Fig. S7.

KCNK1 does not contribute to the resting K⁺ current in PKD2L1 cells. (A) The current recorded from a KCNK1-AA-GFP–transfected HEK cell under conditions designed to unmask the current. Note that in 130 mM Rb⁺ (with 20 mM TEA), the current magnitude was much larger than that in 130 mM K⁺ extracellular solution (also with 20 mM TEA) as previously reported (57). Cs⁺ was not an effective blocker of KCNK1 current (58). (B) Same experiments as in A performed with a K_IR2.1-transfected cell. Note that the current in Rb⁺ is much smaller than that in K⁺ solutions, and that Cs⁺ blocks the current effectively. (C) The current recorded in a PKD2L1 taste cell. Note that the current magnitude in Rb⁺ is smaller than that in K⁺, similar to the K_IR2.1-mediated current. (D) The ratios of current in 130 mM Rb⁺ (I_Rb⁺) to that in 130 mM K⁺ (I_K⁺) for KCNK1-AA, K_IR2.1, and PKD2L1 taste cells. Using these data, we estimated the contribution of KCNK1 to the taste cell K⁺ current by rearranging a set of linear functions assuming that the inward currents in high Rb⁺ and K⁺ are generated solely from the contributions of KCNK1 and K_IR2.1 (SI Methods). This calculation showed that KCNK1 accounts for no more than 1% of the resting K⁺ current.