Mode switching characterizes the activity of large conductance potassium channels recorded from rat cortical fused nerve terminals

Abstract

Inside‐out recordings from rat cortical fused nerve terminals indicate that the most common channel observed was a large conductance K+ (BK) channel with characteristics dissimilar to conventional cell body calcium‐activated BK (BKCa) channels. BK channels exhibit mode switching between low (mode 1) and high (mode 2) activity, an effect not influenced by membrane voltage. Increasing internal Ca2+ concentration increased time spent in mode 2 as did application of protein kinase A, an effect not mimicked by protein kinase C or protein kinase G. Mode 1 activity was voltage independent although depolarization increased mode 2 channel activity. Global average channel activity was voltage and Ca2+ dependent. Alkaline phosphatase treatment induced channel activity to reside permanently in mode 2, where activity was voltage and Ca2+ dependent but unaffected by protein kinases A, G or C. Internal application of tetraethylammonium blocked BK channel activity in a manner identical to that reported for BKCa channels. These results indicate that nerve terminal membranes have large conductance K+ channels with significant differences in gating kinetics and regulation of activity compared with BKCa channels of other neuronal preparations. The BK channel subtype may play a unique physiological role specific to the nerve terminal.

Modal gating of GluN1/GluN2D NMDA receptors

“…In l -type and P/Q-type calcium channels, modal gating has been attributed to both phosphorylation and voltage dependence (Hess and Tsien, 1984; Ochi and Kawashima, 1990; Yue et al, 1990; Dzhura et al, 2000; Alt et al, 2004; Fellin et al, 2004; Luvisetto et al, 2004; Hashambhoy et al, 2009). In addition, phosphorylation has been implicated in modal gating in K + channels (Marrion, 1996; Smith and Ashford, 1998; Singer-Lahat et al, 1999; Mullner et al, 2003). Voltage, auxiliary subunits, G-protein subunits, and other intracellular signaling molecules lead to models of modal gating in a number of other channels, including voltage-activated Na + and Ca 2+ channels as well as acetylcholine activated channels (Howe and Ritchie, 1992; Delcour et al, 1993; Naranjo and Brehm, 1993; Imredy and Yue, 1994; Chang et al, 1996; Peterson et al, 1999; Singer-Lahat et al, 1999; Wakamori et al, 1999; Meir et al, 2000).…”

Modal behavior of the Kv1.1 channel conferred by the Kvβ1.1 subunit and its regulation by dephosphorylation of Kv1.1

“…Modal gating behavior with slow shifts between modes has been described for several channel types including voltage-gated Ca 2+ , Cl -, Na + channels and Ca 2+ -dependent K + channels [1,2,5,6,7,8,12,19]. Indeed, the single αβ channel displays a clear bimodal gating that fulfills all necessary criteria.…”

Structure-Activity Analysis of Niclosamide Reveals Potential Role for Cytoplasmic pH in Control of Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling

“…To measure pH i , BCECF dye was excited alternately at 452 and 488 nm, and the emission intensity at 515 nm was measured using a fluorescence ratio imaging system (Atto Bioscience, Rockville, MD). Background-corrected BCECF emission intensity ratios were converted into pH i values using the high K ϩ /nigericin technique (56,57).…”