Question

How does the CFTR protein in cystic fibrosis defect cause an imbalance of Cl- and Na+ ions?

Answer 1

Cystic fibrosis:

· Cystic fibrosis is genetic disorder (autosomal recessive), due to mutation in CFTR (Cystic fibrosis transmembrane conductance regulator) gene.

· CFTR functions as ATP-responsive chloride channel.

· Due to mutation in CFTR gene, the biosynthesis of CFTR protein is altered, the protein thus synthesized may be retained in the endoplasmic reticulum and not transported to the cell surface (apical epithelia).

· Also if the protein reaches the surface, it may not fold properly to function as channel protein.

· Thus, mutation affects transport of negatively charged (anion channel) Chloride ions.

· Choloride transport in turn regulates the movement of water molecules in the cells (especially functioning in lungs and pancreatic cells, which alter the mucous consistency, or inflammation of pancreas).

· The mutation also affects sodium transport in epithelial layers.

· Damages occurring in lungs lead to arterial hypoxia, which alters oxygen affinity of hemoglobin.