抄録
The action of phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 on human Kv1.5 (hKv1.5) channels expressed in Chinese hamster ovary (CHO) cells was investigated using the whole cell patch-clamp technique. LY294002 rapidly and reversibly inhibited hKv1.5 current in a concentration-dependent manner with an IC50 of 7.3 μM. However, another PI3K inhibitor wortmannin had no inhibitory effect on hKv1.5 current. The LY294002 block of hKv1.5 progressed with time during depolarizing voltage with a more rapid block at higher concentrations. The LY294002 action was voltage-dependent with a steep increase over the voltage range of channel opening however, its inhibition changed little when the channels were fully activated. LY294002 markedly shifted the voltage dependence of channel opening to more hyperpolarizing potentials and significantly accelerated the deactivation time course. Inhibition of hKv1.5 by LY294002 was use-dependent. In addition, a mutation of arginine 487 to valine in the outer pore region of Kv1.5 (R487V) significantly reduced the degree of LY294002 block (with an IC50 of 16.9 μM), whereas other outer pore mutations (T462C and H463C) had no effect on LY294002 action. The present results suggest that (i) LY294002 acts directly on Kv1.5 currents as an open channel blocker and independently of the effects of LY294002 on PI3K activity; and (ii) the inhibitory target of LY294002 is present in the channel outer pore region, probably related to arginine 487. [J Physiol Sci. 2007;57 Suppl:S227]
