Figure 4.

Niclosamide inhibits TMEM16A currents activated by intracellular Ca²⁺. (A) TMEM16A overexpressed in HEK293 cells was activated by 1 µM Ca²⁺ in the patch pipette filling solution. Acute application of niclosamide (Niclo; 5 µM) significantly inhibited Ca²⁺-activated TMEM16A whole cell currents (n = 7). (B) 15 min preincubation with Niclo inhibited TMEM16A more potently (n = 9–10). (C) Increase in intracellular Ca²⁺ with ATP (100 µM) in HT₂₉ cells. Niclosamide (5 µM) induces a slight and transient increase in [Ca²⁺]_i and inhibits ATP-induced rise in [Ca²⁺]_i. siRNA knockdown of TMEM16A inhibits increase in [Ca²⁺]_i by ATP. Niclosamide shows no additional effects on [Ca²⁺]_i (n = 60–193). (D) ER Ca²⁺ store release and Ca²⁺ influx (SOCE) induced by CPA and niclosamide (n= 40–50). (E,F) Effects of CPA and niclosamide on Ca²⁺ store release and SOCE under various conditions (n = 40–213) * significant inhibition (p < 0.05; paired t-test). ^# significant inhibition (p < 0.05; unpaired t-test).