Dual effects of Arachidonic acid on BK channel: role of β1-subunit

MONCADA, M; PICCININI, L; CASTILLO, K; ASUAJE, A; GONZÁLEZ, C; MILESI, V; MARTÍN, P

Sierra de la Ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Socieda d Argentina de Biofísica

Arachidonic acid (AA) is a polyunsaturated fatty acid involved in modulation of several ion channels activity. Previously, we reported that 10 µM AA activates the high conductance Ca2+ and voltage dependent K+ channel (BK) in human vascular smooth muscle cells where the α subunit of BK is expressed together with the regulatory β1-subunit (β1) [1]. In this work, we studied in depth the action mechanism of AA using patch clamp technique on BK channel heterologously expressed with or without β1. 10 µM AA activated BK only in presence of β1, changing the voltage dependence of activation (left shift on G-V curve, ΔV1/2= -55,2 mV ± 4,4; n=3; p<0,05), and modifying the voltage sensor movement (left shift in Q-V curve, ΔV1/2= -17,2 mV ± 8,1; n=5; p<0,05). Conversely, BK expressed without regulatory subunits, was inhibited by 10 µM AA (n=3) showing a right shift on G-V curve (ΔV1/2= 130,3 mV ± 6,4; p<0,05), a decrease on Gmax (Gmax-AA/Gmax-CONTROL = 0,66 ± 0,06; p<0,05) and no change on gating currents (n=5). The inhibitory effect of AA was Ca2+ dependent, since the inhibition was bigger at 80 µM (first results) than at 8 μM intracellular Ca2+ (ΔV1/2= 73,0 mV ± 4,0 and Gmax-AA/Gmax-CONTROL = 0,91 ± 0,04; n=3; p<0,05). The AA effect was faster when it was applied to the intracellular membrane side, suggesting that AA acts from the intracellular side of the channel. Together, these results suggest that the effect of 10 μM AA depends on the presence or absence of β1, being able to activate or inhibit BK, respectively. [1] Martín, P. and Moncada, M. et al Pflugers Arch - Eur J Physiol. 2014. 1779.