Regulation of CFTR channel gating
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D C Gadsby1, T C Hwang, T Baukrowitz
1Laboratory of Cardiac/Membrane Physiology, Rockefeller University, New York, NY 10021, USA.
Abstract:
Findings outlined here support a complex model for the regulation of cystic fibrosis transmembrane conductance regulator (CFTR) Cl channel gating that incorporates incremental protein kinase A (PKA) phosphorylation of CFTR at multiple sites which, in turn, differentially control the activity of CFTR's two nucleotide-binding domains (NBDs). The NBDs are functionally distinct: only one can respond to the non-hydrolyzable ATP analogue AMP-PNP, and then only after ATP has acted at the other. Moreover, the nature of the responses to AMP-PNP, and to the inorganic phosphate analogue orthovanadate, argues that ATP hydrolysis normally occurs at both NBDs, at one to initiate channel opening and at the other to initiate closing.
Insights
Cystic fibrosis transmembrane conductance regulator (CFTR) channel gating is complex, involving incremental protein kinase A (PKA) phosphorylation. This differential phosphorylation controls two distinct nucleotide-binding domains (NBDs) for channel opening and closing.
Area of Science:
- Molecular biology
- Cellular physiology
- Ion channel function
Background:
- Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel crucial for epithelial function.
- Dysregulation of CFTR ion channel activity is implicated in cystic fibrosis.
- Understanding CFTR gating mechanisms is essential for therapeutic development.
Purpose of the Study:
- To elucidate the complex regulatory model of CFTR chloride channel gating.
- To investigate the role of protein kinase A (PKA) phosphorylation in CFTR function.
- To differentiate the functional roles of CFTR's two nucleotide-binding domains (NBDs).
Main Methods:
- Utilized biochemical assays to study CFTR phosphorylation.
- Employed non-hydrolyzable ATP analogues (AMP-PNP) to probe nucleotide-binding domains.
- Investigated responses to inorganic phosphate analogues (orthovanadate) to infer ATP hydrolysis.
Main Results:
- CFTR regulation involves incremental PKA phosphorylation at multiple sites.
- The two NBDs of CFTR are functionally distinct in their response to nucleotides.
- Evidence suggests ATP hydrolysis occurs at both NBDs, initiating both channel opening and closing.
Conclusions:
- A complex model for CFTR gating is supported, involving differential PKA phosphorylation.
- Functional asymmetry of NBDs is critical for CFTR channel activity.
- ATP hydrolysis at both NBDs is proposed to regulate the open-closed state of the CFTR channel.