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

Abstract

We cloned two L L subunits of large-conductance calcium-activated potassium (BK) channels, hKCNMB3 (BKL L1) and hKCNMB4 (BKL L4). Profiling mRNA expression showed that hKCNMB3 expression is enriched in testis and hKCNMB4 expression is very prominent in brain. We coexpressed BK channel K K (BKK K) and BKL L4 subunits in vitro in CHO cells. We compared BKK K/L L4 mediated currents with those of smooth muscle BKK K/L L1 channels. BKL L4 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 BKL L1. BKK K/L L4 channels were not blocked by 100 nM charybdotoxin or iberiotoxin, and were activated by 17L L-estradiol.z 2000 Federation of European Biochemical Societies.

Inhibition of Ca2+-activated large-conductance K+ channel activity alters synaptic AMPA receptor phenotype in mouse cerebellar stellate cells

“…Although our results show that iberiotoxin produced a marked inhibition of potassium currents in stellate cells, charybdotoxin, a BK channel blocker, failed to reduce the potassium current in basket cells (Southan and Robertson 1998). This could be due to the presence of ␤-subunits that reduce the inhibitory potency of charybdotoxin (Behrens et al 2000) or the higher EGTA (10 mM) concentration of the pipette solution used in their study that suppresses a Ca 2ϩ rise and thus the activity of BK channels. The transient and sustained K ϩ currents play a distinct role in controlling AP firing in stellate cells.…”

Nasal speech and hypothyroidism are common hallmarks of 12q15 microdeletions

“…13,14 Both PTPRB and PTPRR belong to the protein tyrosine phosphatase (PTP) family. This family of enzymes consists of key factors in a variety of cellular processes including cell growth, differentiation, 15 Malfunction of PTP activity is associated with a number of human disorders, including cancers, diabetes, rheumatoid arthritis and hypertension.…”

Down-regulation of BK channel expression in the pilocarpine model of temporal lobe epilepsy

“…BK channel complexes, especially formed by β4 subunits, are widely distributed throughout the mammalian brain (Behrens et al, 2000;Brenner et al, 2000;Ha et al, 2004). The precise distribution and preferential trafficking of BK channels to axon terminals and somatodendritic regions can ultimately determine the function of BK channels in neurons and circuits.…”