Protein interactions, calcium, phosphorylation, and cholesterol modulate CFTR cluster formation on membranes

Area of Science:

• Membrane biophysics
• Molecular cell biology
• Ion channel regulation

Background:

• Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel crucial for ion homeostasis.
• CFTR dysfunction causes disease, and its role extends beyond ion transport through interactions with other proteins.
• CFTR forms mesoscale membrane clusters, but the drivers of this aggregation are poorly understood.

Purpose of the Study:

• To investigate the mechanisms underlying CFTR mesoscale cluster formation.
• To determine the roles of protein-lipid interactions, calcium, and phosphorylation in CFTR aggregation.

Main Methods:

• Computational modeling of protein and lipid interactions.
• Biochemical reconstitution assays on model membranes.

Main Results:

• Multivalent interactions with CFTR binding partners, calcium, and cholesterol induce CFTR mesoscale cluster formation.
• Phosphorylation of CFTR intracellular domains promotes clustering independently of calcium.
• These findings suggest biological phase separation drives CFTR cluster formation.

Conclusions:

• Multivalent interactions are key drivers of CFTR mesoscale cluster formation.
• Both calcium-dependent and independent pathways contribute to CFTR aggregation.
• CFTR clustering is consistent with membrane-associated biological phase separation, offering new insights into ion channel regulation.