Phosphorylation of the R domain by cAMP-dependent protein kinase regulates the CFTR chloride channel

SH Cheng, DP Rich, J Marshall, RJ Gregory, MJ Welsh… - Cell, 1991 - cell.com
SH Cheng, DP Rich, J Marshall, RJ Gregory, MJ Welsh, AE Smith
Cell, 1991cell.com
CFTR, the protein associated with cystic fibrosis, is phosphorylated on serine residues in
response to CAMP agonists. Serines 660, 737, 795, and 613 were identified as in vivo
targets for phosphorylation by protein kinase A. The SPQ fluorescence assay revealed that
mutagenesis of any one of these sites did not affect Cl-channel activity. Indeed, concomitant
mutagenesis of three of the four sites still resulted in CAMP-responsive Cl-channel activity.
However, mutagenesis of all four sites abolished the response. One interpretation of these …
Summary
CFTR, the protein associated with cystic fibrosis, is phosphorylated on serine residues in response to CAMP agonists. Serines 660, 737, 795, and 613 were identified as in vivo targets for phosphorylation by protein kinase A. The SPQ fluorescence assay revealed that mutagenesis of any one of these sites did not affect Cl-channel activity. Indeed, concomitant mutagenesis of three of the four sites still resulted in CAMP-responsive Cl-channel activity. However, mutagenesis of all four sites abolished the response. One interpretation of these results is that the CFTR CI-channel is blocked by the R domain and that phosphorylation on serines by protein kinase A electrostatically repels the domain, allowing passage of Cl-. The four phosphorylation events appear to be degenerate: no one site is essential for channel activity, and, at least in the case of serine 660, phosphorylation at one site alone is suff icient for regulation of Cl-channel activity.
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