BETA-SUBUNITS INFLUENCE THE BIOPHYSICAL AND PHARMACOLOGICAL DIFFERENCES BETWEEN P-TYPE AND Q-TYPE CALCIUM CURRENTS EXPRESSED IN A MAMMALIAN-CELL LINE

Human epithelial kidney cells (HEK) were prepared to coexpress alpha 1 A, alpha 2 delta with different beta calcium channel subunits and gree n fluorescence protein, To compare the calcium currents observed in th ese cells with the native neuronal currents, electrophysiological and pharmacological fools were used conjointly. Whole-cell current recordi ngs 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 del ta produced a robust inactivating current detected in 10 mM Ba2+, reve rsibly blockable with low concentration of omega-agatoxin IVA (omega-A ga IVA) or synthetic funnel-web spider toxin (sFTX), Barium currents w ere 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 combi nation 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 cha nnels given the rate of inactivation and the high sensitivity to omega -Aga IVA and sFTX. More importantly, the specificity of the channel bl ocker is highly influenced by the beta subunit associated with the alp ha 1A subunit.