An unidentified K + channel in human smooth muscle cells shares properties with both TREK and BKCachannels

MARTÍN, P; ROLDÁN PALOMO, AR; ENRIQUE, N; FLORES, LE; REBOLLEDO, A; MILESI, V

Salta

Congreso; 3rd Latin American Protein Society Meeting & XXXIX Annual Meeting of the Argentinean Biophysical Society 2010; 2010

Latin American Protein Society y Sociedad Argentina de Biofísica

Our objective was the electrophysiological (patch clamp) characterization of K+ channels in smooth muscle cells isolated from human umbilical artery (HUA). We focused on a channel which frequently appeared in the cell-attached (CA) configuration (symmetrical K+, plus iberiotoxin and 4-aminopyridine). In CA conductance was of 135.3±5.9 pS and the open probability (NPo) of 0.262±0.083 (+40 mV, n=11), which upon patch excision (inside-out, symmetrical K+) changed to a conductance of 251.5±7.8 pS (p<0,05) and NPo = 0.005±0.001 (+40 mV, n=11; p<0.05). Both NPo were voltage dependent. In CA dibutyryl cAMP (200µM) increased the NPo. In inside-out, lowering the bath solution pH (from 7.4 to 6.0) and arachidonic acid (10 µM) significantly increased NPo (n=6 in each case). Augmenting the bath Ca2+ concentration (to 1 µM) generated a dramatic increase in NPo and changed its voltage-dependence: the channel showed a high activity also at hyperpolarized potentials (-40 mV). Bupivacaine (300 µM) provoked a fast block of the channel reducing its conductance (n=4). So, CA conductance,activation by acidic pH and arachidonic acid, together withbupivacaine blockade point to a TREK-like channel. However, classical TREK channels are inhibited by dibutyryl cAMP and increase their NPo upon patch excision, contrary to what our results show. Up to date there are no data regarding its Ca 2+ sensitivity. On the other hand, inside-out conductance value, Ca2+ and dibutyryl cAMP activation may point to another identity for this channel, namely a high-conductance Ca 2+ -activated K+channel coupled to a regulatory beta 4 subunit, which confers iberiotoxin insensitivity