U-type inactivation of Kv3.1 and Shaker potassium channels.
We previously concluded that the Kv2.1 K(+) channel inactivates preferentially from partially activated closed states. We report here that the Kv3.1 channel also exhibits two key features of this inactivation mechanism: a U-shaped voltage dependence measured at 10 s and stronger inactivation with repetitive pulses than with a single long depolarization. More surprisingly, slow inactivation of the Kv1 Shaker K(+) channel (Shaker B Delta 6--46) also has a U-shaped voltage dependence for 10-s depolarizations. The time and voltage dependence of recovery from inactivation reveals two distinct components for Shaker. Strong depolarizations favor inactivation that is reduced by K(o)(+) or by partial block by TEA(o), as previously reported for slow inactivation of Shaker. However, depolarizations near 0 mV favor inactivation that recovers rapidly, with strong voltage dependence (as for Kv2.1 and 3.1). The fraction of channels that recover rapidly is increased in TEA(o) or high K(o)(+). We introduce the term U-type inactivation for the mechanism that is dominant in Kv2.1 and Kv3.1. U-type inactivation also makes a major but previously unrecognized contribution to slow inactivation of Shaker.
Klemic
K G
KG
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Kirsch
G E
GE
Jones
S W
SW
D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D004594:Electrophysiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009479:Neuropeptides / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D012313:RNA / Q000235:genetics / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels; D051670:Shaw Potassium Channels; D019789:Tetraethylammonium / Q000494:pharmacology; D014982:Xenopus laevis
D029721:Drosophila Proteins; D009479:Neuropeptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C496929:Sh protein, Drosophila; D051637:Shaker Superfamily of Potassium Channels; D051670:Shaw Potassium Channels; D012313:RNA; D019789:Tetraethylammonium