Pitt-led Research Team Creates Process With Potential For Better Development, Testing of Cystic Fibrosis Drugs

A team led by researchers from the University of Pittsburgh developed a process that, for the first time, allows the individual stages of the protein deterioration that leads to cystic fibrosis (CF) to be observed, and possibly interrupted. Although it needs further refinement, the technique could be instrumental in developing pharmaceutical treatments for CF and for testing recently developed drugs that may ultimately be used to treat the disease.

The researchers—led by Jeffrey Brodsky, professor and Avinoff Chair in Pitt’s Department of Biological Sciences in the School of Arts and Sciences—describe the process in the current edition of the journal Cell. Brodsky and Pitt research associate Kunio Nakatsukasa worked with Johns Hopkins University professor Susan Michaelis and research associate Gregory Huyer.

The team focused on the protein created by the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Normally, this protein acts as an ion channel on the outer membrane of cells—primarily in the lungs, pancreas, and intestines—and regulates the balance of chloride within the cell. With CF, a mutation blocks the ability of this protein to be transported to the cell membrane. As a result, the levels of chloride, other salts, and water inside and outside of the cell become unbalanced. This ultimately manifests as the thick mucus, pancreatic malfunction, and breathing difficulty commonly found with CF.

Normally, even healthy CFTR proteins can degrade quickly, so the process has been difficult to replicate in the laboratory using human cells, Brodsky said. Therefore, he and his team first genetically engineered yeast cells to produce the CFTR protein. (They reported on this accomplishment in 2001.) Once this system was established, the team generated cell membranes already containing CFTR proteins and recombined them in a test tube. Brodsky and his colleagues then monitored how the CFTR protein was selected and then “tagged” by the short protein ubiquitin prior to being degraded.

Ubiquitin’s primary function is to mark other proteins for destruction.

“Until now it was difficult to define individual steps during the destruction of CFTR or other similar disease-causing proteins,” Brodsky said. “We hope that this system will open up new methods to identify drugs that will block the degradation of this protein and help treat the disease.”

The team also repeated the process for two other defective proteins in the test tube, suggesting that the newly developed system will be widely applicable. They have reproduced yeast systems for proteins that lead to ailments such as Alzheimer’s disease and alpha 1-antitrypsin deficiency, a condition marked by defective lung and, sometimes, liver function. The team will next attempt to control the degradation of these proteins using the process for CFTR proteins, Brodsky said.

To read the complete paper, visit the Cell Web site at www.cell.com/content/article/abstract?uid=PIIS0092867407014754.