FIGURE 2.
Channel function of C-FLAG CFTR. a, activation of C-FLAG CFTR by cAMP-dependent protein kinase (PKA)-dependent phosphorylation and ATP. Single channel currents were obtained from an inside-out patch from HEK293 cells expressing C-FLAG CFTR. After phosphorylation, ATP alone can gate C-FLAG CFTR. Vm = -50 mV. The dashed line indicates the closed level. b, ATP-dependent macroscopic currents of cAMP-dependent protein kinase-phosphorylated C-FLAG CFTR in the inside-out configuration. The concentrations of ATP in the bath are indicated above. Vm = -50 mV. c, ATP concentration dependence of macroscopic currents of C-FLAG CFTR expressed in HEK293 (red) and Chinese Hamster ovary (green) cells. Vm = -50 mV. These results are also comparable to the channel function of non-FLAG-tagged wild-type CFTR (10-12, 18, 19).