title: Internal aluminum block of plant inward K(+) channels.
abstract: Aluminum (Al) inhibits inward K(+) channels (K(in)) in both root hair and guard cells, which accounts for at least part of the Al toxicity in plants. To understand the mechanism of Al-induced K(in) inhibition, we performed patch clamp analyses on K(in) in guard cells and on KAT1 channels expressed in Xenopus oocytes. Our results show that Al inhibits plant K(in) by blocking the channels at the cytoplasmic side of the plasma membrane. In guard cells, single-channel recording revealed that Al inhibition of K(in) occurred only upon internal exposure. Using both "giant patch" recording and single-channel analyses, we found that Al reduced KAT1 open probability and changed its activation kinetics through an internal membrane-delimited mechanism. We also provide evidence that a Ca(2)+ channel-like pathway that is sensitive to antagonists verapamil and La(3)+ mediates Al entry across the plasma membrane. We conclude that Al enters plant cells through a Ca(2)+ channel-like pathway and inhibits K(+) uptake by internally blocking K(in).
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
authors.forename: K
authors.initials: K
authors.lastname: Liu
authors.forename: S
authors.initials: S
authors.lastname: Luan
mesh_terms: D000535:Aluminum / Q000494:pharmacology* / Q000633:toxicity; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D004594:Electrophysiology; D004734:Energy Metabolism; D007887:Fabaceae; D007700:Kinetics; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D010946:Plants, Medicinal; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics; D024661:Potassium Channels, Inwardly Rectifying; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D014700:Verapamil / Q000494:pharmacology; D014981:Xenopus
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010940:Plant Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011994:Recombinant Proteins; D014700:Verapamil; D000535:Aluminum