beta subunits influence the biophysical and pharmacological differences between P- and Q-type calcium currents expressed in a mammalian cell line

Human epithelial kidney cells (HEK) were prepared to coexpress alpha 1A, alpha 2 delta with different beta calcium channel subunits and green fluorescence protein, To compare the calcium currents observed in these cells with the native neuronal currents, electrophysiological and pharmacological fools were used conjointly. Whole-cell current recordings of human epithelial kidney alpha 1A-transfected cells showed small inactivating currents in 80 mM Ba2+ that were relatively insensitive to calcium blockers. Coexpression of alpha 1A beta Ib, and alpha 2 delta produced a robust inactivating current detected in 10 mM Ba2+, reversibly blockable with low concentration of omega-agatoxin IVA (omega-Aga IVA) or synthetic funnel-web spider toxin (sFTX), Barium currents were also supported by alpha 1A, beta 2a, alpha 2 delta subunits, which demonstrated the slowest inactivation and mere relatively insensitive to omega-Aga IVA and sFTX. Coexpression of beta 3 with the same combination as above produced inactivating currents also insensitive to low concentration of omega-Aga NA and sFTX. These data indicate that the combination alpha 1A, beta Ib, alpha 2 delta best resembles P-type channels given the rate of inactivation and the high sensitivity to omega-Aga IVA and sFTX. More importantly, the specificity of the channel blocker is highly influenced by the beta subunit associated with the alpha 1A subunit.