Figure 5. Rescue of ΔF508 CFTR function at permissive temperature depends on CSNK2A1 phosphorylation of Thr⁴²¹ to Ser⁴²⁷.

A. Quantification of phosphorylated sites Ser⁴²² and Ser⁴²⁷, methylation site Lys⁴⁴² and ubiquitination site Lys⁴²⁰ at 37°C (red bars) or at permissive temperature of 30°C (blue bars). B. Quantification of ΔF508 CFTR phosphorylation at Thr⁴²¹, Ser⁴²² and Ser⁴²⁷ by synthetic heavy-labeled peptides shows reduced phosphorylation upon shRNA- mediated knockdown of CSNK2A1. C. Western blot showing that shRNA-mediated knockdown of CSNK2A1 impairs ΔF508 CFTR maturation at permissive temperature. Detection of b-actin was used as loading control. D. Representative traces of forskolin (F) and genistein (G) stimulated ΔF508 CFTR short circuit currents (/_sc) showing that knockdown of CSNK2A1 (right) or treatment with 10 μM CX-4945 (left) prevent temperature shift (28°C) induced rescue of ΔF508 CFTR channel activity. Specificity of the current is established by treatment with CFTR inhibitor 172 (I). E. Quantification of Δ/_sc currents as log₂ fold change relative to control cells. All data are representative or mean ± S.D. of n=3 independent biological replicates. *P < 0.0332, **P < 0.0021, ***P < 0.0002, and ****P < 0.0001 by one-Way ANOVA with Bonferroni post-test.