Protein kinase A phosphorylation potentiates cystic fibrosis transmembrane conductance regulator gating by relieving autoinhibition on the stimulatory C terminus of the regulatory domain [Protein Structure and Folding]

Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel activated by protein kinase A (PKA) phosphorylation on the regulatory (R) domain. Phosphorylation at several R domain residues stimulates ATP-dependent channel openings and closings, termed channel gating. To explore the protein segment responsible for channel potentiation and PKA-dependent activation, deletion mutations were constructed by removing one to three protein segments of the R domain including residues 708–759 (ΔR708–759), R760–783, and R784–835, each of which contains one or two PKA phosphorylation sites. Deletion of R708–759 or R760–783 had little effect on CFTR gating, whereas all mutations lacking R784–835 reduced CFTR activity by decreasing the mean burst duration and increasing the interburst interval (IBI). The data suggest that R784–835 plays a major role in stimulating CFTR gating. For ATP-associated regulation, ΔR784–835 had minor impact on gating potentiation by 2′dATP, CaATP, and pyrophosphate. Interestingly, introducing a phosphorylated peptide matching R809–835 shortened the IBI of ΔR708–835-CFTR. Consistently, ΔR815–835, but not ΔR784–814, enhanced IBI, whereas both reduced mean burst duration. These data suggest that the entirety of R784–835 is required for stabilizing the open state of CFTR; however, R815–835, through interactions with the channel, is dominant for enhancing the opening rate. Of note, PKA markedly decreased the IBI o...
Source: Journal of Biological Chemistry - Category: Chemistry Authors: Tags: Membrane Biology Source Type: research