The role of the UPS in cystic fibrosis.
CF is an inherited autosomal recessive disease whose lethality arises from malfunction of CFTR, a single chloride (Cl-) ion channel protein. CF patients harbor mutations in the CFTR gene that lead to misfolding of the resulting CFTR protein, rendering it inactive and mislocalized. Hundreds of CF-related mutations have been identified, many of which abrogate CFTR folding in the endoplasmic reticulum (ER). More than 70% of patients harbor the DeltaF508 CFTR mutation that causes misfolding of the CFTR proteins. Consequently, mutant CFTR is unable to reach the apical plasma membrane of epithelial cells that line the lungs and gut, and is instead targeted for degradation by the UPS. Proteins located in both the cytoplasm and ER membrane are believed to identify misfolded CFTR for UPS-mediated degradation. The aberrantly folded CFTR protein then undergoes polyubiquitylation, carried out by an E1-E2-E3 ubiquitin ligase system, leading to degradation by the 26S proteasome. This ubiquitin-dependent loss of misfolded CFTR protein can be inhibited by the application of 'corrector' drugs that aid CFTR folding, shielding it from the UPS machinery. Corrector molecules elevate cellular CFTR protein levels by protecting the protein from degradation and aiding folding, promoting its maturation and localization to the apical plasma membrane. Combinatory application of corrector drugs with activator molecules that enhance CFTR Cl- ion channel activity offers significant potential for treatment of CF patients. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).
Department of Cell and Developmental Biology, 526 Taylor Hall, Mason Farm Road, UNC-Chapel Hill School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA. eturnbul@email.unc.edu
Emma L
EL
Turnbull
Meredith F N
MF
Rosser
Douglas M
DM
Cyr
D000818:Animals; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes / Q000502:physiology*
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D043743:Ubiquitin-Protein Ligase Complexes; D046988:Proteasome Endopeptidase Complex