hKCNMB3 and hKCNMB4, cloning and characterization of two members of the large-conductance calcium-activated potassium channel β subunit family

AbstractWe cloned two β subunits of large-conductance calcium-activated potassium (BK) channels, hKCNMB3 (BKβ1) and hKCNMB4 (BKβ4). Profiling mRNA expression showed that hKCNMB3 expression is enriched in testis and hKCNMB4 expression is very prominent in brain. We coexpressed BK channel α (BKα) and BKβ4 subunits in vitro in CHO cells. We compared BKα/β4 mediated currents with those of smooth muscle BKα/β1 channels. BKβ4 slowed activation kinetics more significantly, led to a steeper apparent calcium sensitivity, and shifted the voltage range of BK current activation to more negative potentials than BKβ1. BKα/β4 channels were not blocked by 100 nM charybdotoxin or iberiotoxin, and were activated by 17β-estradiol