Ubiquitin C-terminal hydrolase-L1 protects cystic fibrosis transmembrane conductance regulator from early stages of proteasomal degradation

Mark J. Henderson, Neeraj Vij, Pamela L. Zeitlin

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ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) degradation involves ubiquitin modification and efficient proteasomal targeting of the nascent misfolded protein. We show that a deubiquitinating enzyme, ubiquitin C-terminal hydrolase-L1 (UCH-L1), is highly expressed in cystic fibrosis (CF) airway epithelial cells in vitro and in vivo. We hypothesized that the elevation in UCH-L1 in CF cells represents a cellular adaptation to counterbalance excessive proteasomal degradation. The bronchial epithelial cell lines IB3-1 (CF, high UCH-L1 expression) and S9 (non-CF, low UCH-L1 expression) were transiently transfected with wild type (WT) or ΔF508 CFTR, WTUCH-L1 or small interfering RNA-UCH-L1, and a variety of ubiquitin mutants. We observed a positive correlation between UCH-L1 expression and steady state levels of WT- or ΔF508-CFTR, and this stabilizing effect was confined to the early stages of CFTR synthesis. Immunolocalization of UCH-L1 by confocal microscopy revealed a partial co-localization with a ribosomal subunit and the endoplasmic reticulum. The UCH-L1-associated increase in CFTR levels was correlated with an increase in ubiquitinated CFTR (CFTR-Ub). Co-transfection with mutant ubiquitins and treatment with proteasome inhibitors suggested that UCH-L1 was reducing the proteasomal targeting of CFTR during synthesis by shortening conjugated polyubiquitin chains. Although not sufficient by itself to rescue mutant CFTR therapeutically, the elevation of UCH-L1 and its effect on CFTR processing provides insight into its potential roles in CF and other diseases.

Original languageEnglish (US)
Pages (from-to)11314-11325
Number of pages12
JournalJournal of Biological Chemistry
Issue number15
StatePublished - Apr 9 2010


ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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