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Chloride conductance expressed by delta F508 and other mutant CFTRs in Xenopus oocytes
M L Drumm1, D J Wilkinson, L S Smit
1Department of Human Genetics, University of Michigan, Ann Arbor 48109.
Abstract:
The cystic fibrosis transmembrane conductance regulator (CFTR) is associated with expression of a chloride conductance that is defective in cystic fibrosis (CF). Xenopus oocytes injected with RNA coding for CFTR that contained mutations in the first nucleotide binding fold (NBF1) expressed chloride currents in response to raising adenosine 3',5'-monophosphate (cAMP) with forskolin and 3-isobutyl-1-methylxanthine (IBMX). The mutant CFTRs were less sensitive than wild-type CFTR to this activating stimulus, and the reduction in sensitivity correlated with the severity of cystic fibrosis in patients carrying the corresponding mutations. This demonstration provides the basis for detailed analyses of NBF1 function and suggests potential pharmacologic treatments for cystic fibrosis.
Insights
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) NBF1 impact chloride channel function. Reduced sensitivity to activation in cystic fibrosis (CF) models correlates with disease severity, suggesting therapeutic targets.
Area of Science:
- Molecular biology
- Ion channel function
- Cystic Fibrosis research
Background:
- The cystic fibrosis transmembrane conductance regulator (CFTR) protein regulates chloride ion transport.
- Defective CFTR function leads to cystic fibrosis (CF).
- The first nucleotide binding fold (NBF1) is crucial for CFTR activity.
Purpose of the Study:
- To investigate the functional impact of NBF1 mutations in CFTR.
- To correlate CFTR NBF1 mutation severity with cystic fibrosis patient outcomes.
- To explore NBF1 as a target for potential CFTR pharmacologic therapies.
Main Methods:
- RNA injection into Xenopus oocytes.
- Expression of wild-type and mutant CFTR constructs.
- Measurement of chloride currents in response to cAMP stimulation (forskolin, IBMX).
Main Results:
- Mutant CFTRs with NBF1 alterations showed reduced sensitivity to cAMP-mediated activation.
- The degree of reduced sensitivity correlated with the clinical severity of cystic fibrosis in patients.
- Demonstrated functional consequences of NBF1 mutations on CFTR chloride conductance.
Conclusions:
- NBF1 is critical for proper CFTR activation and function.
- CFTR NBF1 mutations contribute to cystic fibrosis pathogenesis.
- Targeting NBF1 may offer a strategy for novel cystic fibrosis treatments.
