Abstract
Metabolic labeling experiments followed by immunoprecipitation were performed to investigate the kinetics, location and inhibitor sensitivity of degradation of both wild-type (wt) and mutant (ΔF508) cystic fibrosis conductance transmembrane regulator (CFTR). At the earliest stages of the biosynthetic process, both wt and (ΔF508 CFTR were found to be susceptible to degradation by endogenous proteases. Virtually all (ΔF508 CFTR and 45-80% of wt CFTR were rapidly degraded with a similar half-life (t( 1/2 ) ≃ 0.5 h). The remaining wt CFTR attained a protease-resistant configuration regardless of whether traffic between the endoplasmic reticulum (ER) and Golgi was operational. Metabolic energy is required for the conformational transition, but not to maintain the stability of the protease-resistant wt CFTR. Intracellular degradation of (ΔF508 CFTR and of incompletely folded wt CFTR occurs in a non-lysosomal, pre-Golgi compartment, as indicated by the sensitivity of proteolysis to different inhibitors and temperature. Accordingly, products of the degradation of (ΔF508 CFTR could be detected by immunoblotting in isolated ER, but not in the Golgi. Together, these results suggest a dynamic equilibrium between two forms of wt CFTR in the ER: an incompletely folded, protease-sensitive form which is partially converted by an ATP-dependent process to a more mature form that is protease-resistant and capable of leaving the ER. The inability (ΔF508 CFTR to undergo such a transition renders it susceptible to complete and rapid degradation in a pre-Golgi compartment.
Original language | English (US) |
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Pages (from-to) | 6076-6086 |
Number of pages | 11 |
Journal | EMBO Journal |
Volume | 13 |
Issue number | 24 |
DOIs | |
State | Published - Dec 15 1994 |
Keywords
- Cystic fibrosis transmembrane conductance regulator
- Post-translational modification
- Protein folding
- Proteolysis
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology