Ongoing Research: CF RESEARCH

Cystic Fibrosis (CF) is characterized by recurrent lung infections, and it is the most common lethal genetic disease in Caucasians.

Channel Function: CF is caused by a defect (mutation) in an ion channel protein called the cystic fibrosis transmembrane conductance regulator (CFTR).   This ion channel protein is large and complex (see schematic diagram on the left).   Our laboratory studies the CFTR protein to learn its normal activities and how defects affect its function and lead to disease.

CFTR functions as a chloride-selective ion channel, and a major focus of the laboratory is measuring ion flow through isolated channels.   A patch clamp setup, used to measure picoamp currents through CFTR channels, is shown on the left. Dr. Christoph Randak is interested in structure / function relationships of the CFTR nucleotide binding domains and how enzymatic activity of these domains regulates channel opening and closing.   He is further interested how the cytoplasmic R (regulatory) domain of CFTR and the C terminus participate in that process. There is also interest in mechanisms of channel gating, using homology between CFTR and other proteins (ABC transporter NBDs) to predict how the channel is normally regulated by intracellular nucleotides and how mutations affect channel function.   The picture on the right shows the crystal structure of a bacterial ABC transporter NBD in the background, and CFTR single channel openings in the foreground.

Localization: CFTR protein is normally located in the epithelial cells lining the airway. Dr. Lynda Ostedgaard studies CFTR localization.   Many of the mutations in the CFTR protein that cause CF disrupt the normal apical localization.

Lynda is also investigating cellular trafficking of CFTR and the protein sequences that cause retention at the apical membrane.   She is also looking at intramolecular interactions in CFTR, and how those influence targeting.

Structure: Some CFTR mutations that cause CF affect function more than localization.   To begin to understand how these mutations cause disease, we are studying the structure of parts (domains) of the CFTR protein.  Lynda is expressing portions of the CFTR protein in bacterial cells, with the goal of making fully functional domains.

Transport Electrophysiology: Defects in CFTR channel function and localization disrupt normal ion flux across the airway epithelium.   To measure transepithelial electrical properties, we culture human airway cells and use an Ussing chamber (pictured on the left) to measure voltage and resistance.   A frequently used functional assay used in the laboratory is to measure the chloride channel currents in untreated CF disease cells and compare those currents to CF cells that have been treated with gene transfer methodology.   Phil Karp is the lab's master of this technique.