Activation of G551D CFTR channel with MPB-91: regulation by ATPase activity and phosphorylation

Area of Science:

• Medicinal Chemistry
• Molecular Pharmacology
• Ion Channel Modulation

Background:

• Cystic Fibrosis (CF) is a genetic disorder caused by mutations in the CFTR gene.
• The G551D mutation impairs CFTR channel function, leading to ion transport defects.
• Developing small molecules to correct CFTR dysfunction is a key therapeutic goal.

Purpose of the Study:

• To design and synthesize novel benzo[c]quinolizinium derivatives.
• To evaluate their efficacy in restoring the activity of the G551D CFTR mutation.
• To investigate the mechanism of CFTR activation by the lead compound.

Main Methods:

• Synthesis of benzo[c]quinolizinium derivatives.
• Functional assays including iodide efflux, whole-cell patch clamp, and short-circuit current recordings.
• Biochemical assays measuring ATPase, GTPase, and adenylate kinase activities.

Main Results:

• MPB-91, a novel benzo[c]quinolizinium derivative, restored G551D CFTR activity (EC50 = 85 microM) and activated wild-type CFTR in Calu-3 cells (EC50 = 47 microM).
• MPB-91 did not affect the ATPase activity of CFTR NBD1 or NBD2 domains.
• CFTR activation by MPB-91 was independent of protein kinase A phosphorylation.

Conclusions:

• MPB-91 is a potent activator of CFTR, including the G551D mutant.
• The compound's mechanism of action is independent of phosphorylation and direct interaction with CFTR nucleotide-binding domains.
• MPB-91 represents a promising therapeutic candidate for cystic fibrosis.