Expression and characterization of the cystic fibrosis transmembrane conductance regulator

Cystic fibrosis (CF) is the most common deadly inheritable disease among Caucasians. CF is characterized by defective salt transport in organs, particularly the lungs, sweat glands, intestines, and pancreas. The major cellular defect in CF patients involves the function and regulation of chloride channels. These channels, which are proteins embedded in the membranes of epithelial cells (which form the exterior layers of most body surfaces), allow the movement of chloride ions from the cell interior to the exterior. In normal epithelial cells, the chloride channel opens when it is phosphorylated (modified by the addition of phosphate) by a kinase (a type of enzyme). In CF cells, chloride channels are present but they cannot be activated by the kinase, and thus cannot secrete chloride ions or fluid. A major research finding in 1989 was the isolation of a gene which had a mutation in 70 percent of patients with CF. The gene codes for a protein called the cystic fibrosis transmembrane conductance regulator (CFTR), but the actual function of the protein has not yet been determined. This article describes work done with the gene to allow synthesis of the protein from the gene information by means of laboratory techniques. The results show that the protein is a membrane-associated protein to which sugar molecules attach during synthesis, which is common for membrane-bound proteins. In addition, this synthesized, or recombinant, CFTR can be phosphorylated by the kinase, which regulates chloride channels (as well as other proteins). Antibodies that recognize the native protein also recognize recombinant CFTR. These results indicate that recombinant CFTR is structurally and functionally equivalent to CFTR, and this will allow CFTR function to be studied with the aim of improving diagnosis and therapy of cystic fibrosis. (Consumer Summary produced by Reliance Medical Information, Inc.)