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J Biol Chem. 2009 Nov 6;284(45):30754-65. doi: 10.1074/jbc.M109.056010. Epub 2009 Sep 9.

Curcumin cross-links cystic fibrosis transmembrane conductance regulator (CFTR) polypeptides and potentiates CFTR channel activity by distinct mechanisms.

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  • 1Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

Abstract

Cystic fibrosis (CF) is caused by loss-of-function mutations in the CFTR chloride channel. Wild type and mutant CFTR channels can be activated by curcumin, a well tolerated dietary compound with some appeal as a prospective CF therapeutic. However, we show here that curcumin has the unexpected effect of cross-linking CFTR polypeptides into SDS-resistant oligomers. This effect occurred for CFTR channels in microsomes as well as in intact cells and at the same concentrations that are effective for promoting CFTR channel activity (5-50 mum). Both mature CFTR polypeptides at the cell surface and immature CFTR protein in the endoplasmic reticulum were cross-linked by curcumin, although the latter pool was more susceptible to this modification. Curcumin cross-linked two CF mutant channels (Delta F508 and G551D) as well as a variety of deletion constructs that lack the major cytoplasmic domains. In vitro cross-linking could be prevented by high concentrations of oxidant scavengers (i.e. reduced glutathione and sodium azide) indicating a possible oxidation reaction with the CFTR polypeptide. Importantly, cyclic derivatives of curcumin that lack the reactive beta diketone moiety had no cross-linking activity. One of these cyclic derivatives stimulated the activities of wild type CFTR channels, Delta 1198-CFTR channels, and G551D-CFTR channels in excised membrane patches. Like the parent compound, the cyclic derivative irreversibly activated CFTR channels in excised patches during prolonged exposure (>5 min). Our results raise a note of caution about secondary biochemical effects of reactive compounds like curcumin in the treatment of CF. Cyclic curcumin derivatives may have better therapeutic potential in this regard.

PMID:
19740743
[PubMed - indexed for MEDLINE]
PMCID:
PMC2781474
Free PMC Article
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