Figure 1.

PCMBS increases KCa3.1 steady-state current. Macroscopic current records from KCa3.1 channels heterologously expressed in HEK cells to determine sensitivity to PCMBS. PCMBS (500 µM) was added to inside-out patches excised in 0.3 (A), 0.6 (B), and 10 µM (C) Ca²⁺_i after the establishment of steady-state current level. PCMBS washout lasted at least 1 min to ensure channel activation was due to covalent binding, rather than an indirect interaction between channel and compound. (D) KCa3.1 current record demonstrating that PCMBS cannot activate the channel in the absence of Ca²⁺_i. PCMBS can only increase current when the channel is in the open state. The patch was initially excised in 10 µM Ca²⁺_i, followed by the addition of a Ca²⁺_i-free solution, and then a Ca²⁺_i-free solution+PCMBS (500 µM) was added to the bath solution. PCMBS+Ca²⁺_i-free solution was washed out with 10 µM Ca²⁺_i to reactivate the channel. After reaching a steady-state current level, PCMBS (500 µM) was reapplied to the patch, resulting in channel activation.