(A) Data reanalyzed from ref. 4. Left: UMAP projections of major cell types. Right: Ion channel expression in large/small airways. (B) Fully differentiated, primary normal human bronchial epithelial cells exposed basolaterally to 5 μM elexacaftor (24 hours). To assess BK activity, cells were permeabilized basolaterally in Ussing chambers under a basolateral to apical potassium gradient (3). To increase intracellular calcium, cells were stimulated with 0.1 μM ATP in the acute presence of 10 μM CFTR_inh172 mimicking minimal function CFTR variants (CFTRMF). Short circuit currents represent basolateral to apical potassium flux. F508delCFBE cells were used without CFTR_inh172. Differently sourced elexacaftor potentiated BK approximately 2-fold. (C and D) F508delCFBE cells exposed basolaterally to 5 μM elexacaftor and 5 μM R- or S-vanzacaftor for 24 hours. (C) S-vanzacaftor modulates CFTR (***P < 0.05 Friedman; short circuit current inhibition by CFTR_inh172 after forskolin stimulation). (D) R-vanzacaftor potentiates BK (*P < 0.05 Kruskal-Wallis). (E) Oocytes; Log or fold-increase in BK (hSlo1±LRRC26) activity (NP_O at –80 mV, 0 Ca) over vehicle (mean ± SEM, n = 13–25 patches per condition), fit with Hill equations (see Supplemental Figure 2). (F and G) Acute exposures of CFTRMF cells to vanzacaftor enantiomers after basolateral permeabilization with basolateral to apical potassium gradient (Ussing traces in F and summary data in G). S-vanzacaftor is the most efficacious BK activator (n = 4). (H) CFTRMF cells: 24 hour basolateral exposures before testing BK potentiation with ATP (see above) show that R-vanzacaftor is the most efficacious BK potentiator (n = 4). (I) Only R-vanzacaftor (3 μM basolaterally for 24 hours) improves mucociliary transport (MCT) in CFTRMF cells. ****P < 0.0001 ANOVA and Tukey after passing normality test (n = 10). (J–L) CFTRMF cells with KCNMA1 or LRRC26 knockdown (BKKD, LRRC26KD). (J) KCNMA1 (left) and LRRC26 (right) mRNA expression (n = 8–11). One-way ANOVA / Tukey (left) or Kruskal Wallis (right). (K) BK potentiation by 3 μM R-vanzacaftor (24 hour basolaterally) is eliminated by KCNMA1 and LRRC26 KD. (L) R-vanzacaftor’s effect on MCT (treatment/DMSO) in CFTRMF (3 μM for 24 hours; n = 15). Baselines: 2.9 ± 1.3 μm/s. *P < 0.05 by Mann-Whitney.