Arachidonic acid modulation of BK (Slo1) channels: Role of the β1 accessory subunit

MARTÍN, P; MONCADA, M; DUCCA, G; ORSI, F; CASTILLO, K; GONZALEZ LEÓN, C; MILESI, V

Valparaíso

Congreso; Society of General Physiologists (SGP)73rd Annual SymposiumSociedad de Biofísicos Latinoamericanos (SOBLA) Annual Meeting; 2019

Centro Interdisciplinario de Neurocieincias de Valparaíso

Arachidonic acid (AA) is a fattyacid involved in modulation of several ion channels. Previously, we reportedthat AA activates the high conductance Ca2+- and voltage-dependent K+channel (BK) in vascular smooth muscle cells where the channel is expressedwith the accessory β1-subunit (β1) [Martín et al. 2014. Pflugers Arch. 466(9):1779-92]. Here,we studied in depth the action mechanism of AA using the patch-clamp techniqueon BK channel heterologously expressed with β1. 10 µM AA activated the BK channel by a left shifton 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, since activation persisted in the presence of AA metabolic enzymesblockers (Indomethacin, CDCand 17-ODYA to block the COX, LOX and CYP450, respectively). Consideringthat activation by AA requires the presence of β1,which modulates the apparent Ca2+ sensitivity, stabilizes the voltagesensor domain in its active configuration, and the intrinsic opening of thechannel, we analyzed whether AA acts in these processes. By measuring the gating currents, we evaluated if thevoltage sensor domain is affected by AA, observing that it produces asignificant 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 the intrinsic channel openingprobability (NPoi). The results showed that AA increases NPoi 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 independent of the intracellular Ca2+concentration (ΔV1/2=-59.8 mV ± 4.8 and -67.5 mV ± 8.8 at 3 nM and 1 µM Ca2+, respectively,n=5-6, p>0.05). These results indicated that BK activation by AA depends onthe presence of β1-subunit, affecting the voltage sensor domain andincreasing the intrinsic openingof the channel.