S5-P) Outside the Selectivity Filter" Journal of Biological Chemistry.
2. NALCN ion channel:
Channels, Volume 2, Issue 7
The cover image illustrates the ambiguous and bipolar nature of the orphan NALCN ion channel which has features of both sodium and calcium channels and has baffled investigators.
Senatore, A., Monteil, A., van Minnen, J., Smit, A.B. and Spafford, J.D. (2012) “NALCN leak conductance channel expresses in vitro and in situ with alternative selectivity filters resembling calcium channels or sodium channels” PLoS ONE 8(1): e55088. doi:10.1371/journal.pone.0055088.
3. Cav1 (L-type), Cav2 (nonL-type) and Cav-beta subunits:
Structural views of (R)-isradipine docked in human L-type channel Cav1.2. The dihydropyridine ligand is shown by sticks. Drug-sensing residues are space filled and hydrogen atoms are omitted for clarity. Calcium ions in the selectivity filter are shown as yellow spheres. Three amino acid residue differences in snail L-type channel pore-ling residues (N3o18Q, F3i10Y, I4i12M) out of 15 identified by Tikhonov and Zhorov (2009) model is responsible for the weak isradipine binding to snail L-type calcium channel. Taken from Figure 5 in Senatore et al. Channels, 2010.
Senatore, A., Boone, A.N., Lam, S, Dawson, T. F, Zhorov, B.S., and Spafford, J.D. (2011) “Mapping of dihydropyridine binding residues in a less sensitive invertebrate L-type calcium channel (LCav1)” Channels (5(2):173-87.
Online video publication of optimized ion channel transfection and patch clamp electrophysiology technique.
Senatore, A., Boone, A. and Spafford, J.D. (2011) “Optimized Transfection Strategy for Expression and Electrophysiological Recording of Recombinant Voltage-Gated Ion Channels in HEK-293T Cells” Journal of Visualized Experiments (JoVE).