title: Molecular Basis for Fe(III)-Independent Curcumin Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Activity.
abstract: Curcumin potentiates the phosphorylation-dependent activity of human cystic fibrosis transmembrane conductance regulator (CFTR) in Fe(3+)-dependent and Fe(3+)-independent manners. Although the Fe(3+)-dependent curcumin potentiation results from removal of endogenous inhibitory Fe(3+) at the interface of the regulatory (R) domain and intracellular loop (ICL) 3, the molecular mechanism of Fe(3+)-independent curcumin potentiation is still unknown. Here, HEK-293T cells cultured in an Fe(3+)-containing medium were transiently transfected with CFTR constructs, and the role of a highly conserved ICL1/ICL4 interface and a stimulatory phosphorylation site S795 or S813 at the C-terminus of the R domain in this potentiation pathway was investigated. The results showed that highly conserved aromatic and positively charged residues at the ICL1/ICL4 interface and phosphorylation site S813 were sensitive to curcumin regardless of whether Fe(3+) and nucleotide-binding domain 2 were removed. More importantly, spontaneous disulfide cross-linking between curcumin-sensitive ICL1 and S795 was observed to be enough to promote channel opening as curcumin did. Therefore, the phosphorylated R domain, once released from ICL3, may function as a length- and gating-regulatory cross-linker between two transmembrane domains to promote the stimulatory interactions between the R domain and the ICL1/ICL4 interface. Curcumin may potentiate CFTR activity not only by removing inhibitory Fe(3+) to release the R domain from ICL3 but also by stabilizing the stimulatory R-ICL1/ICL4 interactions. Therefore, the future potentiators with two linked aromatic rings could utilize this potentiation pathway to bypass the need for ATP to rescue the activity of cystic fibrosis mutants with an ATP-dependent gating defect.
authors: Department of Physiology and Biophysics and Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35294, United States.|Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada 89557, United States.|Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, California 95616, United States.
authors: Guangyu
authors: G
authors: Wang
mesh_terms: D000818:Animals; D003470:Culture Media; D003474:Curcumin / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D005290:Ferric Compounds / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D051379:Mice; D009154:Mutation; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D017434:Protein Structure, Tertiary
chemical_list: D003470:Culture Media; D005290:Ferric Compounds; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D017868:Cyclic AMP-Dependent Protein Kinases; D003474:Curcumin