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This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: mol.106.026070v1 mol.106.026070v2 70/6/2015    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Artigas, P. Articles by Andersen, O. S. Search for Related Content PubMed PubMed Citation Articles by Artigas, P. Articles by Andersen, O. S.

2,3-Butanedione Monoxime Affects Cystic Fibrosis Transmembrane Conductance Regulator Channel Function through Phosphorylation-Dependent and Phosphorylation-Independent Mechanisms: The Role of Bilayer Material Properties

Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, New York, New York (P.A., L.F.D., M.S., S.S.); Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York (S.J.A., E.A.H., O.S.A.); and Instituto de Ciencias Biomédicas and Centro de Estudios Moleculares de la Célula, Facultad de Medicina, Universidad de Chile, Santiago, Chile (L.F.D.)

2,3-Butanedione monoxime (BDM) is widely believed to act as a chemical phosphatase. We therefore examined the effects of BDM on the cystic fibrosis transmembrane regulator (CFTR) Cl^- channel, which is regulated by phosphorylation in a complex manner. In guinea pig ventricular myocytes, forskolin-activated whole-cell CFTR currents responded biphasically to external 20 mM BDM: a rapid 2-fold current activation was followed by a slower ( 20 s) inhibition (to 20% of control). The inhibitory response was abolished by intracellular dialysis with the phosphatase inhibitor microcystin, suggesting involvement of endogenous phosphatases. The BDM-induced activation was studied further in Xenopus laevis oocytes expressing human epithelial CFTR. The concentration for half-maximal BDM activation (K_0.5) was state-dependent, 2 mM for highly and 20 mM for partially phosphorylated channels, suggesting a modulated receptor mechanism. Because BDM modulates many different membrane proteins with similar K_0.5 values, we tested whether BDM could alter protein function by altering lipid bilayer properties rather than by direct BDM-protein interactions. Using gramicidin channels of different lengths (different channel-bilayer hydrophobic mismatch) as reporters of bilayer stiffness, we found that BDM increases channel appearance rates and lifetimes (reduces bilayer stiffness). At 20 mM BDM, the appearance rates increase 4-fold (for the longer, 15 residues/monomer, channels) to 10-fold (for the shorter, 13 residues/monomer channels); the lifetimes increase 50% independently of channel length. BDM thus reduces the energetic cost of bilayer deformation, an effect that may underlie the effects of BDM on CFTR and other membrane proteins; the state-dependent changes in K_0.5 are consistent with such a bilayer-mediated mechanism.

Address correspondence to: Dr. Pablo Artigas, Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, 1230 York Ave., New York, NY 10021. E-mail: artigas{at}rockefeller.edu