title: Property of large conductance Ca(2+)-activated K+ channels from Fasciola hepatica incorporated into planar lipid bilayer.
abstract: Fasciola hepatica causes biliary epithelial hyperplasia and obstructive jaundice in humans and animals. Using a planar lipid bilayer technique, we further characterized the single channel property of large conductance K(+)-permeable channels that were previously identified from F. hepatica. The single channel conductance was 254.7±17.9 pS under a symmetrical 200/200 mM (cis/trans) KCl gradient. Open state probability (P(o)) varied from channel to channel at a given membrane potential and Ca(2+) concentration, but increased with voltage (-60 to +40 mV) and cis Ca(2+) (1-200 μM). Under a near bi-ionic condition of 200 mM [K(+)](cis)/200 mM [Na(+)](trans), the permeability ratio of K(+) to Na(+) was 5.0. Charybdotoxin (1 μM) inhibited P(o), whereas tetraethylammonium reduced the conductance (K(D)=67.8mM). Taken together, the results show that the single channel properties of the large conductance K(+)-permeable channels in F. hepatica are similar to those of large conductance Ca(2+)-activated K(+) (BK) channels in general, but distinct from typical BK channels in the extent of voltage- and Ca(2+)-dependence, as well as permeability to Na(+). This study further reveals a variant BK channel in F. hepatica that could serve as a new drug target to treat fascioliasis.
authors.affiliation: Department of Pharmacology, Research Institute of Veterinary Science, College of Veterinary Medicine, Seoul National University, 599 Gwanank-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Jung Hee
authors.initials: JH
authors.lastname: Jang
authors.forename: Jin Bong
authors.initials: JB
authors.lastname: Park
authors.forename: Sun Don
authors.initials: SD
authors.lastname: Kim
authors.forename: So Yeong
authors.initials: SY
authors.lastname: Lee
authors.forename: Sung-Jong
authors.initials: SJ
authors.lastname: Hong
authors.forename: Pan Dong
authors.initials: PD
authors.lastname: Ryu
mesh_terms: D000818:Animals; D018999:Charybdotoxin; D055724:Electrophysiological Phenomena; D005210:Fasciola hepatica / Q000378:metabolism*; D015640:Ion Channel Gating; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium; D019789:Tetraethylammonium
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D008051:Lipid Bilayers; D018999:Charybdotoxin; D019789:Tetraethylammonium; D012964:Sodium