CONICET | Buscador de Institutos y Recursos Humanos

Arachidonic acid (AA) is apolyunsaturated fatty acid involved in modulation of several ion channelsactivity. Previously, we reported that 10 µM AA activates the high conductanceCa2+- and voltage-dependent K+ channel (BK) in humanvascular smooth muscle cells where the α subunit of BK is expressed togetherwith the accessory β1-subunit (β1) [1]. In this work, we studied in depth the actionmechanism of AA using the patch-clamp technique on BK channel heterologouslyexpressed with β1. 10 µM AA activated BK only in presence of β1, changing the voltage dependence of activation (leftshift on G-V curve, ΔV1/2= -55.2 mV ± 4,4; n=3; p<0,05). We also demonstrated that the modulation of the channel by AA isdirect, without involving its metabolites since activation persisted in thepresence of AA metabolic enzymes blockers (Indomethacin, CDC and 17-ODYA to block the COX, LOXand CYP450 enzymes, respectively). Considering that activation by AA requires thepresence of β1, which modulates theCa2+ and the voltage sensor, and the intrinsic opening of thechannel, we analyzed whether AA acts changing the β1modulation of these processes. Bymeasuring the gating currents, we evaluated if the voltage sensor is affectedby AA, observing that it produces a significant left shift in the Q-V curve (ΔV1/2=-17.2 ±8.1 mV, n=5, p<0.05). We also studied the effect of AA on theintrinsic channel opening probability (NPoi). The results showed that AA increasesNPoi in all tested cells (control: NPoi= 0.0013 ±0.0008; AA: NPoi= 0.0245±0.0051; n=4; p<0.05). Finally, the AA-induced BK channel activation was independentof the intracellular Ca2+ concentration (ΔV1/2= -59.8 mV ± 4.8 and -67.5 mV ± 8.8 at3 nM and 1 µM Ca2+, respectively, n=5-6, p p<0.05). These resultsindicated that BK activation by AA depends on the presence of β1-subunit involving changes in both the voltage sensoractivation and in the intrinsicopening of the channel. [1] Martín et al. Pflugers Arch Eur J Physiol. 2014.