Fig. 3.
CK2 phosphorylation of EnaC is necessary for inhibition by TBB. ENaC-transfected CHO cells were treated with TBB. A: treatment with 2 μM TBB significantly decreased the magnitude of macroscopic ENaC current density in transfected CHO cells (Student’s paired t-test). B: a dose- response curve was created between 200 and 2,000 nM TBB. The IC50 of the TBB-mediated inhibition was 760 nM. R2 = 0.99 for regression to a 4-parameter logistic equation. C: known phosphorylation sites in β and γ ENaC were mutated to alanine and expressed in CHO cells. αβγT649A, αβS631Aγ, or αβS631AγT649A had significantly less sensitivity to inhibition by TBB compared with control (ANOVA, Dunnett’s posttest). *Indicates P < 0.05, **indicates P < 0.01, ***indicates P < 0.005.