FIGURE 5.

Role of purinergic signaling for activation of TMEM16A in HEK293 cells by cell swelling. A, activation of whole cell conductance by increased extracellular hypotonicity in cells expressing empty plasmid (mock), TMEM16A or TMEM16A together with P2Y₂ receptors. B, swelling activation of whole cell currents in a HEK293 cell and inhibition of the current by suramin (100 μm; gray bar). C, inhibition of the swelling-activated whole cell conductance by suramin (100 μm), apyrase (3 units/ml), and ATP-free pipette solution, the cysteine reagent MTSET (2.5 mm), and the inhibitor of extracellular-regulated kinase (ERK1/2) U0126 (25 μm). D, summary of swelling-activated (Hypo) and ATP-induced whole cell conductance in TMEM16A expressing HEK293 cells, under control conditions and after removal of Ca²⁺ from both pipette and bath solution. Both ATP and swelling-induced whole cell conductance were reduced under Ca²⁺-free conditions and when two ERK1/2 consensus sides in TMEM16A were mutated. E, activation of whole cell currents by ATP (open bar, 10 μm), before and after swelling activation of whole cell currents (Hypo). F, summary of whole cell conductance in the absence and presence of ATP hypotonic bath solution. Mean ± S.E., (n) = number of cells measured. *, significant ATP effect (paired t test). #, significant difference when compared with control (unpaired t test). §, significant difference when compared with the absence of hypotonic bath solution (unpaired t test).