Partial restoration of cAMP-stimulated CFTR chloride channel activity in DeltaF508 cells by deoxyspergualin

Deletion of the codon encoding phenylalanine 508 (DeltaF508) is the most common mutation in cystic fibrosis (CF) and results in a trafficking defect. Mutant DeltaF508-CF transmembrane conductance regulator (CFTR) protein retains functional activity, but the nascent protein is recognized as abnormal and, in consequence, is retained in the endoplasmic reticulum (ER) and degraded. It has been proposed that this retention in the ER is mediated, at least in part, by the cellular chaperones heat shock protein (HSP) 70 and calnexin. We have investigated the ability of deoxyspergualin (DSG), a compound known to compete effectively for binding with HSP70 and HSP90, to promote trafficking of DeltaF508-CFTR to the cell membrane. We show that DSG treatment of immortalized human CF epithelial cells (DeltaF508) and cells expressing recombinant DeltaF508-CFTR partially restored cAMP-stimulated CFTR Cl- channel activity at the plasma membrane. Although there are several possible explanations for these results, one simple interpretation is that DSG may have altered the interaction between DeltaF508-CFTR and its associated chaperones. If this is correct, agents capable of altering the normal functioning of cellular chaperones may provide yet another means of restoring CFTR Cl- channel activity to CF subjects harboring this class of mutations.