Fig. 6.

Membrane currents associated with heterologous expression of KCNN4. A: whole cell membrane currents recorded from control [i.e., green fluorescent protein (GFP) transfected] and KCNN4-transfected Chinese hamster ovary (CHO) cells under quasi-physiological ionic conditions. Currents were evoked by stepping (200 ms) V_Hold from 0 mV to a series of values between -110 and 30 mV; pipette [Ca²⁺] was 0.5 μM, and arrows indicate the zero-current level. B: relationship between I (means ± SE) and V_Hold for KCNN4-expressing cells with the pipette filling solution in which [Ca²⁺] was buffered to 0.5 μM. Data were first recorded under control conditions and then after the application of 10 μM clotrimazole (n = 6). C: extent to which Ba²⁺, clotrimazole, apamin, and iberiotoxin blocked the currents recorded from KCNN4-associated conductance CHO was determined by quantifying the inhibition of the membrane current required to hold V_m at 30 mV (I_30mV). ***P < 0.005. D: data (n = 3; mean values, errors lie within symbols) from KCNN4-expressing cells showing the relationship between V_m and [K⁺]_o; the solid line was fitted to the experimental data by linear regression, whereas the dashed line shows the relationship predicted (Nernst equation) for a selective K⁺ conductance.